salvaged PV-12
64.142.80.24 |
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| Posted on November 2, 2009 at 10:25:04 | ||
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Posts: 102
Joined: February 19, 2005 |
I thought it was time to post a little story about my recently acquired Conrad-Johnson PV-12L preamp. I had been looking at tube preamps for some time, hoping to work one into the budget at some point. I have been running a hybrid home theater/2-channel system, with a Denon 3805 AV receiver functioning as the preamp for 2-channel, into a Rogue stereo 90 tube amp and sonus faber grand piano domus speakers. I thought that replacing the Denon, for two channel, with a good preamp would possibly be a step up, although I wasn't completely sure. The Denon has a pure direct signal path, and seems pretty transparent. I had never experienced first-hand how much difference the preamp can make. I was at a local swap meet a couple months ago, and a woman had a table piled with audio components, mostly cheap HT stuff, obsolete and questionable. At the very bottom of a large pile was a Conrad-Johnson PV-12 preamp. It stood out strikingly, with its 19 inch wide enclosure and nice, simple looks. I of course was familiar with the name, but did not actually know anything about any of C-J's products. I asked the woman about it, she didn't speak much english, and she insisted I could try it out to verify it worked (she had an extension cord for power). I knew enough not to try it out, first because I could ruin something by powering it up after years of not being used, and second because how was I going to verify it worked anyway? It's not like I have an amp and speakers with me. She sold it to me for $20.00. I had no idea if it worked, what type of preamp it was. I took it home and found it was a tubed PV-12L, linestage without phono. The tubes looked OK and all parts appeared intact. I couldn't believe my good luck. The main board was fairly grimy, and it looked like it had mouse droppings in it. I considered trying to clean it, but didn't know how to do it without damaging something. I had a friend put it on his variac and slowly bring it up to power. I then tested it, and the tubes and front panel light were lit up, but no sound came out of the outputs. I contacted Conrad-Johnson and they told me they still service the PV-12 (I guess they service everything they ever built). They shipped me a new box (for a reasonable fee) and I shipped the preamp to them. C-J had the preamp for a month or so, during which time I would check in weekly to see how it was going. They were always very nice and courteous. On one call, the C-J staff person told me that the repair person had finally opened up my preamp and looked at it. He was not in that day, but had left a post-it on the preamp. He said it had two words: "cat piss?" I later learned that the diagnosis was confirmed. Also the repair person was able to clean it. A few other minor repairs (new volume control, new power cord) and they shipped it back to me. Total repair cost about $250. I think they may have replaced the tubes as well, as they look brand new. I hooked up the preamp to my Rogue, and plugged my turntable phono stage into the PV-12. Put on a record. Just amazing! I couldn't believe the difference, the level of transparency, the ability to hear the sound of the room, the improved imaging. I knew right then I was not going back to using the Denon. That was my first impression, great sound quality, air and transparency. My second impression: what happened to the bass? I realized that the bass, which had been very strong and extended, was largely missing. I had seen reviews saying the PV-12 was not strong in the bass, but I couldn't imagine it could be this bad. Then it occurred to me--I had forgotten to swap the speaker connections, and the PV-12 phase inverts. Is the phase inversion responsible for messing up the bass? I addressed that, and switched the integrated subwoofer to do phase inversion as well. However I couldn't notice much of a difference, at least not in the bass. That night I worried about this some. The next day when I went to listen again, I noticed that the bass sounded quite a bit better, fuller. Then it struck me--it's breaking in! After who knows how many years sitting unused, it probably needs to break in for some time. Indeed, each day it has been sounding better. The additional interconnects that had been sitting unused for some time probably needed to break in as well. Now, the PV-12 is sounding very good. It is extremely quiet--I cannot hear any tube sound or background noise. Combined with the Rogue amp, it packs a wallop. I really have to keep the volume level in the low range. Listening to all my music again--you know the story. The PV-12 doesn't have a headphone jack but I am able to use a record out for my Grado headphone amp. There are two features that I had expected I would need in a preamp, which the PV-12 lacks. A remote volume control would be nice, as I have a large, open house and can listen from another room easily. It can be a long walk to turn down the volume. The home theater, with it's master IR controller, has spoiled me on that. However I like the idea of an all manual 2-channel system, I tend to listen to vinyl mostly these days anyway. The other preamp feature I expected I would need was a home theater bypass, as I need to use the front speakers for the home theater. For now, I am running the home theater front channels out of the Denon into a regular line input on the PV-12. (By the way, I use phantom center, so no problem with front soundstage). This works and sounds OK (now that the bass has come back), but it does require cranking up the level on the preamp to what would be an earsplitting (and probably speaker injuring) level if the input on the preamp is changed. However the input on the preamp will not be flipped accidentally, it takes quite a bit of force to turn it. I have made a habit of turning the level all the way down before ever switching inputs. For the family, using the home theater, I just tell them not to touch the preamp and just use the Denon for everything. If this gets to be a problem I figure I can sell the PV-12 and get a newer preamp, but at this point I hope I don't have to do that. The PV-12 is so nice to listen to.
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 The cat piss tweak......................................................... - Marc Bratton 17:51:31 11/05/09
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Tube buffer - sbrians 12:53:42 11/03/09
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RE: salvaged PV-12 - DustyC 11:39:19 11/03/09
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RE: salvaged PV-12 - Palustris 10:22:51 11/03/09
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RE: salvaged PV-12 - Steelhead 20:05:22 11/02/09
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| Tube buffer, posted on November 3, 2009 at 12:53:42 | |
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Posts: 292
Joined: March 4, 2002 |
I have done the same for years - front channels of HT go through my PV-10BL.
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