As an alternative to an SDS board for a Dyna ST-70, I was thinking about
using Antique Electronic Supply's 80-40-20-20 @ 525V, using the 40uf section
as the first cap in the string with the 80uf section tied to the plates.
Thoughts? Has anyone else though of / tried this?

It will work.
Change also the filter caps for neg bias and also change the diode to
1N4007.
"Eric" wrote in message
...
As an alternative to an SDS board for a Dyna ST-70, I was thinking about
using Antique Electronic Supply's 80-40-20-20 @ 525V, using the 40uf
section as the first cap in the string with the 80uf section tied to the
plates. Thoughts? Has anyone else though of / tried this?

I did exactly that, works good.
Mark S
"Eric" wrote in message
...
As an alternative to an SDS board for a Dyna ST-70, I was thinking about
using Antique Electronic Supply's 80-40-20-20 @ 525V, using the 40uf
section as the first cap in the string with the 80uf section tied to the
plates. Thoughts? Has anyone else though of / tried this?

Were you able to notice any improvement in bass response?

"Mark S" wrote :I did exactly that, works good.
Mark S

Yep, and increased the bias caps to 220uf, and changed the first 10K bias
resistor something like 12K.

Did notice an improvement in bass? I realize that quadrupling the
capacitance at the plates should help bass response but still, 80uf ain't
much...

"Dan Nicotera" wrote:
It will work.
Change also the filter caps for neg bias and also change the diode to
1N4007.

"Eric" wrote in message
...
Were you able to notice any improvement in bass response?

"Mark S" wrote :I did exactly that, works good.
Mark S

Eric,
I did the can cap replacement as part of a complete overhaul, replaced most
every cap and resistor in the amp. The performance of the amp afterwards was
improved, but not reborn so to speak. Bass response or control was somewhat
improved as I recall. Are you using a Dyna PAS pre amp? Some have commented
that the bass response performance of the PAS / ST70 (as well as MK III's)
was limited by the PAS as much as the power amp.
Mark S

in article et, Mark S at
wrote on 5/15/05 6:15 PM:


"Eric" wrote in message
...
Were you able to notice any improvement in bass response?

"Mark S" wrote :I did exactly that, works good.
Mark S

Eric,
I did the can cap replacement as part of a complete overhaul, replaced most
every cap and resistor in the amp. The performance of the amp afterwards was
improved, but not reborn so to speak. Bass response or control was somewhat
improved as I recall. Are you using a Dyna PAS pre amp? Some have commented
that the bass response performance of the PAS / ST70 (as well as MK III's)
was limited by the PAS as much as the power amp.
Mark S


Good thinking, Mark.

I think the stock PAS 2 or 3 sounds just awful. I'll commit blasphemy by
claiming that you'll get better results with almost any SS preamp in
conjunction with the Dyna. Hafler SS preamps make a good match with the
ST-70 (guess they should - calabash cousins, after all).

The bass response of a stock ST-70 is unremarkable. I tried the Van Alstine
LP filter and to my ears it sounded a lot worse. You'll get optimum bass
response with Mullards or Siemens EL34s, I think.

7199s don't always age well, either. That could be part of a perceived bass
deficiency.

It's a big undertaking to install the Welbourne Labs mu stage driver, but it
offers an undeniable improvement in sonics overall. It also gets rid of
those pesky 7189s. Got a notice a few days ago that Welbourne is having a
sale. You can buy their PCB(s) and the top metal piece and stuff everything
yourself, and save a buck.

If you're interested, shoot me an e-mail and I'll send you photos of my Dyna
ST-70 that had an "extreme makeover" - chrome plated chassis, new everything
except for iron and bias resistors.

Good luck!

jon

Mark:

Thanks for the reply...

My preamp is a homebrew lineamp using 12AU7s in an SRPP-like variant
(mu-stage?) configuration and supplies ample bass to other amps.

Most of the signal path components were recently replaced and, as a
result, I heard improvements in mids and highs, but not so much with
bass. I'm aware of the effect of newer, larger filter caps on bass ,
but didn't want to 'spoil' it's utilitarian appearance by move the caps
underneath - a la an SDS board. I've order the Antique's cap and will
give it a try. Thanks again...

Eric...