In Reply to: Anyone try 6BL8 as a driver in ST70? posted by bcguitar on April 26, 2010 at 14:09:34:
bcguitar,
As others have mentioned, the 6BL8 has a different pinout than the 7199. I think there is more than one replacement board for the ST70 that uses the 6GH8A.
The 6BL8 is part of a family of tubes that as far as I can tell are more or less interchangable:
6GH8, 6U8, 6BL8, 6EA8 ratings:
tube....pentode Trans.....power.....triode Trans....power
6GH8....8500 umhos......2.5W......7500 umhos....2.5W
6U8.......7500 umhos......2.5W......5000 umhos....3W
6BL8.....5000 umhos......1.5W.......6200 umhos...1.7W
6EA8.....6400 umhos..... 3.1W..... 8500 umhos... 2.5W
-As you can see the ratings vary a bit- the 6GH8A output is more enthusiastic than the 6BL8. I read that the 6GH8 was developed for television and to avoid NOS branded for TV. I use an Amperex 6GH8 as substitute for the 6U8 in a McIntosh MR67 tuner as recommended by designer Modaferri. I can not distinguish the Amperex 6GH8A from the 6BL8 (ECF80) in construction.
The MR67 uses the 6BL8 as the "pre-pre"-amplifier tubes and I think the sound is fantastic. There is a premium 6BL8 (Euro des. ECF80) called either E80CF or 7643. Theses are gold pin, military and low noise, and ruggedised. I bought 6 brands of E80CF including the glamourous Valvo red label, pinched waist, but found that there are really only two designs- the Philips/Amperex/Valvo/Mullard with the heavy triangular getter support and the German one Telefunken/Siemens which are made by Telefunken. Of the two, I much prefer the construction quality and sound of the Philips one.
I liked the sound of the 6BL8 enough that a couple of years ago I looked around for a headphone amp that used it.
If fussing with an ST-70, you might benefit from visiting the Dynaco Doctor forum of this site:
http://www.audioasylum.com/forums/dynaco/bbs.html
I have a PAS 3 and ST70 which I hope to someday revive, though I imagine they will be redone more or less as stock- I'm not knowledgeable enough to hot rod anything,..
Cheers,
Bambi B
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Follow Ups
- No, but it's been done more or less, with the related 6GH8A - Bambi B 09:05:39 04/27/10 (7)
- RE: No, but it's been done more or less, with the related 6GH8A - Eli Duttman 19:16:29 04/27/10 (0)
- RE: No, but it's been done more or less, with the related 6GH8A - becketma@yahoo.com 13:21:36 04/27/10 (5)
- 6BL8_ECF80_E80CF_7643 - Bambi B 15:28:21 04/27/10 (4)
- RE: 6BL8_ECF80_E80CF_7643 - becketma@yahoo.com 22:39:18 04/28/10 (2)
- Yes, I found only two European designs - Bambi B 06:59:15 04/29/10 (0)
- RE: 6BL8_ECF80_E80CF_7643 - becketma@yahoo.com 22:42:41 04/28/10 (0)
- Thanks for all the info and - bcguitar 19:19:22 04/27/10 (0)