Considering switching from Audio Research to PrimaLuna, troube with VS115 amp

I caved and put the KT150s back in after just under 3 days.  It's all the loveliness of the EL34s, but at SCALE.  Everything is just "more" of what the EL34s have.  Soundstage is much much larger, bass is deeper and a little tighter.  Sparkle a little more real on cymbals.  No downside I can find, other than perhaps I'm in the first or second row of the presentation where I was more like 10th or 12th row with the EL34s, which is not a downside to me (preference), just a difference.

I caved and put the KT150s back in after just under 3 days.  It's all the loveliness of the EL34s, but at SCALE.  Everything is just "more" of what the EL34s have.  Soundstage is much much larger, bass is deeper and a little tighter.  Sparkle a little more real on cymbals.  No downside I can find, other than perhaps I'm in the first or second row of the presentation where I was more like 10th or 12th row with the EL34s, which is not a downside to me (preference), just a difference.

I think that is a perfect description.  I do worry that guys get the impression that it's a REQUIREMENT in PL gear when it's obviously not. It's not huge.  But real. I can also say that at the super low plate voltage and easy way they are biased they will go and go and go.  I run the heck out of mine and after 2 years they measure 90% of new.  One pair of 12AU7's can be similarly effective.  

fsonic, I don’t think upscale suggested buying amps by their looks. He set up a listening session comparing 2 PrimaLunas to an AR integrated that was more than twice the price of the PLs, after all. He invited everyone to attend. Those who did attend listened and selected the PrimaLunas as sounding better. A single listening session is not enough to determine which component will sound best in the long run, of course.

He also suggests that you look at build quality as part of your buying decision making process. Good advice, I think, but far from suggesting that you buy with your eyes.

Thom_mackris : I like your thinking. What’s your take on Rogers then? Cathode bias, and I suspect they run the tubes hot. Yet they say this on their website. It’s all true, except I’ve not seen a cathode bias amp with "the longest tube life". :

• Auto Bias Circuit– For long tube life and ease of operation. Self Bias circuit for adjustment free operation and longest tube life. Customer does not need to adjust tube bias. As the tubes age, they adjust for bias changes automatically. The customer can change tubes at any time or replace a single tube rather than the full set of 4 and the amp will automatically re-bias for the change.

Hi Kevin (@upscaleaudio),

The first box I look to check off when considering a product is reliability and ease of service. My earlier rant was partially based on this prerequisite. Obviously, great construction doesn’t mean you have a stable design, or good sound, but any component that doesn’t pass this test is immediately eliminated from further consideration. It’s a big trigger point for me.

For a vacuum tube product, you should be able to go to any reliable tube vendor and pick up replacements that won’t blow up your gear. Others are free to disagree.

People tend to forget that back in the day, vacuum tube gear wasn’t considered unreliable – when our “greatest generation” depended on military radios working reliably in the field because lives were at stake. Unfortunately, a segment of our industry has gone off the rails with respect to this, and it hurts all of us – the consumer as well as the manufacturer who honors this tradition.

Some manufacturers will have you believe that a component being on the knife edge of instability is an entry point into the inner sanctum of world class sound – that theirs is a finely tuned, thoroughbred circuit and this is the price of admission. My opinion about this can’t be repeated in polite company.

I haven’t had the opportunity to listen to any of Rogers’ products but it’s clear that he checks off this very important (to me) box. His thermal stress testing is impressive. One could conclude (correctly?) that his circuit designs are stable. Great engineering doesn’t necessarily mean great sound, but that’s what auditioning is about.

Of course, cathode bias means that you run a slightly higher B+ in order to achieve the same plate to cathode voltage, but it’s the quiescent current in conjunction with the plate to cathode voltage (not plate to ground voltage, which includes the voltage drop of the cathode resistor) which sets the plate dissipation of the tube. I’ve never heard anyone relate tube life to choice of biasing (fixed vs. cathode), but rather to operating points (plate dissipation).

This reliability pain point reminds me of a customer’s experience – something I think all too many people can’t or won’t admit to (a bit of Stockholm Syndrome, methinks) …

I had a customer who was looking to break in a Hagerman Trumpet phono stage. Jim Hagerman used to supply a small, inverse RIAA circuit that also dropped the signal by 40dB. The idea was that you could run your digital source into this small board and then into your phono stage. Playing on repeat, you could quickly log 25-50 hours on your phono stage.

He called me up to ask: “do I have to run my power amp in order to do this?” Well, his big amplifier (4 KT-88’s per side) had a penchant for blowing screen resistors, and every time he powered it up, he experienced angst. It’s that sort of thing that (in my opinion) is ruining the industry.

People shouldn’t be afraid to power up their gear. This hobby is supposed to be fun. Now, it’s my turn to start chasing kids off my lawn ;-)

Cheers,
Thom @ Galibier Design

Of course, cathode bias means that you run a slightly higher B+ in order to achieve the same plate to cathode voltage, but it’s the quiescent current in conjunction with the plate to cathode voltage (not plate to ground voltage, which includes the voltage drop of the cathode resistor) which sets the plate dissipation of the tube. I’ve never heard anyone relate tube life to choice of biasing (fixed vs. cathode), but rather to operating points (plate dissipation).

Many of the cathode bias amps I've seen come through here run hotter than hell.   I think people are attracted to them being"auto bias" when they are "self bias" and the fact that so much power goes up in heat isn't well-known.  

This come back to you statement about tube amps not being considered a problem back in the day.  Squeezing the last bit of dissipation out of a tube wasn't something that Marantz would have done in the old days.