Amp Tech Thread / Ask a tech Q

[Hemisaurus]

[spookstrickland]

Hemi,

Great thread!  what do you know about the Peavey VTX head.  It has a 4ohm out and I think the tubes are self biasing.  Can I run a 16 ohm cab off of it.  I've heard that a less hardy amp would blow but peavey's are supposed to be pretty forgiving.

thanks

[VOLVO)))]

Amazing, and stickied!

[nonoman]

My butcher blew a 1 amp fast acting board fuse. I read they should be slo blo since fast acting fuses can just pop in a healthy amp. Does this ring true with you?

[Hemisaurus]

Hemi,

Great thread!  what do you know about the Peavey VTX head.  It has a 4ohm out and I think the tubes are self biasing.  Can I run a 16 ohm cab off of it.  I've heard that a less hardy amp would blow but peavey's are supposed to be pretty forgiving.

thanks

The Peavey manual specs it into an 8 ohm cab at the Lo power setting, my gut would say 16 might be a little high, especially as it thas all that self biasing transistor stuff.

Two solutions:

1. Call or email Peavey, they are pretty responsive, I think now they make you sign up for their support forum to ask a question, but it still works.

2. Easy one, rewire the cab so it is 4 ohms, or make it switchable.

Or you could buy one of Weber's impedance matching transformers $48, and be able to run any load you like within reason

[beardofcthulhu]

The guys on the Peavey board are VERY helpful.  You'll get several immediate responses, and there is a huge archive of owner's manuals on the site as well.

[Hemisaurus]

My butcher blew a 1 amp fast acting board fuse. I read they should be slo blo since fast acting fuses can just pop in a healthy amp. Does this ring true with you?

Slo Blo and Fast acting fuses both belong in an amp, on different sides of the Power transformer usually, but if you are talking about F1 which is the only 1A fuse I can see, then according to the schematic it's a Slo-Blo.

http://music-electronics-forum.com/attachments/11449d1288300024-peavey-butcher.pdf

Unrelated, this just looked cool
http://www.davidsonamp.com/woodland_gallery/gallery_butcher.php

[VOLVO)))]

This was my butcher, at one point. Never had an issue with it. Never popped a fuse, nothing. Soon as nonoman got it... problems galore. Wtfm8?

[spookstrickland]

Thanks Hemi,

I got two cabs so I can just run them in Parallel for 8 ohms and the low power mode is damn loud anyway. 

Thanks again

Hemi,

Great thread!  what do you know about the Peavey VTX head.  It has a 4ohm out and I think the tubes are self biasing.  Can I run a 16 ohm cab off of it.  I've heard that a less hardy amp would blow but peavey's are supposed to be pretty forgiving.

thanks

The Peavey manual specs it into an 8 ohm cab at the Lo power setting, my gut would say 16 might be a little high, especially as it thas all that self biasing transistor stuff.

Two solutions:

1. Call or email Peavey, they are pretty responsive, I think now they make you sign up for their support forum to ask a question, but it still works.

2. Easy one, rewire the cab so it is 4 ohms, or make it switchable.

Or you could buy one of Weber's impedance matching transformers $48, and be able to run any load you like within reason

[nonoman]

Unrelated, this just looked cool
http://www.davidsonamp.com/woodland_gallery/gallery_butcher.php

That IS cool, wish I could do that, lolz.
Thanks for the fuse help also.

SunnO))), I'm putting about 8 hrs a week on this thing, or do they usually wear better w/o incident than this?

[bloodofkings]

Now you say older amps marked with a jack that says "Ext Speaker" has a different set if rules. Could you explain those rules in detail Hemi?

[Hemisaurus]

I said might have a different set of rules, it differs from amp to amp, model to model.

If you have the specific make and model, it's best to check the schematic.

Some are wired in series with the main speaker / speaker jack, rather than in parallel like a modern one. I actually saw a solid state Rickenbacker where using the EXT Speaker jack would actually reduce the output power, as you were increasing the impedance on the output jack, weird huh

[beardofcthulhu]

I'm a tube noob, so somebody needs to school my ass on attenuators.  Will any one do?  Should it match wattage and impedence?  Hellllllp!  Just got a VTM60, and even the lowest of volume settings rumbles the shit out of my hoose.  I'd like to get optimum tone even whilst just piddling around...is this the way to go?

[Hemisaurus]

Almost anyone will do but some may sound better than others.

At it's simplest the attenuator is an extra impedance you add onto your speaker / amp that wastes some of the amps power and prevents it from reaching the speaker.

As long as the attenuator is within the amps impedance range it should be fine, however a purely resistive attenuator, may not make your amp sound and respond the same, as one that uses inductance to closer model the response of an actual loudspeaker.

Beware the $15 attenuator box on eBay. A buddy of mine bought one of these, and it's just a 100K pot in a little box. Connect this to a tube amp and you'll blow something valuable, like a set of tubes, or your transgormer.

Ted Weber .com has some inductive attenuators.

[justinhedrick]

I said might have a different set of rules, it differs from amp to amp, model to model.

If you have the specific make and model, it's best to check the schematic.

Some are wired in series with the main speaker / speaker jack, rather than in parallel like a modern one. I actually saw a solid state Rickenbacker where using the EXT Speaker jack would actually reduce the output power, as you were increasing the impedance on the output jack, weird huh

i had one of those ricks. i sold it to a kid who was from vietnam. i wonder whatever happened to that amp. it had the craziest "dying battery" sounding fuzz.

[mortlock]

you guys are such brainiacs..please tell me why i can take my bass and plug it into any amp and it sounds like me..i honestly thing some of the amp stuff is total bull. you pick an instrument that fits you..hence me customizing my j bass. after that ill sound like me no matter what amp i run through..maybe its just me..carry on.

[Hemisaurus]

you guys are such brainiacs..please tell me why i can take my bass and plug it into any amp and it sounds like me..i honestly thing some of the amp stuff is total bull. you pick an instrument that fits you..hence me customizing my j bass. after that ill sound like me no matter what amp i run through..maybe its just me..carry on.

Yeah, this is one of those DUH!!! questions.

Of course it's going to sound like you, it's you playing. If I were to pick up your bass, plug it into any amp, it's not going to sound like you atall.

The point of this thread was to prevent people blowing shit up, and save them a few bucks in repair fees.

If you can point to the total bull, maybe I can explain it to you.

[mortlock]

thanks for clearing that up..i really wasnt trying to start any trouble..it was more of a drunken observation..

[VOLVO)))]

How would I wire in an expression pedal input to a trem pedal? I doubt I can afford one that comes with one, already... haha.

EDIT: Can I send wires from the wiper/case to a jack, and plug a pedal into it, and have it change value, or will it stay the same since the wiper isn't moving, for realz?

[VOLVO)))]

Also, home-made expression pedals. DOING SHIT ON A BUDGET THAT HAS NO ROOM FOR EXCESS SPENDING.

[dogfood]

Tech Q,

I built up a germ fuzz face from byoc.  Sounded shitty then paid for a new set of germs and voila it sounded like it should-fantastic.  I guess he thought he would send the crappiest sounding germs to me and perhaps I wouldn't know the diff?!  Anyway, the pedal comes with sockets for the germ transistors so you can fast swap'm with silicon and perhaps more importantly you don't damage the germ transistors when soldering them in place with over heating.  The problem is that my germs don't contact the sockets well ie it won't function.  Should I solder them in and ignore the possibility of damage to a great sounding set of germs or is there a solution I'm not seeing?

[VOLVO)))]

Just use a heat sink. Take a pair of hemostats and clip them onto the lead, so that they absorb the heat..

[dogfood]

got it.

[LogicalFrank]

• Never run a tube amp without a speaker attached
• Always set the impedance switch to the proper value, or use the proper impedance of speaker, unless the manufacturer says otherwise (some Peavey tube amps have a minimum impedance but don't care otherwise)

Additionally, if you for some reason have to run mismatched impedance cabs, it is better to have the speakers impedance be lower than what the amp is rated for (this would be opposite of the rule for solid state). In general, people seem to think a 2:1 mismatch either way is tolerable but you will get maximum volume and life from your tubes if you match exactly.

[justJon]

See if I understand correctly. You're saying, for example, an 8-ohm tube amp into a 4-ohm cab is ok, if less than ideal? While an 8-ohm solid state should run into 8 or 16 ohms? Or am I totally out in left field?