Re: Yes,..

Posted by Al Sekela (A) on May 7, 2002 at 09:40:51

In Reply to: Yes,.. posted by Lew on May 7, 2002 at 07:31:06:

Let me try to be as clear and plain as I can. According to Fred Volz, the Sira uses 6080 as pass tube, 6186 (7-pin pentode similar to 6AG5) as error amplifier, and 5651 gaseous voltage reference (90 volts) as the voltage reference for the B+ voltage regulator. This is pure tube voltage regulation.

The Sira also uses 5651 and 0A2 in active load and current source circuits for voltage amplifier and cathode follower, respectively. These are also pure tube circuits.

Fred made comments about sonic improvement over the less-expensive Erato which has transistor current source for the cathode follower. It may well be the case that the Erato also uses transistors and Zener diodes (I don't see enough tubes in the photo for tube regulation) in the power supply, but he did not go into that level of detail.

Getting back to the original point of this thread, the question is whether Michael should use his gaseous voltage reference tubes instead of Zener diodes in his projects. Based on the physics of how they work, my opinion is they are not worth the effort. Lew pointed out there is at least one contemporary design, the Emotive Audio Sira, that does use them. The designer reports audio benefit from using all-tube current sources in place of transistor/Zener diode designs, and has parallel product experience with both designs to add substance to his assertion. It appears he has not built a hybrid, with Zener reference for tube current source, to find out whether the gaseous references in themselves contribute audible benefit, but this is my assumption based on his comments.

The number of possible component permutations in even a simple circuit is very large, and I cannot fault a designer for not anticipating my somewhat idle curiosity in his or her development of a product for sale. If Fred sells more Sira preamplifiers because they have lots of gaseous reference tubes on them, and his customers are happy with their performance, then peace and prosperity to them all, and I am content to not know through their experience whether Zener diodes would have worked sonically just as well or better. Now, does anyone know of another contemporary audio design that uses gaseous voltage reference tubes?

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Follow Ups Full Thread

Topic - Voltage reference tubes, any good ? - Michael Appelt 13:03:14 05/02/02 (16)

Voltage Reference vs. Voltage Regulator Tubes - mark 09:29:20 05/03/02 (2)

VR-tubes, ignition peak - Michael Appelt 12:42:19 05/03/02 (1)

Re: VR-tubes, ignition peak - mark 12:58:07 05/03/02 (0)

Re: Voltage reference tubes, any good ? - Al Sekela 19:23:32 05/02/02 (12)

Emotive Audio pre-amps - Lew 08:53:34 05/03/02 (10)

Re: Emotive Audio pre-amps - Al Sekela 20:49:35 05/03/02 (9)

Re: Emotive Audio pre-amps - Al Sekela 10:51:28 05/04/02 (8)

I love my MP1 more, but... - Lew 07:03:43 05/06/02 (7)

"Voltage Reference" -vs- "Voltage Regulation" - Paul Speltz 13:58:39 05/06/02 (6)

Yes,.. - Lew 07:31:06 05/07/02 (4)

Re: Yes,.. - Al Sekela 09:40:51 05/07/02 (3)

Re: Yes,.. - R. Robb 16:44:01 05/07/02 (1)

Re: Yes,.. - Al Sekela 06:49:00 05/09/02 (0)

Sorry, Al.. - Lew 09:57:08 05/07/02 (0)

Re: "Voltage Reference" -vs- "Voltage Regulation" - Al Sekela 19:14:17 05/06/02 (0)

I 'll use zeners...... - Michael Appelt 23:41:42 05/02/02 (0)

Follow Ups

Re: Yes,.. - Al Sekela 09:40:51 05/07/02 (3)

Re: Yes,.. - R. Robb 16:44:01 05/07/02 (1)

Re: Yes,.. - Al Sekela 06:49:00 05/09/02 (0)

Sorry, Al.. - Lew 09:57:08 05/07/02 (0)

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