Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Preamps and Effects => Topic started by: GuitarLord66 on September 27, 2011, 07:34:28 AM

Title: COMPLETED! :D modifying laney combo to rack preamp
Post by: GuitarLord66 on September 27, 2011, 07:34:28 AM
Hey guys! It's been a long time since I was on here! But I think you guys will help a lot more then UG... Last time I posted there they told me "sell everything and buy a decent amp"...
You might remember me from this post http://www.ssguitar.com/index.php?topic=1785.0

Ok well here's my current gear...

(http://i236.photobucket.com/albums/ff77/guitarlord66/GuitarsandGear.jpg)

My current setup is LTD kh-202 into akg wireless into behringer v-amp pro send g major send v-amp pro into peavey bandits power map input all controlled by fcb1010 midi controller

The v-amp seems to suck my tone, and do horrible things to it, my guitar has almost no sustain and just doesnt sound "real" enough to me... So I decided I would try plugging my guitar directly into my Laney PL100 Twin which has terrible tone pots that are scratchy and sounds really trebly as an amp... but then I ran out the "send" of that amp and into the "power amp in" of my peavey bandit and I was shocked... It sounded like a real guitar! nice and crunchy on the dirty channel and really nice cleans. The response of my guitar was so nice! Playing fast, sweeping etc just felt like it was instant, I guess with the v-amp there must have been latency issues? :s

Here's a picture of the laney after I refurbished it all and replaced the writing on the front:

http://i236.photobucket.com/albums/ff77/guitarlord66/After.jpg

But the whole point of this thread is to ask, how plausible is it to take the laney's preamp out of the amp and mount it into a rack unit? I'm good with electronics as long as I'm not starting from scratch, I can modify things quite well. I would replace all the pots with new ones (how do I go about finding out what rating each pot is?) and replace all the input and output jacks. I haven't taken the laney apart in a long time and I have no photos of the inside but I will probably do that tomorrow and post it here :) I hope it would fit in a standard rack unit either single or double in height...

Then I'll take the v-amp out of my main rig and just use it for recording :)
Title: Re: Considering modifying laney combo to rack preamp
Post by: phatt on September 27, 2011, 09:15:16 AM
Hi Guitarlord,
             Before embarking on what seems like a long and tedious mix an match which has the nightmare potential for the novice.
Try running the Laney poweramp into the Peavy speaker?  (Remembering to disconnect the poweramp in the Peavy first of course).

If that sounds good,, then the old Laney may just need better drivers. :tu:
That may cost more but a far better chance of success.
Speakers count for a lot with guitar amps.


IMO those Bandits have way to much hi frequency content in the preamp section.
I've had reasonable success by altering a Bandits preamp response curves,,though it was an earlier model than yours. 
You may wish to tweak that after the Laney refit?

Also remember that open back Amps against a wall will certainly alter the sonic outcome.

Cheers, Phil.
Title: Re: Considering modifying laney combo to rack preamp
Post by: GuitarLord66 on September 27, 2011, 04:26:39 PM
Thankyou for your input :)

Yeah the rehousing project does seem like it would be quite a mission to complete, but I also enjoy doing projects like that.
I will try your suggestion of running the Laney with it's power amp through the Peavey's speaker though.

The Laney seems very old, if you looked at the thread I linked at the top of this one you can see the condition I got it in. That's why the tone pots are so scratchy, it's not my fault, I actually look after my gear :P haha

My old school is upgrading their hall at the end of the year and because I'm still in contact with my old music teacher, she said once they have finished and all the gear their not using any more is sorted out I'm welcome to whatever I want that is either broken or not being used. I'm hoping to obtain a rack microphone stereo power amp that I saw sitting in the corner last year not being used, and hopefully convert it from mic input to guitar input... and make the necessary adjustments. That way I should be able to run my setup in stereo and finally take advantage of stereo chorus, phaser, delay etc from my tc electronics g major :D

The goal of this project was to get the Pre amp out of the Laney and into my rack, at the end of the year clean up, convert and fit the power amp into my rack and then take the speakers out of my Laney and make a 2 x 12" stereo cab...

As you can tell I'm obsessed with racks... and also a wishful thinker there's no guarantee I'll get that power amp...

I agree, I've never liked the Bandit on it's own, I noticed that it's very bassy. That's why I've been using it's power amp with my v-amp pro. But seriously when I hooked up that Laney preamp to my bandits power amp, it was sooo nice to play. It doesn't really make sense but I swear my v-amp must have latency issues or something because my guitar just felt so responsive!


EDIT!!!

I just got home from my university audition for bachelor of popular music, It went great! :D Hope i get in!! :D Just excited :P I didn't have to say that :P haha

Ok back to the project, I decided to pull the brains of the laney out and have a look, it's quite wide, wider then a 19" rack that I want to make it...

Here's a few pictures of it, there's a tag that says "DAVE 14 JUNE 90" so I'm guessing someone called dave either serviced it or built it in 14th of June 1990?

FRONT
(http://i236.photobucket.com/albums/ff77/guitarlord66/IMG_8806-1.jpg)
TOP
(http://i236.photobucket.com/albums/ff77/guitarlord66/IMG_8807.jpg)
Front Circuit
(http://i236.photobucket.com/albums/ff77/guitarlord66/IMG_8810.jpg)
Back Circuit
(http://i236.photobucket.com/albums/ff77/guitarlord66/IMG_8809.jpg)

Now here's my questions :P

Do you think I could cut the circuit board between channel 1 and 2 and reconnect the the board with wires and then in the rack unit put the second channel below the first?

Secondly the back circuit looks to be the power amp section, but the front circuit board connects to it with 6 wires (red) starting to wonder whether it would be easier to mount the full unit, preamp and power amp in the rack unit and then just have pre amp output? not exactly what I had in mind and the power amp wont be used but anyway what do you guys think?
Title: Re: Considering modifying laney combo to rack preamp
Post by: GuitarLord66 on September 27, 2011, 11:37:46 PM
Well I went ahead and took the front circuit out to have a look, I think it might be hard to split it and re join it in a section...
Here's some pics:

As you can see the front circuit is too long to fit in a standard rack unit, any ideas how I can make it fit?
(http://i236.photobucket.com/albums/ff77/guitarlord66/IMG_8812.jpg)

Circuit top
(http://i236.photobucket.com/albums/ff77/guitarlord66/IMG_8813-1.jpg)

Circuit bottom
(http://i236.photobucket.com/albums/ff77/guitarlord66/IMG_8814.jpg)


ONCE AGAIN ANOTHER EDIT!!!!

I put the photo in photoshop to see if I could cut channel 2 off the main board and put coloured dots where wires would have to be soldered to join it back together, to my understanding I CAN do that can't I? The picture shows the bottom view with the solder dots, and the top view where it would be cut...

(http://i236.photobucket.com/albums/ff77/guitarlord66/Untitled-1-4.jpg)


Title: Re: Considering modifying laney combo to rack preamp
Post by: morgoth2006 on September 28, 2011, 04:43:22 AM
Well, I would never destroy a working amp and cutting the pcb is a good way to do that.
If you like the preamp of the Laney why don't you build one? You could then customize it to your liking and it wouldn't wreak a perfectly good amp.
The top pcb is the output unit and the power supply. It then provides power to the lower board. With a multimeter you can see what voltages come out.
Title: Re: Considering modifying laney combo to rack preamp
Post by: GuitarLord66 on September 28, 2011, 04:56:23 AM
Well it's not a perfectly good amp, all the tone and volume pots are ruined, they sometimes cut out and are scratchy when turned, I've tried cleaning them to no prevail, so I'd have to replace all of them as well.
Every time I've tried to make a circuit it didn't work so I've pretty much completely given up on that.
So if I did go ahead and cut the PCB and rewire it, I could just find out what the voltage input is and then use the other wires as output? or is the output unit used for more then just the power amp?
If i can successfully cut the pcb and rewire it I wouldn't mind housing the entire unit into a 2 space rack enclosure anyway, and add a few more options to it, such as a pre-preamp output that would go to a rack tuner for example and making all the pots wired so I can choose where i want them placed on the new front panel.
It's still all just ideas and I love all your feedback, I'm trying not to ignore the "don't destroy a working amp" comment, but I really have my mind set on converting it to a rack pre amp... I know someone out there will understand what I mean haha :P
Title: Re: Considering modifying laney combo to rack preamp
Post by: J M Fahey on September 28, 2011, 05:22:57 AM
Well, it *is* a perfectly working amp, with scratchy pots and switches.
It does not need any *electronic* servicing and replacing all pots and switches will cost peanuts and can be accomplished in a little over one hour, after which it will be as good as when Dave built it in the 90's.
In a way, I'd compare it to a perfectly good car .... just out of gasoline.
Not to forget that when mounting it in a rack, you will need to replace those pots and switches anyway. (I guess).
Not to discourage you, just that it's a little too large for what you want, and I don't think cutting a PCB is a good idea.
You may *electrically* join both halves, but grounding and layout will be different, you may be opening a can of worms there.
Laneys are very well made and very logically laid out amps.
They use a modular approach, they can easily mix and match between a few Preamps and Power amps to create many interesting models.
Try that with single_huge_board monstrosities such as Fender !!!!
Or Valvestates. Or most others.
Title: Re: Considering modifying laney combo to rack preamp
Post by: GuitarLord66 on September 28, 2011, 05:46:45 AM
Just out of curiosity then, if I was to cut it and "electrically" connect the halves how does that affect the grounding? Wouldn't it be the exact same if I made sure all the connections are secure? Obviously I've been put off now, but I'm just wondering :P

If I had the money to buy that parts (and spares) I'd attempt building an amp but every circuit I've ever tried to make has failed.. and I've already wasted enough money down that road, thats why modding existing gear seems appealing to me :)

I really love the tone, I took the "brains" or whatever you'd call it out of the Laney and I have it sitting on top of my rack, all hooked up... all the circuit boards exposed... I know that's a bad idea but the tone is so good (to me) that I don't want to put it away D: and obviously running 2 combo amps and only using half of each isn't the best idea either...

I'm considering just rehousing the "brains" as compact as possible to connect to my setup, just another question because it is a solid state amp the power amp doesn't have to be connected to any speakers does it? because that's how I've been running it for the past few hours of jamming... :s

EDIT I can't help it, I really want to rackmount this amp... :/

I had another idea, and it involved cutting the pcb, this time from the end

On the left side of this image, just taking off the two jacks, the two large resistors and the input for those 6 red cables
(http://i236.photobucket.com/albums/ff77/guitarlord66/IMG_8813-1.jpg)

On the right side of this image...
(http://i236.photobucket.com/albums/ff77/guitarlord66/IMG_8814.jpg)

That way I just solder the 6 wires to where they have to go, I'm getting rid of the reverb from the amp because it doesn't work anyway so no need to re install that jack and then it's just the foot controller jack, get a small piece of pcb to put the resisters on, and cut off that end of the pcb and it should make the clearance to fit in a rack enclosure, I only need another 30 - 40mm for it to fit... So how's that idea sound?
Title: Re: Considering modifying laney combo to rack preamp
Post by: joecool85 on September 28, 2011, 08:21:17 AM
I still think you need to try the good speakers in the Laney and see how you like that.  You will probably find that it is more than sufficient.  Generally speaking in solid state gear, a power amp is a power amp, they are all the same.  No point in using your Laney as a preamp and Peavey as Poweramp when you could just use the Laney to begin with.  That is, unless the Peavey puts out way more watts and you need the power.
Title: Re: Considering modifying laney combo to rack preamp
Post by: GuitarLord66 on September 28, 2011, 08:34:20 AM
Oh sorry, I thought I'd mentioned earlier... I'm HOPEFULLY getting a free stereo power amp soon (hopefully it works!) and that's a big reason why I want a good sounding pre amp so I can run it into my TC g major and then run stereo speakers for stereo delays, chorus, phaser, etc :)

I looked more closely at the front circuit of the Laney, there's not much involved in cutting 40mm off of the end, I'm ditching the reverb (obviously since its mounted in the cab but it never worked anyway) and the purple and black wires that run along the top are all that go to the channel switching, so I just need ground as well, I can ditch the power LED since I'm going to hook up a few blue LED's to the power supply and have it illuminate a custom logo with my surname (hopefully) and other then all that it's just the 6 red wires which I can solder to their corresponding locations and the 2 large resisters which I'll just put on a small piece of proto board :P and link it to the circuit with a few wires.

So yeah I did persist with my idea and hopefully will start work on it soon enough :P We have plenty of thin aluminum that I can build the enclosure out of, then just remove the pots and run wires from all the pots connections to brand new pots located and arranged to my liking on the front panal and same for the jacks except I'll put all the jacks on the back, no need to have any of the front when I have a rack rig :)

The only other thing is a lot of the pots are push/pull dpdt, so I'm thinking I will get a bunch of small dpdt switches and place them above the corresponding pots :) I'd prefer push button switches then push/pull pots :) and I might make the push/pull switches for the gain on both channels controllable by foot switch (well it will go into my g major and it will use it's relays to select channels and if the gain is on for off and control that with my fcb1010 midi controller), that way it gives me 2 channels with gain on and off :)

I have a lot of planning and designing ahead, I will keep posting my process here and hopefully I don't destroy the amp, but well it wasn't being used in it's current state anyway and I did obtain it for free  :)
Title: Re: Considering modifying laney combo to rack preamp
Post by: morgoth2006 on September 28, 2011, 08:12:49 PM
You mention that all the circuits that you have built fail. How do they fail? No sound? Problems with the pcb etching?Interference?
I started with electronics again last year, after a 15 year break and boy, do my early circuit had problems  8)
A year later I can make a circuit with a lot less problems than my early prototypes in protoboard or even point to point.
Misshaps still happen but in a small scale. I got zapped this weekend with 300 volts wich destroyed the pic controlling the voltage booster xP
Title: Re: Considering modifying laney combo to rack preamp
Post by: J M Fahey on September 29, 2011, 12:57:25 AM
Well  , I was about to suggest that, don't have tour board measurements, of course, but cutting just a little of the end which only has the input resistors and jacks, and hadrwiring them might do.
What I was referring to as "can of worms" is that often you ground "here" and you have a clean working amp, and then ground "just 1 inch to the left or right" and start listening to some Hip Hop FM, or your friendly Police base station or Channel 5 TV or some spook telling another one who *really* killed Kennedy.
If you want to have a dedicated preamp, and that Laney works so good, why don't you just give it it's own custom made enclosure (even if longer than 483 mm) and sit it over a lot of proper-rack-size stuff?
Title: Re: Considering modifying laney combo to rack preamp
Post by: joecool85 on September 29, 2011, 10:09:53 AM
Well, you're doing it even though most of us advised against it.  Now you're starting to sound like me!

Good luck with it and keep us posted, if it works, it'll be one for the books.
Title: Re: Considering modifying laney combo to rack preamp
Post by: GuitarLord66 on September 29, 2011, 08:19:45 PM
When I said all my circuits fail, it's never been an audio circuit, I tried just making simple photogates with relays and stuff like that, and even then that didn't work, I always used protoboard though...

I used to get zapped all the time when I was building coilguns :P I used to have charged capacitor banks at like 330volts 2200 micro farads and have it all discharge between both my hands, running through my arms and over my chest... That's something I don't want to experience again...

So with the grounding, does that include the round transformer? I forget what their called :3 but does that need to be the same amount of space away from both boards? because I gotta shift all the circuitry around to fit in the enclosure I'm going to make.

Even though I'm going to be using it as a dedicated pre amp, I can still leave it all intact right? With it power amp? I think it will be too much trouble trying to remove the preamp section, unless anyone has any ideas?

Thanks again everyone, I know you all advised against it, but it's hard to stop something after you got your mind set on it :P

I will definitely keep you all posted!
Title: Re: Considering modifying laney combo to rack preamp
Post by: J M Fahey on September 30, 2011, 06:52:51 AM
Dear guitar lord
QuoteI used to have charged capacitor banks at like 330volts 2200 micro farads and have it all discharge between both my hands, running through my arms and over my chest... That's something I don't want to experience again...
At most, you must have lightly brushed your hands across those termin als, which anyway will give you the jolt of your life (literally).
If you had actually *grabbed* those wires, simply stated, you wouldn't be here with us.
That's truly a "once in a lifetime" experience, simply because lifetime ends abruptly there.
Good luck and take care.
PS: I haven't built coilguns, but high power flash units, with similar power packs,  photography being my second hobby.
Title: Re: Considering modifying laney combo to rack preamp
Post by: GuitarLord66 on September 30, 2011, 09:20:07 PM
I had a voltmeter connected when I touched the terminals and the caps dropped to 0 volts so I'm pretty sure I drained them, it was the worst feeling ever, I just stood there shaking and couldn't move for a few minutes. It was the scariest moment of my life!

I should be getting started on the amp project early next week so I will make sure I keep you guys posted about how it goes :)
Title: Re: Considering modifying laney combo to rack preamp
Post by: GuitarLord66 on October 07, 2011, 01:56:00 AM
Sorry it took me so long... I cut the pcb then I couldn't find any wire, but I did about 2 hours ago so I went straight ahead and rewired the small section :) Here's a picture:

(http://i236.photobucket.com/albums/ff77/guitarlord66/IMG_8832.jpg)

I plugged it in for about 10 minutes to test it, sounds the same, at least I think from what I remember haha

Now after I unplugged it, I've never done this before though so it's hard to say but the 2 large black resistors were really hot, and I know it looks brown around their connections but they have always been that way... Is it normal for them to get hot? or should I replace the wires that go to them with a larger gauge wire?

Next job to do is to buy all new pots and jacks and rewire them all up... any tips of removing pots? especially the ones with a dpdt switch... by the way i'm replacing the push-push pots with a standard pot and a small dpdt toggle switch :)

EDIT:
Thought you guys should get a shot from the bottom as well :)

(http://i236.photobucket.com/albums/ff77/guitarlord66/IMG_8833.jpg)
Title: Re: Considering modifying laney combo to rack preamp
Post by: joecool85 on October 07, 2011, 01:24:43 PM
Looks good so far.  Glad to hear it appears to be working.  I'd say the wires are large enough given their short length.  As for the resistors, I'm not totally sure.  How hot is really hot?
Title: Re: Considering modifying laney combo to rack preamp
Post by: GuitarLord66 on October 07, 2011, 07:35:55 PM
Thanks :)

I played the amp for another hour last night, and after I turned it off and unplugged it I tried touching the resistors and they were so hot that if I didn't take my finger off they would have burnt my finger... They haven't exploded though so that's a good sign... and they always had brown burnt looking spots at their solder connections so maybe they have always got that hot?
Title: Re: Considering modifying laney combo to rack preamp
Post by: J M Fahey on October 08, 2011, 08:24:25 AM
Although I don't like that very much, it's "normal" . Oh well.
*If* you want to rack mount only the preamp, you may dispense nwith tham by building a small PSU that supplies +/-15V at reasonable current, without needing to drop them from +/-40 or whatever they use as "big" power rails.
Title: Re: Considering modifying laney combo to rack preamp
Post by: GuitarLord66 on October 08, 2011, 11:11:04 PM
So it's normal for the resistors to get really hot then?
I'm gonna rack mount the whole thing and "slave" the preamp section, it's easier for me that way... and I will still have the speaker output, just in case I do want it again for some reason...

so what's the easiest way to remove pots and push pull pots from a circuit? just slowly unsolder them? and try not to force it and break it?

EDIT

oh and because the resistors get hot, should I put a small fan in the back of the rack mount enclosure I make? to help cool it down? or is that going overboard?
Title: Re: Considering modifying laney combo to rack preamp
Post by: teemuk on October 09, 2011, 06:58:27 AM
Quoteoh and because the resistors get hot, should I put a small fan in the back of the rack mount enclosure I make? to help cool it down? or is that going overboard?

I'd rather choose some of the other options that make more sense...

- Substitute the resistors with ones that have higher power rating, or alternatively use a bank of parallel resistor. Anyway, the main point is increasing power handling or decreasing dissipated power per each resistor, which means less heat.

- Redesign the regulator circuit to use integrated regulators instead. Not only is it better option than the discrete shunt zener diode regulator with voltage dropping / current limiting resistor scheme, it also allows more convenient heatsinking of the parts that heat up.

- Do what Fahey suggests and change the power supply to a lower voltage one. You don't need the high power reserve (and high voltage brought down) if you don't need the power amp. Since you say you'll keep the "speaker out", I assume you will actually keep the power amp though, in which case this option is not valid. I hope you have considered the issue of providing sufficient heatsinking of the power amp section in this conversion... otherwise it will say "poof" quite fast.


Quoteso what's the easiest way to remove pots and push pull pots from a circuit? just slowly unsolder them? and try not to force it and break it?
You most certainly do not want to slooooowwlyyyy unsolder them. That means heating up the board drastically, which results to damage.

You want to:
- If possible, clip off the potentiometers and jacks before you start unsoldering their leads. Effectively, you want to minimise the heat-sinking thermal mass as much as possible. If you can, leave only stubs of the leads on the board. Sometimes the body of the component simply just obstructs snipping out the part and you're left with no other option but to deal with considerable thermal mass.
- So, get a big soldering iron that can heat up things fast...
- Then grab that manual vacuum solder sucker and some solder wick and suck off the solder one pin at the time as soon as it melts.
Title: Re: Considering modifying laney combo to rack preamp
Post by: GuitarLord66 on October 09, 2011, 09:01:52 AM
So if your suggesting I change the resistors, I'm just wondering why they get so hot? I never changed them, they are the ones that came with the amp? I just thought maybe because the wire I used was quite thin that could be why they got hot?

I don't particularly want to redesign any parts of the amp, I wanted to keep the power amp intact also... It's pretty much just a rehousing project for me :)

The power amp has, (which I think are SCR's) on a heat sink that I will be moving the new enclosure.

Ok I should be able to snip the pots off no trouble, there seems to be enough room I think, just the push pull pots will be a little more difficult...
I will look into getting a solder sucker when I buy the new pots, switches and jacks :)

EDIT

I been thinking about it and how much is involved in making the pre amp dedicated and just getting rid of the power amp section?
If there's 6 wires between the pre amp and power amp section what are they most likely to be? I'm assuming 2 are ground? and then power? and output?
Would I have to make an output circuit as well? or would 2 of the wires be able to be soldered directly to sleeve and tip for output? or would the 2 wires that seem to be ground also be the sleeve of the output? I'm pretty confused on how that would work and what would be involved in salvaging just the pre amp section? can anyway help clear that up for me? :)
Title: Re: Considering modifying laney combo to rack preamp
Post by: teemuk on October 09, 2011, 11:06:40 AM
QuoteI'm just wondering why they get so hot?
They decrease the voltage from whatever it is to zener voltage of zeners, likely there's about a 15 volt drop across each. ...and in addition they have to supply all the current that the preamp draws. voltage x current = power. power = heat

QuoteIf there's 6 wires between the pre amp and power amp section what are they most likely to be? I'm assuming 2 are ground? and then power? and output?

Don't assume; find out. Where do the wires go in the concerned circuit sections?

- One connects to power supply ground
- One connects a potentiometer lead to ground
- Two connect from their individual voltage dropping resistors to their individual zener diodes and filtering caps. So that's your positive and negative power supply rails for the preamp.
- One wire connects to a potentiometer wired as rheostat, one end grounded. I believe it's the "presence" control, which, according to other pro linebacker series schematics connects to power amp's feedback loop.
- the final one I can't deduce from the photos but since it links the power amp and preamp boards together its likely preamp output signal / power amp input signal.

All those six pins are also used by the molex, which means you have the molex connector feeding:
- positive high voltage
- negative high voltage
(both which are then dropped down to maybe +-15V by the regulator circuitry - resistor + shunt zener + filter caps - on the preamp board you have cut in pieces)
- signal ground
- power ground
- input / output signal
- connection to presence pot

There's your answer.

QuoteI been thinking about it and how much is involved in making the pre amp dedicated and just getting rid of the power amp section?
Above lies your answer. Not much.
Title: Re: Considering modifying laney combo to rack preamp
Post by: GuitarLord66 on October 09, 2011, 07:22:43 PM
Oh whoa thank you very much!

EDIT 4... I'm only doing this so I don't double post haha!

I went ahead and soldered two wires to the last 2 wires that I was unsure about and soldered a jack to them and tried it. It worked! I'm not 100% sure whether it sounds the same as the "send" function on the back of the amp though. Would there be a difference?

So all I need to get is the 15v+ and 15v- power supply from jaycar, and the toroid that goes along with it. 3 jacks, one for input, output and controller. and I'm trying to decide whether or not to replace all the pots... I think I need to replace all the push/pull ones because I want to add dpdt toggle switches to turn the boosts on, not pulling the pot... the volume pots are the ones that are playing up, but maybe it's best to replace the lot? opinions? Thanks for all the help!

Power Circuit - http://www.jaycar.com.au/productView.asp?ID=KC5418&keywords=power+supply&form=KEYWORD
Toroid - http://www.jaycar.com.au/productView.asp?ID=MT2086&keywords=MT2086&form=KEYWORD

Ignore whats below! haha it's just my thoughts and questions that I seemed to work out :)

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EDIT 3 before you read the full post I might as well put my latest thoughts at the top haha :)

I'm almost 100% sure that the power supply I posted at the bottom of this post will work :) The only question I really have is whether or not the last 2 wires are the output signal from the pre amp or does it need a buffer circuit or something like that before output? I'm considering just soldering 2 wires to the connections, soldering them to a jack and plugging it straight into my peaveys power amp. I don't want to blow anything up but I think it's the only way I'll find out for sure whether that's what those 2 wires do :P
-------------------------------------------------------------------------------------------------------------

I'll use a multi meter sometime later tonight and find out what the voltages are along the wires, that should help me work out what wire is what and what voltage the input power is :)

With the molex connection the two center wires are joined in the circuitry as grounding, and the wires I ran from them went to ground on the top and bottom of the circuit, the closest wire was to the presence ground and that's why I linked it there. Would that be grounding or negative voltage?

So positive and negative high voltage, I didn't know about those, I always thought a circuit was positive (voltage) and negative (ground) learn something new everyday :) Also would the signal ground be the same as the power ground?

The guitar inputs are on the front of the amp, with the knobs, so by input/output, are you talking about preamp output/poweramp input? as the same wire? (which makes sense)

So if I wanted to bypass the power amp, I'd need to build a small power circuit? Could I just use say for example a 15volt dv wallwart?

So no more circuitry is involved in outputting the pre amp signal? I could just connect them straight to a jack, and that could go out to my effects (tc g major, dbx equalizer) and then to the power amp of the peavey?

Again thank you so much, you have been very helpful! thank you for putting in the time to help me with this :)


EDIT!

I went ahead and used my multimeter to check out the voltages... Before the large resistors it's -45.8volts and +45.6volts, and after them its -15.55volts and +15.36 volts. The other 2 wires I couldn't work out and I didn't want to try combinations of touching them with the multimeter in case I shorted something out :s So I now understand what you mean with positive and negative power rails, so how would I go about making a circuit that would output 15 volts positive and negative? and those other 2 wires, are they the output? like could they be soldered directly to tip and sleeve of a jack? or is there more involved? thankyou :)


EDIT 2!!

I was looking for a power supply on the jaycar website (australian electronics store) here's what I found

http://www.jaycar.com.au/productView.asp?ID=KC5418&keywords=power+supply&form=KEYWORD
"Headphone Amplifier Power Supply Kit

To ensure the best possible performance to the Headphone Amplifier Kit, this will provide regulated
+/- 15V and +5 outputs.
Toroidal transformer required use MT2086
The kit comes with all specified board components and quality fibreglass tinned PCB.
PC board size: 56.5 x 80mm"

And it says it requires this:

http://www.jaycar.com.au/productView.asp?ID=MT2086&keywords=MT2086&form=KEYWORD
15V-0-15V 20VA Toroidal Transformer - Low Profile

The power supply kit costs $19.95
The toroid costs $23.95

That's $43.90 for the kit and toroid... a bit more then I want to pay for just the power supply...
Because add in the new pots, new jacks, knobs, etc, this will be a well over $100 project... and well I don't have that much money to use :(
Title: Re: Considering modifying laney combo to rack preamp
Post by: GuitarLord66 on November 05, 2011, 03:35:37 AM
This project is far from dead :P sorry I haven't been keeping you guys updated I've only just had the money in the past week or two to get started on it again :) Everything is pretty much done circuit wise, I just have to cut the rack enclosure down to a smaller size and then fit everything in, and finish making the new front panal design in photoshop to stick on the front :) Here's the latest pictures of the amp, sorry their bad quality, I had to take them with my phone.

Here's what's left of the original amp, it's been cut down a fair bit, a few of the pots were replaced and the two gain pots that were also "push pull" pots were replaced with standard pots and a dpdt toggle switch. A few pots were also removed, such as the reverb and presence, which I didn't want or need. All the jacks were taken off, the input, output and control jacks will all be located at the back of the unit.
(http://i236.photobucket.com/albums/ff77/guitarlord66/111105-1411.jpg)

In this picture you can see the power supply I built and the new torroid transformer, it will be laid out something similar to this eventually
(http://i236.photobucket.com/albums/ff77/guitarlord66/111105-1621.jpg)
Another angle
(http://i236.photobucket.com/albums/ff77/guitarlord66/111105-1621001.jpg)

This picture is the rack enclosure put together, the bottom of the ruler is where the rack enclosure will be cut down to
(http://i236.photobucket.com/albums/ff77/guitarlord66/111105-1628.jpg)

All up everything has cost almost $200 so hopefully it all works and is worth it in the end...
I will keep you guys up to date with how it goes, and I will post pictures of it when it's finished :)
Title: Re: Considering modifying laney combo to rack preamp
Post by: morgoth2006 on November 05, 2011, 08:20:36 AM
Looking good  :tu:
Title: Re: Considering modifying laney combo to rack preamp
Post by: joecool85 on November 07, 2011, 08:46:41 AM
Wow, quite the project.  Did you make your own PCB for the power supply or purchase one?
Title: Re: Considering modifying laney combo to rack preamp
Post by: GuitarLord66 on November 10, 2011, 07:36:53 PM
I cut the case down smaller, to a similar size of my tc electronics g major's rack enclosure, because the original case was too long to fit in my rack case, it stuck out the back :s so today I will hopefully mount the torroid and the power supply, get all the wires cut to a appropriate length and joined and then remove everything, spray the case with a black to clean up the spots where it was cut and then stick my new front panel on with all the labels and stuff for the pots :)

I bought a power supply kit :) So I just had to follow the instructions and solder all the components to it :)
Title: Re: Considering modifying laney combo to rack preamp
Post by: GuitarLord66 on November 11, 2011, 02:54:22 AM
All was looking well, I got it all fixed in the case and wired up and when I tested it, the first channel works perfect, but when i changed to the second channel, (which is clean on this amp) doesn't work, if I strum my guitar really hard, it kinda comes through but VERY distorted and only a few crackles really come out of the amp... So I'm going to have to work out whats causing that, once I sort that out and finish it I will post pictures of the final product :)

I spent all night working on the amp and I couldn't work out whats wrong with it... It's only the clean channel that has the problem... the dirty channel works fine...
Title: Re: Considering modifying laney combo to rack preamp
Post by: GuitarLord66 on November 13, 2011, 12:22:21 AM
FINISHED! :D :D

I sorted out all the problems and now it works perfectly :) Here's the pictures:

After I finished soldering everything together and adding heat shrink where I thought necessary
(http://i236.photobucket.com/albums/ff77/guitarlord66/IMG_8838.jpg)

After the front panel I designed in photoshop was printed and clear lacquered on, you can see a line where I had to join the two pieces of paper but its not that big of a problem and after the knobs were put on
(http://i236.photobucket.com/albums/ff77/guitarlord66/IMG_8839.jpg)

Once it was put in my rack, I didn't have enough rack screws so I will have to buy some more sometime, doesn't really matter at the moment
(http://i236.photobucket.com/albums/ff77/guitarlord66/IMG_8840.jpg)

A little blurry but here's once everything was turned on :)
(http://i236.photobucket.com/albums/ff77/guitarlord66/IMG_8841.jpg)

Close up on the rack when switched on
(http://i236.photobucket.com/albums/ff77/guitarlord66/IMG_8845.jpg)

And here's some closeups of the preamp in the rack
(http://i236.photobucket.com/albums/ff77/guitarlord66/IMG_8846.jpg)
(http://i236.photobucket.com/albums/ff77/guitarlord66/IMG_8847.jpg)

So happy now it's all finished :)
Title: Re: COMPLETED! :D modifying laney combo to rack preamp
Post by: J M Fahey on November 13, 2011, 03:13:58 AM
Congratulations !!!!!  :dbtu: :dbtu:
It sure looks impressive  :dbtu: :dbtu:

To minimize blurring on low light pictures, use a tripod (best) or a couple books on a table or at least steady both your forearms and wrists on some furniture.
Press the button smoothly and be ready to become a statue for at least 10 seconds, even if it seems to take less to take the picture.
Also take a deep breath before and hold it.


Congratulations again.
Title: Re: COMPLETED! :D modifying laney combo to rack preamp
Post by: mexicanyella on March 27, 2012, 01:03:33 AM
Wow! I'd love to hear it. If you ever get any clips you can post...