opinion of using a 6SN7 over a 12AU7 in an amp driver boards

airtime

airtime

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I'm using a VTA ST70 amp that uses the 12AU7, but I'm actually using the 12BH7's in it's place. I have to say it is a stellar performing amp. It's crisp, articulate and bass can hold its own against any SS amp.

I just want to make this perfectly clear. This amp is an amazing performer. This all has to do with MY taste and nothing to do with the amp.

However ---- my taste leans more towards a romantic fuller midrange sound signature. I've tube rolled to the point were I know it's never going to be what I want.

I'm asking this as a last ditch attempt to warm up the midrange ONLY option. Knowing that the 6SN7 is basically an earlier version of the 12AU7, is there any chance this tube would present a more "romantic fuller midrange" sound in this amp????

I'm gonna be honest. I can get the same sound, and in many cases more pleasant sound. from my SS amps.

I've also considered reverting the driver board back to original and use my 7643 driver tubes.
 
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I would guess that the 6sn7 will not sound substantially different than the 12AU7 you have right now.
Reducing the amount of global feedback may be more likely to get you there. Reducing the feedback can be done with a few cents worth of resistors, versus totally rebuilding the driver stage to run different tubes, which is likely to cost greater than $100.
 
try a 6CG7 or 6FQ7. Basically the same thing as a 6SN7 but in the smaller bottle. I'd be surprised if adapters do not exist to make it work, the only change is to the heater connections.
 
If your power transformer can handle the extra heater current , I say try it and see. Also , the 6cg7/6fq7 is another option to try .
 
trainbuftony said:
I would guess that the 6sn7 will not sound substantially different than the 12AU7 you have right now.
Reducing the amount of global feedback may be more likely to get you there. Reducing the feedback can be done with a few cents worth of resistors, versus totally rebuilding the driver stage to run different tubes, which is likely to cost greater than $100.
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I've tried tweaking the NFB several times. The sound only got muddy-ish sounding and still no midrange.
 
Are you using a preamp? SS or tube?

I'm thinking that feeding the amp a signal with a warmer midrange might be more effective.

But no harm in trying some adaptors first.
 
I have a Latino VTA ST 120. I wanted to experiment with 6SN7 tubes. I first got three tube socket converters. It seemed to work well. I then got a kit to build the VTA board using 6SN7 tubes directly. I had some trouble finding quiet 6SN7 tubes. Long story short, is that I put the 12AU7 driver board back in the amp and now I'm using RCA clear-top 12AU7's and I'm very happy. So, the experiment was interesting but ultimately served only to drain the wallet.
 
airtime said:
I'm using a VTA ST70 amp that uses the 12AU7, but I'm actually using the 12BH7's in it's place. I have to say it is a stellar performing amp. It's crisp, articulate and bass can hold its own against any SS amp.

I just want to make this perfectly clear. This amp is an amazing performer. This all has to do with MY taste and nothing to do with the amp.

However ---- my taste leans more towards a romantic fuller midrange sound signature. I've tube rolled to the point were I know it's never going to be what I want.

I'm asking this as a last ditch attempt to warm up the midrange ONLY option. Knowing that the 6SN7 is basically an earlier version of the 12AU7, is there any chance this tube would present a more "romantic fuller midrange" sound in this amp????

I'm gonna be honest. I can get the same sound, and in many cases more pleasant sound. from my SS amps.

I've also considered reverting the driver board back to original and use my 7643 driver tubes.
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Yes, I have done the direct comparison and prefer the 6SN7, even better, a pair of 6J5-GT's each of which equals exactly one half of a 6SN7 and there are adapters available on Ebay.

The best pure 6SN7 GTB's were made by Hitachi in Japan IMO and have many different labels, most common are ITT and HitRay.
Stick with black plates only.
 
6BL7, is a possibility. Looking at the Kegger sticky uptop, there is a schematic he drew up for an amp that used 2 6SN7 tubes originally and Kegger modified it to use 1 @ 6BL7, right before the final PA tubes. Post 13. If you can find some old Soviet military chrome based 6SN7s, they might work also.
 
6DZ7 said:
You are so off base with this idea of a tube, by itself, having a stronger midrange presence. Any such tube that does is faulty at best. Audio frequencies are a piece of cake for any any driver to produce uniformly. The tube manufacturer would toss to the trash any tube that tested out this way.
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I've used the same source on several other amps. So I know how my source sounds. With the amp in question, I've tried it with a SS preamp, Tubed preamp, buffer and passive line in. All produced the same thin midrange results.

I understand amps have a "sound". However, you're not understanding that this AMP IS causing some sort of distortion by wiping out the midrange.
 
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airtime said:
I've used the same source on several other amps. So I know how my source sounds. With the amp in question, I've tried it with a SS preamp, Tubed preamp, buffer and passive line in. All produced the same thin midrange results.

I understand amps have a "sound". However, you're not understanding that this AMP IS causing some sort of distortion by wiping out the midrange.
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I have 4 pairs of 6SN7 tubes and each pair has a different sound. 1 pair adds some bass, one pair is very bright with a thinner midrange while another really brings forward the midrange and vocals. I read people saying that tubes should all sound the same, they don't and these differences are not subtle. It's like saying all source masterings sounds the same.

If you have the money, I'd say it's worth trying. There are a lot of other much more expensive things people toss money at in audiophile gear.
 
Could be your speakers . you are aware the CJ preamp is phase inverting. so may try reversing your speaker leads.
 
billyz said:
Could be your speakers . you are aware the CJ preamp is phase inverting. so may try reversing your speaker leads.
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Yes, I know. I've also tried this amp with several other preamps as well as buffers and passives
 
A couple of things. You're adding almost an amp of heater current. Can the power tranny handle that without overheating? Is it an upgraded PT?

Second, IMO from long experience, the 12AU7 is not a very nice tube. It is NOT the same as a 6SN7. The only decent implementation I've heard is in the Heathkit W5 and they managed to work some magic with it in terms of operating points and harmonic complementing of the output stage. Even at that, I struggle to find a good sounding 12AU7 for my W5 clones, whereas any old 6SN7 sounds okay in my Williamsons, though I prefer some over others. I just find the 12AU7 *disappointing*.
 
6DZ7 said:
Ok, I'll keep playing the game. ... Are they all tested as fully good tubes? And more to the point in recommending someone spend money on a crapshoot based on fantasy, what should he buy? Exacly to get to his goal? Maybe he gets a set like you have that is thinner in the mids right off the bat. Then he has triple less mid output. Taste, amp problem, tube with curved frequency response. What a solution...
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All tested NOS, 2 of the sets I have were new in the box other than being tested. The 6H8C OTK tubes seem to have a flat response, I also like the early tall bottle Sylvania 6SN7.

I see people raving about how a $350 power cord transformed their amp, but you really want to go down the path that all tubes sound the same?
 
Clearly all tubes do not sound the same, but when a given tube is used in a feedback amp where the feedback loop encompasses the tube being rolled, the feedback itself tends to even out the differences--at least somewhat--depending on the amount of feedback applied.

It will be easier in my opinion to fix or adjust a given sound by rolling a tube that is not inside a feedback loop, for example a tube in a preamp that does not use feedback around the part of the circuit where the tube is being rolled, or in an SE amp with no feedback whatsoever.

That being said, I can hear slight differences in some tubes even when used in a circuit with feedback. But I really don't know if those differences are the tube itself (as in the manufacturer) or if those sonic differences are introduced because of the variability of electrical parameters between those tube samples. For example if a given tube type from manufacturer A has slightly more grid to plate capacitance than the same tube type from manufacturer B, then the way those two tubes interact with the rest of the circuit could change how the tube samples sounds--the first tube from manufacturer A perhaps rolling off the highs at a slightly lower frequency than that same tube type from manufacturer B.
 
I built the octal board for my M125’s. I used Miflex capacitors and Shuguang CV181-t (6SN7 equivalent) so it’s hard to say which is responsible for the improvement. I agree the 12au7 tube is acceptable but there are some fantastic 6SN7 tubes out there. Or you could do what I did and use Shuguang or PSVane tubes.
 
StepheK said:
I see people raving about how a $350 power cord transformed their amp, but you really want to go down the path that all tubes sound the same?
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So I should by a $350 power cord. In some forums that WOULD be the answer. Yeah, I'v seen those posts.
 
You should spend $350 On some basic test gear and stop guessing.
You need an equalizer.
That's the tool which gets the job done until you have the ability to collect some data.
 
trainbuftony said:
You should spend $350 On some basic test gear and stop guessing.
You need an equalizer.
That's the tool which gets the job done until you have the ability to collect some data.
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I have the most important test gear in the world - my own ears.
 
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