Russian Tube Preamp, No Return, Here I go again

The seller already told you in explicit terms that the unit he is selling is not “flawless”. So you shouldn’t expect or demand flawless.

Here is a useful website: https://www.radiomuseum.org/tubes/tube_6n4p.html
From that page, you can also look up the 12AY7 and 6072.  To my eyes, the latter two should be cross-compatible with the 6N4P. (Be careful if you do your own research, because apparently there is also a Chinese 6N4P, and it is not the same as this Russian 6N4P.)  The caveat is the filament voltage.  For the 6072/12AY7, they can be run on either 6V or 12V filament supplies.  I am not sure from the information on the given website that the same is true of the 6N4P, which may require 6V.  Still, I don't see why he says you cannot use the 6072/12AY7.  The pin connections to plates, grids, and cathodes are identical to those of the 6N4P, and the electrical parameters are close enough. Ask the seller.

Somewhere much earlier in this thread, I got the impression that your preamp uses the 6N23, which is replaceable by the 6922. I don’t know about the 6N4P, without doing more research on it. Am I losing my mind, or did you once mention the 6N23? Yes, 6072 and 12AY7 are essentially different names for the exact same tube. I will look to see whether there is any evidence that the 6072 can replace the 6N4P.

https://www.head-fi.org/threads/6922-tube-review-17-top-6922-6n23p-e88cc-cca-7308-e188cc-tubes.76107...
6N23 can be replaced by 6922 or any of its congeners, and they are all over the place.  I am not at all sure that tubes are the problem, but it is not the case that the 6N23 cannot be replaced outside Russia.

Are you referring to 6N23 types?  Didn't we agree that the ubiquitous 6922 and its many congeners are substitutes for the 6N23, as per this website as well:https://www.head-fi.org/threads/6922-tube-review-17-top-6922-6n23p-e88cc-cca-7308-e188cc-tubes.761078
I don't think it is necessarily a tube problem, but if it were, then substitutes for the 6N23 are readily available everywhere.

With the chassis open to view, pick the unit up and give it a good shake. Do you see any parts moving around?  Turn it upside down; does anything hang down or fall out on the floor? I am sure the actual problem is minor and due to something having come loose or a solder joint having weakened during shipment.  If he's honest, I feel bad for the seller.

All is not lost. Broken can always be fixed.

Have you double-checked to be sure you got it right?  If so, then I would take the problem to the seller and ask him to reaffirm his instructions to you regarding tube placement.  After that doesn't lead you to a solution,  you need a good tech. 

Are you absolutely certain that you have the right tube in the right socket? Because if you have misplaced the tubes in their sockets, all bets are off, and any symptoms could be explained by that, particularly the ones you mentioned. And no, the power cord is not causing that much in the way of problems. Even if you think you installed each tube correctly, I would open the chassis and take another look at where you placed each tube in relation to the instructions you were evidently given.

We’ve been over this ground before. I convinced you that I am more invested in “vintage” than you are. I never said you shouldn’t own or like your Mc tuner/preamplifier. But a 40-50 year old piece of tube gear is likely to benefit from some new or upgraded parts, and any tube tuner of that era is likely to need re-alignment if that’s never been done during its prior life. Your visual inspection of its innards means only that it has never been on fire.

If it’s 50 years old and REALLY never been serviced, it’s broke in some way, you can be sure. At the very least it will need an alignment. Chances are it has been serviced at some point, or you would not love it so much.
Wait! Did you say your Russian preamp was delivered somewhere and now "only" needs a 120V transformer to be installed?  Where was it delivered, and who is doing that work?

Bill and Elliot, of course the pin out cannot be the same; one is an octal base and the other has 9 pins. One has a wider diameter base and thicker pins than the other. Elliot was asking about an adapter that hat I assume would solve those problems. But it’s still a bad idea because the two tubes are electrically very different. Also, he hasn’t even received the preamp yet. Wouldn’t you want to listen first before tube rolling? Filament current draw is not that different between the two and most designs have some flexibility as to current available for the filaments. But the 6922 is apt to draw a lot more plate current than would be good for a 6SN7. Also there are dozens of electrically identical or similar subs for a 6922.

In a word, don’t.

6N23 = 6922, etc. They are the same tube so far as I can tell.

Did some research for you. 6DJ8/6922 are equivalents. This is a whole family of tubes sold under different alphanumeric designations. You could hardly have a wider choice. Go to Tubes Store for example. Oy.

Elliot, you need not fret about the availability or lack of 6N23 tubes in the US or the shipping expense from Russia. I’m sure there are some very suitable substitutes that are readily available here. Moreover you have thousands of hours of listening ahead of you before you even have to solve this non-problem. That’s assuming you like the SQ of the Russian preamp. If you don’t, you’ll be selling it before the tubes wear out.

I own a BDP83SE (from the estate of a friend), an Oppo BDP105, a Sony 2400ES, and an Ayre C5Xe-mp.  These are all at least "good" CDPs, but I like the Ayre and the BDP105 best, with an edge to the Ayre.  The BDP105 and the 205 are possibly the best DVD players ever made that are not astronomically expensive. I actually hesitate to rate the Sony, as I rarely use it for listening, and my wife uses the BDP83SE for movies most of the time. The Ayre has a possible issue if you use it to feed electrically unstable downstream components.  For max audio quality, it does not have a low pass filter on its output. Thus it puts out some "noise" at very high frequencies, like 250kHz.  This only helps the audio, but it can upset any downstream components that have a tendency to oscillate. The Sony and I presume the Oppo devices do have such filters.

Thanks. Good for Elliott.

But that means it is only just cleared to leave Russia (which is ridiculous), how? By boat?  In that case, having it by your 75th may be realistic.  By air? Then maybe 2-3 weeks.

OK. I am not that, either.

Well, you don’t own it, so there is no controversy. I just said what I would do, because I am not an interior decorator.

First thing I’d do is remove the wood case. It impedes cooling. Tubes will last longer without it. Keep it for resale value.

I can lighten up on my Valium.
I don't think you have to worry a bit, if you miss out on this particular unit. There have been more than a dozen of them placed on sale, mostly on eBay, since March 10.  Check "Hi-Fi Shark".

I am having palpitations!

With no circuit upgrades, the 7C is not even “good” by today’s standards. I say this from experience, having owned and used two of them in my audio life. Lovely to look at however.

Carver is or was an interesting and very smart guy. His products are full of gimmicks. Some work to enhance SQ. Some are just sand in your eye.

Elliott, You noticed I am sure that the Luxman asking price is nearly 4X what you paid for the Russian unit.  You could buy a Marantz 7C, perhaps the king of vintage tube preamplifiers, for $3000 to $6000, too. But you would be paying for the collectibility as much as for SQ.  I'm sure the Luxman is very nice.

SA5.1 is v nice sounding.

Tubes do not inherently "hum", unless a particular tube has a defect that causes hum.  Circuits in which we place tubes can be prone to hum if not designed properly, and most commonly hum is due to grounding problems. So use whatever is the recommended substitute for the 6N4P and stop worrying about nothing.  12AY7 is also known as 6072.  Both types are thought to be excellent sounding.  Most likely the Russkies copied the 12AY7 (a classic) and re-named it the 6N4P.  Furthermore, you should have a few thousand hours of use ahead of you before you even need to think about replacing tubes.

In my opinion, that AI Modulus is a bit overpriced, as it does not include a built-in phono stage.  As such, it would not even fulfill your needs. The one worth having would be the 3A version with a phono stage designed by John Curl (if memory serves).  That one on eBay is worth a few hundred bucks, tops.  Again, in my opinion.

My statement stands as written. Why the difference between the two countries is probably explained in your post. I have had some bad experiences with merchandise coming from Canada into the US. In one case, my turntable was delivered to someone in Iowa. (I live in Maryland.)  The remedy for that was to send it back to Canada and THEN to me. One Canadian who wanted to buy something from me (the opposite direction of shipping) asked me to send it to an address in North Dakota. He planned to drive across the border to pick it up, rather than to endure the customs delays (and worse, damage sometimes).

Elliot, I'm sure you'll be fine.  But the argument regarding size puzzles me. It would seem that those domestic vintage pieces on the eBay page you cited would be about the same size as the unit you are buying.  Just saying.  A 500C chassis is larger, I grant you that.  But it's all in one and darn nice sounding if properly refurbished.

“If you want Russian get Lamm from Vladimir.” That’s pretty funny. Lamm from Vlad costs 20X or more than what E is buying. Also, I have looked inside a Lamm phono stage. While they are nicely laid out, and there is nothing unsavory about it, the parts quality is what I would  call good but not mind blowing for the amount of money you are spending. And the chassis’ are nothing to write home about. This is not at all to claim that Lamm phono stages are not excellent in sound quality.. Bling is overrated.

High Gm tubes like 5687 and 6922 types are “goofball”?

US Priority Mail has long been the best bargain available. I hope they don’t screw it up.

In support of what Chak says about expedited shipping, I have purchased various capacitors from Russian vendors on eBay.  The shipping time is very short, sometimes as little as 4-5 days.  Much faster than buying from Canada, most of the time.  I stopped using one Canadian parts supplier because customs was so slow.

Why do you wish for 12AU, T, or X7s?
6SN7s and 12AU7s don't have sufficient gain for a phono input tube but could be used elsewhere in circuit, I suppose. The Russian triodes tend to be re-makes of older very high transconductance triodes, like 5687 and 6922, etc.  Not a bad thing, IMO. I don't think tube replacement is going to be a big problem for Elliot.

What’s done is done, and I wish you the best of luck. But for $400 or $500 there is a lot of good vintage equipment that you can buy right here in the USA with known brand names and known quality. I am just saying. Not unlike the stuff you already own.