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VAC 70/70 mk3 tube rolling question

I recently purchased a VAC 70/70 mk3 s. Where can I find more information about the tubes diagram for the amp? I know it uses two 6sn7 per channel. Are there any differences in functionality between the two 6sn7 used for each channel? For example, do I need to use a matching pair of 6sn7 per channel?

I have one matched pair of RCA red base 6sn7 and a matched pair of Raytheon vt231 6sn7. The RCA are good for lush mids with 3d soundstage and Raytheon vt231are good for speed and accuracy.

They were meant to be used for the Schiit freya plus which uses a pair of 6sn7 for output stage and another pair of 6sn7 for voltage gain stage. Now since I already get a VAC renaissance 5 preamp, I am wondering if I can use my two pairs of 6sn7 on the VAC 70/70 amp.

My question is can I use one RCA + one Rayheon vt231 for each channel of the VAC? Or should I use a matched pair of 6sn7 for each channel? What are the recommended settings?

Also, any experiences about tube rolling on the VAC 70/70 mk3 are welcome. Like which 300B amps or 6sn7 combinations give you the best results.
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roxy54's avatar
roxy54
7,684 posts
 
He has helped me many times on and off this forum, and I have the utmost respect for him as a person.
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yuhengdu_tiger OP
87 posts
 
@lowrider57  I heard back from Kevin this morning. Actually it is V1 and V4 are drivers and V2 V3 are phase splitters. Here is Kevin's response:


"Yes, it is perfectly fine to mix brands of 6SN7. In your scenario, use one brand for the V1x positions, and the other for the V2x positions.

Technically, 6SN7 GTA or GTB types should be used, but we have not heard of any significant problems with earlier NOS version, although they do have lower maximum ratings.

With respect to matching, when operating the 70/70 with zero negative feedback, matching the gains of the tubes between the left and right channels helps to keep the center image centered. Section matching within each V2x tube is desirable but not highly critical."

Anyone needs the diagram he send me, I can also email to you if needed. 
lowrider57's avatar
lowrider57
5,393 posts
 
Interesting and valuable info.

The RCA red base is a 5692 which requires less voltage. But it's good to hear VAC is ok with running all versions of the 6SN7.

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vineland
7 posts
 
Hi, I just received a VAC 70/70 iii, and this thread is great!

I have a question:  could I drop the Psvane CV181 T Mark ii in as driver tubes?  I have a pair of these, and I'd love to hear how they sound in place of the EH currently in there.

I don't know if they're 6SN7A, 6SN7B or something else that is 6SN7 ish - I don't want to mess up the amp, since it just came back from service.

Thanks!
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