Russian Tube Preamp, No Return, Here I go again

lewm,

thanks for trying to help.

yes, we did discuss substitute 6922 for 6n23p. The seller in a message about this problem said the 6n4p should not be substituted. (even though the item description on eBay mentions using 12ay7) (12ay7 can be swapped for 6072).

At this point, I am unwilling to buy and try new tubes, substitute or original.

I paid $533. total delivered including tax

seller offered me: $400. keep the unit. Noisy unit, mine $133.

IF I knew the noise was JUST tubes, then it’s a good deal, I buy substitute tubes, get lucky.

I sent the seller 3 videos: noise increases at 3 volume settings: low/med/high. both channels. noise with TT connected; Noise with nothing connected.

.........................

I asked about tube substitutes

" New message to: raketoffI

hooked it up again, phono l/r/g to unit. 3 other inputs with rca plugs. unit to amp (no open inputs). Identical hiss-prevalent noise, increases with volume, both channels.

How much do you suspect the problem is noisy tube(s)?

to be clear about substitute tubes:

1. unit has two Russian 64np. Can 12ay7 be used without modification? Can 6072 also be used without modification?

2. unit has one 6n23p. Can 6922 be used without modification? E88cc used without modification? 6dj8 used without modification?

3. unit has one 12ax7 which is easy to get here."
..........................................

Why bother trying? I can hang tough, get full $533, and probably keep the unit even then.

I looked all over, there is nothing that fits on top of my bookcase that I like, especially low price. I don't need this, never did: I just thought it was an easy way to get tubes in the office, it's compact size, it's wood sides. I still like the idea.

Sergey's response, he says NO to using substitute for 6N4P

"

Dear Elliott!

 

Suppose nothing was shaken during transportation and the preamplifier is in good working order.

Why there may be noise:

- bad connecting cable. This happens. I have a couple of factory cables that are noisy and made by myself - no noise.

- incompatibility of components, low input impedance of the power amplifier. A similar case was with one of the AT-11s sold in Russia. After connecting to another power amplifier - thanks for the sound.

- it is possible that the power supply network in your house is phoning. You have an abundance of technology there, so it is quite possible.

 

About tubes. They are very unlikely to cause noise, provided they are properly installed in their nests.

12AY7 and 6072 - CANNOT be installed instead of 6N4P.

 

6922, E88CC 6DJ8 - can be installed instead of 6N23P.

 

But it can also be assumed that some kind of contact has departed during transportation. If the noise is low frequency, maybe something has fallen off (or on the verge of it) in the power circuits.

 

What a shame I can't look at the preamplifier. As a designer, I am very worried about my work. How so - 4 pieces sent to different countries sound perfect, but with yours - such a disaster ...

Best regards,

Sergey"

I tried again: changed power cord; changed the 12ax7; found/tightened another partially loose screw on the phono card; moved to my office system; existing TT and direct to existing amp.

Worse, it now makes thumps during it's 'soft start' period, then the same noises. I'm done.

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.