Preamp tube advice needed: tight and focused

[iiipopes]

The point is that the tube circuits used in the hi-fi world are often quite different than in the bass/guitar amp world. The circuitry in the hi-fi world often maximize the linearity of a tube, while the circuit in the bass/guitar amp world typically attempt to do mostly the polar opposite.

This is why conclusions can't be drawn between the two types of equipment. (I have designed in both worlds, the techniques are often really different).

Yes, but as I said above, it's not about the circuit, it is about the tubes. The OP posted that the characteristics he is looking for in a preamp tube are the same characteristics that hi-fi or audiophiles look for in tubes.

 

[ThisBass]

There are some Telefunken marked tubes that were not made by Telefunken.

True, there are some of it, and these were (mainly) made by RFT in German Democratic Republic.
It was pretty common back in the day that manufacturers "helped each other" thus there are many NOS tubes out there where the labeld "brand" does not match the origin of production.

The RFT ECC83 tubes have been proved to be high quality tubes with pretty low microphonic properties.

There is absolutely nothing wrong with RFT ECC83 tubes that are labeled as Telefunken.

 

[Inconnu]

So that suggests the circuit is fairly sensitive to the tube's characteristics. Picking a tube by how it sounds in a different circuit may not give the same results in your preamp pedal. Perhaps if you shared the exact pedal you have, someone will have experience with different tubes in it.

So, really, the only thing you can do is experiment. 12AX7, 12AU7, 12AT7, 12AY7, ECC81, ECC83, and many others all have compatible pin connections , so you can try them. Do you have a guitarist friend with a tube amp who maybe has some spare tubes to try? Or is adventurous enough to let you borrow some tubes from their amp as an experiment?

Obligatory caution: tube circuits usually involve voltages that can cause injury or even death. Tubes get dangerously hot when operating. Disconnect power and let everything cool down before swapping tubes!

The preamp is a Carl Martin Bass Drive. I happen to have a few tubes around here myself. I just tried a 12au7 (a second one, which is better than the first I tried) and got interesting result but… I’d like more room with the gain knob before the tube breaks up. I’m using high output basses and it seems the tube goes Grrr fast and I’d want it to go Brrr if it makes sense.

 

[beans-on-toast]

Speak to your tube reseller and ask for a recommendation. Tell them that you want a tube the falls into the area of late onset of distortion on the bell curve. They should know what that means.

With a high output bass you could be fighting a loosing battle because the signal can overwhelm the input and drive it into distortion. If your bass is active, some have an internal pot that lowers the circuit’s gain. That could help.

 

[ThisBass]

Another consideration on JJ (ECC83 compatible) tubes.

Once the Telefunken production of tubes was shut down, the most part of their tube machinery park was sold and shipped to Tesla.
Tesla continued to produce the famous "frame grid" Telefunken ECC803s on the old (former) Telefunken machinery, named as E83CC

JJ Electronic was founded in 1993 by Jan Jurco, using the old Tesla machinery for the manufacture of vacuum tubes.
And JJ as well continued to produce a "frame grid" ECC83 tube, named as E83CC

 

[agedhorse]

Yes, but as I said above, it's not about the circuit, it is about the tubes. The OP posted that the characteristics he is looking for in a preamp tube are the same characteristics that hi-fi or audiophiles look for in tubes.

You are missing the point. When the circuits are different, The characteristics of the differences in tubes will be different (based on the different circuits). You can’t extrapolate a tube’s difference in one circuit to another circuit.

Speak to your tube SOMMELIER and ask for a recommendation. Tell them that you want a tube the falls into the area of late onset of distortion on the bell curve. They should know what that means.

With a high output bass you could be fighting a loosing battle because the signal can overwhelm the input and drive it into distortion. If your bass is active, some have an internal pot that lowers the circuit’s gain. That could help.

I fixed it for you…

 

[iiipopes]

You are missing the point. When the circuits are different, The characteristics of the differences in tubes will be different (based on the different circuits). You can’t extrapolate a tube’s difference in one circuit to another circuit.


I fixed it for you…

I just know that due to weight, heat, expense, maintenance, no real advantage tonally anymore, and all other reasons, I gave up tube amps for bass over three decades ago when the price of re-tubing an SVT head I had at the time was the same as purchasing a new Carvin PB300 head. So I sold the SVT, purchased the Carvin, gigged with it for decades, and I still use it in my band's rehearsal hall with no repairs or modifications, only because I now go direct box to the band's PA - no bass amp on stage. For smaller gigs I have a solid state combo that sleeps peacefully in my equipment room, awakened when needed. My life has been much better, and I have had more gigs, and I have had essentially no issues with amplification equipment since I went solid state. I recommend this approach to everyone instead of chasing the tube, boutique, fx, or other dragons.

 

[Passinwind]

Yup, I mean actual tube, not a tube device. I’ve tried a different 12ax7 in a preamp pedal and it changed the sound quite a bit, I want to try to go further in that direction.

Context is everything. What preamp pedal are you using, please?

 

[rickdog]

The preamp is a Carl Martin Bass Drive. I happen to have a few tubes around here myself. I just tried a 12au7 (a second one, which is better than the first I tried) and got interesting result but… I’d like more room with the gain knob before the tube breaks up.

The manual for that unit gives me the impression it's designed to be a distortion effect. It may not be suited to provide what you are trying to get out of it. If your budget permits, consider getting something else (watch for one of the Arkham tube preamps in the classifieds). Maybe you can sell the Bass Drive to a heavy metal guitarist?

Keep experimenting with a variety of tubes. A 12AU7 seems like a reasonable choice, it has low gain. But it also has some other different characteristics and in a circuit designed for distortion, who knows what it will do? I can think of reasons it might distort more. So try going in the other direction: put in the highest-gain 12AX7 you can find and turn the Gain knob waaaay down....

 

[ThisBass]

12AU7 tubes sometimes work fine in circuits designed for 12AX7, quite often they don't.
If the difference is "clearly" noticeable/audible once there is a 12AU7 placed for 12AX7, then there is a good chance the 12AU7 does not work properly in the 12AX7 circuit in question.
If think its a good idea to look for a different (tube-)preamp.

 

[ThisBass]

@Inconnu
Honestly, to me it makes no sense to read suggestion for pricy NOS tube stuff, and just the same time (provided by other folks) read suggestions to try totally different tubes such as 12AU7, and others more.
That's a contradiction on its own as contradiction can be.

I happen to have a few tubes around here myself. I just tried a 12au7 (a second one, which is better than the first I tried)

and if you try a third 12AU7 you may get a differnt sound off of the preamp rather than with the former two ones.

It looks like as if the circuit (designed for 12AX7) does not provide consistent results with 12AU7 tubes.

and got interesting result but…

which is a good indicator that the 12AU7 does not work properly/fine in this preamp/circuit (designed for 12AX7)

I’d like more room with the gain knob before the tube breaks up.

It may happen the preamp design is not for you!

I’m using high output basses and it seems the tube goes Grrr fast

That's not uncommon with ANY kind of tubes cause the headroom at the initial input is (rather naturally) moderate if compared to todays demands (active on board EQ's).
I think you should look for a preamp with switchable -10dB level pad (level attenuator) for the input stage.
Btw. most of all preamps do have such a -10dB pad but, those pads are quite unpopular by most of all players thus rather rare players do really use it.
Most part of all players "think" the sound was noticeable better without "engaged" -10dB pad.

and I’d want it to go Brrr if it makes sense.

-10 dB pad may fix your issue

 

[ThisBass]

btw the headroom at V1 of a tube preamp isn't as big as some players might think about.
Roughly the headroom at V1 equals ~0dBu (some give or take).
With active Pickups and active on board EQ (some boost) its quite easy to gain higher levels than V1 can handle on its input.
If the level coming off of the instrument exceeds the ~0dBu input headroom of V1, the tube will begin to saturate the signal on its input rather than on its output.

Sometimes folks "try" to "gain" some additional headroom for V1 by rolling different tubes such as 12AU7 (and likely others more) were a engaged -10dB pad at the input stage may fix the issue quite easily.

 

[ThisBass]

Yes, the JJ ECC83S often seems very mid focused to me. It's so extreme that it gives me the impression of limited bandwidth. My perception is that it has slightly lower than average gain for the tube type and often seems to have kind of a gritty quality, like it's on the verge of breaking over into distortion.

Once a tube saturates in cathode/basis gain stage, about 50% of saturation and "grind" is produced on the tubes input, at the grid.
This means, 1/2 half of saturation of the voltage swing, once the tube does saturate, does "saturate" on its input rather than on its output.
Independent of "gain" of the tube, 1/2 of saturation is determained by the input headroom (negative grid voltage) of the tube circuit.

edit: "grind" is proberly mainly caused by the saturation of the input (the grid) cause it saturates "harder" than the other 1/2 of voltage swing at the output stage of the tube.

 

[Wasnex]

Once a tube saturates in cathode/basis gain stage, about 50% of saturation and "grind" is produced on the tubes input, at the grid.
This means, 1/2 half of saturation of the voltage swing, once the tube does saturate, does "saturate" on its input rather than on its output.
Independent of "gain" of the tube, 1/2 of saturation is determained by the input headroom (negative grid voltage) of the tube.

edit: "grind" is proberly mainly caused by the saturation of the input (the grid) cause it saturates "harder" than the other 1/2 of voltage swing at the output stage of the tube.

My understanding of tube theory is pretty basic. My impression is JJ ECC83s often has sort of a gritty quality with the gain well below saturation. It's sort of a weird texture the tube seems to add.

The ECC803S has what I describe as a harmonic shimmer. Sort of a glossy quality in the mids. I would not really describe this as a texture, as it seems integrated with the sound, rather than seperate.

I am sort of curious if the shimmer of the ECC803S and grit of the ECC83S are due to the same underlying process developing in a slightly different manner.

 

[ThisBass]

IMO, saturation is often hard to comprehent, even for some experts out there.
The "ears" need some time duration to recognize satuaration as saturation. The integration time to notice saturation equals (roughly) 0.2..03 sec.
Anything of saturation shorter than that will be noticed as kinda compression (at some content) and/or texture to the signal.

A tube stage does not "saturate" perfectly evenly. It may happen that saturation at the input (the grid) starts little earlier to saturate versus the tubes output, and visa versa, both with different outcome of "texture" to the tone/sound.

Actually that's at least ONE (but by far not the only one) of several reasons WHY some folks may get noticeable different tonal results when they place a 12AU7 where a 12AX7 should be.

edit:
gritty
as far as I can comprehent "gritty" as sound attribue. To my understanding "gritty" belongs to saturation territory, give or take.

 

[agedhorse]

Something else that changes how a tube may behave contrary to what "marketing" and "urban myth" might suggest is that in some circuits and in some particular loadings, when the tube is driven hard, the grid can conduct current and the tube begins to be affected by the modulation of the space charge. This is very drive circuit dependent, and can lead to some unexpected results depending on what you are expecting.

 

[Inconnu]

@Inconnu
Honestly, to me it makes no sense to read suggestion for pricy NOS tube stuff, and just the same time (provided by other folks) read suggestions to try totally different tubes such as 12AU7, and others more.
That's a contradiction on its own as contradiction can be.


and if you try a third 12AU7 you may get a differnt sound off of the preamp rather than with the former two ones.

It looks like as if the circuit (designed for 12AX7) does not provide consistent results with 12AU7 tubes.


which is a good indicator that the 12AU7 does not work properly/fine in this preamp/circuit (designed for 12AX7)


It may happen the preamp design is not for you!


That's not uncommon with ANY kind of tubes cause the headroom at the initial input is (rather naturally) moderate if compared to todays demands (active on board EQ's).
I think you should look for a preamp with switchable -10dB level pad (level attenuator) for the input stage.
Btw. most of all preamps do have such a -10dB pad but, those pads are quite unpopular by most of all players thus rather rare players do really use it.
Most part of all players "think" the sound was noticeable better without "engaged" -10dB pad.


-10 dB pad may fix your issue

Thanks for all the replies. I found a 12au7 that fits my needs.

 

[ThisBass]

Thanks for all the replies. I found a 12au7 that fits my needs.

From all what I do know with mods, and I did a lot of them, many do sound quite good instantaneoulsly for a while, yet rather less mods do sound really good in a long term view.

You'll notice in the long term view if the 12AU7 really meets your sound goal.

I have got some vague idea what kind of (12AX7) circuit desin might come close to your sound goals. Obviously highish gain circuits stuff is not the road for you to go. Moderate gain structure yet some tubish "texture" if wanted (controlled with the gain knob) might be the way to go for you.

 

[ThisBass]

JJ Electronic was founded in 1993 by Jan Jurco, using the old Tesla machinery for the manufacture of vacuum tubes.
And JJ as well continued to produce a "frame grid" ECC83 tube, named as E83CC

I think I have to ad some supplement about the JJ frame grid tubes.
A while a ago JJ did a short production run of frame grid tubes labeled as E83CC. This tube is not listed at the website anymore.

The frame grid tube that is still in production by JJ, and still produced on the "oldish" TFK machinery is
JJ ECC83s

Feel free ro ask a question to JJ directly in this regard.

At least it makes me very wonder WHY some folks spend extremely lots of money for NOS TFK ECC803s tubes while very close high quality and specs is available for a couple of bugs.

 

[Wasnex]

I think I have to ad some supplement about the JJ frame grid tubes.
A while a ago JJ did a short production run of frame grid tubes labeled as E83CC. This tube is not listed at the website anymore.

The frame grid tube that is still in production by JJ, and still produced on the "oldish" TFK machinery is
JJ ECC83s

Feel free ro ask a question to JJ directly in this regard.

At least it makes me very wonder WHY some folks spend lots of money for NOS TFK ECC803s tubes while very close high quality and specs is available for a couple of bugs.

Have you tried E83CC? They may be out of production, but they are still available. I was planning on eventually buying a few just out of curiosity. Guess I better not wait too long. What do they sound like (IYMO)?

The way Telefunkens ECC83 are described seems more inline with JJ ECC803S than ECC83S. However, I suspect Telefunkens have a bit more air than the JJ ECC803S.