filthy dirty Peavey Classic VTX hybrid amp just handed to me, how do they sound?

[Silvertone Jockey]

Unexpected Peavey 212 Classic VTX hybrid amp with Scorpion speakers just walked in my door for next to nothing. First How do they sound? from the looks of the front panel it appears that it might be able to get rude, or maybe just annoying, opinions on that?

Next is it possibly a keeper or better suited as a fresh canvas of unmolested sheet metal with many front panel options that can be almost any circuit imaginable with creative drilling for more worthy tone possibilities?

I am looking for an amp that has overdrive to complement my TFL5005D and 1484 clean sounds, but I really dislike most solid state amp distortion characteristics

It may not even work, the tubes look to have been red plated. If the pre-amp section is non functional this will probably end up as a start from scratch project amp

Edit: OK I'm reading that these do the southern rock sound thing. Could be interesting maybe..................

[Silvertone Jockey]

So how does the cathode bias on this amp work? I measured 14.7 volts positive on the grid which appears correct from the schematic? Tubes red plate soon after stby is thrown

[g1]

What schematic? Please post.

[tedmich]

related thread here:
http://music-electronics-forum.com/t16601/

schem?
http://www.shadowstorm.com/cb/schema...TX_Classic.pdf

[Jazz P Bass]

This is indeed a strange output section.
Where most amps vary the grid pin, Peavey varies the cathode.
The signal enters in at Ic U8B/ pin 6.

If the amp is redplating, you should check the driver stage for shorted transistors & such.
The expected transistor base voltages are shown on the schematic.

[g1]

This is similar to the Musicman power amp design. Grids are held at a fixed +15VDC. Cathode DC level sets bias, and signal goes into the cathode.
What are the cathode voltages? Difference between cathode and grid are what set the bias.
DC voltage across R126 and R130 at idle (divided by 5.6) will tell us the idle current.

[Enzo]

Exactly. Bias is not "the grid is at -50v", bias is the difference in voltage between the cathode and grid. If the cathode is at +65 and the grid is at +15, then your cathode is 50 volts more positive than the grid, which is exactly the same as your grid being 50v more negative than the cathode. What matters is the difference, not where it comes from.

[Silvertone Jockey]

Thanks for the replies, working so no time till the weekend but I read the other thread, and will do some testing this weekend. This amp reminds me of the many (triode, tetrode amps are grid driven usually) RF amps I have worked on which are almost always cathode driven, but the circuitry on those is usually much simpler. Ground the grid. Ground the cathode through a choke, give it some high voltage and a signal to the cathode and that's basically it, minus the tank circuit.

[nashvillebill]

I have a Classic VTX which I have refurbished, and it is a very nice sounding amp. Great clean tones, takes pedals well, and the built-in phaser works nicely. Pull the phaser knob out and it "locks" in, which gives a nice texture. Note you must have the footswitch to access the Clean channel (or is it the other way around). If you don't have a footswitch with it, make a 3 button one (reverb, phaser, clean/lead), the schematic gives us the pinouts on the DIN plug.

I've got Eminence Little Texas neo speakers in mine to shave some weight off. The Lead channel can give some very good sounds with a little bit of patience, just don't crank the saturation all the way up or it will be the 80's box-full-of-bees distortion....unless you WANT the box-of-bees sound....

[Silvertone Jockey]

just don't crank the saturation all the way up or it will be the 80's box-full-of-bees distortion....unless you WANT the box-of-bees sound....

Well I have a 1484 and a Bandmaster TLF5005D which I run in tandem that gives me everything I could hope for in a clean tone, but (sadly) the pedal driven overdrive although OK is not the best. If this VTX can do some 'crunch' with maybe a TS9 as opposed to a box full of bee's, for what I paid for it I'll be a really happy camper. So far from doing some reading this amp gets fairly good reviews which is encouraging being as I expected less.

WTH the damn thing walked into my door, I wasn't looking for an amp, just had a few "if you run across any guitar related items" feelers out there with a couple friends.

I tend to believe that destiny can have an impact in your life when you initiate something with other people like the quoted feeler above, and all the people that they know made free will choices that end up bringing something you want into your hands, so there's a good chance this amp may be exactly what I'm looking for regarding some crunch............know what I mean?

If not, well damn, remove the circuit board and the chassis couldn't be more wide open

[nashvillebill]

There's a few Youtube videos of this amp in action. One with clean sounds, one with effects (reverb and phaser) and one of the saturation. I am not sure how they mic'd the distortion recording, so take those sounds with a grain of salt. It's been a couple of years since I've gigged with mine but to me it had plenty of crunch when driven pretty hard (loud, in other words!)-- without cranking the Saturation to the max. Speaker choice makes a huge difference, also whether being driven by humbuckers or single coils.

Mine kinda appeared the same way. I had bought a Classic VTX new back in the early 80's but for some goofy reason sold it in the late 90's. (Threw in two NOS USA 6L6's too when I sold it....what was I thinking?) Then five or six years ago an ad appeared on CL for a Classic VTX for $20, "it had a hum" was the reason it was being sold cheap. I replaced the power supply caps for a few bucks and it played fine, so I eventually replaced all the electrolytics (quite easy, and I highly recommend it, as one of the e-caps in my preamp section had completely gone south). I'm not a big believer in rolling op-amps but a lot of folks swore the OPA2134 sounded better in the Peavey preamps than the stock op-amps, so I popped a few of them in the first few op-amp spots, what the heck. I'm no audiophile so I won't swear the op-amp swap was an improvement, but to my ears now, this is a very good sounding amp. In fact it immediately became my #1 gigging amp and I sold my Classic 50.

[Silvertone Jockey]

OK a quick in circuit test shows one of the 5884 tube driver transistors bad. (edit: question answered by an Enzo post somewhere else) So I need to replace both of those and should replace their their drivers too, as a matter of course? Another question, does anyone have a link to any good semi conductor cross references? I did some searching but haven't come up with much other than manufacturer specific ones.

[Silvertone Jockey]

Exactly. Bias is not "the grid is at -50v", bias is the difference in voltage between the cathode and grid. If the cathode is at +65 and the grid is at +15, then your cathode is 50 volts more positive than the grid, which is exactly the same as your grid being 50v more negative than the cathode. What matters is the difference, not where it comes from.

I've been studying the schematic but I still don't understand where the cathode gets this +65 volts that you mention. Help me out here if you don't mind

[Jazz P Bass]

I've been studying the schematic but I still don't understand where the cathode gets this +65 volts that you mention. Help me out here if you don't mind

The output tubes are 'cathode biased'.
The voltage is developed through the cathode resistors R1236 & R130.
The resistors are grounded at one end, so the other end will be a positive voltage.

The transistors Q6 & Q7 at idle will be 'just on' & a signal at their bases will vary the cathode voltage.

[g1]

Think of it as a voltage divider. On the top half, you have the B+ around 525V at the plate. Then you have the tube, the transistor, and R126 all in series between B+ and ground. Each of these three drops a certain amount of voltage depending on it's series resistance.