Joseph Audio Pulsars and VAC Renaissance 70/70 Mk III

Hi all,
I currently use the Pass Labs XA30.8 in combination w/ PSAudio BHK Preamp to drive the Joseph Audio Pulsars with very good success, but something about the sound of tubes that I would like to go back to.
Has anyone in this forum ever tried this combination and don't mind sharing your opinions? What do I expect to loose and gain by going to the VAC?
That combination sounds like it would be great. You had a renaissance almarg, what do you think?
Thanks, John (Roxy54) :-)

I agree that it is likely to be a great combination, assuming the amp (which may be something like 20 years old) and its tubes are in top condition. And its three output taps and six feedback settings (including zero feedback) would provide a great deal of flexibility in fine tuning the sound.

Confidence is also added by the very benign impedance characteristics of the speakers, as shown in Stereophile’s review. And while its 83.5 db measured sensitivity is about 14 db less than the sensitivity of my speakers, if the XA30.8 has been able to provide enough power for the OP’s purposes I would expect that the VAC amp would as well.

As to how the sonic character that would be provided by the VAC amp would compare with what the XA30.8 is providing, I wouldn’t want to speculate beyond stating a suspicion that it would be a bit richer sounding. While I’m now using a Pass XA25, that is a considerably different animal than the Pass .8 amps, with which I have no experience.

Finally, I’ll point out that the BHK preamp is described as being fully balanced, while providing RCA as well as XLR outputs. So I suppose a possible downside of going to the VAC amp would be that since it only provides unbalanced inputs the potential advantages of the preamp’s fully balanced design might not be entirely realized. Personally I wouldn’t be too concerned about that, as the great majority of the preamp’s fully balanced internal signal path would still be utilized, but I know that would be a consideration to some.

Good luck. Regards,

-- Al

Do you already own the VAC?  All things equal I'd rather try it with the VAC Phi 170.
A great thank to all for taking time to chime in. 
There is a 70/70 currently on AG auction list that I might give a shot if the price is fair. Talk about price, what is the fair price for one nowadays?
I've owned various tube amps from KT88 to EL34, KT120, and even KT150 but never experienced the 300b tubes as I keep hearing the magic of 300b and I don't want to miss out.
I'm aware that I might lose some sparkle and airy at the top end the PASS provides but if by a very small margin instead better mid range then that is the sacrifice that I'm willing to take.
Assuming you are referring to the listing by seller SkyFi, given the inclusion of a new set of tubes and the stated condition, as well as the seller’s extensive perfect feedback, the price is very fair. The shipping cost is also very fair, given the amp’s 100+ pound weight. If you were to wait for what would probably be a **long** time to find a unit in similar condition from a private seller who is not in the business of buying and selling audio equipment you might be able to get a somewhat lower price, but this seller’s price is certainly well within reason.

However, I would make a point of asking him if the new set of tubes was supplied by VAC, and if not what assurance there is that the 300Bs are suitable for use in this amp. 300Bs that are compliant with (or better than) the original Western Electric specifications for maximum current, voltage, and power are said to last pretty much forever in this amp (exaggerating just slightly). But those that are not compliant with those specs (and a number of currently produced 300Bs apparently are not) will suffer a very quick and probably spectacular demise. And could very well damage the amp when they fail. If the tubes were purchased from VAC, though, they should be fine.

Also, I would recommend replacing the Chinese 6SN7s with vintage tubes. Among many others I tried in my amp I had excellent results with 1950s and 1960s Sylvania and GE 6SN7GTBs, which can be had for reasonable prices. (Non-suffix vintage 6SN7s, btw, are NOT suitable for use in at least two of the four positions in this amp. I’m not sure about 6SN7GTAs).

One reason I make that suggestion is that although I’m pretty certain the tube set in my amp was purchased from VAC by the previous owner just prior to my acquisition of it, one of the Chinese 6SN7 tubes it came with abruptly developed an internal short after about two hours of use, suddenly resulting in a blood-curdling noise from one of the speakers. Fortunately I was in the room and had the amp shut down within about four seconds.

The Chinese 300B-98s that came with my amp, though, which I believe were purchased from VAC as I said, worked great throughout the seven years I owned the amp.

Good luck. Regards,
-- Al