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Messages - phatt

Hi Joe, Yep can be confusing.
My understanding, it's about the Z (impedance) of the input.
A low Z input on guitar amps is for big signals or even line input.
While a Hi-Z input is very sensitive so as to pickup very small signals.
In the early days guitar PU's were low output and needed a very sensitive input to amplify well. (Hence the 1Meg grid resistor on the old Valve gear)
These days even the cheapest guitars have much bigger outputs than the 40's 50's era so the preamps will redline much earlier on the dial using the pu's around nowadays.

The old Fender circuits used 68k resistors on the Grids of V1 for LOW input. while the HIGH input switched the input Z to 1Meg. far more sensitive.

With super hot pickups you are likely better served by limiting the input Z to about 220k.
I've noticed this with some of the hotrod boutique Amps.
A Carvin Legacy is an Example of this where in put grid R is 220k.
With multi stage preamps this keeps thing from going stupid and also helps keep circuit noise lower.
Agree, Mr Thud
If it has master volume then likely it has a gain pot as well
Try turning the master to full then turn down the gain pot.
And after that I'd be looking into the limiter wrapped around the Power amp section, as it maybe faulty.
The master volume switch might be connected to that as well ,, hard to tell.
Also there is a feedback setup in the power amp but not connected to the output?? maybe a drawing omission.

Limiter is Q1&2, &Q11
Feedback is at R15

Thanks G1,
          Yep your eyes are better than mine. ;)
Hopefully *Victor* might like to take some close up Clear Pictures of the Inside of the Chassis might help us to confirm just how to help.
Victor,Regards the Loop;
Signal splits at pin 7 of IC4B. (see TP7)

Dry goes through R73 & R77 across to input of IC4A.
Meantime signal also goes through R84 to input of DSP (the Send). The DSP FX is then sent back via Return line through R101 where it is mixed with the dry signal.

The CD or aux input is also mixed at this point.

Note Q24 is the mute circuit,, you will find label D is linked right at the input socket.
So when you remove the guitar lead it kills all signal.

As you seem to imply that you don't really need the DSP then it's a fair bet some of the channel selections may work without the DSP.
Which is why I mentioned joining R to T.
It may at least bypass some of the DSP control over the analog parts of the circuit.
Of course I'm just guessing as there is not enough info on the Schematics to work out how the DSP interconnects.
Be aware that a lot of those pin header connectors are very cheap and often don't like being plugged in and out many times before they no longer connect. A gentle push around the wires and plugs can often find a faulty connector and amp comes to life again.  they are not really suited for guitar amps which tend to get a lot of abuse due to speaker vibration and road handling.
Hum,,My thought, What about Bridging R and T?
Find them at Test point 8 after IC4A also at J21

The DSP seems somehow interconnected with the channel switching. Hard to tell?
Though it seems to me that Modes A,B & C are direct to circuit, while Solo OD, B2 & A-B modes are activated via the DSP chip.
Maybe Post some pictures might give us some better plans.
Amplifier Discussion / Re: 12w Marshall
November 11, 2022, 09:47:39 PM
Brilliant work TassieV,
Can I ask how much this has cost you so far?
Of course one would still have to add the cost of a Chassis and a Cab for a complete build.
Hi Joe,
Yes, trimming the hi Freq is critical to getting a good sound and it's more than one might assume.

If it helps, "mictester" (Member on FSB) posted a circuit called "Really Smooth Overdrive" (RSO) which I breadboard tested which pretty much kills anything above 1kHz,, (IIRC).

With big fat humbuckers you will instantly recognize the signature sound of guys like Santana.

You should be able to read this without being a member if not I'll ask Mic if I can repost it here.

Only down side, it was a bit noisy due to the 3 series 100k resistors (I think) but that was on the open BBoard so maybe in a box it might be better.
You will most likely need a tone stack Pre or post the circuit to get the best out of it.

With regards to low end cut,,, well if you have an Amp with a lot of headroom then likely you will have little problems but with small low wattage practice amps or anything that has a less than ideal power supply then you have the issue of the bass farting out at higher volumes due to the simple reality that bass frequencies require a lot of power/ current to stay clean.

The first vid on that MG400 link by "Sophie Burrel' You can hear the hi freq crud spitting in and out on some of the notes in some of the riffs (Especially the first one).  This is the whole reason why I hate those kind of pedals.
The spitting is very similar to grid blocking distortion in Valve rigs where the sound actually cuts off for a few Millie seconds.
I honestly can't understand how one could possibly enjoy trying to play screaming riffs with that happening.

I understand metal players seem to like that edgy stuff but to my ears you loose note definition and hence clarity it just becomes a blur of buzzy annoying sound.
that pedal would be ok if you wipe off the hifreq and fix the that cutting out issue then I'd think about trying one out.

My rig (which I just posted a video about) can do heavy metal if I wanted to do so and it does not spit or splutter,, each note holds and sustains perfectly with Really Smooth Distortion. Hey I might even try to do another short demo with it on full,, but life is full up for the next few weeks.

I have an old Digiteck RP200 and I spent many hours trying to dial in anything worth using and found some of the modulations were useful but most of the cabs/Amps sims where just totally annoying buzz saws.
I did send the output into my PhAbbTone and analog cab sim and it did kill off the extreme HiFreq Hash. my cab sim setup kills the hi at around 3.5kHz.
IMExperience A lot of those cheaper modeling pedals go way past 5kHz.

I checked the link,,  Humm???
well Except for one, all the video demos are about metal sounds which of course is fine for the younger gens,, oh sure I'm getting old but there are still some of us who actually play live and play tunes,songs and melodies. NOT just scales.

Without Melody music is just Noise. (Rant below)

My old fart brain is leading to this observation;

Yes there is a place for this stuff,, sure in a studio or in your room it's great to experiment and I urge folks to do that but it's only one part of a very complex
You can spend hours tweaking all the parameters at home thinking you have dialed in tone nirvana only to find on stage it becomes a mind numbing blur of noise.
Sadly most of them you can't instantly tweak on the fly in the middle of your well practiced lead break. :-X

I've watched this disaster unfold many times on stage to players who use all in one pedal boards. What sounded fantastic at home often sounds crap on stage.

Which is why I have learned to use basic pedals into flat response Amps.
My rig is bandwidth limited to remove all the Hi Freq hash which is nearly always present, especially in digital gear.
Players having heard me singing/playing on stage, (often younger ones) ask me why they can't dial a decent tone like mine?

Simple answer; You have Way too Much Bandwidth.

I have here an old RP200 all in one digital pedal unit that I scoured for a few dollars.
I spent a few days trying to coax something useful but nothing was gleaned from all my tweaking. I have repaired many of these types of pedals so I know what to expect.
Interestingly I ran it through my Phabbtone and Analog cab sim box and it did improve the result. So even with all the digi fancy pants amp/cabsims there was way to much hash. (read below, rant on guitar bandwidth)

Sadly that RP200 unit is all about distortion and very little chance of pulling a touch sensitive response from that unit.
Of course the RP stuff is old tech now and there is much improved gear now.
But still I've not seen/heard the newer stuff pull of the touch sensitive trick that well. I'm sure the Kemper and like are vastly better but I'll never have the money for that. ::)

So for me I only need about 3 or 4 sounds which I can access on the fly.
The occasional tap tempo on the echo and a tweak to the tone is all that is needed
I use 3 OD pedals so one on gives a little triode rattle, 2 on gives a driven sound ,3 on gives the fat distortion. The Gain knobs on all 3 OD's are only dialed at around 9,10 O'clock. This gives a far better transition from clean to full Distortion.
I've found that using one Dirt pedal to "Do I All" has never worked well for me, you need to build it with a few units.

Rant on Bandwidth;
Learn to understand your instrument.
the low E string is around 82Hz, top open E is 328Hz, top E 12th fret is 656Hz,
If you have 24Frets then the highest note that can be played is 1,312Hz.
So ~95% of every sound produced is below 1,000Hz (1kHz)
So double that for some harmonic content you have 2,524Hz,, and again for sibilance you have around 5kHz, which is the outer limit and hardly useful for 90% of the time.

Now if all you want to do is strum a few chords through a super clean Amp then 20/20 bandwidth might sound half decent. But the moment you want OD/Distortion then the game DRAMATICALLY changes. Even with light OD  all that excess harmonic content is just full of crud/Hash that will destroy any hope of note definition and clarity.

I have found with a lot of Amps/Gear when you turn up the treble, you also get a lot of hifreq boost way above the 1,2 an 3kHz. which defeats the goal.
This is why I depend on my analog Cab circuit, anything above 4kHz is dramatically suppressed. So now when I turn up my treble pot it is only boosting that 1kHz to 3Khz and everything above that is effectively not heard.
Tweaking the "Whole System Tone" in this manner goes a long way to resolving what for the Average player with little TRUE understanding of tone shaping becomes a never ending search, often emptying there bank account and still not finding meaningful results. 

In the older Valve amps, (Note I said older) the circuits "By Design" rolled off a lot of hifreq crud so when they distorted they were not so harsh on the ears.

As I have come to understand this can be done with SS gear,, in my case relatively cheaply.

       You can learn every scale until your fingers melt but without Melody it's just notes that become a blur of noise. and annoys Mum. >:(
Tiss good if you learn scales but don't ever loose sight of the Melody
Chaps like Joe Satriani are examples,, a true master of how to use those scales to enhance the song but they always lead back to the main melody. Listen to "Always With Me, Always With You" and "Surfing with the Alien" as example.

**A simple FACT;
Melody, is how we remember Songs,, Few will be able to remember all the fancy scales you spent years learning,, but they will instantly remember a tune, even years later.**

Well that's enough from me today,, hope it helps someone out there in this over tecked up industry that often does not deliver.
Preamps and Effects / Re: My rig explained with Vid
October 21, 2022, 04:07:22 AM
I found this by accident,
Jim Has spent a lot more money on his research than I have and has arrived at a similar observation as myself about guitar Sound/Tone?

Well worth the time if you want to know just how to make it work without spending a fortune.

Make sure you watch the last part about his Tackle Box,, it will seriously challenge the tube freaks.
Preamps and Effects / Re: My rig explained with Vid
October 12, 2022, 08:59:25 AM
Tech marketing for another form of tone control.
Passive EQ,Shelving EQ, Graphic EQ, Parametric EQ, Cab sim EQ.
They all work in different manner but when it all boils down cab sims is a fancy tone control circuit.
Now every other new pedal gizmo has a digital version of every cab you can name.

Every stage of a circuit can alter the tone shape, sometimes a little sometimes a lot. from pickup to speaker all can effect the end tone result.
I think Joe means you have a TRS  (Tip Ring Sleeve)

Short the Tip to the Ring gives you the 3rd possible connection which may trigger the 3rd option.
Preamps and Effects / Re: My rig explained with Vid
October 07, 2022, 08:47:51 PM
Thanks Joe,
I was not sure what the hell I was trying to play.  lol
The cameras audio setup tends to compress a fair bit which effects the outcome which does not give a true representation of the sound/tone and dynamics, but better than nothing.
Here is the PhAbbToneV4 schematic for you, Also adding pics of the rig.
Preamps and Effects / My rig explained with Vid
October 07, 2022, 03:46:55 AM
Being that a have talked a lot about how to shape your guitar sound, I thought it was about time I posted a link to my Rig setup.
Just a 10min vid of my gear and a basic explanation of how it all works.

I've tried to keep it short and keep talking to a minimum and let the gear speak for itself. An All SS setup using a cheap strat copy.

I could not find a way to show the Amp, Pedalboard and myself in the same frame so I figured the best idea was to show the guitar and pedal as that's what most will wish to know.

My aim was to create a small rig that was versatile for my needs which is playing, singing and some lead sounds that covered the basic needs of a decent Rock&Roll guitar rig.

Might help folks who are searching for ideas on how to setup a rig.
Amplifier Discussion / Re: Fender 112 Deluxe Plus
September 30, 2022, 07:41:38 AM
Glad it helps,, I'm not qualified enough to understand some of the more complex power amp designs but yes once you remove the current protection it makes more sense.
I've designed a few plain and simple power stages and had great success just by installing a PTC on the output. In this case one PTC would replace 18 extra parts and as likely in this case the Protect circuit may well be adding to the problem.
If a poly switch fails the amp stops working and you only need to replace one part.
PTC is a Poly Thermal Capacitor, Often called a poly switch because they switch to high resistance when they reach the set threshold. They do this switch faster than a power transistor can fail, effectively doing the same job as the rather complex current limit in the power amp.
BTW Tassie I buy them at Jaycar if you want to source some. ;)   

Re my drawing;
I'm still miffed about R69 & R66. ???
I think R66 is added Fback from output but R69 is really weird as they connect to
C37 & C38 which are filter caps for the opamp supply which I would assume would normally go to ground but they are summed at R65 which goes back to main output.
While R66 takes it back to the junction of R62 & C35.
Maybe better minds might like to comment on that subject.