6N23P/ECC88/E88CC/6922 tubes

spiritofmusic

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Hi y'all.

Struggling a little to get reliable versions of these tubes for my Nat Audio Utopia pre.

The stock ones are lacking, new production Tesla and Electro Harmonix are flat and lifeless.

The Siemens 6922 I tried were microphonic, and two lots of Voskhod Rockets mid 70s NOS have gone noisy within 4 wks.

I'm now trying Reflektor Silver Shields NOS.

If these fail, I'm stuck as to a way fwds.

Any input appreciated.
 

spiritofmusic

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Tbh Mark, I'm a little irritated my dealer doesnt suggest these things. Exactly what settings are these and how does one adjust them? I know you're not familiar w Nat, but what is the general protocol here?
 

Sablon Audio

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Marc, you might also want to check your wall voltage as a starting point since it could be running a fair bit over the 230v nominal spec of the amp. Then take things from there with the dealer / Nat factory. The amp might be running hot and need a different power transformer. Alternatively some of the resistors feeding the input stage may need adjusting.
 

microstrip

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Marc,

Check the filament voltage. If it is close to 6.5V you should be able to use the PCC88 . Conrad Johnson did it for the version 2 of the GAT. You can easily get good PCC88's, the demand is much lower than that for the EC88/6922.

I suppose Sablon Audio is considering that the Utopia is a power amplifier - usually much more sensitive to mains voltage value.
 

Kcin

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Mar 27, 2016
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These are not normally user adjustable settings for bias on small signal tubes. The bias and operating points are set normally with a fixed resistor.

The factory should give you a recommended tube type- perhaps they have with your "lacking" comment above.

The EH variants and the Voskhod are not real 6922s but are tougher. If you are eating through those there is not much you can do. If you don't like the sound then you will have live with constant replacements of expensive NOS- Early edition CJ GATs and certainly ,Audiblie Illusions pre amps, for example, were/are known tube eaters.

Bias set high =often sounds good but unfortunately turns the pre into meltdown for this tube type. Checking your incoming voltage is a good start. Try at different times of day for the inquiry. Of course, good mfrs. account for this in their regulation of the operating B+ and heater voltages- but some do not employ regulation.

Failing that send it in. If it is ok then they may re-set the operating points with fixed resistors- be aware it will sound different- or you will have to live with "lacking" tubes that are tougher.

The ECC88/6922 is a tough one I have got hundreds of different types and they all sound different. Some are inherently noisey its good when you find one that works- ususally those are expensive now a days. If you can find a Amperex PQ or USN try those. I also found the late 70's,early 80's Siemens to be microphonic although I like the ECC83- very telefunken like.

You can try some 7dj8's or 7v filiment types they may be tougher and you may or may not like the sound. Frankly, if the the Vokhods dont work then these may not either- worth a try.


Good Luck.
 
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bazelio

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Amperex PQ 7308/6922 are warm though. I have several that you can try and buy if you happen to like them.

If you like lively sound, try Mazda 7308. Slightly sweet and great dynamics. If the preamp puts two tubes in series, Mullard 6922 with Mazda 7308 is a great combo. Both are great tubes and they compliment one another.
 
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spiritofmusic

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Well, the factory are of minimal help (lack of English), and my dealer is not massively open to alternate solutions. The 220V versus much higher user voltage may well be critical. I'll investigate as many suggestions as I can. I do know that by definition I shouldn't have chewed thru two sets of Voskhods, let alone one. Let's see where the Reflektor Silver Shields take me.

If this cannot be remedied, and an engineer cannot help me, I may be forced to go for an alternative like LTA MicroZotl, Java LDR or TMayer 10Y.
 

Sablon Audio

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I suppose Sablon Audio is considering that the Utopia is a power amplifier - usually much more sensitive to mains voltage value.

Micro, we have an unusual situation in UK where the standard wall voltage is 240v though in rural locations it may actually hit 253v. The EU simply averaged our 240v with the 220v in many European countries to arrive at the notional 230v standard. Depending on exact specification of the power transformers used by equipment manufacturers it is quite easy for them to be optimised at less than 230v and the circuit could potentially be running @10% ‘hot’.

You are right however that I confused pre and power amps,
 

spiritofmusic

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Mark, as you say, I'll check voltage at my distribution block. I'm assuming that it will be close to 230V, because my BPT dealt w my 245-255V nominal in London, wrangling it to 230-233V. I can't imagine it wouldn't be doing the same thing here.
 

spiritofmusic

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Jun 13, 2013
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Amperex PQ 7308/6922 are warm though. I have several that you can try and buy if you happen to like them.

If you like lively sound, try Mazda 7308. Slightly sweet and great dynamics. If the preamp puts two tubes in series, Mullard 6922 with Mazda 7308 is a great combo. Both are great tubes and they compliment one another.
Thanks for the offer, appreciated.
 

spiritofmusic

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They are Justin. But it's not likely they're the issue. More the Utopia tube pre.
 

bonzo75

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Mark, as you say, I'll check voltage at my distribution block. I'm assuming that it will be close to 230V, because my BPT dealt w my 245-255V nominal in London, wrangling it to 230-233V. I can't imagine it wouldn't be doing the same thing here.

I remember your dealer Peter saying that he got 245v trannies for the Nat he bought. Maybe I am mistaken but best to confirm.
 

spiritofmusic

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Hi Ked, that's good to know, thanks. I'll check. If the Utopia traffo is indeed 245V, then overdriven tubes will not be the issue.

Trying to differentially diagnose noise in amps using btwn them 4 types of tubes, 14 tubes in total, the 211s being very hard to rule out (I have no spares and no way of biasing even if I did). With the possibility this may not be a tubes issue but more the amps themselves.

Certainly if I'm even going to entertain considering horns, I need to get the Nats way quieter or think about something different.
 

bonzo75

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Think about that when you get horns.
 

spiritofmusic

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Ked, horns are a long shot for me, just aspirational atm. And abs no go if I can't sort my noise issue out. Unfortunately it's a long slog getting to the bottom of this. Fortunately there are "manageable" alternatives like Thomas Mayer 10Y/46 stereo, Java LDR or LTA MicroZotl MZ3 pre/1W integrated with Blue58 45 monos.
 

bonzo75

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Why do you want to sort out noise issue for an atm aspiration
 

spiritofmusic

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I heard the Azzolina Gran Sferas at The General's, and I know these could work for me. These were a prototype pr, so pricing would be manageable, but the need for dead silent tubes is mandatory.

And since the verdict at The General is that the Nats were second to the Mayers, it makes sense if I go true 107dB+ that I also go for low power/high quality tubes, 46, 45 or 2A3.

I've heard the Mayer 46 monos at The General and Blue58 45 monos at Barry's, both are fine pwr amps. I've also heard The General's Mayer 10Y and Barry's Java LDR, and Sound Of Tao highly recommends the LTA MicroZotl pre, so plenty of choice.

I'm just being forced a little to look beyond my Nats re lack of total silence. Manageable w c.100dB Zus, but unacceptable North of 107dB.
 

spiritofmusic

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Ked, noise is the enemy. I can handle hum from my subs. Even Barry has that in his Duos subs. And if I was listening to a constant diet of Trentmoller or Pantera my noise issue would be marginal. But I'm listening to way more delicate classical, and noise is more jarring.

It may be that I switch to an affordable silent alternative on pre like Java LDR or LTA MicroZotl MZ3, this synergises nicely w my Nat monos and Zus, and I'm done. But also I've always turned down the option of horns because the Nats are not dead silent. If I get closer to silent amps, well then horns become way more possible...
 

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