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

Hello everyone, I have question that I hope some of you either can answer or have an opinion on. Ever since I was 17, I have always wanted to own Audio Research equipment. I’m 56 now, and finally was able to fulfill my life long dream. My first acquisition was an ARC LS15 pre-amp bought here used in mint condition. I paired it with a Vincent 331MK hybrid amp also bought here used in mint condition. The resulting sound was impressive. After that, I started looking for an ARC amp I could afford. The resulting search found me an ARC VS115 amp also here in used, awesome condition. This is where my problems and my doubts started. Upon hooking up the amp to my system, a tube in the left channel arced and blew a resistor. I had to take the amp to an ARC dealer and he installed a new resistor and suggested I buy all new tubes from ARC for the amp. I did and when I got back home, I again hooked up the amp and immediately upon turning the amp on, I started to hear thumping sounds coming from my left speaker, then, two left channel output tubes started to glow a very bright orange, and then white smoke started to rise from one of the tube sockets. I immediately turned the amp off. I called the dealer and he suggested I mail the unit back to ARC. I did and I am now waiting to see what they say.

During this time, I started to search out other brands and came across one called PrimaLuna. I have watched their videos and seen them compared to ARC equipment. Their build quality seems to be superior to ARC and the reviews are over the top. I am looking at their Dialogue Premium HP amp and their Dialogue Premium pre-amp. For what they cost, considering how they are built and supposedly sound compared to units costing 3 to 4 times their price, they almost seem too good to be true. Anyway, my bubble has been burst, and in simple terms, I am considering jumping ship and going with another company instead of ARC, despite all those years of drooling and waiting.

My main question is this, is there anyone out there that either owns PrimaLuna or has had experience with the equipment and can give me their opinion on owning and using it. Then, my second question is how does PrimaLuna really compare to other high end equipment such as ARC. Kevin Deal in his videos on PrimaLuna makes a very compelling case for the equipment. In one video, he compares an ARC LS17SE to the PrimaLuna pre-amp.

My last question is in regards to my ARC VS115 amp problems. Anyone have an opinion on what is going on with my amp or a VS115 in general. For those of you who want to know what else is in my system, I am using KEF 104ab speakers, a Cambridge Azur 752BD Blu-ray player as my CD player, Morrow Audio Cables and I am considering getting the Sony HAP-Z1ES music player for my digital files.

I greatly appreciate all who take the time to comment and give their opinions. I will be glad to answer any questions you may ask or provide additional. Thanks for your help. Steve.


128x128skyhawk51
upscaleaudio's avatar
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upscaleaudio
258 posts
 
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.  
 

thom_at_galibier_design's avatar
thom_at_galibier_design
724 posts
 
Hi Kevin (@upscaleaudio),

John Atwood (One Electron, Artemis Labs, etc.) has a fairly concise commentary on some of the design considerations you mention (post #2 of this thread in DIYaudio: http://www.diyaudio.com/forums/tubes-valves/132233-fixed-vs-cathode-bias.html).

I'm thinking that the hot running cathode-biased amps you've experienced were more of a design choice for maximum power than anything else.

There are certainly different issues at play with a cathode biased amp from that of fixed bias.  For example, the quality of the cathode resistor's bypass capacitor can have a noticeable effect on the amplifier's sound.  Typically (due to the required value), they're electrolytics, although bypassing them with a high quality cap can work.

I'm not arguing in favor of one technique over another, but one serendipitous attribute of cathode bias is that you might loose fewer (or no) parts if a tube shorts out (a plate or screen to cathode short).

Of course you can build protection into a fixed bias amp to address this.  I think the Prima Lunas do this.  It's a nice feature.

I think that sonic considerations for fixed/auto bias are more evident in guitar amps where the output stage is pushed very hard.  At this point, the time constant in a cathode biased amplifier (the recovery time) John refers to in his post comes into play, and cathode biased guitar amps have a slightly softer edge to them as a result.

My thinking about audio in general, is that as design architectures "mature" (move higher up the sonic food chain), their sound converges ... toward reality.

And so it goes ...

Cheers,
Thom @ Galibier Design



upscaleaudio's avatar
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upscaleaudio
258 posts
 
Hey folks I'm getting on a plane now and may be out of touch for a bit. My wife is cool and loves audio but I better be present if you know what I mean. Vacation time.
skyhawk51's avatar
skyhawk51 OP
14 posts
 
Update for everyone and a great big thanks to Kevin,
Been listening to my ARC system for awhile now and no problems to report. Sounds great. Very impressed with the low noise floor of the preamp. I can turn down the volume to zero while music is playing and the sound goes to zero. Can't hear a thing. Back when I had the Vincent amp hooked up, I could not do that. You could still hear the music a little.
In a earlier post, Kevin stated he had a PS Audio Direct Stream Digital DAC for sale. I looked into that and could not believe all the great reviews about it. Watched videos on it when it was unveiled back in 2014. Was going to purchase the Sony HAP-Z1ES but could not pass up the incredible deal Kevin had on the PS Audio DAC. I knew at some point down the road I would go with an external DAC but figured it would be awhile before I could afford that option. With the price Kevin had on the PS Audio DAC, I couldn't pass on it. Kevin was very helpful in answering all my questions which helped me decide what to do. Thanks Kevin.
Anybody out there have any experience with that DAC? Some people say it compares to the dCS line of DACs.
FYI, PS Audio is planning on coming out with a new product this Fall to go along with that DAC. It will store digital files on a SSD and come with an app for use on a tablet to manage the music. They hope to unveil it at the Rocky Mountain Audio Fest this October. No word yet on what it will go for.
crwindy
121 posts
 
Interesting to see this as I also have the Vivid 1.5 and am looking to upgrade amplifier. Presently have CARY SLI-80 Sig F1. Thinking of the Primaluna as well. Wondering if it is worth going to the Dialogue Premium HP with the standard EL34 vs the Dialogue Premium but putting in KT 150 tubes. The HP has 8 tubes, so it will be pricey when time to retube as compared to the regular premium with 4 output tubes. It does have significantly more power, and if it runs cooler, the tubes could last longer.
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