Opinions about Dynaco ST-70, PAS 2 & 3, etc.
Martin
I'm inclined to believe I should buy a rebuilt Dynaco ST-70 & PAS 2 or 3,
but first I need answers for these questions:
1. Are the Dynaco PAS 2 or 3 good, are they as good as the Dynaco ST-70?
2. Is the Dynaco PAS 3 superior to the PAS 2, and if so how much superior?
3. Is the ST-70 sound improved or degraded by replacing the PAS 2 or 3
with a solid state transistor pre amp?
4. Is fidelity improved by useing two Dyna ST-70s as "mono blocks," i.e.,
using two Dyna ST-70s (each in mono mode) to create the two stero
channels?
5. Does anyone want to sell a reconditioned Dynaco ST-70 & PAS-3, and
what would be the price?
Thank you, Martin
Mr. Steven Bender
Martin wrote on Tue, 23 Sep 1997 15:39:45 GMT:
> I'm inclined to believe I should buy a rebuilt Dynaco ST-70 & PAS 2
or 3, but first I need answers for these questions:
>
> 1. Are the Dynaco PAS 2 or 3 good, are they as good as the Dynaco
ST-70?
Subject to significant opinion, but I think a properly working PAS is
somewhat at a higher level than a properly working ST-70. But.... the
tube in it will mostly affect the results. Your mileage may vary :-).
> 2. Is the Dynaco PAS 3 superior to the PAS 2, and if so how much
superior?
PAS-3 has same circuit as PAS-2, just different faceplate and knobs.
The pots had changed to different external metal piece to accommodate
the metal knobs.
PAS-3x has slightly altered controls and sightly altered circuitry, and
can even drive some transistor amps without distortion.
> 3. Is the ST-70 sound improved or degraded by replacing the PAS 2 or
3 with a solid state transistor pre amp?
If you use rocks < solid state >, it sounds like rocks...
> 4. Is fidelity improved by useing two Dyna ST-70s as "mono blocks,"
i.e.,
> using two Dyna ST-70s (each in mono mode) to create the two stero
> channels?
Dunno, never did that.
> 5. Does anyone want to sell a reconditioned Dynaco ST-70 & PAS-3,
and what would be the price?
Prices are all over the place, as units vary from completely rusted
out and non-functional; to pristine-mint, like-new out of the box.
You've seen the condition of dollar bills ? Some are falling apart
crap, barely readable, and won't work in a cash changer; others have
that crisp feel, are unfolded, barely creased, untouched by human
hands...
Steven L. Bender, exq...@prodigy.com
*** See my current series of articles: The BENDER-2pp. a Transistor to
Tube Amplifier Rebuild. - NUTS & VOLTS Magazine. February / March /
April 1997 issues ***
Home Page: http://pages.prodigy.com/sbender
" If we're not supposed to eat animals, how come they're made out of
meat " ??? -Tom Snyder
SAS4340
The stereo 70 at this time is 25-35 years old and needs service. most
don't have much above 12k. . When rebuilt they are fine amps.There are many
rebuilds offered. I have 2 super 70i's . they are complete rebuilds using
audio by Van Alstine mods . I even have new AVA power transformers (no
longer avail.) They sound real nice. To answer your question about monos :
The mono switch on the amp does not work well it will just paraell the
outputs and add distortion. I have been useing a AVA phase inverter bridge
for my 70's for the past 3 years . It will give almost 100 watts per
channel. The soundstage just blows out and there is no crosstalk between
channels. Detail is also improved. Look at his website
http://www.avahifi.com and read. I might be willing to sell all or part of
my system. I am currently useing a pair of MK III's and I am building a new
preamp . Basic diy . I now just buy boards and do everything else myself
includeing . getting silk screening done. I may also have a super pas 3-i
for sale soon .The 3i is a what I think you want the original pas to
do.Frank at AVA has kits if you choose to DIY . they are advanced kits all
boards have to be stuffed.
Good luck ,Sam
Samuel Strongin sas...@aol.com
Jim Kroger
In article <19970928134...@ladder01.news.aol.com>,
sas...@aol.com (SAS4340) wrote:
Where do you get silkscreening done and how much does it cost?
Thanks,
Jim
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Randy Nachtrieb
Hi Sam,
Stock ST70's, even those which are 35 years old, generally have HF
response well beyond the audible range. The VanAlstine modification
however, rolls-off the HF respone above 12khz.
In a "Sensible Sound" comparison ("Variations on the Dynaco Stereo
70", Spring '87), the Van Alstine was found inferior to even a stock
unit with a simple parts upgrade. Ours(Enlightened Audio) was the most
highly rated version.
Regards,
Randy Nachtrieb
Enlightened Audio
New Art Loudspeakers
Donald P. Bilger
The stock AVA Super 70 incorporates a bandpass filter at its input. The
low-pass leg of this filter is a first-order filter with a -3 dB corner
frequency at 23.4 kHz. The response of this filter will be -1 dB at 11.7
kHz. On very analytical speakers, this may be audible as a slight
softening of the treble.
In his 1982 Audio Basics article on upgrading the Stereo 70, Frank Van
Alstine noted that the shunt capacitance in the lowpass filter could be
reduced if the amp had a first-rate tube set. I used 470 pF caps in
place of the 680 pF standard values in my Super 70 for a -1 dB point at
16.9 kHz. The amp sounds far better than the stock ST-70 to which I
recently compared it, with a clean, subjectively extended treble and none
of the stock amp's bass muddiness. I'm completely satisfied with the Van
Alstine mod in my amp and would recommend it to anyone who wants to get
the most from the ST-70.
--
Regards,
Don Bilger
Ned Carlson
"Donald P. Bilger" <DBI...@FORD.COM> wrote:
>
>
>The stock AVA Super 70 incorporates a bandpass filter at its input. The
>low-pass leg of this filter is a first-order filter with a -3 dB corner
>frequency at 23.4 kHz. The response of this filter will be -1 dB at 11.7
>kHz. On very analytical speakers, this may be audible as a slight
>softening of the treble.
-3 db at 23.4Khz is OK?
Maybe at the home of the Grenada & Pinto (uggh)!
Sorry, I'm a Mopar Man, I couldn't resist the
free pot-shot...
> I'm completely satisfied with the Van
>Alstine mod in my amp and would recommend it to anyone who wants to get
>the most from the ST-70.
Phooey..the S/N ratio is worse than the original ST70,by a bunch.
So is the distortion spec.....
The EF86 + 12AU7 combo that yours truly and my late lamented friend
Ken Schurak (mecca is at Cortland & Austin in Chicago, Il, if you
wish offer a prayer)developed beats any 6GH8 board. Period.
That may be why some NASA scientist guy opted to copy
our board rather than Van Alstine's....
Ned Carlson, Triode Electronics, Chicago, IL http://www.triodeel.com
Open 12:30-8 PM CT, 12:30-5 PM CT Sat Closed Wed
ph:773-871-7459 fax 773-871-7938 "where da tubes are"
Email catalogs: email our CataBot: cat...@triodeel.com
Donald P. Bilger
Ned, please re-read my post. I opened up the filter bandwidth on my
modified ST-70 to -1 dB at 16.9 kHz and -3 dB at 33.8 kHz. The stock AVA
bandwidth seemed too narrow to me, and my tubes (NOS Sylvania 6GH8As and
Mullard and National EL34s) were good enough to support the broader
bandwidth. Subjectively, the signal-to-noise didn't suffer, either; I
kept the GZ34 and the choke filtering and upsized the quad cap modestly
to 40/40/20/20. The AVA driver and phase splitter may not be the
absolute best available, but they deliver a lot of sound quality for the
price.
--
Regards,
Don Bilger
Jim Kroger
In article <34309073...@news.chicago.il.ameritech.net>,
postm...@triodeel.com wrote:
> That may be why some NASA scientist guy opted to copy
> our board rather than Van Alstine's....
>
They use ST-70s in space?
Sheldon D. Stokes
In article <60mhv2$q4m$1...@newsd-113.bryant.webtv.net>, gat...@webtv.net
(Randy Nachtrieb) wrote:
> Stock ST70's, even those which are 35 years old, generally have HF
> response well beyond the audible range. The VanAlstine modification
> however, rolls-off the HF respone above 12khz.
Here's a data point. My ST-70 was made in 1964, and before I replaced
everything passive, it measured flat out past 20 KHz. And one of the phase
splitter resistors had drifted in one channel; so the phase splitter was
unbalanced, and it still made it out past 20 KHz.
> In a "Sensible Sound" comparison ("Variations on the Dynaco Stereo
> 70", Spring '87), the Van Alstine was found inferior to even a stock
> unit with a simple parts upgrade. Ours(Enlightened Audio) was the most
> highly rated version.
I haven't heard all the valieations, but the ones I've heard do some things
better than stock, but in general I prefer stock topology, with all new
parts.
Sheldon
--
Remove SPAM_BE_GONE. from my address to reply to me.
WJohn96600
>The EF86 + 12AU7 combo that yours truly and my late lamented friend
>Ken Schurak (mecca is at Cortland & Austin in Chicago, Il, if you
>wish offer a prayer)developed beats any 6GH8 board. Period.
>our board rather than Van Alstine's....
Some NASA scientist guy also opted to put Bose speakers in the space shuttles.
WQJ
Sheldon D. Stokes
> Phooey..the S/N ratio is worse than the original ST70,by a bunch.
> So is the distortion spec.....
> The EF86 + 12AU7 combo that yours truly and my late lamented friend
> Ken Schurak (mecca is at Cortland & Austin in Chicago, Il, if you
> wish offer a prayer)developed beats any 6GH8 board. Period.
> That may be why some NASA scientist guy opted to copy
> our board rather than Van Alstine's....
I guess I'm the NASA guy, but to be honest, I copied it, but not in a
stealing bread from Ned's mouth kind of way. At the time I copied it, Ned
wasn't selling them any more. He's now selling them, and you should buy
one from him although, the board layout is on my web site. IT's a nice
mod, although if the board size would accomodate it, I would use a pair of
single triodes insead of the 12AU7, that way the filament draw is uniform
for each winding, and both channels have equal loading.
http://www.clarkson.edu/~stokessd
Sheldon
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#include(dumbquote.h)
Remove SPAM_BE_GONE from my e-mail to reply directly to me
Sheldon D. Stokes
> Some NASA scientist guy also opted to put Bose speakers in the space shuttles.
Although I'm grateful to NASA for funding my PhD research, I have to tell
you that the don't have any taste in audio gear. They threw away about 6
MK III's and a ST-70 and a bunch of solid state audio gear over the past
couple of years, in one building alone, at one center. Fortunatly, I'm not
above dumpster diving for those treasures, and I'm listening to the above
mentioned ST-70 now.
A mint MC275 went away and I didn't catch it, I'm still bummed.