High Plate Sky w/ Individual Bias pots

[talbany]

So after years of working on tube amps, I've collected a rather large stash of old vintage tubes. Some are pulls from older amps where the customer wanted new ones and just gave me the pulls, others are just singles or mismatched pairs handed to me over the years. Many of these tubes still tested strong and had some life left, but just mismatched I couldn't bring myself to just toss them,so after a recent power transformer change on my old High plate #102 I had a Z mount Peavey Power X-former sitting on the shelf I thought I would use to replace it. This gave me some extra room in the amp so just for grins I thought I would retro-fit this one with separate bias pots so I can finally use some of those older working tubes. The other good thing about it is between the individual bias pots and the PI balance I can perfectly balance the output section to the mA
So now I can finally load it up with some of these old RCA 60's Black Plate's

Anyway I thought some of you would find it interesting
Tony

[fred.violleau]

Nice work Tony! How does it sounds?

Fred.

[talbany]

Nice work Tony! How does it sounds?

Fred.

Thanks Fred!
The Vintage glass is like icing on the cake for me and the amp sounds great! It's hard to describe the differences between new production 6Ls and the old black plates you just have to play through them. Since the ODS is really a pretty simple design output tubes can make a noticeable difference in how the amp sounds (especially the clean channel).I love the sound of the vintage glass so I am really happy with the upgrade and am glad to finally get to use these old tubes

Thanks for asking!

Tony

[norburybrook]

Nice work Tony! How does it sounds?

Fred.

Thanks Fred!
The Vintage glass is like icing on the cake for me and the amp sounds great! It's hard to describe the differences between new production 6Ls and the old black plates you just have to play through them. Since the ODS is really a pretty simple design output tubes can make a noticeable difference in how the amp sounds (especially the clean channel).I love the sound of the vintage glass so I am really happy with the upgrade and am glad to finally get to use these old tubes

Thanks for asking!

Tony

thats really cool Tony. Could you describe the difference between old 6L6's and new ones? I've never had any NOS cool valves so have no epxerience in this at all. Posts like this though do get me curious


I've a few random 6L6 pulls from 80's peavey amps so I supose I could give those a go ;D for starters, I just don't know if they're worn out or not as I don't have the new ones to compare.


Marcus

[talbany]

Could you describe the difference between old 6L6's and new ones? I've never had any NOS cool valves so have no epxerience in this at all. Posts like this though do get me curious

Hey Marcus

There are many different 6L6 types designated G/GC/WGC/7581 STR's (Which I think is what you have in the Peavey) within the 6l6 family the list is too long to describe each one and would take forever to try!. I am really left to say that each type within the designation has it's own sonic footprint, as well as all the different personality, 's within the different brands of 6L6's made in a given era by a specific company mainly due to manufactures construction methods the alloys used /plate structures/envelope size/power dissipation ratings/ impedances etc etc. If you have never heard of the RCA Black Plates they are arguably some of the most revered and sought after 6L6GC ever made to date. They have a very distinct sound and were Fender's tube of choice during the grail (Blackface era) 60's time frame.If you google RCA Black plate 6l6 review's you will see what I am talking about. If you could be a little more specific on who made your Peavey tubes and I have used those tubes you mention maybe I can give you my opinion on it and how it performs in a given ODS model or generation. Sorry your question is simply to broad and impossible for me to answer!

Please let me know

Tony

[Reeltarded]

I love the short bottle 6l6s. They are my favorites of the type. They are thick and grumpy when they yell. I have GE marked RCAs in my Bandmaster ODS thing. It's extra sweet with those. I have a pair of tall Phillips white boxes super matched that sound fantastic in a Marshall thing but not as solid sounding in the OD amp. RCAs are what your ear expects if you heard enought blaring twins.

Splitting bias is a great idea for these amps even if you have close matched tubes, huh?

Cool!

[erwin_ve]

What is your opinion on these Tony?
They come from a Peavey deuce: RCA 6L6GC with a marking: 7604, surrounded with incredible dirty layers of dust.
It's interesting to see how you partially moved the PI section, no hum from that area I suppose?

[talbany]

Erwin
Those are commonly referred to as the RCA Black Plates
You can tell by the orange letters inked on the base that say RCA and the plates of the tubes are well black! I think 7604 is (i believe)the date code 1976
They are a later version but basically the same tube as what is in my shot above!..Score!

They are thick and grumpy when they yell.

Kinda like the wife

Tony

[erwin_ve]

Erwin
Those are commonly referred to as the RCA Black Plates
You can tell by the orange letters inked on the base that say RCA and the plates of the tubes are well black! I think 7604 is (i believe)the date code 1976
They are a later version but basically the same tube as what is in my shot above!..Score!

Tony

I didn't have a clue did I? thanks! They are a few years waiting as spares. Gonna pull the JJ's out and put these thick and grumpy ladies in.

[talbany]

Erwin
Those are commonly referred to as the RCA Black Plates
You can tell by the orange letters inked on the base that say RCA and the plates of the tubes are well black! I think 7604 is (i believe)the date code 1976
They are a later version but basically the same tube as what is in my shot above!..Score!

Tony

I didn't have a clue did I? thanks! They are a few years waiting as spares. Gonna pull the JJ's out and put these thick and grumpy ladies in.

Erwin
If they are any further than 10 mA apart I wouldn't use them. Immediately put them in a box and ship them to me ASAP!..

Good Luck with those old loud "grumpy tubes"

T

[martin manning]

Looks like you have four bias pots. Do you see an advantage over this vs. one for each side? Either way you balance current but still have miss-matched Gm.

[talbany]

Looks like you have four bias pots. Do you see an advantage over this vs. one for each side? Either way you balance current but still have miss-matched Gm.

Martin
I still have a pretty tight range to work with since I am feeding off 1 supply there is still some interaction between the pots. So the tubes still have to be somewhat close to pull it off.(within 10 mA) I initially thought about doing the pair but thought I would do something different and do all four. Yes I am aware of the possible transconductance inbalance and so far doesn't appear to be a big issue. (The tubes have been tested for Gm) I honestly don't really care about it

btw. The main advantage to the 4 is just I am able to balance current draw on each side perfectly.I don't know if that buys me much in the way of THD or balance or if it would be that noticeable.I would need to do a lot more real-world playing testing!


Tony

[norburybrook]

well because of this thread I've ordered direct from Russia some 6PS3-E military 6L6 NOS valves as a punt. I bought a pair for my Tweedle Dee and they sound great so thought I'd give them a shot in one of my ODS amps, probably the bluesmaster. Larry Carlton said my Blues master sounded a bit 'sterile' compared to my #102 so maybe these valves will be an interesting swap.


Anyone else tried these? there seem to be plenty around at the moment.



Marcus

[martin manning]

Yes I am aware of the possible transconductance inbalance and so far doesn't appear to be a big issue. (The tubes have been tested for Gm) I honestly don't really care about it

btw. The main advantage to the 4 is just I am able to balance current draw on each side perfectly.I don't know if that buys me much in the way of THD or balance or if it would be that noticeable.I would need to do a lot more real-world playing testing!

You can certainly match idle current exactly with one pot for each side, and of course when setting the PI trimmer you are compensating for miss-matched Gm. I just don’t know if four has any advantage over two!

[talbany]

You can certainly match idle current exactly with one pot for each side

So then the obvious advantages from this become. Increases the chances of even tube wear over time translating to longer tube life as well as the ability to compensate for current draw drift (from each tube) over time, therefore prolonging the life expectancy of the quad. Right?
Another advantage would be if for some reason I had an outright failure in 1 tube . I could technically replace that tube adjust the PI balance and be back up and running again prolonging the quad

Not sure I would do that but does make it possible

Tony