[nunhgrader]

I am looking for tube options for my new preamp - Aric Audio 3.6 which came with 2ea 12AT7's (ECC81's).

In particular, can one use the 12AU7's?  How about the 6201's? How about the 12AX7's?

Also was interested in everyone's opinions on tube options for my Dynaco ST-70's EL34's  (I've been told the KT66's are drop in replacements). Also I have a set of 7199's and 1ea GZ34 rectifier.


Thanks in advance for any opinions and/ or advice!

[ken]

You can use 12au7's as a replacement for 12at7's but 12ax7's should not be used.  There are alot of solid NOS 12au7 tubes available that won't break the bank, unsure about your dynaco question though.  Is there a particular Kt66 tube you're interested in using?

[Niteshade]

I think 12AU7's are the best. What is the plate voltage? His B+ voltage is low, isn't it?

[nunhgrader]

You can use 12au7's as a replacement for 12at7's but 12ax7's should not be used.  There are alot of solid NOS 12au7 tubes available that won't break the bank, unsure about your dynaco question though.  Is there a particular Kt66 tube you're interested in using?

Thanks for the information!

Dynaco ST-70 currently uses EL34's - the engineer/ rebuilder said I could try rolling KT66's - I was wondering what other tubes could be used in place of these two tubes to give me a bunch of options - I am also interesting in people's opinions / experiences with different brand names.

[nunhgrader]

I think 12AU7's are the best. What is the plate voltage? His B+ voltage is low, isn't it?

Thanks Nightshade for responding - I have been reading alot of people's stated opinions that the 12AU7's were the best. I'm not sure about the plate voltage....kinda weird because my Dynaco ST-70 is a rebuild and I bought the Auric 3.6 (neither do I have accurate data on) as a hold me over until I get to purchase three preamps I want:

  1. A Tubed Alstine T8+
  2. Beacon Two (look familiar)
  3. Dynaco Pas 3 rebuild from the same person who rebuilt my amp

I also would like to keep a vintage tube pre, a bottlehead, decware and eventually start diy a nice preamp/ headphone amp myself  

[Niteshade]

I used 6L6's in my old ST-70. You could use KT66, KT77 and probably KT88's in there. The bias may have to be changed to accommodate these other tubes.

[nunhgrader]

Kind of surprised to see the 6L6's can be used!

I am wondering how long a set of 7199's will last since they are no longer making them and the prices for NOS are starting to shoot up!

[Niteshade]

Yeah, 6L6's were GREAT! Clean and less filament current reduced heat from the power transformer. A Win-win situation.

Don't know about the 7199's. Stay away form them if they're difficult/expensive to replace. I only use mainstream tube types.

[dbear44]

The ARC makeover of the st-70 used 6l6's since running those 7 input tubes there was not enough heater current left in the stock power trans. to use el34. I built one (as a kit) for a friend. It was a wondedrful amp, if overly complex.

http://www.arcdb.ws/ST70C3/ST70C3.html

[ltr317]

I would also stay away from any preamp/amp that uses 7199 or any no longer made tube type.  I had a pain getting a replacement for my Scott Integrated.  It took three tries to get a good working used one, which ended up costing a total of $90.

[medium jim]

Thanks for the information!

Dynaco ST-70 currently uses EL34's - the engineer/ rebuilder said I could try rolling KT66's - I was wondering what other tubes could be used in place of these two tubes to give me a bunch of options - I am also interesting in people's opinions / experiences with different brand names.

I have a ST-70 and I use EL34's as that what they're voiced for...a trick is to bias them on the low side...the factory settings are 1.56V DC, but they sound the best at around 1.45V.  Also, ditch the selenium rectifier for a modern diode...it will make it much safer as those selenium rectifiers will go bad and can take out the tranny's and tubes in the process.

The 7199's will last a lifetime in many instances....yes, they cost because they're not made in new production tubes....hint, you don't need to buy a matched pair, or even the same make....and can buy test good used ones that will be just fine. 

There are nice front-end kits with better capacitors and such that are easy to install, but I still like the original boards better.   If you do go the new board route, as already noted, go with 12AU7's...

The ST-70 is a timeless amp that happens to sound darn good....

Jim

[bunky]

Thanks for the information!

Dynaco ST-70 currently uses EL34's - the engineer/ rebuilder said I could try rolling KT66's - I was wondering what other tubes could be used in place of these two tubes to give me a bunch of options - I am also interesting in people's opinions / experiences with different brand names.

i have had numerous amplifiers that used EL34 and i have had several that used 6L6GC / KT66 and for my taste i always prefer 6L6GC / KT66 over the EL34's. the best current manufacture KT66's are the Genelex Gold Lion KT66 and the Black Treasure KT66. i own both and i prefer the Gold Lion KT66 over the Black Treasure KT66 and the beauty of that is the Gold Lion KT66 is less expensive  www.tctubes.com has the GL KT66 on sale for $30.80 each. they do a 48 hr burn in above and beyond what the factory does and they match them free of charge.