e.oelberg

investigating the russian 6S6B-V tube
« on: June 19, 2017, 01:30:40 PM »
this is the start of a thread to cover the Russian 6S6B subminiature tube. Mainly for substituting the ac701 tube (which is just getting too expensive nowadays). Couple of folks on the forum received already some tubes others are about to do that. I start the thread with an obscurity. A  spdif driver with this particular tube for warmer sound, it is available on ebay right now, I absolutely agree with the seller, it will warm up (the tube).
http://www.ebay.com/itm/SPDIF-output-tube-stage-6S6B-for-CD-player-upgrade-marantz-CD94-philips-CD880-/172498550529

that aside the tube might be the right thing for mics, let's check it out.

Nicholas


Re: investigating the russian 6S6B-V tube
« Reply #1 on: June 19, 2017, 02:29:27 PM »
Is this  mistery Russian triode also substitute for Vf14?

e.oelberg

Re: investigating the russian 6S6B-V tube
« Reply #2 on: June 19, 2017, 02:59:41 PM »
not at all

RuudNL

Re: investigating the russian 6S6B-V tube
« Reply #3 on: June 19, 2017, 04:04:32 PM »
I did some tests yesterday, underheating the 6S6B-V.
I started with 5 volts and there was no measurable change in performance. (Not in gain, distortion and self noise.)
Even at 4 volts I did not notice any difference.
This may have a couple of advantages: if it would be possible to run the tube at 4 volts, no changes would be necessary if you replace the AC701 with a 6S6B-V.
The only thing to keep in mind, is that the heater current of the 6S6B-V is higher than an AC701. Also the amount of heat produced by the tube will be lower. In my opinion the 6S6B-V gets a lot warmer than the AC701 when operated from a voltage of 6.3 volts. And as an extra bonus, the tube will last longer.
Just some thoughts...

Edit: I just looked at the Ebay tube buffer for the SPDIF (digital!) signal.
I suppose that will make a big difference, hahahaha!!!!  ;D  ;D  ;D  ;D
« Last Edit: June 20, 2017, 02:46:36 AM by RuudNL »
There is a solution for every problem!

http://www.vansteenisaudio.nl

Ericbazaar

Re: investigating the russian 6S6B-V tube
« Reply #4 on: June 19, 2017, 04:54:13 PM »
I did some tests yesterday, underheating the 6S6B-V.
I started with 5 volts and there was no measurable change in performance. (Not in gain, distortion and self noise.)
Even at 4 volts I did not notice any difference.
This may have a couple of advantages: if it would be possible to run the tube at 4 volts, no changes would be necessary if you replace the AC701 with a 6S6B-V.
The only thing to keep in mind, is that the heater current of the 6S6B-V is higher than an AC701. Also the amount of heat produced by the tube will be lower. In my opinion the 6S6B-V gets a lot warmer than the AC701 when operated from a voltage of 6.3 volts. And as an extra bonus, the tube will last longer.
Just some thoughts...

Edit: I just looked at the Ebay tube buffer for the SPDIF (digital!) signal.
I suppose that wil make a big difference, hahahaha!!!!  ;D  ;D  ;D  ;D

That sounds interesting Ruud. What about the sound of the tube?
Hope i get my tubes this week to test it out.

Flatresponse and me count the impedance of the tube and the result is 4-6 kohms Impedance. The Haufe T8974 that we use has 1,3kohm Impedance at 1khz primary. So i think that will works fine. Hope we've count right ::)
Grosser told me: The output Impedance of the Tube must be 4 Times higher then the Input Impedance of Transformer to drive that in the right way.

That numbers let me hope.

e.oelberg

Re: investigating the russian 6S6B-V tube
« Reply #5 on: June 25, 2017, 04:27:09 PM »
just to keep everything together, here is the russian datasheet, most term should be self explanatory, nevertheless I can read cyrilic if neededhttps://wolke7.grandprixdamour.com/index.php/s/PLxV7IEA50OI3Xq

RuudNL

Re: investigating the russian 6S6B-V tube
« Reply #6 on: June 26, 2017, 05:32:52 AM »
There is a solution for every problem!

http://www.vansteenisaudio.nl

Re: investigating the russian 6S6B-V tube
« Reply #7 on: June 26, 2017, 05:43:16 AM »
I did some tests yesterday, underheating the 6S6B-V.
I started with 5 volts and there was no measurable change in performance. (Not in gain, distortion and self noise.)
Even at 4 volts I did not notice any difference.
This may have a couple of advantages: if it would be possible to run the tube at 4 volts, no changes would be necessary if you replace the AC701 with a 6S6B-V.
The only thing to keep in mind, is that the heater current of the 6S6B-V is higher than an AC701. Also the amount of heat produced by the tube will be lower. In my opinion the 6S6B-V gets a lot warmer than the AC701 when operated from a voltage of 6.3 volts. And as an extra bonus, the tube will last longer.
Just some thoughts...

Edit: I just looked at the Ebay tube buffer for the SPDIF (digital!) signal.
I suppose that will make a big difference, hahahaha!!!!  ;D  ;D  ;D  ;D

dear Ruud
be careful if you use this tube with an original neumann PSU
the heating current is twice higher
the transformer could cut , not in the beginning , but after a while

if you  hugely underheat a tube , the tube may have its cathode caked prematurely
 
the 6s6b is the 5703 equivalent , and has twice the transconductance , you may need to replace the plate resistor and the bias.

please could you post also about your feelings concerning the sound quality of this tube in the modified mic circuit ?
regards

« Last Edit: June 26, 2017, 05:59:56 AM by granger.frederic »

RuudNL

Re: investigating the russian 6S6B-V tube
« Reply #8 on: June 26, 2017, 06:44:40 AM »
I have no intention to use this tube with a Neumann power supply.
About the heater current, I already mentioned:
"The only thing to keep in mind, is that the heater current of the 6S6B-V is higher than an AC701."
So far, I have only done technical tests.
But I have very few doubts about the sound quality; Flea uses the same tube in their M49 remakes!
There is a solution for every problem!

http://www.vansteenisaudio.nl

Re: investigating the russian 6S6B-V tube New
« Reply #9 on: June 26, 2017, 09:37:12 AM »
I have no intention to use this tube with a Neumann power supply.
About the heater current, I already mentioned:
"The only thing to keep in mind, is that the heater current of the 6S6B-V is higher than an AC701."
So far, I have only done technical tests.
But I have very few doubts about the sound quality; Flea uses the same tube in their M49 remakes!

ok we agree that for a direct replacement , this tube is unsuitable if you have a neumann PSU.
what about x2 transconductance and underheating/cathode caking (BTW why underheating if the tube isn't noisy ...) ?
i would like also your feelings about the sound / a real ac701 (all equal) , not " it is used in X/Y mics thus it sounds good"
thanks again
regards
« Last Edit: June 26, 2017, 01:20:16 PM by granger.frederic »