Forums - Phase Inverter Tubes

yostjacob

Verified Member

Posts: 31

Phase Inverter Tubes
12/28/25 at 14:25:05

The manual states the following:

UBE SUBSTITUTIONS
The 5U4 rectifiers can be replaced with 5AR4. 5U4 and 5AR4 typically give the best
performance.
The Voltage regulation tubes OA3 are used to feed the input stage of the amplifier,
and can not be changed except to another brand without changing the sound of the
amp.
The input tube (6N1P-EV) can be substituted with a 6N5P (Russian Tube) if a better
focused sound is desired with a touch less gain. Also you may use 6922, 7DJ8.
Since there are two of these 9 pin tubes on each channel, you should understand
that the rear one is almost always best served by the high current 6N1P-EV and the
front tube is the one that can be changed for different voicings.

And under specifications:
PHASE INVERTER TUBE CHOICES 6N1P

Which is unfortunate because the 6N1P is not in current production which means on a potentially arbitrarily long time frame, this tube could be hard to come by.

Are there viable current production alternatives to the 6n1p?

Or should I just rabbit hole like 8 of them now?

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CAJames

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"I've run every
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Posts: 2987

Re: Phase Inverter Tubes
Reply #1 - 12/28/25 at 15:17:19

Quote:

Posted by: yostjacob Posted on: Today at 06:25:05

...Are there viable current production alternatives to the 6n1p?

Or should I just rabbit hole like 8 of them now?

Yes the 6N1P is out of production but there are still a gazillion military surplus tubes out there, you can easily finds lots of 100+ on ebay. So they should be available for the foreseeable future, and Decware is pretty much married to them. That said, the future is unwritten and having a stash on hand is never a bad idea IMO. Steve lists the alternatives, 6922/6DJ8/ECC88 are current production, but the 6N1P is probably the best option. I don't have a Torii myself but you could look through the forums to see if others have experience with different inverter tubes.

In general I think it is good idea to have (at least) one complete set of replacement tubes on hand even it you aren't a compulsive tube roller (pass the candle

). You never know when a tube will go bad, and the best way to test for a bad tube is to swap for a new one.

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Tony Seasoned Member "Life without...music is inconceivable" A.Einsteln Posts: 836	Re: Phase Inverter Tubes Reply #2 - 12/28/25 at 15:59:19 If you start looking for a pair of 6N1P-EV, let me know as I have 4 unused tubes that I could pass along.
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yostjacob

Verified Member

Posts: 31

Re: Phase Inverter Tubes
Reply #3 - 12/28/25 at 17:05:37

Quote:

In general I think it is good idea to have (at least) one complete set of replacement tubes on hand even it you aren't a compulsive tube roller (pass the candle ). You never know when a tube will go bad, and the best way to test for a bad tube is to swap for a new one.

You make a solid point I should probably squirrel away some OA3 regulators as well.

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Lon Seasoned Member "Love without guts is worthless!" Philip K. Dick Posts: 27178	Re: Phase Inverter Tubes Reply #4 - 12/28/25 at 18:03:54 Absolutely essential to have full complements of backup tubes. (Although I have way overdone that with dozens of 6P15, 6N1P, compatible rectifiers, 12AU7, 6922, all sorts of voltage regulaton, etc. tubes. . . need to thin the herd soon).
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yostjacob

Verified Member

Posts: 31

Re: Phase Inverter Tubes
Reply #5 - 12/28/25 at 18:16:40

Yeah my rectifiers got noisy(one was very noisy, and the other was noisy when the other one wasn't noisier), and one of the regulators looks like it was on its way. The regulator was weird, it glowed brighter, and the myca plate at the top was scorched and bubbly and the reflective coating around the base was worn away. The rectifiers were noisy in relation to how much black build up was around the top.

So I ordered some PSvane 5u4g from their horizon series, replaced the regulator from Decware (I originally thought it was the noisy one since it was glowing different than hte other one). So I swapped in the spare one I have from a CSP3 I don't have connected to anything at the moment.

I considered ordering the sophia electric 274Bs, as they have a new Aqua3 which is supposed to be friendlier in decware amps, but $350 per tube seemed like a lot for a more consumable item.

When I get another bonus I may order some fancy output tubes, and put the 6ca7 that it came with in the soon to be tube drawer.

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CAJames

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Re: Phase Inverter Tubes
Reply #6 - 12/28/25 at 20:41:02

Quote:

Posted by: Lon Posted on: Today at 10:03:54

...Although I have way overdone that with dozens of 6P15, 6N1P, compatible rectifiers, 12AU7, 6922, all sorts of voltage regulaton, etc. tubes. . . need to thin the herd soon...

Yeah, people like you and me have a different "issue."

Quote:

Posted by: yostjacob Posted on: Today at 09:05:37

You make a solid point I should probably squirrel away some OA3 regulators as well.

If you're shopping for VR tubes you might consider adding 0B3s to the mix as well. Will give the amp a slightly different sound. But no pressure, just FWIW.

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[Volumio | Jay's CDT2 MRK3] -> Denafrips Terminator 2 + Gaia
Sumiko Pearwood -> Mapleknoll Athena -> Luxman SUT -> Mapletree Phono 3E
STR-1002 -> Woo WA22 -> 2x UFO25s, balanced monos
Omega SAM , Hifiman Arya, Audeze LCD-XC

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yostjacob Verified Member Posts: 31	Re: Phase Inverter Tubes Reply #7 - 12/28/25 at 21:35:23 Why not? Whats 15 volts between friends?
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