1970's Peaveay "Classic" (not classic, 30 or 50) Low Volume Problem

[themeantime]

Hey guys,
I have a 1970's era Peavey Classic amp, not the classic 30 or50 but what they called the Peavey "Classic", Type A amp.
I have not had a lot of luck finding that much info on the amp itself, but through this forum and other i was able to get a manual and a schematic.

Now, on to the problem.
The amp works fine but it is definitely too low in volume, it can barely be heard over drums. At first I thought i would need the output tubes replaced; however before I did that I did some troubleshooting.

I hooked up another amp that I have (A 60's Silvertone 50w all tube amp, loud as hell) to the speakers on the classic. The volume was also very low, not getting anywhere near as loud as the 2x12 cab that i have the silvertone usually paired with. Both amps connected at 4 ohms. Both speakers work. What do you guys say? shitty speakers? I am thinking that the speaker cable might be a little shot too but it doesnt crack up or anything.

thanks for the help.

Alex.

[52 Bill]

First thing I see, is that the speakers are plugged into the wrong jack. Use the number 1 jack first.

The speakers may be bad, check them with a meter for resistance.

[Mark Hammer]

Aw man, now you got me all nostalgic. I had one exactly like that in 1974.

I hated the speakers. They had one personality at practice volumes, and an entirely different one at gig volumes. Just when you thought you knew how to set the tone controls for a given tune, you had to re-learn. If I had one of those amps now, I'd probably swap the speakers.

[Gibsonman63]

You may want to check if the speakers are wired in the same phase. If one is pushing while the other is pulling, they will tend to cancel each other out. Just stick a 9-volt battery on the speaker plug and see if both speakers move the same way.

[Enzo]

My first thought was also out of phase speakers, but between photo 3 and 5, it appears they are correct.

But Bill is also correct, plug the speakers into the correct jack first.

And connect the amp to some other speakers, using the correct jack. How does that sound?

[nashvillebill]

+1 on Enzo's suggestion to try other speakers (and of course use the correct jack)

Also, when you try these other speakers, use a different speaker cable as well. I've seen cables short internally at the plug, where a strand or two of one wire will work its way a little loose and start touching the other conductor. Unlike the typical broken wire, which is obvious from intermittent crackling and/or not working, the wire-shorting failure mode may not crackle and can instead just be manifested by a very low volume.

[themeantime]

Quick update.
I have not been able to try the amp with a new set of speakers, but I did buy a new cable. Unfortunately, there is no difference in sound I am still getting a low volume. I guess I have to move on to new speakers. Any recommendations? I play music in the style of the Kinks, Stones, british invasion stuff...

Also, another quick question..How does one go about biasing tubes on an amp without a standby switch. Knowing that there are lethal voltages etc. etc. in the amp I am most likely not going to mess with that but I was just curious. This amp only has output tubes.

Thanks so much, this forum is really great.

[Jazz P Bass]

I do not know for sure on this amp but historically Peavey does not allow for bias adjustment.

[nashvillebill]

I do not know if that amp shares the same design as the slightly later Classic VTX that I have, but mine has a circuitry that biases the amp in a different manner than most other designs (I'm not very good at explaining it so I won't try) and no bias adjustments are possible, its not feasible to add a bias adjust potentiometer to the VTX design.

Jazz P Bass is correct, at least AFAIK. Peavey did not typically put bias adjustment pots on their amps (I believe my Classic 400 bass head is an exception in that it does have a factory bias adjust pot.) But I do not suspect bias is your problem.

Back to your original dilemma: Before buying new speakers, I still recommend you either (a) try your amp with other speakers or (b) try your speakers with another amp. Even your home stereo, plugged into your amp's existing speakers, played at low to moderate volumes, would tell you if the speakers are OK. Naturally, you must not also have your speakers plugged into the amp at the same time!

If your speakers do indeed work fine when driving them with your home stereo, then your amp needs service. Where are you located? Enzo is the Peavey expert on here, but if you're not close to him, perhaps somebody else on here can help you check your amp out. If you're close to Nashville I'd be glad to assist (though I'm only a hack compared to the experts on here).

[Enzo]

This is a Classic, the VTX came after the VT even. The VTX has the cathode drive ala Music Man. This is an old A series Classic. And in fact it does have a bias adjustment inside. Really old PV amps had bias adjustments until they realized the adjustments caused more trouble - mainly from amp owners messing with them - than they cured. SO then no more adjustments.

But I agree, a misadjusted bias is not the cause of a gross loss of power.

There are a lot of good techs on this board, factory authorized or not, but this is not rocket science, there are authorized PV repair shops all over this land, and for that matter, ANY competent amp tech could sort out this problem.