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Old 10th February 2012, 12:28 PM   #1581
regal is offline regal  United States
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Quote:
Originally Posted by Original Burnedfingers View Post
Just on a maintenance standpoint alone it would not be practical to use a 26 in a recording studio and or radio station. The 26 takes a lot of circuitry to obtain it clean clear output. Studios would not have the time to keep it running correctly because of being booked non-stop all day long. Another thing to consider is the tube availability and cost. They haven't made the 26 for probably 80yrs or so. Never worked in a studio yet that uses tube gear for mix purpose or recording purpose. You might hear a tube amplifier on a pair of monitors but that would be about it.

Leave the 26 where it belongs...in your home system.


Quote
use separate floating power supply's of 1,5 V ( a battery is absolute humfree

Tried batteries and still had hum.

That was my initial thoughts but the studios have been cranking out so much digital brickwalled/compressed garbage for years I commend this guy for trying something different. We know studios add compression, harmonic distortion, reverb, you name it via DAW so why not use a DHT to add a little compression and harmonics rather than some crappy algorithm?

The biggest issue will be 60hz noise (or 50hz in europe) and its harmonics. Even if the filament supply is perfect any choke or transformer in the circuit will pick it up like a radio receiving FM. I would use it with a high pass crossover 200hz and leave the bass to solid state. But its open-mindened creativity like this guy that the studios need to get out of the mess they are in.
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Old 10th February 2012, 12:45 PM   #1582
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If anyone likes the idea of valve-based recording, and you have not seen it - enjoy the article on Toe Rag Studios in London. It's analogue-only, & valve dominated:

Analogue productions aplenty at ToeRag - StudioNews-content | PSNE Magazine Online & In Print

.
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Old 10th February 2012, 01:42 PM   #1583
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I don't see maintenance as an issue or obtaining stocks of 26 - plenty about - and I don't think studios are that busy these days. I see this as a project for any part of the chain requiring maximum clarity and sound quality. Not sure where that would be exactly - I thought most recording was digital. But I do see noise/hum/chokes/transformers as needing some design solutions. All in favour of creative solutions!! That's the whole fun of designing.

andy
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Old 10th February 2012, 02:21 PM   #1584
Magz is offline Magz  United States
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Default Glow Tube Regulators - Advantage or Disadvantage?

Hi all,

I'm about to begin my 26 preamp project, and I have a question about two alternative schemes for B+. I already have a CLCLC supply to use, so that is set in stone. Here are the two scenarios:

1) CLCLC power supply (340V) to CCS-fed 0A3-0D3 in series (225V) (one set of CCS and regulators per channel) to CCS on plate of each 26 (135V or so, whatever the CCS sets it at for 6mA). First CCS set at 26mA, second at 6mA. Bypass 0A3-0D3 pair with .056uF cap to reduce noise. 9V Battery grid bias.

2) CLCLC power supply (340V) directly to CCS on plate of each 26 (6mA, ~135 V), with no shunt regulators. 9V battery grid bias.


Please only consider these two scenarios (no mosfet shunt regs, etc.). Is there a clear advantage in sound quality to adding the extra CCS and gas regulators to the circuit, or are they simply unnecessary complexity? My concern is that the regs may actually add more noise to the system than they remove. Following the KISS principle I'm leaning toward #2, but the lure of four glowing regulator tubes keeps me coming back to #1.

I'll most likely end up trying both scenarios anyway, but I'm looking to learn from the experience of others if I can. Anyone?
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Old 10th February 2012, 02:42 PM   #1585
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After reading all 159 pages here ....

It seems as if your second choice maybe the one preferred. A couple of people who had gas regulator tubes in their system eventually took them out...But surely try both if you have the parts on hand !
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Old 10th February 2012, 02:54 PM   #1586
Magz is offline Magz  United States
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Quote:
Originally Posted by Steven-H View Post
After reading all 159 pages here ....

It seems as if your second choice maybe the one preferred. A couple of people who had gas regulator tubes in their system eventually took them out...But surely try both if you have the parts on hand !
I read all the pages, too, and this topic did not seem to have a clear resolution; some liked them some didn't. Also, I didn't see anything about using two gas tubes in series per channel - I wonder if that might cause even more noise than a single tube.
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Old 10th February 2012, 04:08 PM   #1587
Magz is offline Magz  United States
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As with everything else, it seems that it's a matter of personal taste. I'll try both.
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Old 10th February 2012, 05:00 PM   #1588
massimo is offline massimo  Italy
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I favour the KISS solution, but to get rid of >200V (from 340 to 135VDC) is definitely not an easy task...
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Old 10th February 2012, 05:36 PM   #1589
Magz is offline Magz  United States
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The CCS should be able to drop that much on each channel without an issue. Since each 26 only pulls 6 mA, it comes out to about 1.2W dissipated per channel.

I'm using 340V because that's the power supply I have handy. If I find that the 26 preamp beats my current preamp (that uses the 340V power supply) I'll build another PS for the 26 with lower output voltage, probably LCLC.
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Old 11th February 2012, 10:07 AM   #1590
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Quote:
I don't see maintenance as an issue or obtaining stocks of 26 - plenty about - and I don't think studios are that busy these days. I see this as a project for any part of the chain requiring maximum clarity and sound quality. Not sure where that would be exactly - I thought most recording was digital. But I do see noise/hum/chokes/transformers as needing some design solutions. All in favor of creative solutions!! That's the whole fun of designing.


I'm not trying to throw water on the idea by any means. My experience with studios here in the U.S. has been that they are always booked. They generally abuse equipment and or leave it on all the time. Considering the life of a #26 tube I don't see leaving it on 24/7 as a good idea. While there are some #R6's left if studios were to adopt the idea I think the price of the 26 is going to go up and the supply will go down. I don't happen to see a source of new 26 anywhere. I personally feel that the studios will continue to employ equipment that is both cost effective and maintenance free so to speak.
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