5150 mods? - Enzo?

[HTH]

Enzo/anyone,

I've just got one of the new 5150s (6505s) and it's a great amp - does just what I wanted. BUT, after the usual playing with preamp valves I'm thinking "how much better can this this sound?"

I've put chokes in Sound City amps before and liked the results - has anyone tried putting a choke in a 5150 and liked what it did?

this amp also has a surprising amount of hiss/noise - anyone got any tips over and above using metal film resistors?

btw, I'm namechecking Enzo because I've noticed he always pipes up on 5150 threads.

Cheers... Ian

[Enzo]

I pipe up on troubleshooting threads mostly. I'm not a modster, I'm a problem solver.

There is a ton of gain in the 5150, and gain and hiss go hand in hand.

What do you want from your mods? WHat do you expect a choke to do? It wouldn't be difficult to add one, the standby switch is between the plate and screen nodes. Break into the wires there. Ditch the 400 ohm resistor.

[HTH]

I pipe up on troubleshooting threads mostly. I'm not a modster, I'm a problem solver.

There is a ton of gain in the 5150, and gain and hiss go hand in hand.

What do you want from your mods? WHat do you expect a choke to do? It wouldn't be difficult to add one, the standby switch is between the plate and screen nodes. Break into the wires there. Ditch the 400 ohm resistor.

well I don't need any more gain thats for sure, I'm running the gain just over 6 before the tone looses focus. I'm more interested in getting rid of some of that hiss/noise. getting a bit more sparkle from the clean channel wouldn't harm either - but would this affect the OD channel?

from previously adding a choke to amps that didn't have them I've found that the bass end is faster/tighter - I'd imagine this to be an improvement to the 5150.

[Enzo]

Well remember that the resonance control, and the presence for that matter, are ACTIVE controls and they respond different at different levels. SO maybe back off the resonance at higher levels to keep the bottom from flabbing as much. Have you searched? SOmeone must have tried a choke already.

Remember this amp doesn't really have a "clean" channel, it has a rhythm channel - a not quite as distorted channel. No chimes.

Get the PV Triple XXX schematic, or the JSX. Those have a couple of noise suppresion diodes added in the lead channel to reduce hiss. That would be easy to add to the 5150.

[HTH]

Well remember that the resonance control, and the presence for that matter, are ACTIVE controls and they respond different at different levels. SO maybe back off the resonance at higher levels to keep the bottom from flabbing as much. Have you searched? Someone must have tried a choke already.

Remember this amp doesn't really have a "clean" channel, it has a rhythm channel - a not quite as distorted channel. No chimes.

Get the PV Triple XXX schematic, or the JSX. Those have a couple of noise suppresion diodes added in the lead channel to reduce hiss. That would be easy to add to the 5150.

thanks for the advice Enzo, think I'll just add a choke and see how it goes since nobody seems to have tried this.

do you have the XXX and JSX schems? - if so could you email them to me please?

[Enzo]

Email parts@peavey and ask for them. To be polite I might ask for one at a time.

[Amp Kat]

I've done one on a 5150 and it didn't really change very much at all. To each his own just my experience. The mod I really liked was adding two bias pots one for each side.

[Enzo]

Did you mount them on the "wrong" sides like Marshall? Left knob for the right tubes and right knob for the left tubes?

[Amp Kat]

That is very easy to do I gues which way you look at it but I did mount them on the top and sent two meter jacks out the back.

[Enzo]

I was joking of course. It baffles me why Marshall mounts the little bias pots with the three pins for test points so that the left pot adjusts the right tubes and vice versa.

[Valvehead]

HTH--

you definately need to do the "bias mod" if its the 6505 model (5150). Peavey sets it at about 18ma per tube!

It wakes up the amp in a big way and seems to improve the clean channel as far as headroom.

its real easy to do, just snip one end of the the 15k in the bias supply and add a 4.7k in series with a mini 10k pot. Then adjust to about 35ma or so .

Really beefs up those amps. Not going to affect the hiss though .

[HTH]

HTH--

you definately need to do the "bias mod" if its the 6505 model (5150). Peavey sets it at about 18ma per tube!

It wakes up the amp in a big way and seems to improve the clean channel as far as headroom.

its real easy to do, just snip one end of the the 15k in the bias supply and add a 4.7k in series with a mini 10k pot. Then adjust to about 35ma or so .

Really beefs up those amps. Not going to affect the hiss though .

thanks for the tip, I always make sure my amps are biased correctly though - I've not had time to open the amp up yet - I suppose the guesswork is taken out now though... one 4K7 and a 10k trim

the amp came with Ruby (Chinese?) 6L6s so I'd imagine there is certainly room for improvement there. I'd imagine these account for some of the fuzzy edges on the tone. all things said though, I'd very happy with the amp right out the box and with some decent NOS ECC83s.

some JJ 6L6s will be going in there when I do the bias mod. I bet 6550s would be monsterous in this amp (I'd be worried about the PT taking it though - maybe just two 6550s).

[Valvehead]

right now ive got sovtek 5881wxt's and JJ 12ax7's in my 5150. Not fizzy at all .

[Enzo]

The Ruby 6L6GCSTR are Chinese, but they aer good tubes, I like them. They have always worked well for me and are reliable. I have always thought they were particularly well suited to the 5150.

As to that bias mod, don't you mean replace the 15k with the pot and resistor, rather than adding them in (and leaving the 15k resistor)? The 10k pot and 4.7k resistor make up about 15k right there. Leaving the 15k in place would mean th bias voltage would go even higher.

[Valvehead]

Here's that mod Enzo.



http://blueguitar.org/new/schem/peav...0_bias_mod.pdf