5150/6505 Hater No More!

[harddriver]

Back in the early 90's I played the new 5150 when it came out, of course being a traditional 2203 player I never dreamed an amp could have so much gain so of course I set the gain knob to 8-9 like my marshall and of course it was Flubby bee like distortion, HATED IT!

In my current stable of modded Marshalls are ones I have built and my 1979 Splawn modded 2203, I have also played a Cameron Ocean and Jose.

Fast Forward 20 Years! I just picked up a 6505 from Mr. Shiny_Surface(Great Seller BTW). If you keep the gain set below 3-4 the amp is tight has some killer controlled feedback, killer low end and a decent clean. I could definitely gig with this and be completely happy!

With a cleanboost and judicious use of the gain knob set between 1-3 I can get some great high gain tight tones, I may do the Cam mod 10pf cap but I think the R9 mod would ruin the amp IMO.

I hear a bit more high end detail in an SLO but if you bump the presence and treble there it is a gainer SLO'ish tone.

Anyway I admit to being a former Peavey hater but no more! I have been disproved. I can see why Peavey has not messed with the 5150/6505 design for over twenty years. I have to say in retrospect it's a nice amp that stands up to the best high dollar customs IMO!

Crap now I'm looking at 6505+'s!!!

 

[needtopractice1]

Peavey is sooo underrated.

 

[Mailman1971]

Yeah when I had mine...the gain never saw its way past noon.
Thats the ticket. Turn the gain down to about 2-3 and hit it with a boost....whole new flavor.

 

[Anonymous]

posts all the way up. gain to control volume.

see what you think then.

or pres around 5-6 and post above 2....pure metal.

dont bother with the 10pf mod...it's barely noticeable. the r9 will reduce gain, but it's hard to settle on a set value. better off controlling gain with the gain knob, or a 12at7 in v1 or v5.

throw a good set of NON JJ power tubes in it, and a sovtek LPS in the PI slot, and you will have great results.

if you're going to do ANY mods, the bias mod will help you get into the classic rock territory if you wanna run your power tubes hot and be less metal, more classic.

there are some other good mods you can do too, if you know anything about amps and schems, you can come up with your own.

 

[Shiny_Surface]

Glad you're digging it, great amp series.

The only variation I haven't tried yet is the 6534+

 

[glpg80]

posts all the way up. gain to control volume.

see what you think then.

or pres around 5-6 and post above 2....pure metal.

dont bother with the 10pf mod...it's barely noticeable. the r9 will reduce gain, but it's hard to settle on a set value. better off controlling gain with the gain knob, or a 12at7 in v1 or v5.

throw a good set of NON JJ power tubes in it, and a sovtek LPS in the PI slot, and you will have great results.

if you're going to do ANY mods, the bias mod will help you get into the classic rock territory if you wanna run your power tubes hot and be less metal, more classic.

there are some other good mods you can do too, if you know anything about amps and schems, you can come up with your own.

This. All of it.

I have been playing 5150's for 8 years and he speaks the truth - they respond very well to tube changes/differences and the best part of a 5150 is the application of the volume knob. The amplifier really wakes up past 3. The bias mod is essential just for proper operation of the amplifier since it is class AB biased. The bias modification should be done regardless as you will see much improvement in cleans and more headroom for high gain territory in terms of low end response and top end detail.

 

[Buckeyedog]

What are the best speakers for these??

 

[glpg80]

They aren't speaker dependent. They will work with just about anything. Only speaker that I ever came across that did not agree with 5150's were G12-65's since they are voiced with a mid-emphasis that 5150's do not need.

 

[harddriver]

posts all the way up. gain to control volume.

see what you think then.

or pres around 5-6 and post above 2....pure metal.

dont bother with the 10pf mod...it's barely noticeable. the r9 will reduce gain, but it's hard to settle on a set value. better off controlling gain with the gain knob, or a 12at7 in v1 or v5.

throw a good set of NON JJ power tubes in it, and a sovtek LPS in the PI slot, and you will have great results.

if you're going to do ANY mods, the bias mod will help you get into the classic rock territory if you wanna run your power tubes hot and be less metal, more classic.

there are some other good mods you can do too, if you know anything about amps and schems, you can come up with your own.

Definitely going to have to try this approach! THX! for the tips!

I think the colder bias setting is intentional. In my experience 6L6, 6550 and KT88 tubes can get mushy on the lowe end is biased too hot. An EL34 tends to like a hotter bias but the low end isn't as tight as a 6L6 IMO.

 

[harddriver]

Glad you're digging it, great amp series.

The only variation I haven't tried yet is the 6534+

THX for the extra effort in packing the amp for shipping, if every seller were to pack their amps as you did there would not be so many issues with destroyed amps.

Yep digging the amp quite a bit!

 

[MississippiMetal]

Peavey set the bias intentionally cold for a couple of reasons, as told to me by a Peavey engineer. The main reason was to keep the tubes operating beyond warranty. The secondary reason was the fact that this amp was, like most modern high gain amps, designed to derive most of its tone from the preamp.
With a hotter bias, the power tubes have less clean headroom and therefore affect the overall tone to a greater degree because their signal swing is larger and THD is increased.

 

[Anonymous]

Peavey set the bias intentionally cold for a couple of reasons, as told to me by a Peavey engineer. The main reason was to keep the tubes operating beyond warranty. The secondary reason was the fact that this amp was, like most modern high gain amps, designed to derive most of its tone from the preamp.
With a hotter bias, the power tubes have less clean headroom and therefore affect the overall tone to a greater degree because their signal swing is larger and THD is increased.

this is a perfect explanation!

exactly my reasoning when i had mentioned a higher bias for classic rock/rock tones, but keeping it lower for metal.

the ONLY speaker i dont like with the 5150....the dreaded g12m70. haven't tried it with 65's.

but the g12m70.......eeeeyuck!

i mentioned jacking the post and controlling the pre for certain things.....a decent clean sound this way is one of them with a 5150.

 

[harddriver]

Is there any kind of bias adjustment on these like a bias pot or slider or are these fixed bias like Mesa Boogie does? I've never had a 5150 chassis out so sorry for the newbiness.

All my Marshall's are biased at 50% maybe 60% of plate dissipation, I'm not a big believer in the 70% rule that alot of people tout as the golden rule. Maybe EL34's but definitley not 6L6's or 6550's/KT88's as I have found over the years. A 6l6 or 6550 loses it low end definition biased hot IMO.

 

[MississippiMetal]

The 5150 II/6505+ has a bias control, however the 5150/6505 does not. It's a common mod to place a trim pot in the bias circuit. In the II/+, even though there is a control, the sweep is rather cold so a modification is necessary to allow the bias control to sweep hotter. I don't recall if the mod widens the voltage range or simply shifts it upward but I imagine it's the latter.

 

[glpg80]

Peavey set the bias intentionally cold for a couple of reasons, as told to me by a Peavey engineer. The main reason was to keep the tubes operating beyond warranty. The secondary reason was the fact that this amp was, like most modern high gain amps, designed to derive most of its tone from the preamp.
With a hotter bias, the power tubes have less clean headroom and therefore affect the overall tone to a greater degree because their signal swing is larger and THD is increased.

Bias has nothing to do with headroom and absolutely everything to do with proper operation of a class AB biased amplifier. Each set of tubes is amplifying a phase of the sine wave which the transformer converts to high current/low voltage to swing the speakers. Headroom is a function of B+ and power supply efficiency along with what tubes you're using. Colder biased tubes have crossover distortion and therefore you do not have a perfectly amplified sine wave.

Also the amplifier was fixed biased cold because that is what eddie preferred. You're forgetting this was a signature model for EVH himself. He played the amplifier at higher volumes and preferred crossover distortion in his tone. From an efficiency standpoint it has nothing at all to do with preamp voicing and everything to do with proper functionality.

The 5150 II/6505+ has a bias control, however the 5150/6505 does not. It's a common mod to place a trim pot in the bias circuit. In the II/+, even though there is a control, the sweep is rather cold so a modification is necessary to allow the bias control to sweep hotter. I don't recall if the mod widens the voltage range or simply shifts it upward but I imagine it's the latter.

Tubes are transconductance devices not voltage devices like MOSFET's. You're changing the bias current which sets the idle current draw from plate to cathode for proper modulation.

 

[MississippiMetal]

Peavey set the bias intentionally cold for a couple of reasons, as told to me by a Peavey engineer. The main reason was to keep the tubes operating beyond warranty. The secondary reason was the fact that this amp was, like most modern high gain amps, designed to derive most of its tone from the preamp.
With a hotter bias, the power tubes have less clean headroom and therefore affect the overall tone to a greater degree because their signal swing is larger and THD is increased.

Bias has nothing to do with headroom and absolutely everything to do with proper operation of a class AB biased amplifier. Each set of tubes is amplifying a phase of the sine wave which the transformer converts to high current/low voltage to swing the speakers. Headroom is a function of B+ and power supply efficiency along with what tubes you're using. Colder biased tubes have crossover distortion and therefore you do not have a perfectly amplified sine wave.

Also the amplifier was fixed biased cold because that is what eddie preferred. You're forgetting this was a signature model for EVH himself. He played the amplifier at higher volumes and preferred crossover distortion in his tone. From an efficiency standpoint it has nothing at all to do with preamp voicing and everything to do with proper functionality.

I simplified my explanation for the readers who aren't tech savvy.

Now that being said, bias DOES affect headroom. A composite load line will show you that. Bias affects everything. You know that. So why are you disputing it?

Crossover distortion is not the same as the clipping that occurs when a valve is driven past its maximum signal amplification potential. Again, something we both know.

Now with regards to the reason for it, my info came from an engineer at Peavey. I never said it was correct, but I did point out how the info made sense.

That being said, I find it difficult to imagine Eddie's personal amps were bone stock. And him preferring crossover distortion seems rather counterintuitive to his tone leading up to that point, what with all the stories of melting down power tubes and having his tech adjust the bias on the fly during shows or studio work.

The 5150 II/6505+ has a bias control, however the 5150/6505 does not. It's a common mod to place a trim pot in the bias circuit. In the II/+, even though there is a control, the sweep is rather cold so a modification is necessary to allow the bias control to sweep hotter. I don't recall if the mod widens the voltage range or simply shifts it upward but I imagine it's the latter.

Tubes are transconductance devices not voltage devices like MOSFET's. You're changing the bias current which sets the idle current draw from plate to cathode for proper modulation.

Exactly, and how do you change the current? By changing the voltage.

 

[glpg80]

I simplified my explanation for the readers who aren't tech savvy.

And you oversimplification was wrong and full of opinions which is why we are having this conversation.

Now that being said, bias DOES affect headroom. A composite load line will show you that. Bias affects everything. You know that. So why are you disputing it?

Load resistance plate to plate, meaning tubes in parallel with a load or one another, affects signal response. It does not change with bias which is nothing but a throttle of idle current draw of a tube - not a resistive or inductive property like a load. Once again it has nothing to do with the bias of the amplifier and you have nothing to prove that it does other than your own beliefs which are simply wrong. The tonal response to bias has more to do with the OT winding design, tubes used, and PT efficiency than anything else in regards to headroom.

Now with regards to the reason for it, my info came from an engineer at Peavey. I never said it was correct, but I did point out how the info made sense.

Your information came from a Technician at Peavey's repair center. James Brown was the lead design Engineer for the 5150 and is the guy you want to speak to.

Crossover distortion is not the same as the clipping that occurs when a valve is driven past its maximum signal amplification potential. Again, something we both know.

Tubes do not clip. They compress. And this is assuming your power supply can supply the plate current required.

how do you change the current? By changing the voltage.

Voltage is inversely related to current. You change current by changing resistance. Ohms law 101

 

[MississippiMetal]

Load resistance plate to plate, meaning tubes in parallel with a load or one another, affects signal response. It does not change with bias which is nothing but a throttle of idle current draw of a tube - not a resistive or inductive property like a load. Once again it has nothing to do with the bias of the amplifier and you have nothing to prove that it does other than your own beliefs which are simply wrong. The tonal response to bias has more to do with the OT winding design, tubes used, and PT efficiency than anything else in regards to headroom.






Your information came from a Technician at Peavey's repair center. James Brown was the lead design Engineer for the 5150 and is the guy you want to speak to.



Tubes do not clip. They compress. And this is assuming your power supply can supply the plate current required.


Voltage is inversely related to current. You change current by changing resistance. Ohms law 101

Im sorry but I just laughed at that entire post. Tubes don't clip? LMFAO.

 

[glpg80]

Nope. Tubes are not like their solidstate counterparts. When driven into saturation solidstate devices go into hard clipping and the transistor becomes unstable which can lead to overheating and permanent damage. When tubes are driven into saturation they naturally compress which is also understood as power tube distortion. You wont see a tube driven into hard clipping because it is a part of their imperfect design as to why they cannot be put into a state of hard clipping/saturation.

 

[Anonymous]

Is there any kind of bias adjustment on these like a bias pot or slider or are these fixed bias like Mesa Boogie does? I've never had a 5150 chassis out so sorry for the newbiness.

All my Marshall's are biased at 50% maybe 60% of plate dissipation, I'm not a big believer in the 70% rule that alot of people tout as the golden rule. Maybe EL34's but definitley not 6L6's or 6550's/KT88's as I have found over the years. A 6l6 or 6550 loses it low end definition biased hot IMO.

no, there isn't in the 5150. you'll have to install one. it's not hard.

i agree, 6L6 output tubes sound less defined and mushier when running hotter than designed, even running at 50, some start to feel mushy and sluggish to me.

you'll have PLENTY of power without the bias mod, it's just another further option one can take advantage of...that with either channel post 3 or above (providing you're 4 output tubes are running optimally) is unbearably loud for most people.

i personally LOVE mine around 3-4...it really starts to come alive.

most guitar players play amps with crossover distortion built into the circuit anyways, and most wouldn't know what it sounds like, or know how to identify it on an oscilloscope...IMHO, crossover distortion became one of those internet guitar forum techie terms that every day guitar players started throwing around not even knowing WTF they were talking about.

can it be heard? yes. depending on what you hear.

will most guitar players even hear the tonal difference (other than volume) between 11ma cold and 32 ma hot on a matched OR unmatched quad or pair of output tubes...IMHO. yes, depending on their ears. most likely, i think most guitarists actually FEEL the difference relative to playing/hearing and really dont know why or what it is...ie, people hear what they wanna hear.

i've seen people obsessing relentlessly if tubes in a matched quad are off more than 1ma, let alone the standard 5ma most quads i've seen tend to be off by right out of the package. most of these guys wanna claim to have eric johnson's ears too, but the reality is, blindfold them all, and maybe 1/100 will hear the difference in a full battery vs a dying battery...let alone the difference in output tube matching.

you can chase this rabbit down the hole as far as you'd like to go. point is, MOST people are fine throwing a boost in front of said amp and calling it a day. and theres NOTHING wrong with that.

prime example, i let my buddy a/b his bone stock, STOCK tube 5150 against my hot rodded one.

he didnt like a hot bias. he didn't like certain other mods i did compared to the stock mode settings, except the sweepable mid knob. my stock amp goes toe to toe with his stock amp though. one amp dialed dark and low end heavy on it's own, and one dialed brittle and harsh on it's own, combined to sound ginormous together.

like i said, you can chase that rabbit and argue specifics on forums forever.