Can you mod an old Peavey Bandit 112 solo series?

eagertokill · Post by **eagertokill** » 13 Nov 2010, 03:37

I got an old Peavey bandit 112 solo series from Craigslist for $20 because it did not work. Turns out all it needed was a new fuse! Not a bad score because it sounds great, better than the new ones. When I had the chassis out I could see it was all analog and had 2 original TI JRC4558 chips in it. That got me thinking. Can this be modded to improve on the sound? Well? I would like to know if the dirty channel can be made more quiet, can the reverb be improved(less cavernous) and can it be generally "hot rodded" with better components to make it a better amp? I want to do it just because so don't ask why. Besides, it is one of the better sounding SS amps out there and I got it for $20. I attached the schematic for review. THANKS FOR ANY HELP!!!

Hides-His-Eyes · Post by **Hides-His-Eyes** » 13 Nov 2010, 09:15

"Can it be 'hot rodded' with better components?"

I'm gonna take a chance here and say "No."

If you can identify specific ways you'd like the tone stack or gain control to act differently, etc., maybe, but as for just general "improve", I'm not really sure you'll get anywhere.

You might be able to do something with the reverb, is it a tank or an IC?

phatt · Post by **phatt** » 13 Nov 2010, 13:29

Hi eagertokill,
Depends a lot on what you wish to achieve?
If the stupid treble response drives you mad go find a less intense Speaker, some of the older speakers don't have the massive SPL but they often have a more balanced tone if you are chasing sweeter sounds.

From memory??? *C32* next to clipping diodes can be raised a fair bit to help rid the excessive harshness of the hot channel. Also try *C29* (at U2b try 1nF) (this Will change the tone controls a bit)

There was one other mod but for the life of me I can't recall

Note; all this can be done without removing any parts,, you just leave the original parts in place and bridge the new value across, negates removing the whole board from inside the chassis.

Your Amp is a slightly different model to the one I tweaked so don't hold me to it.

Reverb;
*R73* is the mix part of Rev Return you can make that bigger (try 47k)
But you may have to pull the board for that.

The other option is to turn the drive down,,,just hang a 47k R across *R58* leaving the 100k in place.
As with a lot of guitar Amp Rev circuits,, very little effort goes into tone curves for the reverb and this can let down what could be a decent reverb.
These are mostly terrible Amps IMO though some Early models (Pre Transtube) where good gear.

It should be obvious that the amp I worked on was shooting for a more mellow blues sound so if metal is your goal then I'm not much use.
Phil.

eagertokill · Post by **eagertokill** » 13 Nov 2010, 14:52

thanks. I was wondering if replacing some of the components with better quality, different types could improve the sound. I have modded a few boss pedals and a big part of that was replacing the cheap poly caps with better metal film caps. (i think). some of the other mods were not changing the values but the part type. Can that logic work on the amp? BTW, it is a reverb tank.

Hides-His-Eyes · Post by **Hides-His-Eyes** » 13 Nov 2010, 15:07

eagertokill wrote:I have modded a few boss pedals and a big part of that was replacing the cheap poly caps with better metal film caps.

I honestly seriously doubt that was what improved the pedal. Especially if the caps you were replacing weren't ceramic.

mictester · Post by **mictester** » 13 Nov 2010, 15:13

eagertokill wrote:thanks. I was wondering if replacing some of the components with better quality, different types could improve the sound. I have modded a few boss pedals and a big part of that was replacing the cheap poly caps with better metal film caps. (i think). some of the other mods were not changing the values but the part type. Can that logic work on the amp? BTW, it is a reverb tank.

NO!!![/b] Changing the "type" of capacitor will have NO EFFECT WHATSOEVER on the "sound" of the amplifier - changed values may make changes, however. When you change out capacitors from one type to another, if you hear a change in sound, it's ONLY because the value is different to the one you removed.

DO NOT change resistor from metal film to carbon composition - this will achieve nothing apart from adding to the hiss from an already noisy amplifier. Boutique Boobs will claim that Carbon resistors are "better", but that is complete nonsense.

You could replace the 4558s with quieter types like LM833 or NE5532 - the "sound" would remain the same, but the hiss would be reduced.

eagertokill · Post by **eagertokill** » 14 Nov 2010, 00:16

Interesting to know. So is it all just marketing hype when someone uses "orange drop" "zoso" or other name brand type components? There is not "tone" difference between the various types of caps?

RnFR · Post by **RnFR** » 14 Nov 2010, 01:19

here we go...

DrNomis · Post by **DrNomis** » 14 Nov 2010, 01:23

eagertokill wrote:Interesting to know. So is it all just marketing hype when someone uses "orange drop" "zoso" or other name brand type components? There is not "tone" difference between the various types of caps?

Yep,absolutely no tonal difference between two different types of capacitor of the same value.....

mictester · Post by **mictester** » 14 Nov 2010, 01:51

eagertokill wrote:Interesting to know. So is it all just marketing hype when someone uses "orange drop" "zoso" or other name brand type components? There is not "tone" difference between the various types of caps?

Yes. It's entirely marketing hype. Some certain types of components achieved legendary "mojo" status because they were used in pedals that were used by some of the great players.

For example - all the boutique boobs try to get hold of the JRC4558D, because it was used in the original tubescreamers. The ONLY reason that the device was used was that it was the CHEAPEST dual op-amp available in quantity at the time. It wasn't chosen for its sonic properties! I recently saw these for sale on a component sourcing website for $18.40 each. We bought them for $0.018 each in quantity in the 80s!

It may sometimes be true that the type of capacitor will have a detrimental effect on the signal passing through it, but this will only be under conditions of extreme stress caused by high voltages close to the working voltage of the capacitor. At the voltages and signal levels inside stompboxes, there will be no effect at all. The noise and distortion introduced by the diode clippers across the signal path and by the other active components in the circuit will be several orders of magnitude more significant than the degradation introduced by a capacitor!

Don't get suckered into paying stupid prices for "mojo" parts!

mictester · Post by **mictester** » 14 Nov 2010, 01:58

RnFR wrote: here we go...

The sooner the "mojo" myths are dispelled, the sooner some real design will go on. These silly, expensive "mod" kits for cheap guitar effects should be exposed for the nonsense they are. The use of carbon resistors and ancient capacitors and transistors in simple Fuzz Face circuits (and then charging hundreds of dollars for them) has got to be stopped. The idiots on TGP keep on believing in their fairy tales and in mojo components...

It was fun to try a "shootout" of a number of well-known overdrive pedals recently. The winner was the cheapest of them (a £20 Behringer). We had 20 people try the pedals in a "blind" testing scenario - 19 out of 20 of us chose the Behringer!

DrNomis · Post by **DrNomis** » 14 Nov 2010, 02:12

mictester wrote:
eagertokill wrote:Interesting to know. So is it all just marketing hype when someone uses "orange drop" "zoso" or other name brand type components? There is not "tone" difference between the various types of caps?
Yes. It's entirely marketing hype. Some certain types of components achieved legendary "mojo" status because they were used in pedals that were used by some of the great players.

For example - all the boutique boobs try to get hold of the JRC4558D, because it was used in the original tubescreamers. The ONLY reason that the device was used was that it was the CHEAPEST dual op-amp available in quantity at the time. It wasn't chosen for its sonic properties! I recently saw these for sale on a component sourcing website for $18.40 each. We bought them for $0.018 each in quantity in the 80s!

It may sometimes be true that the type of capacitor will have a detrimental effect on the signal passing through it, but this will only be under conditions of extreme stress caused by high voltages close to the working voltage of the capacitor. At the voltages and signal levels inside stompboxes, there will be no effect at all. The noise and distortion introduced by the diode clippers across the signal path and by the other active components in the circuit will be several orders of magnitude more significant than the degradation introduced by a capacitor!

Don't get suckered into paying stupid prices for "mojo" parts!

I scored myself a handful of JRC4558DD ICs from a defunct Otari reel-to-reel tape recorder...for nothing,except the time and effort involved in desoldering them....

eagertokill · Post by **eagertokill** » 14 Nov 2010, 02:38

Thanks for the help guys. I learned something new today and gained some valuable knowledge. So, when I build my own circuits, what factors do I use in selecting the types of components I use and why? I have 3 boards etched and waiting to be populated.

Also, getting back to my original questions, what are some things I can do to make the dirty channel more quiet besides changing the chips? I soldered a socket in place of the chips this afternoon so I will try a few different ones when I get my order.

DrNomis · Post by **DrNomis** » 14 Nov 2010, 02:51

eagertokill wrote:Thanks for the help guys. I learned something new today and gained some valuable knowledge. So, when I build my own circuits, what factors do I use in selecting the types of components I use and why? I have 3 boards etched and waiting to be populated.

Also, getting back to my original questions, what are some things I can do to make the dirty channel more quiet besides changing the chips? I soldered a socket in place of the chips this afternoon so I will try a few different ones when I get my order.

Well,when I build my pedals I take into account the supply voltage,current,and board space when selecting parts,most of the time I try to just use off the shelf parts that are easily avalible to me,when it comes to transistors I take into account three things,the maximum collector current,the maximum collector-emitter voltage,and the Hfe of the transistor....

For resistors,most of the time I'll use 1% metal films rated at 1/2 a watt,occasionally a circuit will call for a 2Watt resistor,but what I do is use a 5 Watt wire wound resistor instead,for reliabilities sake,I tend to overrate the component for the job it has to do in a circuit,for example,if a circuit uses a 1/2 Watt resistor,I'll use a 1 Watt resistor instead....

The capacitors I use are just bog standard Electrolytics,Ceramics,Greencaps,etc,that are easily avalible too...

Hides-His-Eyes · Post by **Hides-His-Eyes** » 14 Nov 2010, 11:48

eagertokill wrote:Thanks for the help guys. I learned something new today and gained some valuable knowledge. So, when I build my own circuits, what factors do I use in selecting the types of components I use and why? I have 3 boards etched and waiting to be populated.

Personally: I use metal film resistors because they cost the same as carbon film when ordered from the right places, I use 'greenie' caps when I'm feeling cheap (but they have non-uniform pin spacing) and box-film caps when I'm not, and I only use ceramic caps when I can't get a film cap that small (and usually use the blue ones, I think the orange ones look horrible)

Mictester will now shout at me for picking components based on how they look, but he's used to designing circuits to build ten thousand of, whereas I probably build one. So yes, it's worth an extra 20p to me for my circuit board to look nice, but not worth an extra £2k to mictesters employers for them all to look nice.

(Also, note that many people use old-style, expensive components because they look cool, which is in my opinion a totally legit reason. There are other considerations; for example Mark tends to use axial caps so that his boards have a consistent (and small) height, for fitting into smaller enclosures)

phatt · Post by **phatt** » 14 Nov 2010, 13:11

eagertokill,

Good to read, Mictester has set you straight on Caps

So getting back to the Amp.
You could just go with what is already in place? There is little to be achieved by swapping opamps.
The secret to great sound is to be found in circuit design,,,Not mojo parts.
(yes if you are a dedicated follower of fancy parts like *Hides-His-Eyes* then by all means paint them orange,,, maybe two pack paint has better tone

)

Meanwhile back at the Amp,
Most of these modern Amps (Valve ones to) are way over designed and I'm yet to meet the owner of a multi channel wizzbang amp that gets satisfaction from both/all channels.

9 times out of 10 they just leave these Amps at one setting and use pedals for the tricky stuff.
So really you are better served just getting a simple but well designed preamp circuit happening first.

If you are deadly serious then go get a bread board and recreate the preamp circuits and tweak away until you find what you wish.
You can then test (without disaster) all the different options as there are heaps of preamp circuits around the net (Some good some bad) just waiting for you to *Learn from*.

Be VERY VERY Warned if you are new to this stuff,
Constant swapping of components on PCB's is the quickest way to destroy a circuit board.
It will eventually dawn on you that the PCB is the only part that cannot be replaced easily.
(Read as $$$$$)
Mess it up and it's just landfill.

Clues to circuit design;
As an old wise radio geek once said to me, "If you want it to work? Solder everything you can".
In his opinion 90 percent of breakdowns occur in *Connections*.
*Don't use sockets* for the final board as they just create another potential failure mode.

You can build a far better stand alone preamp and just plug into the poweramp part of the Peavy. That is how I would work with these amps.

I recently did this very thing for a local lad,, Built a whole preamp setup which bypasses the preamp
section of a SS Fender Amp.
This leaves the amp in original condition which means a better resale value when he eventually
sells it.
The Peavy owner I mentioned before finally decided to sell both his amps as we could not find an easy way to tweak the circuit without me spending weeks re-designing the preamp boards.

You will learn so much by assembling preamp circuits on a breadboard.

I've worn out 3 of them in 20 odd years.

Have fun, Phil.

mojah63 · Post by **mojah63** » 17 Nov 2010, 17:28

Swapping the op amps will make a difference. I have a 1989 Bandit and an 80's Special. There are mods for PV Pedal steel amps that could be ported over to the other amps. PV even sold a kit, may still do... There is also a reverb mod to get a more fenderish tone from them. (I haven't done it you'd have to google for it) I revoiced mine to work with my pod or my guitar straight in. You can see the Nashville 400 mod here:
http://www.peavey.com/support/steelguitaristinfo/
http://www.peavey.com/media/pdf/steelgu ... h400mo.pdf

I found that the Burr Brown opamps plus reducing some of the coupling cap values worked for me, esp the coupling caps to the power amp section. I put a switch there so I can use the amp with a guitar processor or without one. The amp had way too much top and mud to use at loud volumes before, now it's a lot warmer and usable. If you don't have the amp schematic email PV they will send it to you free.

matt239 · Post by **matt239** » 24 May 2011, 08:47

I think there might be some room for improvement here.
Swapping in mojo components, No, but changing some values to change the response might help some.
I don't know enough about what's going on in there to offer very specific suggestions, but
-changing the gain structure, & filtering could help, (reducing gain in the distortion channel, & some post-clipping treble-roll-off..)
-Servicing the amp; cleaning pots, jacks, switches, cleaning up the wiring; moving low level signal wires away from high level signal, & power wires, checking that grounding & shielding are intact.
-The reverb tank could be getting too much drive, or not enough, - too much recovery gain..
-Cutting bass before the reverb, & cutting treble after it might help a lot too.
- I've had good success with the LM833, but I don't know if it would be a huge change? (Couldn't do any harm. -Good thinking using the sockets...)

Anybody else have some ideas for cutting down the noise, etc?

DrNomis · Post by **DrNomis** » 24 May 2011, 10:28

matt239 wrote:I think there might be some room for improvement here.
Swapping in mojo components, No, but changing some values to change the response might help some.
I don't know enough about what's going on in there to offer very specific suggestions, but
-changing the gain structure, & filtering could help, (reducing gain in the distortion channel, & some post-clipping treble-roll-off..)
-Servicing the amp; cleaning pots, jacks, switches, cleaning up the wiring; moving low level signal wires away from high level signal, & power wires, checking that grounding & shielding are intact.
-The reverb tank could be getting too much drive, or not enough, - too much recovery gain..
-Cutting bass before the reverb, & cutting treble after it might help a lot too.
- I've had good success with the LM833, but I don't know if it would be a huge change? (Couldn't do any harm. -Good thinking using the sockets...)

Anybody else have some ideas for cutting down the noise, etc?

One way to cut down the noise is to desolder all the JRC4558D ICs, remove them all, and replace them with TLO72 ICs, these are pin-for-pin compatible with the JRC4558D, but, they are much quieter, they are described as a Dual Low-Noise Fet-Input Op-Amp IC, you could even solder in 8-pin IC sockets and then plug the TLO72 ICs in, I would also suggest replacing all the Electrolytic Caps in the power supply with Brand-New ones of the same or greater voltage rating as the originals too....

matt239 · Post by **matt239** » 24 May 2011, 20:46

Hi. Dr! - Yes, the O.P. had already done the sockets, & was waiting for some chips, but we never heard how it went... ? ? ?

Did the other things I said seem to make sense to you? - You have a lot more experience than me..

I don't know how much trouble it's worth to fix up a Bandit.. I guess a little, if you get it cheap, & do it to learn how..
The reverb is really awful on these, & I don't think it's mostly the fault of the tank. Might be fairly easy to fix?