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VR Tube Noise
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=6850
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Author:  gofar99 [ 08 Jul 2020, 11:09 ]
Post subject:  VR Tube Noise

Hi Everyone, Does anyone know or have done a sim of using VR tubes in sensitive audio gear. At first glance it would seem that they would have to as the ionize the internal gas. But since I have no data on that I don't know. Anyone out there with knowledge or experience with these things?

Good listening
Bruce

Author:  tubelectron [ 08 Jul 2020, 14:52 ]
Post subject:  Re: VR Tube Noise

Hi @gofar99,

I used neon voltage regulators in a preamp / driver power supply of an OTL amp in the past. It used 2x VR100 + VR150 in series with balancing resistors. Sorry, I do not have the schematic on hand, but I can retrieve it if needed. This can be seen on the picture below, in center low position of the chassis :

Image

What do not stand these regulator tubes is to have any paralleled capacitor of any value accross them, because they become relaxation oscillators. But if you take this peculiar point in count, you shoudn't front any noise problem. I never had any noise issue with VR neon tubes in this circuit, and the regulation offered was very efficient - again, I do not have the numbers in mind, but I noted them...

-tbln

Author:  johno9 [ 09 Jul 2020, 17:18 ]
Post subject:  Re: VR Tube Noise

I'm not sure who the author is, but right here on diyaudioprojects.com is a discussion on tube regulators:
http://diyaudioprojects.com/mirror/memb ... /reg2.html

John

Author:  tubelectron [ 10 Jul 2020, 18:01 ]
Post subject:  Re: VR Tube Noise

johno9 wrote:
I'm not sure who the author is, but right here on diyaudioprojects.com is a discussion on tube regulators:
http://diyaudioprojects.com/mirror/memb ... /reg2.html

John


Thanks for the tip ! ;)

-tbln

Author:  EL504 [ 14 Jul 2020, 02:12 ]
Post subject:  Re: VR Tube Noise

EMI used VR tubes in the power supplies of the microphone amplifiers of the REDD.47 recording console.

Shunting VR tubes with (a lot of) capacitance might be possible if the VR tube has an auxiliary (starter, ignition, etc.) anode. See: https://frank.pocnet.net/other/Telefunken/Telefunken_NewVoltageStabilisers_1966.pdf

@ Tubelectron: Your OTL amplifier is a work of art!

Author:  tubelectron [ 14 Jul 2020, 10:45 ]
Post subject:  Re: VR Tube Noise

Thanks EL504 ! ;)

Yes, these ones - built in 1996 IIRC, pictured in the post above and just below - now belongs to a friend :

Image

I decided to rebuilt a pair of OTL amps - still under construction, but coming to the end - in a more lightweight and compact size. You can find details in the diyaudioproject thread, if you are interested in... :)

http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=6834

-tbln

Author:  samc [ 16 Aug 2020, 19:08 ]
Post subject:  Re: VR Tube Noise

tubelectron wrote:
Hi @gofar99,

What do not stand these regulator tubes is to have any paralleled capacitor of any value accross them, because they become relaxation oscillators. But if you take this peculiar point in count, you shoudn't front any noise problem. I never had any noise issue with VR neon tubes in this circuit, and the regulation offered was very efficient - again, I do not have the numbers in mind, but I noted them...

-tbln


This statement is strictly correct. You may, and the spec sheets suggest that you should, shunt the VR tubes themselves with a small capacitor to provide a low-impedance path for higher frequency noise voltages developed across them. Oftentimes the data sheets specify the maximum value this capacitor may have to avoid the relaxation oscillator problem you mention.

I would be very curious if anyone watching this thread has any information about the current, temperature, and frequency dependencies of the noise profile due to VR tubes.

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