How can i add more clarity and definition to a peavay 5150? mods?

[exclamationmark]

The 5150/6505 is known for it's kind of annoying fizzy/grind/buzzy sound when played solo. But the real reason for it's popularity with metal bands is the fact that it sounds absolutely crushing in the mix with little relative effort (and is dirt cheap!). The 6505+ to my ears is slightly clearer but still sounds verrrrry similar.

The only thing the 5150 and the SLO have in common is the cold-clipping stage and a couple of cathode bias/plate resistors (though the overall topology of the circuit, apart from the extra gain stage is sort of similar - perhaps this is what people mean when they say 'brand a' copied 'brand b'). A major difference between the SLO and the 5150 is the fact that the SLO has a Direct-Coupled Cathode follower (while the 5150 has an anode follower - basically a gain stage with heavy feedback). I can say this probably has a large sonic difference, as I remember debating whether my marshall type build should have a cathode follower, or a DCCF. I tried both and preferred the DCCF as the more 'modern' sounding alternative. Dunno if it was any clearer though, I just liked the sound of it. The anode follower stage might even be driven into clipping, which would sound interesting given the large amount of feedback - that might account for some of the 5150 tone as well.

Personally, if I weren't interested in seeing how these things work, I'd scoot down to the local store and try out all the ENGL/Mesa/whatever amps before going through the nightmarish cycle of soldering/desoldering/listening/pullingmyhairout.

[Amp Kat]

It's not that the 5150 is so hard to mod but the way Peavey threw this thing toghether makes it difficult because of the voicing and frequency shaping. One small change to a network up front can have a huge and most of the time bad symtom further down the road. Lots of relay switching and transistors also. Two things that will help tone clarication the most are a power transformer upgrade and OT upgrade. I know Trace at Voodoo has done tons of these and actually could sell Peavey 5150 trannys he's done so many. I'm sure there are maybe some coupling cap swaps that could help and maybe a few bypass changes but just remember that value changes and high frequency networks are all over the place and eliminating and adding can wreak havok. I also agree that maybe for the money you may consider another amp because the 5150 is really not close to a Soldano even though it was originally meant to be. The amp 5150/6505 (same amp) are very noisy and almost impossible to get out. You can put a noise gate in the loop and a sonic maximizer and get it sounding better and an eq in there helps too. Not a really good amp to mod and as suggested above the PCB must be handled correctly are you can cause further damage. I've done some mods and seen lots of mods but they really aren't great for the amp because of what it is. It's a chore at best and a nighmare at worst.

[tubeswell]

High gain amps like the 5150 and the SLO100 are designed to do one type of sound, and when you start to make them more 'fendery' (scooped mids and accentuated highs and lows), this requires changes in the pre-amp voicing and gain which has consequential flow-on effects for the signal path further along.

The reason that the voicing of high gain pre-amps is shaped in order to get rid of high and low frequencies, and focus instead on the mids, is that too many lows result in horrible blocking distortion, and too many highs result in horrible ice-pickiness. This is why hi-gain amps have all the tone-shunting RC networks that dump highs and lows as you go along the pre-amp signal path. They also have more inter-stage attenuation to tame the signal and get it to behave in a predictable manner. This ends up producing a very shiny and metallic, 'buzzy-mosquito' type of machine sound that some people really like. Teenagers really like this 'machine sound' - I did when I was a teenage heavy-metal head. And one of my sons is exactly the same as me in this regard. 8-0

However, once you've got rid of the high and lows in the pre-amp, its really hard to put them back in again without undoing all the tone-shunting and attenuation, and you really need to get rid of half of the gain stages if you want to get back to a more 'simpler' fender sound (that tends to reproduce more of whats going on at the guitar pickup). For a fendery amp, you only need a 2 or 3 pre-amp gain stages to get the wide-band, scooped-mid sound (and this is 'married' to some 6V6 or 6L6 output tubes which have a bigger bias voltage than EL84s or EL34s, to keep the fenders cleaner overall).

In fact, I think its pretty difficult/damn-nigh impossible, to get a fender-clean scooped-mid sound and a hi-gain shiny metallic accentuated-mid sound out of the same pre-amp channel without a really complicated and incredibly-frustrating system of switches and pulleys (I tried this ad-nauseum with a PV C30 for a couple of years - in the end I gave up and just focussed on turning it into a mid-range distortion amp by copying the first four 'channel-switching' stages of the SLO100, and feeding that into the driver/cathodyne splitter stage to drive the 4 x EL84s).

Which is a long-winded way of saying, if you want a fender sound, then use a fender type amp. If you want a 5150 sound, then use that.

Also - on wot Amp Kat said - PV 5150s and C30s etc are really difficult and frustrating to mod. Not only are they PC-board based amps with delicate inter-board jumper leads that are designed to make modding a real PITA, but each time you want to make a mod, you have to pull the entire guts apart to change 1 resistor here or 1 cap there, in order to see how you like it; and if you don't like it, you have to pull it apart again and again and risk breaking/upsetting the delicate fragility of the whole thing more and more. I once pulled apart and put back together a C30 13 times over two days, before I found the jumper lead cable that I had broken in previous modding episodes, which was stopping the amp from working altogether. You have been warned!

[Gregg]

As I suggested earlier try the 5150-II pregain circuit. Just compare the two schematics and you'll see what I mean. it's a simple mod and the difference is well audible (especially if you add a push-pull pot). The gain pot will have a more usable range and definition is also improved.

[Chuck H]

FWIW... Probably my favorite high gain sound in current pop music would be the Foo Fighters. Uber gain but with good definition Very agressive but still musical. I read an interview with Dave Grohl and he said that most of the tracks are recorded with a Vox AC30 and a stomp box. A very un-metal rig. So there you go. My point is, try stuff and play what sounds right to you.

Rod, unless your interested in electronics, modding your 5150 may not give you much satisfaction. Maybe try a couple of mods suggested so far. Just a couple of parts. See if it moves in the right direction. But I wouldn't get obsessive as tubeswell describes. Actually "I" would. But unless your into the whole amp tweak thing I wouldn't if I were you.

[diagrammatiks]

I don't think it's worth it if you want more clarity. Just changing the component type isn't going to do anything.
You'd have to go in and systematically rebuild the circuit.

It would be easier just to get a different amp that did what you wanted it to do.

[Chuck H]

Lower the value of that 39k preamp cathode resistor and I'll bet things change!

[Enzo]

The 5150 family of fine amps was never designed for any clean tones anyway, but aside from ideas already given, you could also experiement with some lower gain tubes in some preamp positions, a 5751 comes to mind.

[Chuck H]

I don't think the OP want's a cleaner tone. Rather, more note definition and attack without being shrill. Which is always a tall order for the uber gain thing. Some amps do it better than others. Usually the expensive ones. I really think some assymetrical coil standard type humbuckers could do it. Just go on Youtube and listen to the 5150 demos. Some are ratty and harsh, some are flabby and bland and others sound just right. What you plug in, your settings, speakers and even your pick can all make a difference. If some guys are using the 5150 and getting good, well defined tone, what is different about their setup?

[Enzo]

Well foo. Chuck is now not taking my baloney in TWO threads. I'm gonna go take a nap.

[Amp Kat]

I don't think the OP want's a cleaner tone. Rather, more note definition and attack without being shrill. Which is always a tall order for the uber gain thing. Some amps do it better than others. Usually the expensive ones. I really think some assymetrical coil standard type humbuckers could do it. Just go on Youtube and listen to the 5150 demos. Some are ratty and harsh, some are flabby and bland and others sound just right. What you plug in, your settings, speakers and even your pick can all make a difference. If some guys are using the 5150 and getting good, well defined tone, what is different about their setup?

The difference is they have lots of gear in the loop which is also another problem with the 5150 loop which is -10 dB down and wreaks havok with the input impedance of most effects units so you have to crank it a tad which adds even more signal to noise ratio but putting a noise gate,EQ and a sonic maximizer does wonders for the tone clarity of the amp. There is not one single mod you can do to this amp that will change it's tone clarity without introducing either high frequency sqeals or bad blocking type distortion. The 5150 has been combed by Peavey and they did the best with what they had to work with. Another problem is the amp has so much gain and amplitude that the bias is really scaled back at a cold -55 volts and is actually into crossover but decreasing it or adding more current to the tubes puts it very loose and lots of ice picking action like Tubeswell was talking about and its very noticable and annoying tstl. As stated try what you want but you have been warned by some who have tweaked on them and it's actually kinda funny that if you think about it that if something could be done to make this amp better circuit wise don't you think Peavey would have done it ? Ok Enzo, get your ass up now and get to work !

[Chuck H]

I love baloney. I'm full of it right now.