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Post new topic What brand of 12AX7 is good for Sarno Black Box.
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Author Topic:  What brand of 12AX7 is good for Sarno Black Box.
Barry Yasika


From:
Bethlehem, Pa.
Post  Posted 5 May 2019 8:54 pm    
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The Sarno Black Box I have, had a Chinese 12AX7 tube installed. The original tube went belly up, so, because Chinese stuff can tend to be either really good or really bad I went with a Russian made Tongsul tube. (May have spelled that wrong) I don't know that I hear a marked difference either way, good or bad from the original tube when it was still working well. I'm just wondering if anyone has tried something that made a big improvement or at least a big difference in sound good or bad. The tube I bought seems to be more or less a like for like change.
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Steven Paris


From:
Los Angeles
Post  Posted 5 May 2019 11:37 pm    
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https://www.thetubestore.com/12ax7-tube-reviews
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Emmons & Peavey
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Dennis Detweiler


From:
Solon, Iowa, US
Post  Posted 6 May 2019 6:39 am    
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NOS RCA or a good used one.
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Jon Light


From:
Saugerties, NY
Post  Posted 6 May 2019 7:36 am    
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If it were me, I would contact Brad directly. As a contemporary, ongoing manufacturer, he would have his finger on the pulse of what he likes right now in the current crop of new tubes (an always shifting field).
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Godfrey Arthur


From:
3rd Rock
Post  Posted 6 May 2019 8:21 am    
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As stated previous, NOS RCA, but there are other brands and PRICES for NOS getting in the Richie Rich-o-sphere.

New tubes would be JJ brand.

Again we get another tube rolling question.

If you want to spend the time and money, start swapping (collecting) different vintage tubes to see what sparks your fancy.


NOS from 1962 Telefunken @ $228 simoleons. Shocked
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Michael Brebes


From:
Northridge CA
Post  Posted 9 May 2019 6:33 am    
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I have found that many of the Chinese 12AX7's clip a lot earlier than most other tubes. I have had good luck with new production JJ and Electro Harmonix in this tube. To me Sovteks tend to be a bit tubby.
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Brad Sarno


From:
St. Louis, MO USA
Post  Posted 9 May 2019 12:10 pm    
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The RULE with the Black Box is to avoid a tube with a "spiral filament". Since the 2nd stage of the Black Box is a low-impedance "cathode follower" driver circuit, that elevates the cathode-to-heater voltage to about 90 volts.

Many modern tubes us a spiral filament. In this situation the spiral heater filaments are prone to shorting out or arcing and having a reasonably spectacular failure. Doesn't always happen by any means, but it can and does sometimes.

SO - we avoid spiral filaments. Modern audiophiles and many boutique guitar amp makers agree that the latest generation of Chinese 12AX7 or 12AX7B is a good "clean" tube, and they don't have the spiral filament issue. That's my standard install.

BUT - you just can not beat a good vintage, American tube like an RCA, GE, Sylvania, Tung-Sol, JAN Philips, etc. RCA's are my favorites for pedal steel. Telefunkens are nice too, but the RCA has an especially smooth top end, clear and warm and smooth.

But if replacing a tube for a Black Box with a brand new, modern tube - I'd stick with the Chinese 12AX7 or 12AX7B. Sometimes they're also marketed under the GT-Groove Tubes brand or the Ruby brand. You can get them directly from Antique Electronics Supply in AZ.


Brad
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Steven Paris


From:
Los Angeles
Post  Posted 9 May 2019 1:39 pm    
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Brad Sarno wrote:
The RULE with the Black Box is to avoid a tube with a "spiral filament". Since the 2nd stage of the Black Box is a low-impedance "cathode follower" driver circuit, that elevates the cathode-to-heater voltage to about 90 volts. Many modern tubes us a spiral filament. In this situation the spiral heater filaments are prone to shorting out or arcing and having a reasonably spectacular failure. Brad

Would the use of a DC-elevated heater supply avoid this problem?
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George Macdonald


From:
Vancouver Island BC Canada
Post  Posted 9 May 2019 1:58 pm     Black Box tubes
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Brad, Is the JJ ECC83-S a tube with a "spiral filament", and one to be avoided? Thanks, George
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George Macdonald


From:
Vancouver Island BC Canada
Post  Posted 10 May 2019 7:48 am     Black Box tubes
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I just found out this morning from "The Tube Store" that the JJ Electronics ECC83-S 12AX7 tubes have the "spiral filament" that Brad suggests avoiding. They do have good reviews for other applications.
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