My gawd I love my 5150

[mrbobo]

I've had this 5150 a long time.... even though I am educated in electronics, and am a electric utility grid operator by profession- I paid a local tech to install a bias pot. Didn't play with the bias much then, assuming he'd set it correctly. Then the next set of tubes, I checked bias and couldn't get the tubes warmer than like 22ma. Oh well, I was busy, playing in a band, etc- and didn't give it much thought. I thought maybe the amp sounded better, and it certainly didn't sound any worse. Years go by. My DAW PC MB bit the dust 2 weeks ago,, so I started actually playing guitar, going over my gear. Downloaded schematics and started reading.

So I take my 5150 out of the case and am looking at what I paid for, whatta joke. The tech simply lifted the ground leg of the bias resistor (15k) and soldered a 5k pot in series with it. Wasn't glued down either, just sitting there. GRRRR So I replaced the 15k with a 6.8k, and bought a panel mount CTS 10k pot. Then I put some fresh winged =C= 's in, set the bias to 35 and HOLY SHIT! This amp never sounded so good. And I don't need to remove the innards from the case, to bias in the future.

So what the hell- after looking at the Duncan tone stack calculator- I slightly modified the tone stack (50k resistor across the 50k mid pot). Really didn't alter the sound much, but made the midrange knob more usable (for me). I didn't need to lift the circuit board for this or the bias mod. That looks to be a PITA on this amp, compared to a Marshall. I'm gonna think hard about it before I replace filter caps....

I know it's been said 150 times on this and any other amp board, if you have one of these monsters- get it bias modded!

 

[CaseyCor]

I never understood why Peavey didn'r include a bial adjustemwnr pot from the factory. Do the 6505's have one?

 

[Erock]

I never understood why Peavey didn'r include a bial adjustemwnr pot from the factory. Do the 6505's have one?

never understood this either, and nope, the 6505 is exactly the same design. The 6505+ has bias pot, but it's so short of a sweep you can't get them hot enough anyway.
My 5150 was reading about 12-14mA with the stock Peavey power tubes, a set of Ruby 6L6 tested for the 5150/6505 from Dougs read about 17-21mA when I put them in. After the bias mod, they are now running at a healthy 32-34mA, and the amp is kicking all kinds of ass.

 

[CaseyCor]

I would love to hear some clips of a properly biased 5150. I never really got along with the 5150 or the 5150+, but I do love the tone The Black Dahlia Murder get's out of them on the new record and live. I was so surpirsed when I heard it was 5150's. Does anyone know if they have their's modded?

 

[loudgtr]

Very cool!!!

Played a combo at a store once for about half an hour and thought it was great! A little more noisy/hissy than I was used to from a high gain amp, but dialed in EVH's amp settings and bingo...lots of fun. Would have bought it for fun if cash was just falling out my pockets

 

[mrp5150]

The 5150 is still my favorite amp ever.

 

[Erock]

I would love to hear some clips of a properly biased 5150. I never really got along with the 5150 or the 5150+, but I do love the tone The Black Dahlia Murder get's out of them on the new record and live. I was so surpirsed when I heard it was 5150's. Does anyone know if they have their's modded?

I wish I had clips of before and after, but the difference was very noticeable. Stock it was running so cold, it was well into crossover distortion buzz. Biasing it correctly got rid of a lot of highend fizz and made it less harsh sounding when the amp is pushed.

 

[Copperhead]

I love my 5150 Combo! Every guitar sounds exactly the same!

 

[Atropos_Project]

Had the combo years and years ago, was forced to sell it due to extenuating circumstances.

Had the head last year, wanted to get it fmj modded to drop it to 60 watts, never bothered, sold it. Like an idiot.

If I ever buy another, I'll have to chain it to some pipes in the basement or something, I swear.

 

[blackba]

What I find interesting is that Mesa's don't have bias pots either and some models are biased pretty cold yet its rare for people to add bias pots to them, but common in the 5150, not sure what that is

 

[Erock]

What I find interesting is that Mesa's don't have bias pots either and some models are biased pretty cold yet its rare for people to add bias pots to them, but common in the 5150, not sure what that is

If I had known how to add a bias pot at the time of owning my Recto, I would have added it for sure. I may have kept it if it addressed some of the things I didn't care for. I would bet the Peavey bias is even colder than most Mesa though. The FJA site says he commonly sees values as low as 7ma-12mA in stock amps. With an average plate voltage around 420Vdc, that's only around %20 max plate dissipation.

 

[blackba]

What I find interesting is that Mesa's don't have bias pots either and some models are biased pretty cold yet its rare for people to add bias pots to them, but common in the 5150, not sure what that is

If I had known how to add a bias pot at the time of owning my Recto, I would have added it for sure. I may have kept it if it addressed some of the things I didn't care for. I would bet the Peavey bias is even colder than most Mesa though. The FJA site says he commonly sees values as low as 7ma-12mA in stock amps. With an average plate voltage around 420Vdc, that's only around %20 max plate dissipation.

7-12mA is way lower than what my mark IV was biased at too, that is pretty damn cold....

 

[FZRJunkie]

I am worried if I get a bias mod for mine to run hotter, the tradeoff is that it won't have that warm "give" any more, and will be too stiff? ie it won't be the same?

thoughts?

 

[Erock]

I am worried if I get a bias mod for mine to run hotter, the tradeoff is that it won't have that warm "give" any more, and will be too stiff? ie it won't be the same?

thoughts?

with the pot fully cranked, it's the same value as the stock bias. It's only replacing the stock 15k resistor with a 5k resistor and a 10k variable resistor(pot). It's actually more stiff the colder it is IME, the higher you take the bias, the warmer it gets. The tradeoff is cooking the tubes and therefore shortening their lifespan. Most people think the ideal range for lifespan vs tone is somewhere between 60%-70% max plate current. That's calculated using the power rating of the tube you use, divided by the plate voltage of the specific amp you're putting the tubes in.

 

[mrbobo]

I had a Boogie Tremoverb bias modded, and ran it in low 30's ma....but if memory serves me right it wasn't set from the factory near as cold as the 5150. I had a cold biased 5150 sitting next to a properly biased TVerb, and *poof* I ebayed the Tverb. That preference would have been even more obvious , had my 5150 been biased right...

Yea, I wish I could make a clip right now....that's the beauty of my post...I can make big claims and don't have to back it up until I either fix my dual core DAW, or upgrade it's guts to a quad core or i7

 

[FZRJunkie]

I am worried if I get a bias mod for mine to run hotter, the tradeoff is that it won't have that warm "give" any more, and will be too stiff? ie it won't be the same?

thoughts?

with the pot fully cranked, it's the same value as the stock bias. It's only replacing the stock 15k resistor with a 5k resistor and a 10k variable resistor(pot). It's actually more stiff the colder it is IME, the higher you take the bias, the warmer it gets. The tradeoff is cooking the tubes and therefore shortening their lifespan. Most people think the ideal range for lifespan vs tone is somewhere between 60%-70% max plate current. That's calculated using the power rating of the tube you use, divided by the plate voltage of the specific amp you're putting the tubes in.

huh. I thought the "give", or "sponginess" maybe, came from under-driving the power section -- or does that have nothing to do with bias?

 

[jessexxx]

i used to be a peavey hater,...i thought my jcm 800 was as good as it gets,..i wouldnt even try a peavey!..why bother right!

now i try to let my ears decide on everything musical,..i still struggle with my snobby-ness,..but i am very very happy with my peavey...even thou i am often looked down upon for my equipment,...

thanx erock you always have great advice,...now i wanna tear my amp apart and replace the existing bias pot to get more sweep!!...

 

[Erock]

Yea, I wish I could make a clip right now....that's the beauty of my post...I can make big claims and don't have to back it up until I either fix my dual core DAW, or upgrade it's guts to a quad core or i7

hehe, yeah, I have a clip, but it's pretty mediocre. I planned on doing something with it, but got sidetracked. Crunch channel boosted with a 7 string, no post eq.

I am worried if I get a bias mod for mine to run hotter, the tradeoff is that it won't have that warm "give" any more, and will be too stiff? ie it won't be the same?

thoughts?

with the pot fully cranked, it's the same value as the stock bias. It's only replacing the stock 15k resistor with a 5k resistor and a 10k variable resistor(pot). It's actually more stiff the colder it is IME, the higher you take the bias, the warmer it gets. The tradeoff is cooking the tubes and therefore shortening their lifespan. Most people think the ideal range for lifespan vs tone is somewhere between 60%-70% max plate current. That's calculated using the power rating of the tube you use, divided by the plate voltage of the specific amp you're putting the tubes in.

huh. I thought the "give", or "sponginess" maybe, came from under-driving the power section -- or does that have nothing to do with bias?

hmm, not sure man. IME, the hotter you bias the tubes, the more warmth and sag you get out of them when you push them. That's how it's sounded with my 5150 and other heads I've owned with fixed adjustable bias. It took away some harshness and added a little warmth with my 5150. With a cold bias, it was a little stiffer and had more fizz on the topend. I do run on the colder side of the recommended bias however, I like it somewhere around 60% personally.

i used to be a peavey hater,...i thought my jcm 800 was as good as it gets,..i wouldnt even try a peavey!..why bother right!

now i try to let my ears decide on everything musical,..i still struggle with my snobby-ness,..but i am very very happy with my peavey...even thou i am often looked down upon for my equipment,...

thanx erock you always have great advice,...now i wanna tear my amp apart and replace the existing bias pot to get more sweep!!...

no problem man, thanks for the kind words. It's an even easier mod for the II/+ series since it already has a pot, you just replace the 12k resistor with a 6.8k resistor. Very simple effective mod IMO.

 

[FZRJunkie]

I've been thinking of getting mine Fudgin' Jerry Approved.

If I did, I was only going to go for a new OT and choke, but I guess I might swing for the bias mod esp. if I can just turn it back to cold, where it was originally. As long as I can get the same warm, sweet lead tone....

Anyone get the transformer upgrades for theirs?
Should I consider the "clarity" mod? or noise reduction knob mod? I don't want to change it too much....

I love my Peavey, too, 6505+ btw. It frustrates me less than all others (Uber, XTC, VHTs, even Soldano -- call me crazy if you want) when it comes to getting a good lead tone with the same settings as my metal-ish rhythm tone. But up really LOUD, it is just a bit too bright, and there is some white noise with fast lead playing. I'd still take my stock Peavey over anything else though, except for the Mako about which I daydream.

 

[Frolid]

I've listened to a lot of 5150s and i have to say that they slayyy