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COMPLETED! :D modifying laney combo to rack preamp

Started by GuitarLord66, September 27, 2011, 07:34:28 AM

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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...

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:


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 :)


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.


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!


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 Circuit

Back Circuit

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?


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?

Circuit top

Circuit bottom


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...


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.


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

J M Fahey

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.


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

On the right side of this image...

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?


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.
Life is what you make it.
Still rockin' the Dean Markley K-20X


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  :)


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

J M Fahey

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?


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.
Life is what you make it.
Still rockin' the Dean Markley K-20X


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!

J M Fahey

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.