Peavey 60/60 upgrade

[BritishSteel]

Hi all, New guy here. I have a tech question for the repair guru's.
I have a Peavey 60/60 Pwr Amp works perfect, but, I would like to improve on what it already there. I would like to install a choke in it. Now I know my way around an amp maintanence wise but for techie stuff like Mods I have not nearly the experience. So My question this; Is this as simple as installing it in parallel at
the molex connector to the main board? Or is it more involved than that? Can someone shed some light on this for me.

Thanks in advance. Rob

[Enzo]

In parallel to what?

First, is there room for a choke in there? It's been a while, but I don't remember a lot of extra space inside those.

ANyway, the most likely place for a choke would be between the plate and screen nodes, where the large 400 ohm 10 watt resistor is now. That is the resistor nestled between the filter caps. Remove it and wire the choke to where it was.

The schematic and layout call it a 400 ohm resistor, but in some units it will be a 390 ohm resistor.

[BritishSteel]

From what I understand, and feel free to correct me at any point, installing a choke in the power transformer circuit can have tonal benefits by improving a more consistant power flow. My only reference to such a mod was a photo. Like I said super mod guru dude I am not, so bear this in mind. I do have some hobby electronic experience so no fear of the soldering iron. The mod I saw (I know it doesn't mean it was done right) basicly showed the choke connected at the output power connector from OTrans to main board and appeared to be wired parallel on the OTrans Molex connector. I this proper? or just a half-assed? I could have this done but will cost more to ship the damn thing than to do it myself. er-go my question. Thoughts?

[Enzo]

Well, without a photo, I have no idea what they did. Since the center tap of the OT is the plate supply node, someone might have found that a convenient spot to connect one end of a choke, but the other end still has to go to the screen node on the board. And leaving the 400 ohm resistor in the circuit in parallel with a choke sorta waters down the choke'seffectiveness, so I doubt they did that.

I would do it as I said, replace the 400 ohm resistor with it. Mount the choke somewhere, remove that resistor and wire the two choke wires to where the two ends of the resistor used to be.

I cannot think of anywhere else in the circuit a choke would want to be, you certainly don't want to convert the B+ supply to a choke input filter.

I am totally unclear what you mean "parallel with a connector." Two parts are wired in parallel when they are wired together at both ends.

I know NY is a large place, but I'd have to think there was a competent tech within driving distance. Yes, shipping it would be expensive.

[BritishSteel]

This is the only photo I found for such a mod. The white text in the pic is my addition for clarity. You can see where the first lead is tapped in at the board. The second one was in my estimation part of a twisted pair or simply hidden behind the other wire. I see now that (after you pointed it out) it probably does drop down behind OT. To where????? obviously I can't tell. Hope this helps my lame-O explantion. It was notated by the owner that the white box is a choke
Rob

[Enzo]

It looks exactly as I suggested. The yellow wire is down between the filter caps where the 400 ohm 10 watt resistor used to be. The one end of that resistor was right behind that Molex with the red wires. I am sure that is where the yellow wire is connected. The other wire is hidden behind the transformer, the white thing peeking out from behind the transformer, and the red wires. It would be connected where the other end of the 10 watt resistor was.

I am not used to seeing inductors in that form - looks like a flourescent ballast - but that seems like a good spot for it on the front panel.

[BritishSteel]

First I'd like to thank you for taking the time to clear that up an to learn me a thing or two.
Secondly, since it essentially replaces the resistor with an inductor is there any substantial tonal improvement to be had with this mod over whats already there. I really don't want to hack into a perfectly mint piece of almost vintage equip unless it's a really good reason.

Thanks much in advance.
Rob

[Enzo]

Oh hack is such an ugly word. I am certain I could remove that resistor and solder wires in its place without disturbing its beauty. And should I ever want to remove it, I am sure I could replace the resistor, and no one would ever know we had ever modified it.

Frankly I doubt it will make much of a difference. But when someone wants to test the laws of diminishing returns, I don't want to discourage them. I suspect the difference will be subtle, but if that ever-so-much-better makes you happy, then it did its job.

Seriously, try it.

[DCinDC]

If you don't know not to wire a choke in parallel with something, stay out of your amp. You'll let all the magic smoke out.

Tonal improvements are more likely found with biasing changes and coupling cap changes in that amp. I strongly suggest a qualified tech do them. No offense.

[Paul P]

Secondly, since it essentially replaces the resistor with an inductor is there any substantial tonal improvement to be had with this mod over whats already there.

BritishSteel, I've been itching to ask you why you want to swap a choke
in place of your resistor. If you are new to working on amps there are
tons of other modifications you could do which would be easier, cost less,
and provide much more change in your tone than the choke ever will.

Your post is the first mention I've seen (I'm no expert but I've read quite
a bit) of installing a choke for tone purposes. The choke's purpose is to
reduce the AC ripple present on your DC supply. This may be beneficial
in reducing hum, and might have some slight effect on the sag behaviour
of your power supply (?) but I don't see it affecting your tone all that
much.

If you could give the people around here an idea of what kind of music
you play, what kind of tone you have now and what you'd like to change
about it then maybe we (well they, actually) could suggest better mods
to get you there.

Paul P

[BritishSteel]

Enzo:
Thanks again for whippin' a little knowledge on me. Appreciate it.

DCinDC:
It seems that people who wish expand their knowlege and learn offends you. I guess I suppose I should have just shut up, and stay ignorant, and be witty

Paul P:
The only reason I brought the whole thing up is that it seems from what I have noticed in my reading (my head is swiming) over the past year or so. It seems to be a common mod along with OT replacement that I would classify as a "Simple Mod" and it is always attached to tone improvement. So I though hmmm, maybe there something to this and the question was why. I am somewhat of a tone slut, always in search of that "sound in your head" and not to believe all the hype in buy our magic product to achieve what has been done low tech a decade or more before(to a point). It's almost like archeology, keep digging and you'll find it. I play old school, classic, 80's metal 90% of the time so this is where I want to do the improvement. My impression was that these two improvements have a noticable effect on Overdrive smoothness. So I wanted to find out why and is it worth doing. Cheers

[Enzo]

When experienced tech people listen to someone posting their thoughts, they tend to get an idea of that person's experience level. I think DCinDC's remarks were more about concern that you don't injure yourself.

I personally don't think youi will hear much difference, but the cost of a choke is not high, and the work involved to do this is minimal, so if you want top try it, there is not a lot to lose, so go ahead. You will be delighted, or disappointed, but you will have tried something and done it yourself.

I don't think anyone here was plucked from the womb and trained to be an amp tech before even seeing one. We all start somewhere and learn on the job, so to speak. And I think anyone who tells you he never got a shock or burnt something up is probably not being honest. SO you have to start somewhere.

But we sometimes worry that maybe the best place to learn soldering and part changing skills in on something that doesn't use voltages that can kill you.

Keep in mind that this is a power amp, there is no preamp here, so any overdrive would not be coming from the 60/60. Unless you are gong to crank it to the sky for power tube distortion. That would be godawful loud. This amp should be strong and loud and pretty transparent. So since the preamp is a separate unit somewhere, any B+ sag in the power amp will not make it to the preamp.

[BritishSteel]

I'm vividly aware of the voltages involved which is why won't venture into an amp unless there is a really good reason. I just detest remarks made on most message boards I've been around from people who add comments for sake of the comment, to postulate with there knowlege, or belittle others, off handed or not. But, no worries

In so far as a marked difference....thats what I thought, not much to write home about. I'd probably have better luck with beefy OT's.

True enough, most of us if they will admit it or not, don't and can't play at max to near max output to take full advantage of PT distotion unless in a studio perhaps. But club and bar players like myself can't take advantage of that unless running a hotplate, etc. and want to buy tubes every other month. I for one do not. My first and only concern is quality of sound and I don't care how I get it. IMHO the ONLY thing that counts is what the audience will hear. If your pant legs are blowing in the breeze and the paint is peeling off the walls, while very impressive and good for a personal chubby, but it sounds like nails on a chalkboard in the crowd, especially after it's been mic'ed by a marginal sound guy, then what's the point(but a whole other thread) Again thats my personal opinion.

Thanks again for all the input. I really appreciate the time.

[The Blues Man]

My Peavy ValveKing 212

In parallel to what?

First, is there room for a choke in there? It's been a while, but I don't remember a lot of extra space inside those.

ANyway, the most likely place for a choke would be between the plate and screen nodes, where the large 400 ohm 10 watt resistor is now. That is the resistor nestled between the filter caps. Remove it and wire the choke to where it was.

The schematic and layout call it a 400 ohm resistor, but in some units it will be a 390 ohm resistor.

So u are saying tha my valveking 212 have a 400 ohm or 390 ohm resistor as a choke in my amp because i cant' find it where is it located?

[Guitarist]

British Steel,

I've been close to where you are a couple times with a stereo, tube power amp. First a VHT now a new Carvin TS100.

Looking at the pic, there should be room for a quad of KT77 s. You could also try swapping in a few different preamp tubes; 12dw7, 12at7, 12ay7. You'll need pairs. These are good to have anyways. I always surprise players just by swapping in tubes - and then they want to buy my private stash. Recently a Hiwatt came to life with a 12dw7 in V1.
Get a rack eq perhaps as well.
Now, you'll have a mother to deal with !!!

Be happy you landed such a fine amp, good going.