Peavey 6505+ 112 vs 5150 mk1

[AMelbye]

It's a pity that such a design difference wasn't shown with a *different* model number.
Confusing.

This is in fact very misleading. I thought I was buying a 6505+, and got a very different amp, unsuitable for the purpose I bought it for.
Hopefully there is something wrong with the one I bought. Marketing a mud monster like this as a 6505+ is not fair.

[Enzo]

Oh dear lord, how many different amps have worn the name Peavey Bandit?

In their defense, 6505 is to peavey what Chevrolet is to General Motors - a brand. Chevy make everything from the Corvette to the VOlt. Your amp may have an issue or it may just naturally sound this way, but you have traced out the circuit, and other than a few details it is clearly related to the big 6505 amps.

[AMelbye]

Oh dear lord, how many different amps have worn the name Peavey Bandit?

In their defense, 6505 is to peavey what Chevrolet is to General Motors - a brand. Chevy make everything from the Corvette to the VOlt. Your amp may have an issue or it may just naturally sound this way, but you have traced out the circuit, and other than a few details it is clearly related to the big 6505 amps.

Well, peavey bandit is different. It's their cheapest line of amps, similar to the Marshall MG, and none of them sound anywhere near impressive, so who cares how the circuit is built?

I like to see it this way: Cheavy makes everything from Corvette to Volt, Peavey make everything from bandit to 6505 (and beyond). If you bought a corvette and the suspension was so loose you had to slow down to 20 every time you wanted to round a corner I bet you'd be disappointed. And that's how I found the 6505+ 112. It looks like a 6505 and has all the horse power (gain) that I expected, but it's too loose and muddy to do most the things you'd want a 6505 for.

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Back to topic:

I changed all the preamp tubes, and it didn't help.

Next I put a patch from the fx loop output and straight to the loop input, and the amp came alive! The whole character of the amp changed, and the noise increased. With the patch cord in, it's still far from perfect, but it's much closer to the sound I expected.

I have no time to look at the circuit right now, but I expect there is something wrong with the fx loop circuit, unless it's just very poorly designed.

[Amp Kat]

Well, peavey bandit is different. It's their cheapest line of amps, similar to the Marshall MG, and none of them sound anywhere near impressive, so who cares how the circuit is built?

I like to see it this way: Cheavy makes everything from Corvette to Volt, Peavey make everything from bandit to 6505 (and beyond). If you bought a corvette and the suspension was so loose you had to slow down to 20 every time you wanted to round a corner I bet you'd be disappointed. And that's how I found the 6505+ 112. It looks like a 6505 and has all the horse power (gain) that I expected, but it's too loose and muddy to do most the things you'd want a 6505 for.

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Back to topic:

I changed all the preamp tubes, and it didn't help.

Next I put a patch from the fx loop output and straight to the loop input, and the amp came alive! The whole character of the amp changed, and the noise increased. With the patch cord in, it's still far from perfect, but it's much closer to the sound I expected.

I have no time to look at the circuit right now, but I expect there is something wrong with the fx loop circuit, unless it's just very poorly designed.

What you basically just did was patch a cable from send to return so sounds like the whole problem is some corroded or cold solder joint jacks so you either need to clean them or replace themor maybe touch them up. Then after that I would look into putting an eq in the loop with a sonic maximizer and a stompbox in front to get the gain and distortion type you are after and you should be good. Of course you could probably get all that tweaking it and adding and eliminating certain components but it would take an awful lot of experimenting and possible trace cutting and hacking which in the long run you'd come out way ahead with what I mentioned.

[exclamationmark]

That's kinda funny. I tend to avoid inserting anything into my 6505+ combo's effects loop as it automatically makes it sound like I'm playing through my rage 158 practice amp I bought about 10 years ago (it gets ridiculously bright and ice-picky)! Probably has something to do with the buffer impedance. I have a feeling without the effects loop engaged, it bypasses the buffer completely and drives straight into the return tube, rolling off high's due to the miller effect. I swapped the tube in this location (the PI/effects return) and it seems to have become *less* noticeable, but noticeable none the less.

To my ears the 6505 and the 6505+ sound very similar. The 6505 has slightly more grind to the tone and is less smooth sounding than the 6505+, but both should be very comparable. Have you tried the head versions of these and tested them? The pre-amp schematic of the 6505+ appears identical to the head version, so a comparison test might be a helpful way to identify potential cold solder/effects loop issues. The power amps are clearly different but it shouldn't make too much of a difference.

[Amp Kat]

That's kinda funny. I tend to avoid inserting anything into my 6505+ combo's effects loop as it automatically makes it sound like I'm playing through my rage 158 practice amp I bought about 10 years ago (it gets ridiculously bright and ice-picky)! Probably has something to do with the buffer impedance. I have a feeling without the effects loop engaged, it bypasses the buffer completely and drives straight into the return tube, rolling off high's due to the miller effect. I swapped the tube in this location (the PI/effects return) and it seems to have become *less* noticeable, but noticeable none the less.

To my ears the 6505 and the 6505+ sound very similar. The 6505 has slightly more grind to the tone and is less smooth sounding than the 6505+, but both should be very comparable. Have you tried the head versions of these and tested them? The pre-amp schematic of the 6505+ appears identical to the head version, so a comparison test might be a helpful way to identify potential cold solder/effects loop issues. The power amps are clearly different but it shouldn't make too much of a difference.

It shouldn't make to much difference if it's working right which obviously his isn't and I put eq's in the loop because it needs them however I agree that other effects don't work well in the loop especially distortion pedals because the loop is -10db down already which is not a guitar level or an amp level. Adding a peak inverter tube change only makes the amp colder and causes a need for a bias change which is why the amp gets ice picky with gain effects or higher gain tubes (or mods to use EL-34's --not recommended) in the loop because it brings it out of crossover distortion which causes this amp to get real loose because it has so much gain and amplitude that hits the grid really hard when biased out of crossover. These amps sound the best with the bias set cold actually into crossover or just barely out of it. EQ's in the loop help dial in that tone and can help get that tinny voicing out and the maximizer tighens the Bass response up. However if you don't have the post control past 3 it will get tinny on you bad and you won't ever get it out until you cross that threshold.