FU-19 (FM30, 829B) Single-Ended Tube Amp!

mick wolfe · « **Reply #100 on:** 5 Mar 2025, 04:50 pm »

What looks like a "pi" symbol = N in the Cyrillic alphabet. So the tube is a 6H3N.

opnly bafld · « **Reply #101 on:** 5 Mar 2025, 06:33 pm »

Quote from: mick wolfe on 5 Mar 2025, 12:14 am

If I find a new tube tech, do you think that will magically make the Russian 6N2P(6H2pi) work in the FU29 The Russian tubes I bought won't work in the FU29 regardless of how many tube techs are brought in for consultation. Maybe another Russian variant would work with my situation being an exception to the norm, but it is what it is. Bottom line, I'm perfectly happy with the Chinese 6N2's anyway.

So are you now saying the two Russian tube designations above are different tubes and a Russian 6N2P will work fine replacing a Chinese 6N2 and the Chinese 6N2 uses pins 4 & 5 for the heater/filament just like the Russian 6N2P ?

renaudrenaud · « **Reply #102 on:** 5 Mar 2025, 09:26 pm »

So this is this one?

https://en.m.wikipedia.org/wiki/6N3P

FullRangeMan · « **Reply #103 on:** 5 Mar 2025, 09:47 pm »

Russian impulse tubes ara named ( i ) not N or И.
6H1n-Bi 0.90 USD LF Double Triode. Pulse modification
Any doubt check with Andrey at GSTube.com
https://www.gstube.com/catalog/?key=6n1p&submit=Find

From a Russian Tech book posted at DIY-Audio by an Russian engineer:
i ( И ) - pulse mode operation, anode conditions may vary radically from "normally designated" valves, always a much shorter guaranteed life in comparison to the standard type, but can be useful.

И (i) higher cathode emission for more current in pulse modes operation, anode conditions may vary radically from "normally designated" valves, always a much shorter guaranteed life in comparison to the standard type, but can be useful.

As is easy understabd on the text above impulse tubes are not intended for audio.
They have a short life and by this are cheaper than the regular version.

mick wolfe · « **Reply #104 on:** 5 Mar 2025, 11:25 pm »

Quote from: opnly bafld on 5 Mar 2025, 06:33 pm

So are you now saying the two Russian tube designations above are different tubes and a Russian 6N2P will work fine replacing a Chinese 6N2 and the Chinese 6N2 uses pins 4 & 5 for the heater/filament just like the Russian 6N2P ?

I think the Russian 6N2P and the Chinese 6N2 look to be interchangeable in most cases. Where I got into trouble was "assuming" the sellers of the FU29 (10 watt version) were totally accurate when stating that the small signal tubes included were 6N2's. This is when I decided to buy some Russian 6N2P's to try in place of what I thought were Chinese 6N2's. When Russian 6N2P's flat out didn't work in the FU29, that's when the mystery started. Then a trip out to my tube tech with both the Russian 6N2P and what I thought was a Chinese 6N2 in hand. This only to find out the two weren't even remotely close to the same type tube. Now just today with my "geezer approved" LED headlamp and a strong magnifying glass I was able to barely make out a weak stencil stating 6H3N. ( the "N" being in Cyrillic) This is something that could never be seen with the naked eye before as it was close to fading into oblivion. In the end, my bad for assuming the 6N2 was indeed the small signal tube included....which it wasn't.

mick wolfe · « **Reply #105 on:** 5 Mar 2025, 11:30 pm »

Quote from: renaudrenaud on 5 Mar 2025, 09:26 pm

So this is this one?

https://en.m.wikipedia.org/wiki/6N3P

Yes, I "think" the Russian 6N3P and my 6H3P are interchangeable.

renaudrenaud · « **Reply #106 on:** 6 Mar 2025, 06:11 am »

Was in Beijing last 10 days, waiting to go back home and listen some Russian or Chinese tubes. There was few records shops in Beijing and found some little jewels there.

renaudrenaud · « **Reply #107 on:** 6 Mar 2025, 06:13 am »

I am enjoying a lot this amp and consider this is crazy for the money.

Total regression

mick wolfe · « **Reply #108 on:** 6 Mar 2025, 06:32 pm »

Agreed. Excellent sonic results....this especially with tube friendly high efficiency speakers. Now to beat that poor dead horse one more time. If you buy one of these 829B amps, just examine and verify that the small signal tubes supplied are the tube type they're claimed to be.

Tyson · « **Reply #109 on:** 6 Mar 2025, 06:39 pm »

Can you run a 2C51 in these amps? I have a few of these in my tube stash.

Jon L · « **Reply #110 on:** 6 Mar 2025, 07:07 pm »

Quote from: Tyson on 6 Mar 2025, 06:39 pm

Can you run a 2C51 in these amps? I have a few of these in my tube stash.

2C51 can directly replace 6N3, so the amp Mick has ("10 watt amp") can use 2C51 instead of 6N3

AI answer:

"The 2C51 tube is a direct replacement for the 6N3, not the 6N2.

The 2C51 is equivalent to several other tube designations, including:

5670

396A

6N3P (Russian designation)

6H3П (Cyrillic designation)27

These tubes are all drop-in compatible despite their different names2. The 6N3P is actually a Russian copy of the American 5670 tube, which is the high-reliability version of the 2C51."

mick wolfe · « **Reply #111 on:** 6 Mar 2025, 07:09 pm »

Tyson · « **Reply #112 on:** 6 Mar 2025, 07:21 pm »

Mick, is this the amp you have?

A300

I ask because it mentions the 6N2 in the description in the ad, not the 6N3.

renaudrenaud · « **Reply #113 on:** 7 Mar 2025, 11:24 am »

Schematic says 6N3.

Tyson · « **Reply #114 on:** 7 Mar 2025, 05:32 pm »

Awesome! Order placed. Here's some tubes I have that I am really excited to try out in this amp:

GE 5670
Haltron C4013
LM Ericsson 2C51
Penta Labs 5670
Sylvania 5670
Tung Sol 2C51
Western Electric 396A

nlitworld · « **Reply #115 on:** 7 Mar 2025, 06:25 pm »

Quote from: Tyson on 7 Mar 2025, 05:32 pm

Awesome! Order placed. Here's some tubes I have that I am really excited to try out in this amp:

GE 5670
Haltron C4013
LM Ericsson 2C51
Penta Labs 5670
Sylvania 5670
Tung Sol 2C51
Western Electric 396A

Of that list, best one I've heard is the WE. Have one in my MHDT dac and it's fantastic. I keep seeing this thread pop up and telling myself to have more willpower. We'll see if (likely just how long) I hold out... Just sounds like a fun little cheap project and a gear tweaker's delight.

mick wolfe · « **Reply #116 on:** 7 Mar 2025, 06:29 pm »

Quote from: Tyson on 6 Mar 2025, 07:21 pm

Mick, is this the amp you have?

A300

I ask because it mentions the 6N2 in the description in the ad, not the 6N3.

Tyson.... The amp I bought is an FU29 A300. ( 10 watter) There is also a 30-40 watt version. All claim to use 6N2's as the small signal tube included. In fact still another version claims 6N3. All I can say is don't count on it. For all I know, I may have the only 6H3N version on the planet, but I doubt it. The only word to the wise I offer is verify what small signal tube that is actually in the amp before going on a tube rolling adventure.
Another note, just for kicks I asked the eBay seller for a quote on a second set of small signal tubes for my FU29. He came back with a quote for 6N2's. I replied that my FU29 uses 6H3N's. He replied "OK" and that was it. We shall see. FWIW, I've already bought a second pair of 6H3N's.

viggen · « **Reply #117 on:** 7 Mar 2025, 08:52 pm »

with the right adapter, the 6n3 can probably work in the flyinsky dac.

i use 396a in the flyinsky dac with a 396a to 6922 adapter.

renaudrenaud · « **Reply #118 on:** 8 Mar 2025, 11:01 am »

Quote from: mick wolfe on 6 Mar 2025, 06:32 pm

Agreed. Excellent sonic results....this especially with tube friendly high efficiency speakers.

I don't know exactly the efficiency of the speakers but 4W is enough for great pleasure with ultra cheap system.

mick wolfe · « **Reply #119 on:** 8 Mar 2025, 05:00 pm »

A DIY Lii 15 has been on my radar over the last couple years. Now I've somewhat focused on the DIY Klipsch/Ojas clone featured on drD E's site. Maybe I'm an oddity, but as I grow older, I'm more intrigued by the challenge of what can be achieved for less.( $ that is)