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6661 Tubes
Mar 29, 2022 21:41:00 GMT -5
via mobile
Post by vanlifeson on Mar 29, 2022 21:41:00 GMT -5
Anyone ever tried these in a browning receiver in place of the 6ba6?
They’re supposed to be a direct substitute from what I’ve read?
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Post by oldgeezer on Mar 30, 2022 15:29:25 GMT -5
The 6661 is same as a 6BH6, not 6BA6. The 6661 is a sharp cutoff and the 6BA6 is a remote cutoff. The 6661 is more subject to overload. It would work, but not correctly.
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Post by 2600 on Mar 31, 2022 0:16:46 GMT -5
The "four-digit" industrial version of the 6BA6 is the 5749.
73
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Post by vanlifeson on Apr 1, 2022 10:20:36 GMT -5
Ok thanks! I saw on vintageradio.com
That a 6661 is a Direct replacement for
A 6ba6. They even gave it a rating of E for excellent.
(They rate them E for excellent or G for a good replacement)
I’ll try them and see since I have some NOS.
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air1
Ratchet Jaw
Posts: 70
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Post by air1 on Apr 1, 2022 10:39:28 GMT -5
In one of my old RCA tube substitution books, they show the 6661 along with a few others as an emergency only replacement for a 6BA6. They do show others as direct replacements.
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Post by vanlifeson on Apr 1, 2022 18:43:42 GMT -5
Interesting stuff. I found another chart on the web from an old S9 magazine and it lists the 6661 as a BETTER replacement for a 6ba6!
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Post by 2600 on Apr 2, 2022 0:21:09 GMT -5
Had this argument decades ago about subbing 6AU6 for a 6BA6. Since the 6AU6 can't reduce its gain in step with the AGC voltage, this tends to bring up the noise level. Got told it was like a "free preamp" for the receiver.
Until a strong station keyed up. The overload and distortion reveal why that tube is different from the 6BA6. The key description in most tube manuals is "remote cutoff". This means that you can control the tube's signal gain with the negative grid bias, not just the tube's DC current. The 6BA6 tube is found in circuits that don't use this feature. The 6661 probably works fine as a sub in that kind of circuit. But a radio receiver DOES use the variable-gain feature. I would expect the 6661 to be a less-than-perfect sub in a receiver's IF stage.
Proof's in the pudding. Trying it won't damage anything, both types are wired with the same base diagram. And if you don't like what you hear, remember you heard it here first.
73
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Post by vanlifeson on Apr 2, 2022 7:53:45 GMT -5
OK, here’s the deal. The 6661 receives fine. But, the meter on the receiver will not settle down. And you can’t adjust it
i’m sure it would be a fine substitute in a AM/FM tube radio.
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Sandbagger
Administrator/The Boss 
Posts: 6,250 
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Post by Sandbagger on Apr 3, 2022 12:42:45 GMT -5
Interesting stuff. I found another chart on the web from an old S9 magazine and it lists the 6661 as a BETTER replacement for a 6ba6! Remember the old saying: "Paper never refuses ink". Just because you read something in print (or worse, on the internet), doesn't mean it's true. Stick with engineering specs and manufacturer's recommended usage. |
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