Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Preamps and Effects => Topic started by: kvandekrol on December 20, 2015, 10:19:00 PM

Title: Lab Series L5 preamp in a box: power handling & biasing
Post by: kvandekrol on December 20, 2015, 10:19:00 PM
I am knee deep in a project to put the Lab Series L5 preamp in a 1790NS enclosure (EHX "XO" series, or around the size of a Fulldrive)

It'll be pretty well identical to the original, except it'll be channel-switchable, with the initial gain stage shared between both channels and a footswitch to switch it from there. I am also replacing the CA3094 with a CA3080 + discrete Darlington per the original schematic in the 3904 datasheet.

Anyway: I have a couple of questions regarding power handling and biasing.

First: the supply. I don't think there is any good reason to stick with the +/-15V from the original, when compared with the difficulty of making such a supply (not to mention the danger of "rolling your own" from AC power). I am planning on using a LT1054 voltage inverter that should work with either 9V or 12V.

The LT1054 can handle up to 100mA. So, I crunched the numbers on the L5 and came up with the following power requirements:

CA3080: 1.2mA each (x2) = 2.5mA
LM741: 3mA each max (datasheet says 1.7-2.8mA) (x2) = 6mA
JRC4558D: 6mA each (3.5 - 5.7 datasheet) x12 = 72mA
LF356N: 10mA each (5-10 datasheet) x1 = 10mA (max)

Total: 90.5mA if everything was at the very top of its specified range. This is also based on their power requirements assuming +/-15v. The draw should be around 20% less at +/-12V and 40% less at +/-9V, so the full circuit should be significantly less than the LT1054's capacity.

So my first question is: Should this theoretically work OK? Or have I made a mistake in my calculations someplace?

Second question is much easier. The trimming/biasing/tuning methods for the L5 are well documented in their service manuals, and the schematic itself is loaded with test voltages at major junctions and test points. If I am using a supply lower than the standard +/-15V, should I aim for the voltages and test results they specify (since we are nowhere near the rails no matter if it's running at +/-9v, 12v or 15v) - or should I plan on everything being proportionally smaller?
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: J M Fahey on December 21, 2015, 12:33:11 AM
Please post the L5 schematic here as a refresher.

And try to get the +/- 15V , you are already adding many variables by chopping it and putting it inside a pedal, avoid at least a few of the unknowns which will pop up.

The idea is to happily build and enjoy it  :cheesy:  not lose hair and sleep chasing problems ... well, not that many  ;)

Even if it's meant to fit in a pedaalboard, it's easy to get roughly +/- 15V from a simple 12VAC wall wart, a few pedals work that way (think MB V-Twin) so it's not an unknown .

You might use +/-12V, no big deal, but I wouldn't go lower.
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: Enzo on December 21, 2015, 03:34:21 AM
I find it odd that you are building a Lab Series amplifier circuit, yet you feel a simple +/-15v supply is "difficult".  certainly the amp circuits are a lot more complex and difficult to build than the power supply.

On that topic, if you need to plan for 90ma, using a 100ma part is really cutting it close.  A 78M15/79M15 is rated for 500ma, plenty of headroom there.
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: kvandekrol on December 21, 2015, 07:44:04 AM
Schematic:
http://www.rru.com/~meo/Guitar/Amps/Lab/Images/Lab_Series_L5_L7_L9_L11_scheme.jpeg

The supply itself would be pretty easy to implement, something like this:

http://www.musicfromouterspace.com/index.php?MAINTAB=SYNTHDIY&VPW=1910&VPH=813

...with a 15vAC adapter and regulators for +15 and -15. But the difficult part would be making space for it in the box, with either the 3300uF caps (MfOS project) or 1000uF like the V-Twin. Much more attractive to use an IC and a couple of caps if at all possible. Especially since at 12v bipolar it should only draw an absolute max of 70mA...
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: phatt on December 21, 2015, 08:18:01 PM
If the MFOS supply takes up too much real estate then this will likely take up less space and deliver enough power. 10 VAC in will become  +/-25~28VDC at regulator inputs.

I'm not sure about the current ability of this idea (better minds may wish to verify) but it is often used in many of the Alesis micro series.
My Alesis Micro parametric EQ runs from a 1300mA 9VAC plug pak.
Phil.
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: phatt on December 21, 2015, 09:04:11 PM
Just a bit sideways but there are other options which will simplify the compression circuit.
I know the L5 compressor might seem pretty slick and I've never played through the L5 but having built a lot of compressor circuits I'd hazza bet it may suffer from the dreaded pump effect which is why I've always disliked compressor circuits.

After some really wacky experiments (some I've posted here) I did eventually stumble upon this dead simple circuit and having now built this into a small pedal unit I'm blown away at how well this works.
Finally a compressor that actually distorts as well as compress,, like a real valve amp. Thank you Mic <3) <3) <3)

Original posting here;
Really Cheap Compressor, by mictester from FSB.
http://www.freestompboxes.org/viewtopic.php?f=13&t=8581

Now if you want pure studio super clean compression DON'T bother,, but if you are wanting something that comes remarkably close to soft clipped Valve power stage compression then this would be very hard to beat.  8)

Nearly all the popular (non optical) comp pedals are way too clean and suffer from the pumping effect which is unnatural. They also introduce a fair share of circuit noise. Some later units use the highly tricked up THAT chip (Boss CS3) which is way less noisy but still do not add the missing rattle.
BTW *Mictester* worked in the factory's that made some of the early pedals (think Maxon Tube screamer days) so a fair bet he knows what works for guitar players. 8|
Phil.
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: kvandekrol on December 21, 2015, 09:28:15 PM
Quote from: phatt on December 21, 2015, 08:18:01 PM
If the MFOS supply takes up too much real estate then this will likely take up less space and deliver enough power. 10 VAC in will become  +/-25~28VDC at regulator inputs.

I'm not sure about the current ability of this idea (better minds may wish to verify) but it is often used in many of the Alesis micro series.
My Alesis Micro parametric EQ runs from a 1300mA 9VAC plug pak.
Phil.

I like that one a lot. I am guessing that for 15v, I'd need to go up to 12VAC wall wart and then use LDO regulators (LM2940 / 2990) since 12V * 1.414 is just a hair under 17V and the 7815/7915's need at least 2V of wiggle room.

Are the 220uF capacitors enough for a ~100mA current draw? Most of the schematics I've seen for these type of supplies call for 1000uFs' or 2200uF's, but it would be fantastic to be able to get away with this.
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: phatt on December 21, 2015, 09:49:58 PM
No no no,,, that is a voltage doubler circuit which means with a 10 VAC input the DC voltage at the regulator will be 28VDC.

This kind of PSU maths is not x 1.4,,, it's 2.8 times the ACV.
So keep the ACV input below 12VAC other wise the raw DCV will get too big and may over dissipate the regulators. 8|
Phil.

Adding; Oh caps,,anywhere around that value ,, 330u,, 470u,, as long as they are rated above the raw DCV. I've built this supply and it's dead quite I doubt the need for larger values.
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: kvandekrol on December 24, 2015, 04:29:17 PM
So, that Alesis doubler schematic led me down a three-day rabbit hole of studying these bipolar PSU schematics, reading through dozens of forum threads discussing it, and I ended up drawing this out as a candidate: (click to see the full thing)

(http://i1249.photobucket.com/albums/hh506/aionelec/l5pre_psu.png) (http://i1249.photobucket.com/albums/hh506/aionelec/l5pre_psu.png~original)

Couple of notes.

1) The parallel caps primarily are for space concerns... the enclosure won't have enough height for bigger caps. For the 100uF booster caps, it also helps share the current load so they don't get too hot - but hopefully using low-ESR caps here will also help.

2) The series diodes after the regulator are for stability - I saw a few references to the 79XX and 79XX's latching up under certain conditions and this supposedly fixes that. I don't know for sure that they are necessary, but the original L5 actually runs on +/-14.4V, so the 0.6v diode drop gets it spot-on with the real thing.

3) The diodes to ground after the regulators are for protection - I saw them in a couple of similar PSU's and in some of the application notes for 78/79's so I am assuming they are good practice, or at the very least won't hurt anything.

Everything look good? This is my first time venturing this far from a 1:1 copy of an existing supply, and while I think I understand what everything does, I could really use a second set of experienced eyes.

We're only looking at a maximum of 200mA current needed... around 100 for all the ICs, and maybe 20mA per LED (there will be three of them). So I am hoping that this is plenty of filtering... I can't spare too much more space on the board!
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: phatt on December 25, 2015, 01:12:21 AM
I have a hunch you might be over thinking this supply.
As I'm not sure of the correct equations to use for caps I can only go on what has already been built.
Seems your current draw is only going to be 100~200mA max which is in the range of units I've worked on.

I would just breadboard the first part (up to regulators) and read the output voltage.
Read Raw DCV with no load, see how fast the Voltage drops as you add a load.
You can use another meter to read output current at the same time.
Increasing Series Cap values will enable more current but AC transformer would limit that.

Keep in mind the the DC current is effectively half Transformer AC current capacity.
(you double the voltage but current is halved)
You will soon get a real world idea of current ability if something gets hot.

Having built many projects from scratch I have learned to test everything on the bench *Before* you commit to a build.
My Micro EQ has 4 LM347n chips and likely draw less than 100mA all up but AFAIK ALL micro units use the same supply including the Microverb unit.

Links;
http://www.play-hookey.com/ac_theory/power_supply/ps_v_multipliers.html

The complete schematic for Micro verb here;
http://bmamps.com/Schematics/Alesis/alesis%20microverb%204_1.pdf
Very last page has the last updated circuit,I note some extra protection on output. :-\
Regards the extra diode protection; AFAIK, If you read the fine print on data sheets for lower voltage regulation it is not needed and obviously pcb real estate is already a bit tight so you may wish to research that a bit more.
Phil.
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: teemuk on December 25, 2015, 04:28:11 AM
QuoteNow if you want pure studio super clean compression DON'T bother,, but if you are wanting something that comes remarkably close to soft clipped Valve power stage compression then this would be very hard to beat.

There's already the A110 chip and involved circuitry, for "tube like" clipping. It employs "soft clipping" characteristics of the CA3094 OTA and drives Iabc terminal with input signal to achieve dynamically varying degree of asymmetric clipping (and related effects to harmonic distortion).

Compressor part of L5 is actually incredibly simpe. There's a JFET source follower working as a "unity gain" amplifier and a CA3080E OTA gain stage essentially working as its variable "feedback loop". In order to properly feed one of OTA inputs the signal must be heavily attenuated (input range is few millivolts). Varying gain of this stage also varies the gain of the entire follower circuit. The stage can be considered as plain "open loop" amp (with lowish gain), but gain can also be controlled by applying signal to Iabc terminal.

Signal from JFET source advances to three places: aforementioned OTA input, power amp input and circuit that generates Iabc control signal for the OTA.
 
So other circuitry is there pretty much just to generate that control signal: First there's a plain resistive attenuator for the "input" signal, then signal is amplified. Two diodes and an inverting amp full wave rectify the signal, C139 and R194 make up the RC circuit for "filtering" the rectified signal. This circuit primarily establishes attack, sustain and decay characteristics of the compression. Very "crude" circuit for anything remarkable on that regard, BTW. The result signal drives transistor Q102 and it's collector circuit in turn drives both the OTA Iabc input and another transistor, which simply drives a LED indicator lamp.

If an amp has an OTA-based compressor then the circuit most likely follows pretty much this architecture. Follower, OTA, rectifier + RC filter, BJT drive for OTA. What you have in L5, IMO, is about the most minimalistic example of an OTA based compressor circuit. Really.
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: kvandekrol on December 25, 2015, 10:49:46 PM
Quote from: phatt on December 25, 2015, 01:12:21 AM
I have a hunch you might be over thinking this supply.

Wouldn't be the first time :) (or the fifth, or the tenth...) I tend to overengineer when I don't understand things as well. Then it gradually gets more sensible the longer I spend on it.

Quote from: phatt on December 25, 2015, 01:12:21 AM
I would just breadboard the first part (up to regulators) and read the output voltage.
Read Raw DCV with no load, see how fast the Voltage drops as you add a load.

Will it regulate without a load? I saw a reference (here (http://www.musicfromouterspace.com/analogsynth_new/WALLWARTSUPPLY/WALLWARTSUPPLY.php)) to putting a 2.4k load resistor to ground after each regulator to get it to start regulating, so you could test out the supply before hooking it up to something live. Is this good practice? It would provide an extremely minimal load from what I understand, just enough to test, so it should have no real impact when the circuit is live.

Quote from: phatt on December 25, 2015, 01:12:21 AM
Regards the extra diode protection; AFAIK, If you read the fine print on data sheets for lower voltage regulation it is not needed and obviously pcb real estate is already a bit tight so you may wish to research that a bit more.

Yeah, the two sets of diodes after the regulator are actually both doing the same thing with regard to polarity protection, which I realized after thinking through it a bit more. I took out the ones that go to ground and left the ones in series so I could get the aforementioned voltage drop. I don't think I am at risk of having reverse-voltage damage to the regulators from the output caps discharging, but I suppose it doesn't hurt.

Thanks for your help. This has been incredibly valuable!
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: phatt on December 26, 2015, 08:18:31 AM
Sorry I meant just test the *Rectifier* section to see how much it sags under load but you may as well just breadboard the whole supply with regulators and start with 2k loads.
Once it's up and running measure the voltages at output of both regulators.
Should be very close to stated output.

Now also read voltage at reg inputs, this is the *unregulated rectified supply* entering regulator inputs,
Write those readings down. 8|

Now implement a very simple load test,, swap the 2k load for 1k load and take another reading.
This will demand more current from the supply and hence your unregulated DC Voltage will drop a bit.

All that matters here is to keep the regulator input DCV at least 3volts above required output Voltage so even a sag down to 20Volts is plenty of headroom to keep regulator working correctly.
If your AC transformer can output say around 1Amp then I very much doubt anything will sag enough to cause a problem.

The reg units might get warm and the load resistors might warm up a bit but leave it on for a while and as long as nothing gets burn da finger hot then it's likely all good to go.
If you want to know for certain just how much current you are passing then do the current test I mentioned before. :tu:

Regards exact voltage for the L5 circuit to work correctly, 14VDC or 15VDC will make no difference to performance.
Phil.
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: phatt on December 26, 2015, 08:30:53 AM
Quote from: teemuk on December 25, 2015, 04:28:11 AM
QuoteNow if you want pure studio super clean compression DON'T bother,, but if you are wanting something that comes remarkably close to soft clipped Valve power stage compression then this would be very hard to beat.

There's already the A110 chip and involved circuitry, for "tube like" clipping. It employs "soft clipping" characteristics of the CA3094 OTA and drives Iabc terminal with input signal to achieve dynamically varying degree of asymmetric clipping (and related effects to harmonic distortion).

Compressor part of L5 is actually incredibly simpe. There's a JFET source follower working as a "unity gain" amplifier and a CA3080E OTA gain stage essentially working as its variable "feedback loop". In order to properly feed one of OTA inputs the signal must be heavily attenuated (input range is few millivolts). Varying gain of this stage also varies the gain of the entire follower circuit. The stage can be considered as plain "open loop" amp (with lowish gain), but gain can also be controlled by applying signal to Iabc terminal.

Signal from JFET source advances to three places: aforementioned OTA input, power amp input and circuit that generates Iabc control signal for the OTA.
 
So other circuitry is there pretty much just to generate that control signal: First there's a plain resistive attenuator for the "input" signal, then signal is amplified. Two diodes and an inverting amp full wave rectify the signal, C139 and R194 make up the RC circuit for "filtering" the rectified signal. This circuit primarily establishes attack, sustain and decay characteristics of the compression. Very "crude" circuit for anything remarkable on that regard, BTW. The result signal drives transistor Q102 and it's collector circuit in turn drives both the OTA Iabc input and another transistor, which simply drives a LED indicator lamp.

If an amp has an OTA-based compressor then the circuit most likely follows pretty much this architecture. Follower, OTA, rectifier + RC filter, BJT drive for OTA. What you have in L5, IMO, is about the most minimalistic example of an OTA based compressor circuit. Really.

Hi Teemu, thanks for the explanation it all helps, :dbtu: Sadly I'll likely never get to hear/play these classic amplifiers to make a real world assessment. I've read BBKing once used this amplifier but that may not mean much as there is a lot of hype in this industry,, And I don't play all blues songs anyway.

All I know is a lot of compressor circuits for guitar are just plain useless and often a noise problem.
Boss CS2 and a lot of others that use the ca3080 chip are a waste of time, IMExperience xP

Some later units use the THAT chip which seems to be less noise prone but still no hair on the edge of the note.
I had access to a Boss GT100 digi pedal recently and it was a pile of trash, the compression was cold and clinical, to it's credit some of the cab sims sounded ok but you just can't get that classic rock sound ,, That little hair on the edge of clean chords / notes that are part of the magic of early rock guitar. Maybe the L5 can do it but I'll never know. :'(

Anyway,, I'll post my new little circuit soon which uses the compressor I mentioned and basic clipper and a cab sim. Just need to find time to record a snippet of audio to keep Mr Fahey happy. ;)
Phil.
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: J M Fahey on December 26, 2015, 02:55:32 PM
Yes, the L5 saturation stage does exactly that, at the same time rounds, compresses, gives edge and generates even harmonics ... all traits of "tube sound" .
In this case there is no hype because Lab folded many years ago, and tubeheads *hate*  "sand" so if BB used that amp it's because it did what it promised.
It was justly dubbed "Twin killer" or "Twin on steroids" , both labels apply, but 99% of the Guitar World dropped Twins in any incarnation and embraced Marshall, so it was doomed anyway.

For the very sad story of Lab Amps and Dan Pearce, the designer, read:
https://www.gearslutz.com/board/attachments/so-many-guitars-so-little-time/311163d1348888612-please-recommend-solid-state-guitar-amp-pearce_lab-amps-history.pdf

feel free to comment :(
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: phatt on December 28, 2015, 06:34:11 AM

Thanks heaps for that link, Some interesting observations in all that.

Obviously driven by the simple desire to build an amplifier that he would want for himself, over built and bullet proof.   Hey I like the guy already :dbtu: :dbtu:

An interesting point here;
I quote;
"We should be quantifying what an amplifier does to the signal, not
how it does the job."

He has my vote on that. 8)
Phil.
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: Rooster on February 07, 2016, 10:01:47 PM
I'm going to spare all parties some grief here. Would you be the kind of guitar player to turn the amp on '10', and turn your HB equipped guitar down to volume '2' to get a clean sound? This is what BB did/does with his Fender Twins, and also what he did with the L5 when he used them. This is the 'secret' recipe for getting the L5 to perform as it did for BB. They have a noticeable hiss when running this way, but certainly fine for live play.

So, if you were to ask me why the Lab series amps didn't catch on, it's as simple as what I've written. BB just happened to approach the L5 as his experience taught him and the result was, well, very usable for him. His way was not like most other players, although I did meet one local pro guy (many years ago) who did figure this out. Imagine my surprise, me owning the same amp and not even getting close to what he had going on. It was laughable but I was not beyond asking him how he was doing this. Talk about a light bulb moment! The idea of making a preamp pedal to capture this result seems virtually impossible, but carry on.
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: phatt on February 08, 2016, 02:13:28 AM

Yes with the L5 it would likely work well but you will have to forgive me I'm having trouble keeping a straight face about doing the same with a Twin,,, Oh how We wish it was that simple. :lmao:

Might just get away with it at rock concert levels but even then, the SPL difference would be too large to be usable.
For the rest of us players it's lower level gigs and you just can't do that stuff if you want the gigs.


Unless I'm the last to know the L5 is a big powerful Amp with a very good compressor which means you can set the absolute Level via a master volume to any level and still retain most of the sustain/compression. You can't do that with a Twin. well not a stock one at least.

The few times I've had the misfortune to play Big Fender twins you would have to be insane loud before they would compress making it unusable for smaller gigs, of course some of the early twins where of much lower wattage and likely some were K biased giving much earlier compression in which case sure it would suit that style of playing.
I'd hazza guess and say a fair chance the Twins BBKing played through were likely not Stock so it's anyone's guess as to what circuitry was inside. xP
As it's highly likely I will never get close enough to even sniff a real L5 I have to work within the limitations of off the shelf equipment or in my case go on a 20 years endeavor to find another way to to do same or similar, as in teach myself DIY electronics.

Today likely Many preamp circuits can do the same thing but understand the mindset of the market place.
An amplifier these days has to look like a Mack truck, has to be loud and have many knobs and must have all the extras built in. Somehow a pedal or small preamp no matter how clever just does not have the same chick pulling effect as a big loud quad box with checker plate head on top. Oh and it must have at least one Valve (with blue led glowing underneath)

I've made enough circuits to fill a shed full of land fill pcbs and on the rare occasions I've had a few light bulb moments. As much as I've always wanted a one rig that does it all in one box I've gone back to pedals as it's just so much less hassle and it's easy to modify on the fly.

I've been using the simple Compressor I mentioned earlier and I've played through enough gear to know that even though it may not be technically as slick as a real L5 it's dead easy to build and way way cheaper than trying to purchase a Real L5. and way more useful than a truck load of brandname amps.
Those are just my observations,
Phil.
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: Enzo on February 08, 2016, 05:01:52 AM
I have an L5 in my shop right now, guy is coming for it this evening.

I never liked that compressor.  It confuses many guys as well.  On most compressors, you turn the knob up to get more compression.  On the Lab series, the knob is a threshold control, so the more you turn it up, the less it compresses, ie the threshold goes higher and you trigger it less.
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: J M Fahey on February 08, 2016, 10:04:13 AM
Yes, and higher threshold not only decreases compression but also increases output level, so turning knob clockwise does the exact opposite than what players expect: smooth even constant volume output for loong sustain.

Typical of Engineers technically savvy but neither players ... nor listening to them.
I mean their ideas and complaints, besides their music.

On the contrary, the Threshold control is what the Doctor ordered for, say, a Radio station or vinyl disc cutting Engineer, so they finely tune "up to" what maximum level they can reach (transmitting or cutting)  without splattering into adjacent Radio/TV channels or having a record groove swing so much as to touch the one besides it, which is a catastrophic failure and means junking the Master disc and starting again on a new blank.

I imagine one of these short sleeve white shirt , glasses and lots of pens in a belt holder Engineers staring glassy eyed to a tatooed pierced wild hair torn clothes Heavy Metal player (how's that for stereotypes?  :lmao: ) and saying: "what do you mean that's a sh*tty compressor?  it's the circuit very successful model made by Pomona Electronics (or some similar name) and used by KJYY FM in LA"
Oh well  ::)

B y the way, it *can*  be setup to work very well, just it's a PITA and counter intuitive.

I bet BB set up his amp *once*  and Krazy glued knobs (or pot shafts)  in place , then the *only* knob he moves is the guitar Volume pot .
He uses it "like an old Twin but louder"   ;)
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: mexicanyella on February 27, 2016, 12:08:18 AM
Hope to hear how this project works out, and what aspects of an L5 appealed to you to make you decide to emulate one in pedal form. Interesting idea.

Phatt, another place to hear a Lab L5, doing a different kind of thing, is on the first four albums by King's X. Ty Tabor used an active Fender Strat Elite and a L5, and via its line out drove a PA-type power amp and multiple 4 x 12 cabinets, as heard here: 

https://m.youtube.com/watch?v=p9sO3bcWdpM

He used the higher-gain channel and got a distortion sound that some people, including me, really like. I think he used some outboard graphic EQs, FX processors for chorusy/delay/reverb stuff...but the dirt and basic tone was L5. He has said in interviews that he used to house the L5 guts in custom rack chassis to disguise what they were, in fact. The video manages to convey the distortion character pretty well...and it was similar on the band's recordings and when I saw them live in '92. All I could see onstage of the rig was four Yamaha 4 x 12 cabs, but the L5 crunch was unmistakeable. I was kind of bummed when he switched to Mesa stuff later on, and got more hyped and spitty sounding.

There's a Youtube guy who nails the tone with the same basic rig...an active Strat Elite and a L5 combo, showing how to play some King's X stuff. His Youtube name is The Scunion...check it out.

I have a BB King video here where he mentions having used the L5 and liking it. But yeah...his whole approach is something loud and clean, cranked hard enough to punish the speakers, and throttled with the guitar controls and picking dynamics.
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: phatt on February 28, 2016, 05:22:52 AM

Hey thanks Mex,, that's very helpful,, now I have a decent reference point to go by. :dbtu:

My setup is obviously not as thick as that but heck I only use (and need) a small rig.

The little compressor I mentioned in combination with a simple booster and the PhAbbtone can certainly pull off very similar results.
I should try and get a sound sample up with my setup so you can all make your own judgements.
But my hard drive is going rather soft on the inside so a major fix up first.,,, I'll be back later,,, of course that could be a while if the partition copy fails.  might need a whole new setup. wish me luck. :-X
Phil.
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: mexicanyella on March 01, 2016, 09:24:45 PM
By all means, please record some clips of it doing its thing. I liked the last ones you posted.

I saw a Lab Series L3 1x 12 combo for sale at a store yesterday but did not get to try it out. I will try to get by there soon and see what it's about.
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: solderdripper on March 02, 2016, 04:04:33 PM
Hi guys, I'm a LAB Series nut and enough of a lurker on here that I registered to chime in with this barely-relevant nugget -- I found this earlier today, actually. http://www.premierguitar.com/articles/Interview_Ty_Tabor_Kings_X 
Interview from 2011, Tabor says that he has two pre-amps specially built for him by Egnator, "We call it the Gretchen Module because it was designed to emulate the Lab Series L5 as best as possible, and they did a really good job at getting very close on that."

I still don't know if it is the compressor or the multifilter that he likes best.  :)
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: mexicanyella on March 02, 2016, 09:35:07 PM
I think I remember reading that he did not use the compressor...don't recall what he did/did not do with the multifilter.

I played through one of the larger lab heads once (L7? L9? L11? can't remember) but I recall that it did have a unique way of breaking up that seemed at once dynamically responsive and not really sounding like Marshally rock tube amp distortion at all. I liked it but it was priced out of my range at the time. I can see how that line of amps would attract a following.
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: J M Fahey on March 29, 2016, 08:47:34 PM
I was onstage in BB's visits to Argentina, he both used L5 and Silverface Twins full blast, no big deal, but shows were either in Buenos Aires Luna Park 12000 to 15000 seats and Obras Sanitarias, some 8000 seats, full blast amps were pipsqueaks there.
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: galaxiex on October 30, 2016, 07:50:20 PM
Sorry to necro bump this thread, but the OP has had this project finished for some time now and selling circuit boards for it.

I mention this cuz I bought one,  ;) and am very close to finishing it up.
Just waiting for a couple of parts to arrive.

I will post here in the effects section when I got it done.

Here's a link to his website and the project.

https://aionelectronics.com/project/lab-series-l5-preamp/ (https://aionelectronics.com/project/lab-series-l5-preamp/)

and a link to madbean pedals forum where he posted about this project.

http://www.madbeanpedals.com/forum/index.php?topic=22746.msg223193#msg223193 (http://www.madbeanpedals.com/forum/index.php?topic=22746.msg223193#msg223193)

Cheers!
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: phatt on November 03, 2016, 04:05:37 AM
Hi galaxiex,

Thanks for the links, interesting. :tu:
I noticed down the end of the page at https://aionelectronics.com/project/lab-series-l5-preamp/
Some comments regarding the way Ty Tabor used the L5 amplifiers.

It seems Ty does not use the compressor which throws a whole different slant on the subject of the compressor section. Maybe he just wanted the tone filter section for some extra tone tweaking. The article then goes on to say the preamp output was sent to a Messa 2Ninety which is a big Valve power rig.
So that would certainly give compression at high output levels which is fine for large live venues but not possible at low volume as just like a big fender twin down low they are just as clean as most SS rigs.

But then a few posts back *mexicanyella* noted he changed the setup
(another guitar player in search of the mojo)  :lmao:

So in the end who knows what is being used and how good or bad some of this gear really works. xP

On the Madbean link I noted a few comments regarding building of the project where some issues were raised. I know from building a few of the well known compressor circuits that used the ca3080 they can be noisy and fussey to setup.

FWIW,,My observations having had a marshall ED comp, a boss CS2 and CS3 and a couple of breadborad test circuits all on the bench at the same I've noticed that the ca3080 circuits are noise prone.
The Boss CS3 is the exception as it uses a THAT chip and is far less noise prone to all the others I had at the time, though it still can't reproduce the classic Valve compression. :grr :grr :grr

needless to say I gave up on compressor circuits. :'( :'(
I went on to try all sorts of hair brained ideas :duh  that were in the end too complex and fiddly to be of any real use. (some I posted here)
But then that chap *Mictester at FSB* posted that simple comp circuit I mentioned on previous page and it was impressive. must be the most simple compressor circuit I've ever seen and it does deliver the compression WITH the magical rattle. <3) <3) <3) <3) <3) <3)

Why am I saying this? Well because it works for R&R guitar and a lot of DIY'ers out there will be hard pressed to find something that delivers that classic sound of a valve amp on the edge of breakup.
No setup fiddling and only 2 knobs. Except for the LDR which you have to make from 2 Leds and an LDR and a piece of shrink tube all the other parts are off the shelf. Bang for buck it's likely hard to beat.

If I ever work out how to make up a video of my gear I'll post a clip of my setup on utube but not sure how well it will reproduce the effect and feel of what I hear through a small cheap camera. :-\

Phil.
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: galaxiex on November 03, 2016, 10:10:59 PM
Hi Phil,

Thanks for all that.  :)

'course my main motivation for buying/building this kit was not solely for the compressor.  ;)

More I was curious about this amp (the actual Lab Series L5) and since I'm not likely to own one,
or even be near one anytime soon, aaaannnnd...
I'm a sucker  ::)
for a somewhat unique, and what appears to be, a very well thought out project.
Not to mention it looks killer too.

I am "familiar" with the L5 only in that I actually remember the ads for them from back in the day,
and as an impressionable youth the ad writers prose had an impact on me.  :o

Didn't hurt that BB King used them too.  8)

I wouldn't know if this pre-amp nails the sound of the original L5 or not,
but I want to explore its potential, whatever that may be.

I saw your original post about the Mictester comp and have looked at his original posting and read thru the thread.
I am very keen to build one....  :)

I'm so neck deep in so many projects right now..... but I will get to it.... eventually....

I was playing a modified Ross comp from Guitar PCB dot com aka the MoRC, and liked it for a while...
but its now gone from my pedal chain as I completely changed my setup.

Previous setup.

Fender Nashville Tele > MoRC comp > EA Tremolo > Boss Blues Driver > Blackstar Soloist 60

New setup.

Fender Nashville Tele..................... tuned std >
Keef Micawber Clone.....tuned 5 string open G >  > Jack Orman 3 way mixer > Boss TU-3 > Boss SD-1 (Keely mod done by me)  > 1978 Deluxe Reverb
Fender 52 FSR Tele...................tuned open E >

I love the Orman mixer based on a TL071.
It adds a slight 3db boost, but best of all when I need to change guitars,
I don't have to un-plug one, and then plug-in the next.
I just put one down and pick up the next and hit the footswitch.

All 3 guitars stay plugged in and the box has a footswitch and LED for each.  8)

(I'm gettin too old to have to bend over pluggin cables alla time.
It's hard enough to sling those axes over my shoulder for a 1 hr set)  ;)

Sorry to ramble on...

Thanks for your thoughts on this  :) ,
and I really will build that Mictester Comp..... curious to see how it works with the Deluxe.

PS I'd love to see a vid and hear your setup sometime.  8)


Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: phatt on November 07, 2016, 03:08:12 AM
Thanks for sharing your ideas,
I'm not able to record anything right now but meantime here is a pic of my pedal board.
(https://s5.postimg.org/qwwah7tqv/Ph_Abb_board2016.jpg) (https://postimg.org/image/i1vg6p4yb/)
image sharing sites (https://postimage.org/)

My Aim is not about making the best amplifier it's really more about extracting the best sound from basic equipment. I refuse to except that one has to empty my bank account to achieve great guitar sound.
You only have to google a few mojo words to find all the greatest pedal claims of tone nirvana,, but the demonstrations are ALWAYS done through very expensive amplification.

Tiss very rare to find a demo of a pedal running through an average SS amplifier using an average guitar. 8|

The Laney Amplifier in that picture is a 3 channel Keyboard amp and although I've done some modifications the circuit is still very basic, only has bass and treble and a gain for each input. So whatever magic is present in the sound is from the pedal board circuitry as the Laney is really quite dull on it's own. The Laney does have tank reverb which is a handy extra. I doubt there is any secret agent mojo circuitry involved just a combination of a few known circuits that when used in the right way make the magic.

The first pedal is a simple Fet circuit I made up and if there is any mojo it's because the treble and bass only CUT, no boost. So tone controls on 10 equals flat response. this pedal is nearly always on and in conjunction with the Mictester compressor it gives the classic rock roll rattle.

The Tweed57 is way too hot, too much of everything, In time it will go.
The Boss OS2 is interesting and I use it to get the darker dirt sounds.
Chorus/Delay,,, need no explanation.

Next comes the Compressor/OD/Cabsim,, The ugly home made black box.
I call it my Cruise Control board,  :)
This 3 part setup runs on 18VDC and that does help quite a bit.

With just the right amount of clean boost from the First pedal the compressor works very similar to some of the old classic Valve rigs I used as a lad. If the input signal is way too big the compressor will jack up a bit and the bass will fart,, but then a lot of classic valve rig do the same thing.  8|

There is an extra diode clipper in between the Comp and Cab sim,, still not sure if it's really needed. The cab sim is based on an old Nobels unit from the 70's then a master volume with a level shift added to give a CLEAN volume boost for the times when your lead bit has to get above a mad drummer.
Then my super simple PhAbbTone circuit.
Depending on the venue,, I do add a graphic EQ and plug in an extra speaker to give the bottom end a bit more grunt in larger gigs.
Cheers, Phil.
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: J M Fahey on November 07, 2016, 06:42:18 AM
Quoteall the greatest pedal claims of tone nirvana,, but the demonstrations are ALWAYS done through very expensive amplification.

Tiss very rare to find a demo of a pedal running through an average SS amplifier using an average guitar.
An old friend plays classic greasy smokey Blues, through some old school Fender amplifier, from a Dekuxe to a 4 x 10" Super Reverb to a full tilt Twin (if the venue allows it), and got VERY excited about
(http://medias.audiofanzine.com/images/normal/boss-fdr-1-fender-65-deluxe-reverb-amp-338967.jpg) reasoning: "I can carry my compact trusty Peavey Bandit 112 anywhere and get real Fender sound usingb this pedal" ... which by the way is quite expensive, doubly so if ordering from Argentina.

End of the story? : he was VERY disappointed with it, "it sounds or much more important, *feels*  NOTHING like a Super Reverb or even the YT demos"

I coughed and said: did you notice that all good demos have this pedal plugged straight into a tube Fender amp? ;)
Title: Re: Lab Series L5 preamp in a box: power handling & biasing
Post by: galaxiex on November 08, 2016, 09:09:27 PM
Phil,
Thanks for posting details of your setup.  8)

I especially like this line...

Quote from: phatt on November 07, 2016, 03:08:12 AM
........extracting the best sound from basic equipment.

It's all too easy to get complicated and think you need a butt load of fancy boo-teek gear to get a good sound.
I've fallen prey to that a few times...  :-[

I now find myself looking to keep my rig as simple as possible...
but with an ear to getting the sound I like with as little gear as possible.

Another lesson I've learned, and it keeps getting hammered into me over and over...

It's NOT about the fancy (or not) pedal chain etc, it's the combination of what you use.
EVERYTHING contributes, and some stuff just doesn't sound right with certain other stuff.
But if you change the combination around, or maybe just a different guitar... it can be magic!
It can be time consuming and frustrating to keep switching gear around but eventually... maybe.... sometimes...
You hit on that awesome combination and it's great!

One such very simple combo I have at home for a practice rig is so simple...

1991 Am Std Strat > Blackstar HT-Dual pedal> The Audition/Teisco amp I posted about in the schematics board.

This setup sounds killer at low practice volumes. Not all guitars sound good thru this... but the Strat is awesome.
I have struggled in the past to have an inspiring low volume tone for practicing, and then of course,
no practicing happens cuz the tone is just not there...

I do ramble on don't I?  ;)
Sorry.

JM,
Excellent point about the demos of those pedals.
I've had this happen too... not with that 65 Deluxe pedal, but others...

I saw that 65 Deluxe pedal a few years ago and couldn't afford it then... and wished I could...
Now I'm glad I didn't buy it.  ;)