@yogiboy, here is the tube layout diagram from Quicksilver’s website (input tube should be the 12AX7 closest to the RCA inputs, gain tube should be the other 12AX7 and the cathode follower is the single 12AT7):
NOS Tube Recommendation for Quicksilver Phono Pre Amp
I recently upgraded from the onboard phono stage in my Technics 1500SL to an all tube Quicksilver Phono Pre Amp. I’m about half way through the 30 hour recommended break-in period and so far, there is a lot to like about this piece of gear: Much thicker/more pronounced bottom end (I’ve had to readjust the gain on my subs quite a bit) and much wider/more defined sound stage. However, because I’m also running an all tube integrated amp (Raven Audio Osprey), there is now a very noticeable "warm" coloration to the music that wasn’t there before. I don’t want to give up on my new phono stage, but it’s like I’m listening to music with a wool blanket over my speakers. I’m thinking rolling the tubes to something a little cleaner/brighter could give me the best of all worlds. There are 3 tubes in the circuit topology: 2 12AX7s (one input, one gain) and 1 12AT7 (cathode follower). I’m currently considering a matched pair of Raytheon JRP black plate 12AX7s and either an RCA or Telefunken for the cathode follower (all NOS). Any and all suggestions/inputs are very much appreciated! P.S. my speakers are Raven Audio Corvus Reference Monitors and my current cart is the always amazing Nagaoka MP-500.
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The sound issue you mention DOES sound like a loading issue which will have a much bigger impact on sound than would tube choice. The VERY long cable to your phono stage would add a lot of capacitance. The best thing is to find a way to locate the phono stage nearer to the table; a long run from the phono stage to line stage or the amp will be far less of an issue than a long run from the table to the phono stage. If you must have a long run from the turntable, you should be looking for the lowest capacitance cables and you should make sure the phono stage is not set to add anything additional. |
@larryi , I'm embarrassed that I didn't know this (I only upgraded from a vintage console ~1 year ago, so I'm still steep on the learning curve). The worst part is, my TT is only ~2 ft from the phono stage on the same rack! I was using that ridiculously long cable (originally bought for my R2R which is across the room) because the cable I ordered specifically for my new QS phono stage hasn't arrived yet (it should be here tomorrow according to USPS tracking). Last night, I took that long cable out and swapped in the 1M Raven Audio Soniquil RCA interconnect cable I was using for my Cassette deck. The sound INSTANTLY improved. A LOT. The invisible wool blanket over my speakers is gone. I'm still interested in rolling the tubes at some point, but the urgency is gone. I think I'm going to start with switching the input tube to a Raytheon/RCA 5751 with windmill getter or the GE 5751 triple mica. When I finally pull the trigger, I'll update this thread with the results, but for now, I think the problem has been resolved. Thanks again for all the help P.S. kudos for identifying the correct issue early in this thread... you had the right idea all along!! |
@onhwy61 gain (mu) is one of the differnces. there are more, and all are significant. 5751 is not a drop-in substitute for 12AX7. they are not interhangeable. any such substitutions are circuit dependent. check with the builder, manufacturer, designer to find out what substitutions are ok. |
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