6505+ Tube Question

[Loudness250]

I was thinking that those all looked like 6L6's,lol

 

[jc986]

Those are biased so cold and there's so little travel in the pot that you don't have to worry about biasing unless you do a bias mod. But as said earlier, stick to 6l6 tubes.

----TRUTH!!!----------------
-a bias mod will be a much bigger benefit to your tone than replacing those tubes...

Absolutely… Those things idle around 10 - 15 mA, it’s just crazy frigidly cold !

Actually, unless you have particularly cold tubes, the average bias range is between about 18ma - 30ma. I just changed tubes in my 6505+ and put in Mesa 6L6GC (Green rating, which is middle of the road). The trim pot's lowest setting read 18.2ma, and highest was 30.3ma.

 

[GregM]

Pics or it's a...oh, shit. I pulled my preamp tube cover to see what was going on in there and found a few Bugera 12ax7c's, a JJ ECC83s, and the rest are Ruby's. My power tubes are all Ruby. I'm probably going to grab a Tung Sol for V1 and some fresh JJ's for the rest of the preamp.

 

[Chupa.Cabra]

Doing some research I saw that you could modify the amp to use EL34 tubes but that you couldn't just mix and match them. Does anyone have any input into this? I've attached a picture for reference.

Stratman95, I see you mostly have the garden variety peanut gallery in this thread giving you all sorts of "wobbly" misinformation.

Let's cut to the chase.

First I would suggest that when you get some free time contact "Bob Pletka" of Eurotubes. You can reach Bob beginning here: https://www.eurotubes.com/store/pc/home.asp

Bob is a certified "expert" when it comes to Peavey amplification, particularly the 5150/5150II/6505+ and its ability to mix and match while swapping either EL34 & 6L6 power tubes in these amps. Or, you can mix 2-EL34 x 2-6L6 (what's known as an integrated quad) as well. Bob and I worked on the IQ configuration many years ago and it may be your cup of tea. You just need to try it out. It's a simple plug and play.

Since the 6505+ is a fixed bias amplifier (no bias adjusting capability) then in order to replace the 6L6 with an EL34 in this particular amp you need to enlist a professional amp tech who has a specialized vacuum tube measuring device such as a "Hickok". This is a device used to measure the "mutual conductance" in the test circuit and used in measuring of the amplification and dissipation of the vacuum tube. Therefore you make the 6505+ (or whatever) "think" that it's using a 6L6.

I won't go into any further detail on this here, but Bob or any one of his techs at Eurotubes will be able to walk you through your options in simple detail.

Good luck!

 

[jc986]

The 6505+ is NOT a fixed bias amplifier. There is a. Adjustable bias pot, albeit the range is limited.

 

[LP Freak]

The 6505+ is NOT a fixed bias amplifier. There is a. Adjustable bias pot, albeit the range is limited.

I contract that last statement

 

[Kordoba]

Doing some research I saw that you could modify the amp to use EL34 tubes but that you couldn't just mix and match them. Does anyone have any input into this? I've attached a picture for reference.

Stratman95, I see you mostly have the garden variety peanut gallery in this thread giving you all sorts of "wobbly" misinformation.

Let's cut to the chase.

First I would suggest that when you get some free time contact "Bob Pletka" of Eurotubes. You can reach Bob beginning here: https://www.eurotubes.com/store/pc/home.asp

Bob is a certified "expert" when it comes to Peavey amplification, particularly the 5150/5150II/6505+ and its ability to mix and match while swapping either EL34 & 6L6 power tubes in these amps. Or, you can mix 2-EL34 x 2-6L6 (what's known as an integrated quad) as well. Bob and I worked on the IQ configuration many years ago and it may be your cup of tea. You just need to try it out. It's a simple plug and play.

Since the 6505+ is a fixed bias amplifier (no bias adjusting capability) then in order to replace the 6L6 with an EL34 in this particular amp you need to enlist a professional amp tech who has a specialized vacuum tube measuring device such as a "Hickok". This is a device used to measure the "mutual conductance" in the test circuit and used in measuring of the amplification and dissipation of the vacuum tube. Therefore you make the 6505+ (or whatever) "think" that it's using a 6L6.

I won't go into any further detail on this here, but Bob or any one of his techs at Eurotubes will be able to walk you through your options in simple detail.

Good luck!

I wouldn't call it plug and play. According to the eurotubes site the 6505+ requires a split bias mod and the addition of twin bias meters to run an integrated quad that includes EL34s.

The 6505 + plug and play option is an integrated quad of 6L6 and KT66. Again, this is from the eurotubes site.

 

[FourT6and2]

The 6505+ is NOT a fixed bias amplifier. There is a. Adjustable bias pot, albeit the range is limited.

That is called fixed bias.

 

[Chupa.Cabra]

That is called fixed bias.

Dood! . . . the fix is in!

 

[Chupa.Cabra]

The 6505+ is NOT a fixed bias amplifier. There is a. Adjustable bias pot, albeit the range is limited.

You more or less made my point. Most if not all tube amplifiers have a bias-pot of some kind or another but are not meant to be used for full-range adjustments but fine tuning at the factory before shipment, +-(2|5)mA at most.

Analogy; when changing strings with a Floyd Rose tremolo system in place, you cannot simply lock the nut down prior to obtaining maximum string tension. The violin fine tuners where not designed to give the required range for this alone.

Now, can I go finish my pizza?

 

[FourT6and2]

That is called fixed bias.

Dood! . . . the fix is in!

Since the 6505+ is a fixed bias amplifier (no bias adjusting capability)...

The term "fixed bias" is a little misleading.

In a fixed bias amp, negative voltage is applied to the power tube grids and the cathode is grounded. Because the voltage applied to the grid doesn't change, the bias is “fixed." It has nothing to do with the bias setting being adjustable with a pot or not. For example, a typical Marshall with an internal bias trim pot is still a fixed bias amp because the power tubes are biased via a constant, fixed negative voltage on the grids. Conversely, in a cathode biased amp the bias will fluctuate and change as you play.

 

[Chupa.Cabra]

Since the 6505+ is a fixed bias amplifier (no bias adjusting capability)...

The term "fixed bias" is a little misleading.

NO! . . . the term is STFU!!!

Enough of your pontificating! Nobody cares. Just leave the guy alone and let him learn a little bit from guys and a guy that knows a hell of a lot more than you do about tube matching technique, bias, fixed bias, effed bias, whatever bias. I worked very closely and "learned" from the experts many years ago, Sir Sparky the 8th . . .

Buenas Noches

 

[FourT6and2]

Oooooook

 

[Chupa.Cabra]

 

[Loudness250]

The 6505+ is NOT a fixed bias amplifier. There is a. Adjustable bias pot, albeit the range is limited.

You more or less made my point. Most if not all tube amplifiers have a bias-pot of some kind or another but are not meant to be used for full-range adjustments but fine tuning at the factory before shipment, +-(2|5)mA at most.

Analogy; when changing strings with a Floyd Rose tremolo system in place, you cannot simply lock the nut down prior to obtaining maximum string tension. The violin fine tuners where not designed to give the required range for this alone.

Now, can I go finish my pizza?

A guy who posted earlier already stated that the bias sweep on a 6505 is about 12mv, not 2 or 5. He just changed his tubes, the range is from 18 to 30mv. On his 6505 that he just changed the tubes on. Read the whole thread.