Does the VH-4 take 2 pairs of tubes or a quad?

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Mizati20

Mizati20

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Probably going to order some 6550's for my VH-4 that gets here tomorrow... was curious if it takes 2 matched pairs or a quad? Or both? I've only dealt with matched pairs for all the amps I've ever bought tubes for... or is this question redundant since technically both would work? Thanks guys!
 
Mizati20":1w26m05k said:
Probably going to order some 6550's for my VH-4 that gets here tomorrow... was curious if it takes 2 matched pairs or a quad? Or both? I've only dealt with matched pairs for all the amps I've ever bought tubes for... or is this question redundant since technically both would work? Thanks guys!
Click to expand...


edit: Quad!!

Make sure you bias your amp for the new tubes.

more info here.
http://diezel.typo3.inpublica.de/tech-corner.3.0.html
 
slyvren":1wvpszg7 said:
Mizati20":1wvpszg7 said:
Probably going to order some 6550's for my VH-4 that gets here tomorrow... was curious if it takes 2 matched pairs or a quad? Or both? I've only dealt with matched pairs for all the amps I've ever bought tubes for... or is this question redundant since technically both would work? Thanks guys!
Click to expand...


Matched pairs. A Quad would be just as fine and subjectively better. You set the bias in pairs.

Make sure you bias your amp for the new tubes.

more info here.
http://diezel.typo3.inpublica.de/tech-corner.3.0.html
Click to expand...


I think that is incorrect, You want a quartet. I have a bias rite and set the bias for all 4 tubes at one time, you cannot adjust one pair different than the other, you move the bias trimmer on the amp and it changes the bias for all tubes.
 
Sorry guys, I saw something about setting the bias for the other side. I was guessing the new amps had dual bias pots.


-editing above...
 
So there is only one bias trimmer in the VH-4? What is my DMM going to read? Is it going to read MA's for all four tubes? I'm a bit confused...
 
Matched quad for the V's. The biasing in pairs is for the VH4S (due to it being stereo) but still requires a matched quad.

V.
 
Right... so when I put the quad of EL34's in, which I would usually bias up to 60 ma for a PAIR... what is my DMM going to need to read? 120ma for all four? Is the correct or do I just do something differently...?
 
The two pairs should read about 60mA inner and 60mA outer or 60mA at the blue wire and 60mA at the yellow wire
in the first picture.

DZLOT.jpg


DZLBIAS.jpg
 
Thanks mark... so the ONE bias trimmer sets the bias for both pairs? Is that correct?
 
PaulyPanacea":17ntj0a3 said:
correct! :yes:
Click to expand...

But it will read as if I were biasing just two pairs? Meaning if my DMM reads 60ma then that's what both tube pairs are set at? so basically I just have to bias it like im biasing 1 pair? That's what I thought.




I fucking love this place :rock:
 
I get where you're coming from - why two shunt method readings if there's only one pot?

Dunno... What I do know is the numbers tend to float a fair bit. So make sure your load is solid and the amp is warmed up, and then get into it. It changes a bit from lead #1 pair to lead #2 pair. Not sure why, I just fiddled with it till it rested happily in the 70mA range last time I did it (by the way, TOTALLY up to you as to how hot you want 'em, there's enough on this topic alone here at RT it'll make yer head spin :student: ).

Peace,
V.
 
Mizati20":l1in2aww said:
PaulyPanacea":l1in2aww said:
correct! :yes:
Click to expand...

But it will read as if I were biasing just two pairs? Meaning if my DMM reads 60ma then that's what both tube pairs are set at? so basically I just have to bias it like im biasing 1 pair? That's what I thought.




I fucking love this place :rock:
Click to expand...

The two pairs are inner 2 and outer 2. They are what's called a Push-Pull power amp. When you buy a quad of matched tubes you are biasing to either the inner
or outer set, but if they are matched well they should all be close in the bias they draw. You are basically checking to see how the other set is biased when you switch from the yellow OT wire or the red OT wire. If you set the inner to 60-70mA and the outer read 65-75mA, your fine. If you test one pair biased at 60-70mA and the other are reading
110-120mA, the tubes are mismatched and will not bias evenly across all four. You can lower the bias to get them in range, but it takes the other two down as well
and they would be much cooler. 5 to 10mA difference between each tube in the quad is the norm for most tube sellers. It's much easier than the old days when VH4's came with fixed resistors....

For your Herbert, each duet biases in a pair. 1/6, 2/5 and 3/4. These you have to set all at your target and re-adjust all three again. When you bias one pair it may draw more or less natural plate current than another pair so your bias can go up or down of 1/6 and 2/5 if you have a really hot drawing duet in 3/4 or another tube type.
After a few minutes of adjusting you can usually get them all to balance out at your target. It's like juggling. :D
 
The two pairs are inner 2 and outer 2. They are what's called a Push-Pull power amp. When you buy a quad of matched tubes you are biasing to either the inner
or outer set, but if they are matched well they should all be close in the bias they draw. You are basically checking to see how the other set is biased when you switch from the yellow OT wire or the red OT wire. If you set the inner to 60-70mA and the outer read 65-75mA, your fine. If you test one pair biased at 60-70mA and the other are reading
110-120mA, the tubes are mismatched and will not bias evenly across all four. You can lower the bias to get them in range, but it takes the other two down as well
and they would be much cooler. 5 to 10mA difference between each tube in the quad is the norm for most tube sellers. It's much easier than the old days when VH4's came with fixed resistors....

For your Herbert, each duet biases in a pair. 1/6, 2/5 and 3/4. These you have to set all at your target and re-adjust all three again. When you bias one pair it may draw more or less natural plate current than another pair so your bias can go up or down of 1/6 and 2/5 if you have a really hot drawing duet in 3/4 or another tube type.
After a few minutes of adjusting you can usually get them all to balance out at your target. It's like juggling. :D[/quote]


...WELL PUT!!! :thumbsup:
 
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