Pass amp vs McCormack with Silver/Gold upgrades...

Thanks John. I posted a long reply but it doesn't seem to have succeeded. In short, I read many comparisons in forums of X vs Y. These two amps seem to rarely be the less preferred in such discussions.

I have ProAc One SCs, with a Marantz 8B and CJ PV-5. I want more clarity. I have listened to my ProAcs against many other speakers at dealers and their systems were much better than mine. The ProAcs are capable of much more clarity. I thought I'd try a SS amp and new preamp. 11x12 room.

Thanks for asking.

Jim

Interesting. ProAc's are very nice speakers and your amp and preamp are legendary products. I would think the CJ is more of your problem than the amp though. CJ are known to be very musical and warm, but so are ProAc speakers and your Marantz amp. I think you have found out that too much of a good thing is not good. CJ is generally known to be warmer than the Marantz amp though. I think you'd be better off changing preamps first, but that's just my humble opinion.

I'd look for a VAC or ARC preamp. Both of those brands are much more revealing than a CJ, with perhaps the ARC being the most transparent. I have warm speakers too (Soliloquy 6.3i's) and I'm very happy with my Coda Model 11 amp and VAC Auricle preamp. I had a CJ Premier LS 16 mk II for a while, but found it to be too warm when combined with warm speakers.

Just be careful if you get a Pass or McCormack amp, as they have relatively low input impedences, which means they don't mate well with many tube preamps.

Cheers,
John

John, thanks very much. Can you educate me a bit about the impedance matching issue with mating preamps with amps?

Your system sounds really nice. I do agree the PV-5 is probably the weak link limiting clarity in my system. Uncle Stu (don't see him here but he is on that other place) has offered to turn my PV-5 into a PV-11 for a fair price. I also have been reading up on ARC, and I think an SP6, SP8, SP14, or LS5 would be great to try but as I'm pinching pennies for a land purchase they are way above my budget...they all seem to be $2K or so. Another option is one of those

I can pick up a SS amp to try a lot cheaper, even a McCormack. I'm also curious about how the bass will sound compared to my 8B. I may pick up a B&K ST-140 as a start; they are very cheap.

I may start a thread on the impedance thing, I should understand this before investing too much...

Thanks much,
Jim

Jim,

There seems to be a general rule of thumb here on the boards that a 10:1 ratio of amp to preamp is sufficient. That means that a preamp with a output impedence of 600 ohms should be fine with any amp with an input impedence of 6Kohm or higher. I don't really agree with this, I tend to think that ARC's requirements of 25 or 30:1 as a minimum is a better estimate. Meaning a preamp with an output impedence of 600 ohms should not be mated with a amp that has a input impedence of under 18K ohms. Generally the higher the ratio the better. For example, my preamp has a 600 ohm output impedence and my amp has a 50K input impedence. When you have an impedence mismatch you tend to hear it as rolled off bass and highs.

If I remember correctly, the McCormack and Pass amp have input impedence's in the 10K-20K range, which is relatively low for a power amp. Many tube amps have an input impedence of 100K-200K ohms. Tube preamps have higher output impedences than their solid state brethren. Many solid state preamps have output impedence under 100 ohms. So the danger is when you match a SS amp with a relatively low input impedence with a tube preamp with a high output impedence. I don't know what the output impedence of your CJ preamp is.

IMHO, going from a PV-5 to a PV-11 will not accomplish much, it's still a warm sounding CJ product. You seem to be looking in around the same price range that I am now in, as I paid $1125 each for my Coda Model 11 and my VAC Auricle. I have owned much more expensive gear, but these units can hang with just about any gear. The VAC is a full function preamp, so I don't need an additional phono stage. Also, I like the Coda Model 11 a lot, because after living with tube amps for a few years, I find that Class A solid state makes it the easiest to transition back to solid state gear. The best SS amps I've ever owned, Coda, Clayton Audio and Threshold, were all pure Class A designs.

Another thought is to try a used VAC Avatar Super integrated amp. Those amps are fabulous, you should be able to get one for under $3K and it will be very hard to beat for that $$$. Your speakers are a bit low on the sensitivity side, but are 8 ohm loads and you have a relatively small room, so 80 wpc of tube power should be plenty. The VAC preamp section is much faster and more transparent than a CJ preamp.

Cheers,
John

Hi John. Just to try something SS without really opening my wallet I just picked up a like-new B&K ST-140 (105w version 2). I know these are a bit weak in the bass and high end, but it will be an easily recovered data point. I waffled between that and an Aragon 2004 MkII also on Ebay but my wallet won.

The only info I can find on the CJ PV-5 output impedance is 200 ohms. The ST-140 input impedance is 24Kohms (Aragon 2004 is 22Kohms). What do you think? I have never had a SS amp aside from receivers in college.

I looked in Audiogon for an Auricle and Coda, Clayton Audio and Threshold amps. There is a Threshold (above my budget) but none of the others. The Avatar sounds very attractive...there is one but it's 4400, a bit special it seems. Moot though as the 3K is out of reach right now.

Many thanks for the thoughts. I think the first thing right now is see what SS sounds like, keeping in mind I'm at the low, low end. I understand some cap changes can alleviate the wooshy bass and rolled highs in the ST-140 and at this price point I would not be afraid to try it myself.

As mentioned I probably need to be working on the preamp instead of the amp so I'll be keeping my eye out. Should you ever decide on an upgrade on the pre, let me know. I'm curious how the Auricle sounds relative to an ARC, CJ, or Audible Illusions...

Jim