|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
68.83.181.118
In Reply to: Tuner fix tricks- 6AU6 picks for kicks? posted by Bambi B on November 30, 2006 at 16:37:15:
Bambi,The 6AU6 is the CLASSIC IF amplifier in VHF receivers. It was made in the billions. Not only did tube FM tuners use them in their IF strips. The 6AU6 could be found in the IF strip of virtually every TV made until the 1970s.
You have some collection. It's no secrect I like RCA tubes. So, I'd keep them. I also like TungSol. There are 2 sets of T/S 6AU6s in my stash, destined to go into a McIntosh MR71.
JMO, sell the Sylvanias and sell that Mullard for all that the traffic will bear.
IIRC, you are not keen on DIY. However, with some tweaking, the 6AU6 can be a pretty good audio pentode. The 6AU6 also serves well as an active load for a cathode follower.
Eli D.
Follow Ups:
Eli Duttman,Good to hear from you.
The collection: Yes, I never intended to end up with so many 6AU6's- it's a case of realising I used quite a few, but also that they're so inexpensive- the Tung-Sols cost I think less than $1 each. The "Telefunken" EF94s are relabelled RCA, Brazil- and $2 each. The boxes, by the way, are old and several still had a cellophane wrapping, so I wonder if Telefunken bought and boxed RCA, Brazil output. Seems unlikely, but a $2 each I felt I couldn't go wrong- as a curiosity. Plus, Telefunken did relabel and box late GE 6201s as Telefunken.
I'm interested in your comment vis a vis RCA vs. Sylvania. All this 6AU6 interest is related to my complete retubing of the MR67 tuner. I was sort f set on using the Sylvania Gold Brand gold pin 6136. Did I simply fall for the cheap glamour of gold pins? -I am certainly a fan of RCA as well- I have new respect for the Command 5814A for example and I like a lot of there other tuner tubes- 6AV6, 6CS6, and am open to the possibility of using RCA "Command" 6136. I thought the Sylvania Gold Brand 6136s were just interesting- again a gold pin premium and steel pin military version seems as though it should be a high performance machine. This was interesting too in light of the Sylvania Gold Brand "GB-1252" that appear to be a premium, gold pin consumer 6678 or military grade 6U8A.
What makes a 6AU6 a good one- a high performer? What do you like about the RCA?
DIY: When I was poking around trying to learn something about the 6AU6, I came across someone who had designed a 1.5W integrated SET amplifier using the 6AU6 as a triode gain device- wiring across sections I think- and I forget the output tubes- -or were those the drivers- 12BA4 or some such. I'm always interested in this sort of project- giving new exciting work to ubiquitous tubes!
May I ask what tubes you're using or planning for your McIntosh MR71?
My MR67 choices:
McIntosh MR67
3- 6AU6> 1st, 2nd IF / 1st limiter :Sylvania Gold Brand 6136- gold pin -NOS
GE 6136 “Five Star”- grey pl halo- NOS > The original “McIntosh” 6AU6s are GE
RCA "Command" 6136-NOS2- 6BL8 > L&R audio amplifiers:
Valvo E80CF / 7643- Philips/Hamburg- red label, military label- pinched waist- gold pin- NOS
12AU7 > MPX oscillator :
Siemens 5814A triple mica- test NOS
CBS 5814A, black plate- square gtr- test NOS,
RCA ‘Command’ 5814A blk pl- halo gtr- NOS
Valvo 6189- RTC- France- dbl getter sup- NOS12AT7 > 2nd RF amplifier, mixer:
Sylvania Gold Brand, gold pin 6201- NOS
Siemens triple mica E81CC-NOS6DS4 > Nuvistor 1st RF amplifier:
Amperex- NOS
6AB4 / EC92 > Oscillator
Telefunken EC92- Germany- NOS
6CS6 /EH90 > 4th IF, 2nd limiter:
Telefunken EH90- NOS
6U8 / ECF82 > MPX amplifier:
Sylvania “GB-1252"/ 6U8A - Gold Brand- -grey pl- halo- gold pin- NOS > I’ve never seen this version before
Sylvania 6678- “Communications Quality”-grey pl- halo- NOS > These appear to have identical construction to the “GB-1252", only without the gold pins
RCA - 6U8A- black plate- stirrup getter- NOS6GHA [for 6U8] > MPX amplifier:
Amperex 6GHA- orange globe label- France- NOS > Modaferri recommends the higher gain 6GH8A in place of the 6U8 in MR67 .
6BL8 [for 6U8] > MPX amplifier:
Amperex PQ 7643- Hamburg- gold pin- NOS > I’ve also heard of people using the 6BL8/ECF80/E80CF for the 6U8. What do you think?6AV6/EBC91 > Muting amplifier:
Telefunken EBC91
Cheers,
Bambi B
RCA and GE are the only 6AU6A tubes I've compared but I found rhe RCA samples to be much less microphonic. As Eli says, this tube in pentode mode makes a good CCS in the tail of an LTP phase splitter - that's what I mainly use it for. I've also found that it's a good linear audio amplifier when strapped in triode-mode. I believe it's also a good AF amplifier in pentode mode but I've never tried that.
This post is made possible by the generous support of people like you and our sponsors: