Preamp tube questions for Einstein - what is actually required?

[Ravager1663]

Hello forum,

In the past, someone who lives around the corner from me helped me with my Einstein, but I haven't received a reply.

Unfortunately, I haven't received a helpful response from BTB or Tubetown either.

I read a lot in the past weeks, and I understand a few things about electronics because it interests me a long time, but I have very little experience with tubes.

Could someone here please tell me exactly what I should order for the Einstein 100W?
Peter Diezel wrote to me saying that they currently use TungSol and TAD Redbase EL34 tubes.
However, I have a few general questions; I’d like to understand the technical logic behind which tube makes sense in which position, so I don't get confused by all the marketing labels.

So, here are my questions:

Can I order a TungSol tube for V1 that has a "selected B-side" (like the Ruby 12AX7AC5 HG+678)? And how important is this factor for the Einstein—or rather, what priority should I give it?

Is it important to use a low-noise/low-microphonics version (selected for V1) in the V2 position as well?

Does it make sense to mix tubes from different manufacturers, or is that somehow illogical from a technical perspective? Could I use a TungSol for V1, a Tubetown TT E83CC Classic (or Shuguang 12AX7B) for V2, and then a TungSol again for V3 or is mixing too much making it worse?

I have absolutely no idea about V4 and V5. If I don't really use the effects loop, do those tubes have any impact on the sound or the signal at all?

Just as a side note—something else I don't understand—is why the TAD set for the 50W Einstein recommends "only" the TAD 12AX7 Redbase Selected for V2 and V3, but the Redbase Premium Selected for V4, V5, and V6. It makes sense for V6 (the phase inverter), but I can't quite grasp why the Premium Selected version wouldn't be suitable for V2 but *is* suitable for V4 and V5. If there’s something specific to understand here, I’d really like to know.

My last point concerns the phase inverter position. Many people like the LPS type there—the Sovtek LPS, for example. That one really ought to be balanced, right?

Now, there was a thread stating that the LPS shouldn't be used as a cathode follower (i.e., in V2 or V3), and Peter wrote that it shouldn't be used as a phase inverter tube either.
On the other hand, it seems a lot of people do exactly that.

Originally, I wanted to put a Genalex CV4004 in the PI position because I’d read about it here on the forum.
They are extremely expensive, of course—and even more so if you get a balanced one.

Is it worth spending €50 on that? Can anyone confirm this tube as a good choice for V6? And how important is it for this tube—which is supposedly of such high quality anyway—to also be balanced?

Is there anyone here who really knows their stuff and can help me sort through these uncertainties and the various options? I just haven't gotten around to ordering the tubes yet because I don't have any real answers or explanations.

 

[MetalHeadMike]

You're way overthinking the tube situation. If you need them, buy whatever tubes are available in your budget. Power tubes....make sure to bias correctly...preamp tubes, any 12ax7 will be fine in any position. Are there differences between power tubes and different preamp tubes in different positions, sure, but its extremely subtle and nothing you can't get more significant change in tone by tweaking the eq knobs. A 10 band eq in the loop will yield 10x the difference any tube swap will.

 

[Ravager1663]

You're way overthinking the tube situation. If you need them, buy whatever tubes are available in your budget. Power tubes....make sure to bias correctly...preamp tubes, any 12ax7 will be fine in any position. Are there differences between power tubes and different preamp tubes in different positions, sure, but its extremely subtle and nothing you can't get more significant change in tone by tweaking the eq knobs. A 10 band eq in the loop will yield 10x the difference any tube swap will.

Thank you for the help.
Yes, you are right; I know that myself, because in the process of overthinking, I listened to the professional technician's side as well. Technically, almost all 12AX7s do have more or less the same specifications, and differences may often just result in a volume difference of 1dB or so.

On the other hand, it is a topic that, as you can read, often leads some people to dislike their amps or "fall in love".
Also, you may have your (preamp) tubes 5 to 10 years in your amp, so how could you overthink this? I know I do.

And I want to say that not one topic about tubes here resulted in the solution, where the best and least expensive price was shared and that this was the solution for the person interested in specific tubes.

But you are right; I actually shouldn't spend 5 to 10 Euros more for a Tung-Sol 12AX7 over another one. Or even more if it's a balanced one.
But I don't want to eventually dislike my amp, either and do it right, because I want to also know my amp.

 

[S̷͖͑m̵͎͂á̵̺s̸͚̈́h̴̬̑]

I use silver dragons in the preamp, not for the tone, though it is good. I use it because they have lower microphonics and this leads to clarity

 

[Ravager1663]

I use silver dragons in the preamp, not for the tone, though it is good. I use it because they have lower microphonics and this leads to clarity

Thanks for the input!
That sounds right, and many people recommend that approach, which also makes technical sense, I suppose. I am always just not sure whether one should always mention what he or she is after - whether it's the clean sounds/channels or whether I am using just the distortion/overdrive channels?!
I am actually just using heavy sounds using the third mode of channel one and the second and third mode of channel two. I know the Shuguang 12AX7B, which I think you mean with "silver dragons", delivers quite a lot. Very quiet operation and aggressive, good gain tones in lead channels. That's what I've heard/read many times now.

 

[S̷͖͑m̵͎͂á̵̺s̸͚̈́h̴̬̑]

Thanks for the input!
That sounds right, and many people recommend that approach, which also makes technical sense, I suppose. I am always just not sure whether one should always mention what he or she is after - whether it's the clean sounds/channels or whether I am using just the distortion/overdrive channels?!
I am actually just using heavy sounds using the third mode of channel one and the second and third mode of channel two. I know the Shuguang 12AX7B, which I think you mean with "silver dragons", delivers quite a lot. Very quiet operation and aggressive, good gain tones in lead channels. That's what I've heard/read many times now.

V1 is almost always going to be your first gain stage, hence why the quietest tube makes a lot of difference there. A clean channel will generally skip the first gain stage

 

[Ravager1663]

V1 is almost always going to be your first gain stage, hence why the quietest tube makes a lot of difference there. A clean channel will generally skip the first gain stage

Okay, maybe I am not understanding enough, but in the service manual, it says for the Einstein that V1 is "input stage, channel 1 mode 1 and 2" and V2 is "channel 2" and V3 = all channels. To me, it sounds like V1 is especially for the clean channel?!
Edit: a conclusion might be, or a possible explanation that Peter wrote, that the Ruby 12AX7AC 5HG+678 is a specially selected tube for the Diezel/Einstein, because its second side of the two triodes is premium-selected. So is it like that for the clean channel: the A side is skipped, and therefore the first gain stage, and that's why it uses the B-side?!?!?
I know - wild speculation here.

 

[S̷͖͑m̵͎͂á̵̺s̸͚̈́h̴̬̑]

Okay, maybe I am not understanding enough, but in the service manual, it says for the Einstein that V1 is "input stage, channel 1 mode 1 and 2" and V2 is "channel 2" and V3 = all channels. To me, it sounds like V1 is especially for the clean channel?!
Edit: a conclusion might be, or a possible explanation that Peter wrote, that the Ruby 12AX7AC 5HG+678 is a specially selected tube for the Diezel/Einstein, because its second side of the two triodes is premium-selected. So is it like that for the clean channel: the A side is skipped, and therefore the first gain stage, and that's why it uses the B-side?!?!?
I know - wild speculation here.

I still think you are overthinking it. If you bought a high gain amp for the clean, then put a 5751 or something in v1 and you will neuter the gain, or just put silver dragons accross and have a ton less hiss.

 

[Ravager1663]

Okay, thank you. You are right, of course.
As I wrote, Peter wrote to me that they are using the Tung_Sols at the moment.
I have now ordered:
V1's:
a set of two Tung-Sol V1's
1 TubeTown TT12AX7 ECC83 V1
1TubeTown TT12AX7 E83CC V1

for testing various positions:
4 Shuguang 12AX7B Standard

for the phase inverter V6:
1 Genalex CV4004 balanced
1 Sovtek 12AX7 LPS

And a Quad Tung-Sol EL34B
And a pair of KT-88 JJ's
I also have an Elmwood Moden 90 with two KT88s, which will get the remaining tubes.

 

[Music&Chaos]

Okay, thank you. You are right, of course.
As I wrote, Peter wrote to me that they are using the Tung_Sols at the moment.
I have now ordered:
V1's:
a set of two Tung-Sol V1's
1 TubeTown TT12AX7 ECC83 V1
1TubeTown TT12AX7 E83CC V1

for testing various positions:
4 Shuguang 12AX7B Standard

for the phase inverter V6:
1 Genalex CV4004 balanced
1 Sovtek 12AX7 LPS

And a Quad Tung-Sol EL34B
And a pair of KT-88 JJ's
I also have an Elmwood Moden 90 with two KT88s, which will get the remaining tubes.

As mentioned, the changes can be subtle between tube types but depending on the circuit, they can be not so subtle as well.

In yours, probably pretty negligible sound difference between manufacturers.

I personally dislike the Sovtek LPs.

I tend to prefer NOS tubes but that is its own rabbit hole.

Glad you got some new glass - it will sound killer!

 

[belensky]

I remember buying a dozen preamp tubes to make the perfect cocktail for my Herbert. I spent an evening meticulously listening to each tube and cherry-picking one for each position. Only later, after buying another Herbert, I learned that it sounded every bit as good with a random set of Shuguang, Sovtek, and whatever other tubes were in there.

Tubes definitely make a difference, but I wouldn’t sweat it too much. I’d just go with whatever is reliable and non-microphonic these days, as long as it’s not JJ, which are way too dark. If Peter says Tung-Sols are good, that’s it. I actually liked them a lot as well. They have some upper-mid bite that works really well with the darker Diezel voicing.

Also, some amps are definitely more picky when it comes to tubes. My Rectifier loves a particular set of tubes, whereas Diezel, at least the Herbert, sounds fine with whatever.

P.S. 12AX7 Genalexe I tried sounded killer, but I didn’t manage to find one with low enough microphonics. Their KT77s are amazing tubes, though, and much more reliable than the JJ KT77s, which failed on me every 6 months to a year.

 

[tricalibur]

Ive had a lot of issues in the preamp of my Einstein. So I don’t think it’s a bad idea to “overthink” a bit with this particular amp. I was told by a reputable amp tech and industry builder/designer that the preamp in Diezels run higher than normal voltages, juicing the preamp tubes extra hard. I got my Einstein back in 2022 and since then Ive fried about four 12AX7’s. Two or three of them were Mullard CV4004, renowned for “robustness” and low-noise. Unfortunately, 12AX7s aren’t as cheap as they used to be. A new JJ will run you around $20 and that’s one of the most readily available and affordable brands available. So if I were you I would worry less about specific tube specs and find as many spare 12AX7-type tubes as possible for a decent price, perhaps in a lot, then roll each position testing for tone, gain and noise until you find a balanced combination you like. You’ll have some extras that way in case you start hearing symptoms of preamp tube failure. I should also admit I tend to run very high gain and volume with all my amps, which shortens tube life. Good luck. Fantastic sounding amps, especially for the money.

 

[belensky]

Blowing through so many preamp tubes shouldn't be normal—maybe there's something going on inside the amp. The Einstein is approaching 20 years old by now, so it might be time for a thorough maintenance inspection. I just replaced all the filter caps in my 2006 and 2007 Herberts because a few were starting to die. That's totally normal, as electrolytic caps generally last 10 to 20 years depending on how often you play.

For what it's worth, I have never blown a preamp tube in a Diezel, though I've had plenty of issues with JJ power tubes. It turned out I had slightly higher mains voltage at my house—240V, sometimes even 245V, where it's supposed to be 230V—so the amp was running a bit hot. As soon as I rewired the stock 230V transformer tap to 240V, those issues completely went away.

The VH4 and Herbert plate voltages are around 480V, which is standard for high-gain amps, and I assume other Diezels are in that same range. I'm not sure about the exact preamp tube voltages—it's best to ask Peter about that—but it was never mentioned that Diezels need anything special in the preamp section, aside from low-microphonic tubes in V1 and V2, which is a standard requirement for any high-gain amp anyway.

 

[tricalibur]

Blowing through so many preamp tubes shouldn't be normal—maybe there's something going on inside the amp. The Einstein is approaching 20 years old by now, so it might be time for a thorough maintenance inspection. I just replaced all the filter caps in my 2006 and 2007 Herberts because a few were starting to die. That's totally normal, as electrolytic caps generally last 10 to 20 years depending on how often you play.

For what it's worth, I have never blown a preamp tube in a Diezel, though I've had plenty of issues with JJ power tubes. It turned out I had slightly higher mains voltage at my house—240V, sometimes even 245V, where it's supposed to be 230V—so the amp was running a bit hot. As soon as I rewired the stock 230V transformer tap to 240V, those issues completely went away.

The VH4 and Herbert plate voltages are around 480V, which is standard for high-gain amps, and I assume other Diezels are in that same range. I'm not sure about the exact preamp tube voltages—it's best to ask Peter about that—but it was never mentioned that Diezels need anything special in the preamp section, aside from low-microphonic tubes in V1 and V2, which is a standard requirement for any high-gain amp anyway.

Good advice here. Wall voltage spikes can also fry tubes. I also just recapped my 20yo Einstein and it sounds much healthier and no problems so far.