Psvane KT88 TII in MC275 MkVI

[robinmtns]

I recently started a thread here to gather any info on folks experience with Shuguang Black Treasure tubes in a MkVI. Wanted some feedback as a) the Mk IV is different than earlier re-issue MC275's and b) the only mention I had found previously on the MkVI and the Treasures was somewhat negative, implicating the Treasures with a hot tube problem and possibly a blown plate resistor. Well I didnt get any info from that thread so went back to my internet search. Did not find any more info on the Treasures but did find three reports of the Psvane TII tubes making for positive sonics and no problems in Mk VI amps.

Based on those 4 reports, I decided the smart choice was probably to go with the Psvanes for the Mk VI. Found that a US vendor (Viva Tubes in MA) was offering matched quads for $300, a price that matched or bettered the China sellers. Got Rick from Viva on the phone who is very knowledgeable and was patient in taking the time to answer my questions and concerns.

I had gotten the impression from others on this forum that higher Ip and Gm is desired. But was concerned this is what might be causing the problems in Mk VIs. Rick confirmed that in self-biasing amps such as the 275, higher Ip is not necessarily better because the self-bias function can only correct so much. The result can be tubes that draw too much current and overstress transformers and other parts (and I imagine including those plate resistors mentioned earlier). It can also result in shortened tube life. Rick pointed out he does sell high Ip tubes but they are useful not in audio, but for guitar and bass amps, where overdriving a tube is needed. He said for audio the tubes they sell range from low 30's to high 40's. He also doubted that anyone could reliably tell the difference between a tube with an Ip of low 30s and one of 50 because overall it is really a small difference. Oh and Rick told me their matched quads are matched to within 5%.

I ordered a quad and told Rick just to 'pick me out a good set'. They arrived two days ago and I now have about 6-8 hours on them. The tubes I received are (Ip/Gm) 44.7/4890; 45.1/4840; 45.4/4430; 47.1/4280.

I can only compare these Psvanes to the stock McIntosh KT88s I've had in my Mk VI since I bought it. But as soon as I fired them up, they sounded better. In the first hour or two there was a slight glaze or hardness on the upper frequencies that has all but gone away now. In my amp the 12AT7s that are driving the 88s are Brimar 6060 Yellow T tubes. The input tubes are RCA 7025s.

Now after a few hours, differences from the stock tubes are:

Tonality/Frequency Response - Biggest difference is the Psvanes show up what must have been a dip in response in the lower midrange with the stock tubes. Didnt realize it before but the Psvanes definitely are more fleshed out there and sound more real. The bass is more articulate and a bit fuller. The highs are interesting. A similar to when you remove noise, say from a power conditioner. First response is that the highs are receded. But then you realize they're all there just less noticeable less 'stuck out' and more natural. Only criticism I could have is that at their present state of burn in they are sounding a little dark. But I can easily fix that if needed with the small signal tubes upstream.

Clarity - More clear, as if distortion has been removed. Clarity presented in a very relaxed non-hyped way. And for sure not bright. Listening to rock music is esp different. No sense of 'wall of sound' or assault on your ears. Very easy to listen into, again, relaxed somehow. Listening now to old Springsteen which I never felt was very well produced. I think the Psvanes have me re-thinking that judgement! All the details are there. Most notable is the initial attack of notes esp noticeable on bass and then long trailing off sustain, esp noticeable on piano. Of course much of this varies with how the recording was produced.

Soundstage/Imaging - First thing I noticed with the Psvanes was the stage dropped back way back. While dropping back it also gave the illusion of the sounds being placed front to back. I think this is the best imaging my system has had. The imaging also now sounds full and delineated across from left to right. Before it did not sound like a continuous picture if you will. Finally, there is a greater sense of each instrument existing in a place and each place has 'space' to it and air around it.

As you might can tell, I am impressed with these tubes. If they get better from here, I will be VERY impressed. And Rick at Viva told me that they have learned to expect conservatively 7,000 hours from these tubes. If that plays out I will be even more happy!

I just checked temperature on each KT88 with an ifrared thermometer. Temps are all over the place!!!! V8 - 130F; V9 - 230F; V10 - 290F; V11 - 321F. The next day or two I will be checking the bias and readjusting if needed. Will report back if I find anything that seems off.

[dolsey01]

Thanks for the great review and the 411 on Viva Tubes. While not exactly local, they aren't too far away.

[robinmtns]

Thanks dolsey, glad I could be useful. Yeah, they must be pretty close to you. You oughta check them out. Heads up though: although they have a storefront, they aren't open on weekends. Not if I can get a good complete set of these Psvanes I'll be happy!