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2 matched pairs versus matched quad 6550

38.127.64.139

As NOS is starting to disappear/prices rising, I been wondering about my output tubes on hand and for future purchases.

I've been using matched 6550 Winged C quads in my ARC D70 Mk1 over the last decade or so. (No, not the same quad. I've changed several times... :)

I have one back-up set remaining.

Then I have some matched pairs only.

I know ideally one would want a matched quad, in fact even a fifth matching power tube.

But as the original ARC specifications call for matched pairs, does it make a big difference if I use two different matched pairs?

I would imagine there would be some hierarchy of preference. Such as...

- Using same brand?

- Dates?

- Same emmission. Or one pair might be at 85/85, the other 95/95?

- Other recommended specifications?

Any comments/experiences on this would be much appreciated.

Cheers!

Jonesy

"I know just enough to get into trouble. But not enough to get out of it."

Follow Ups:

Thanks Everyone! - Jonesy 20:13:10 10/07/14 (0)
Given all the comments looks like matched pairs will be fine.

Jonesy

"I know just enough to get into trouble. But not enough to get out of it."
RE: 2 matched pairs versus matched quad 6550 - Blackdog 14:48:35 10/07/14 (0)
Matched pairs will be fine since you have individual bias.
Dan Santoni
I think it would depend on whether your preamp has a balance control - Jay Buridan 08:26:38 10/07/14 (1)
e.g., the Cary SLP05 has channel balance controls, but not many preamps have this feature.
- RE: I think it would depend on whether your preamp has a balance control - Blackdog 14:43:55 10/07/14 (0)
  Makes no difference to channel balance. Output tubes do not affect channel gain
  Dan Santoni
RE: 2 matched pairs versus matched quad 6550 - truep 08:14:29 10/07/14 (0)
If the amplifier is 2 6650's per channel, you only have to a matched pair in each channel. If it's a parallel push pull, you need a matched Quad unless you can bias each tube individually.
two matched pairs should be fine - FenderLover 13:48:28 10/06/14 (0)
As long as you can adjust the bias of each pair. Independently.

IMO, current passed is the most important matching criteria. Similar subtypes. Brand. General year of production. Specific date manufactured. In that order. JMOOC.

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