Recomendations for Preamp Tube for Genz Benz 500H

Muckaluck · #1 07-09-2010, 10:25 PM

Hi everyone,

I've had an electro harmonix 12AX7 in my Genz Benz 500H for the longest time and lately I've been wishing for a tube that doesn't break up (distort) so quickly. Could anyone suggest a preamp tube that is warm and doesn't break up as quickly as other tubes?

Thanks!

agedhorse · #2 07-09-2010, 11:13 PM

You might try a 12AX7WA. Another option is a 12AU7 but not all 12AU7's will bias up correctly so be sure to try several if you can.

murphy · #3 07-10-2010, 06:28 AM

I think I might try that in my F-2b

esoxhntr · #4 07-10-2010, 06:42 AM

You might want to try a Tung Sol 12ax7. $14.95 at The Tube Store, and I really liked it in my GBE750.

fretno · #5 07-10-2010, 07:10 AM

The Tung-Sol ri is excellent as well the Mullard ri 12ax7 and Shuguang 12ax7 "c9" or Ruby rebranded Shuguang tube and NOS RCA , Philpis JAN or Mullard and many others would work well too .

Muckaluck · #6 07-10-2010, 10:11 AM

Sounds good. I'll order a Tung-Sol from the tube store and get back on how I like it.

Thanks for the advise!

jhines · #7 07-10-2010, 10:23 AM

Once again, I am too late but will second or third the Tung-Sol choice. I have one in my GBE-600 with good results. Happy hunting.

Muckaluck · #8 07-10-2010, 05:03 PM

Tung-Sol ordered!

Thornton Davis · #9 07-10-2010, 11:11 PM

I replaced the stock Ruby 12AX7 in my ShuttleMAX 12.0 recently and installed a Tung-Sol 12AX7 in its place. Huge difference.

L&M sell them for $15.95 Check to see if the Oshawa or Scarborough has them in stock.

TD

Muckaluck · #10 07-12-2010, 11:14 AM

Shoot... I wish I knew L&M had them before I ordered online. Good to know for next time!

murphy · #11 07-12-2010, 03:44 PM

I'm heading off to Long and McQuade

Pilgrim · #12 07-12-2010, 03:59 PM

Quote:

Originally Posted by Thornton Davis

I replaced the stock Ruby 12AX7 in my ShuttleMAX 12.0 recently and installed a Tung-Sol 12AX7 in its place. Huge difference.

L&M sell them for $15.95 Check to see if the Oshawa or Scarborough has them in stock.

TD

Will it make any audible difference in other G-B amps, like the shuttle series?

esoxhntr · #13 07-12-2010, 08:03 PM

Quote:

Originally Posted by Muckaluck

Shoot... I wish I knew L&M had them before I ordered online. Good to know for next time!

Actually, more often than not, they don't.

Muckaluck · #14 08-08-2010, 09:15 AM

So I tried the Tung Sol in my amp and it wouldn't work. Works fine in my Guild thunderbass but no luck in the Genz Benz. Do you think this is a biasing issue?

esoxhntr · #15 08-09-2010, 09:22 AM

WT*?

Stupid question, but are you sure they sent you a 12AX7? You might want to touch base with the Genz Benz guys...

tony_clifton · #16 08-09-2010, 09:31 AM

Not that important but preamp tubes are are never to be biased.

agedhorse · #17 08-09-2010, 10:12 AM

Quote:

Originally Posted by tony_clifton

Not that important but preamp tubes are are never to be biased.

ALL preamp tubes are biased to operate in a specific region on the load line and operating curves. This is not obvious though since the biasing is part of the design of the circuit and not something that the user has any contol of because the bias is part of the cathode load circuit and is inherent in the basic circuit design.

As with any tube, if the specs deviate enough from the standard design specs, it may work ok in one circuit but not in another of different design. There is an incredible difference in the range of specifications (many different specs) between tubes and while one may work in a particular curcuit but not in another, the reverse is also true.

I recommend the WA as it's average spec range is (in general) closest to the design curves I used in the design of the preamp circuit in the GBE's.

esoxhntr · #18 08-09-2010, 02:52 PM

Okay, how come the one I had in my GBE750 worked? Maybe I had a mislabeled tube, or different in some respect? Also, I'm going to experiment with a tube change on my GBE1200, is what you are recommending a 12ax7wa?

agedhorse · #19 08-09-2010, 07:11 PM

Because there is a very wide range of tolerances (as much as 100%) between tubes within a family and each family falls within a range of parameters too. Also, the circuit design is different between the GBE-500 and GBE-750/1200.

Muckaluck · #20 08-09-2010, 09:13 PM

Great support and thanks for the clarification!

I have a sovtec in there right now that sounds ok until it breaks up. Perhaps I will try a 12AX7WA