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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.
128x128yuhengdu_tiger
lowrider57's avatar
lowrider57
5,417 posts
 
One pair 6SN7 are for the gain stage, the 2nd pair are the phase inverters.
Example; RCA L, R gain stage.
Raytheon L, R phase inversion (drivers for output tubes)


rodman99999
6,158 posts
 
Typically; being certain to not use the exact same tube for the first two stages (same channel) of your power amp, will provide a better presentation.     The most referred to 6SN7 comparison (http://www.dehavillandhifi.com/6sn7_vt.htm) mentions the practice of mixing things up, about three paragraphs from the bottom.     More opinions on 6SN7s, here: https://www.head-fi.org/threads/the-reference-6sn7-thread.117677/      No doubt, someone will mention the Melz tubes.     You might want to refer to this thread, regarding their noise, reliability, etc:  https://forum.audiogon.com/discussions/shootout-of-nos-6sn7-tubes?highlight=6sn7%2Bshootout    I guess they can be a nice tube, if you get lucky! 
lowrider57's avatar
lowrider57
5,417 posts
 
Use matched set of Rca, matched set Raytheon.

The input circuitry of the Renaissance Seventy/Seventy is derivative of the unique Williamson circuit, which provides pure, direct coupled, inherently balanced input amplification and phase splitting. Type 6SN7/5692 octal twin triodes do the honors.

https://skyfiaudio.com/products/vac-valve-amplification-company-renaissance-seventy-seventy-70-70-du...



yuhengdu_tiger's avatar
yuhengdu_tiger OP
87 posts
 
@lowrider57  Thanks for the helpful information. Forgive me as I don't understand all the details of the williamson circuit and I can't upload photos here. 

So basically there are four 6sn7 tubes in the front row of 70/70. Assume they are V1, V2, V3, V4 from left to right. My understanding is that V1, V2 are for channel 1, and V3, V4 are for channel 2, is that right?

My question is which ones are for gain stage and which ones are for phase inverters? ( If my above assumption is right, is v1, v3 for gain stage; v2, v4 for phase inverters ?) Thanks!  
lowrider57's avatar
lowrider57
5,417 posts
 
Correct, V1,V2 for left channel.
V3,4 for rt. channel.

Sorry, I can't help identify which is gain and which is driver. Hopefully a VAC owner will chime in.
But, designers like to keep things organised, so I would guess that the gains are V1 and V4. Or they could be V2 and V3.

Have you looked for a user manual online?

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