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RE: What tube subs for a 6BL8

Posted by Bambi B (A) on October 2, 2015 at 09:14:26

In Reply to: What tube subs for a 6BL8 posted by DAK on October 1, 2015 at 13:46:37:

DAK,

Here is a chart of the tubes interchangeable with the 6BL8:

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


The 6GH8 has the highest output and was common as a television tube and is said to be found as low quality when marked as a TV brand.

I have a McIntosh MR67 tube tuner that uses a a pair of 6BL8's a s a "pre-preamp" output tube and the sound is fantastic. The 6BL8 European designation is ECF80 and there are premium version E80CF and military version 7643. Ten years ago , since none of these types were in production, I decided to try a few. As they were inexpensive,- some were $2 or so, I ended up with:

6BL8 /ECF80 /E80CF /7643

2- Telefunken E80CF- gp- NOS -
4- Philips Miniwatt ECF80-- Brazil- NOS -
4- Valvo E80CF Red lbl, pinch waist- gp-DE- NOS
2- Philips SQ E80CF - Germany, gp-USED-TNOS -
4- Philips SQ / Mullard- E80CF- disc gtr- UK- NOS
3- Siemens by Telefunken 7643- s.gtr - gp- DE- NOS
3- Amperex PQ E80CF-gp-Hamburg-db.gtr-NOS 64-
5- Siemens & H by Telefunken E80CF- gp- - NOS
4- Amperex PQ 7643- gp- Hamburg- db.gtr s- NOS
4- GE ECF80 -UK - NOS
2- RCA 6BL8- US - NOS
3- RCA ECF80 -France- NOS
1- Sylvania 6BL8- US

It turned out that were really two basic kinds, the Philips / Amperex / Mullard have two substantial triangular getter supports and the Telefunken / Simens design looks more like a conventional triode. I found I much preferred the sound of the Philips design and use a pair of Valvo E80CF pinch waist, gold pin in the MR67, but the ordinary while label Valvo Amperex are all fine. Very low microphonics and a great soundstage. I used to listen to the MR67 in mono and the sound was just astounding and even imaging was incredible- narrow, but deep, deep deep suggesting very good phase coherence.

I liked the sound of 6BL8's so much I looked to see if there had been any preamps that used them as a gain tube.

Cheers

Bambi B

Oracle II_SME V_AQ 200 / MCintosh MR67 /Cambridge Audio 640C v2 > Audio Research SP10 > Audio Research D115 > Vandersteen 2C (AQ King Cobra IC / AQ Rocket 88 speaker)

This post is made possible by the generous support of people like you and our sponsors:

Kimber Kable

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