Kintaro_Audio
2004-02-26 19:57:24 UTC
Single Chassis Stereo (monoblocked dual) Dynaco ST70. Each stereo st70
output stage is fed from one channel of the highly regarded Sutherland
ST70 FET driver PC-3. The output transformers' 16ohm taps are wired in
parallel giving 70W per channel RMS into 8 ohms.
On ebay as no. 3080146504
Buy it now for $600.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3080146504
NOT "AS IS". Comes with full test report from my audio lab. You approve
before paying. (I'm a MSEE analog electrical engineer working at MIT,
and have a $26K THD analyzer).Unfortunately, I untubed it to move and
can only find 4 of the 8 el-34's! (I'll test one side at a time). You
will need 4 el-34's. Matching not required or audible IMHO...see below.
Image: Loading Image...
Sound is outstanding. Imaging is far better than ~$1000 solid state amps
of the hafler or adcom category. (I've owned Hafler 220, 500, Adcom 535,
Bryston ?) This is an accurate amplifier, with an excellent dampening
ratio due to the high current capability of the monoblocked
configuration. It will drive speakers that dip into the 4ohm range. I
used it for years as my reference amplifier driving Sound Lab
electrostatics.
The power supply is highly modified- Solid state rectification and
6x600uF photo-flash caps directly supply the el34's B+. Voltages are
held to original level via a zener drop. Bias supply is stiff with over
4000uF of capacitance.
The biasing scheme is very flexible- a 8 position front panel knob
selects each individual tubes bias and routes it to a meter with ±5%
defection from the ideal el34 bias point. Individual bias adjustment is
accomplished via 8 potentiometer mounted in the space of one st70's pc-3
slot. This individual biasing eliminates the need for quad or octet
matching of the tubes, and the potential of damaging a tube should the
other phases tube fail. Note pots and meter on picture below.
Input RCA connectors are gold plated heavy duty, Speaker outputs are
Gold 5 way binding post with large knurled nuts.
Included are the cage covers, a new old stock (not photocopied!) Owners
manual, and a original PCB with high-end components and newish (test
100%) matching 7199 tubes.
For ST-70 value, surf ebay...be careful of as-is buys! See
http://www.audioweb.com/Directory/ModelInfo.asp?modelid=4389
This amp is made from two stereo amplifiers, bolted together sideways,
along the original (ugly) front face. None of the 4 channels of
components have been removed...I simply tied each stereo amps outputs
together "in parallel". Each amplifier is then mono with twice the
power. The factory actually describes this in the manual, and, is a
"common" mod. for all of David Hafler's amplifiers. (Hafler founded Dynaco).
As-is it is not a 4 channel amp because I am using only one stereo
sutherland driver board. One could buy another and make 2 st70's (see
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3079904855&category=50593).
Or, use the two tube driver boards (supplied) that I bought the amps
with. I was in contact with Mr Sutherland...he mailed me the parts to
improve the driver board further, for better bass.
Why do this? 70W tubes is a world stiffer than 35W. The stock 35W st70
gets flabby in the bass real quick on anything but antique speakers
(that have no bass anyway). With this amp you get world class imaging
and tube warmth without weak bass.
The amp is undisputably better than 2 mark4's. More power and most agree
the el34 has more finesse than the mark4 bigger beam tetrodes.
In addition, for the last word in linearity, this amp can/could be
modified to run triode mode, or, switchable between triode and pentode.
See Loading Image...
. I can perform this mod
for an additional $100, tested.
I have to charge a $20 packaging fee. Approx 35lbs.
Thanks
-Dan
output stage is fed from one channel of the highly regarded Sutherland
ST70 FET driver PC-3. The output transformers' 16ohm taps are wired in
parallel giving 70W per channel RMS into 8 ohms.
On ebay as no. 3080146504
Buy it now for $600.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3080146504
NOT "AS IS". Comes with full test report from my audio lab. You approve
before paying. (I'm a MSEE analog electrical engineer working at MIT,
and have a $26K THD analyzer).Unfortunately, I untubed it to move and
can only find 4 of the 8 el-34's! (I'll test one side at a time). You
will need 4 el-34's. Matching not required or audible IMHO...see below.
Image: Loading Image...
Sound is outstanding. Imaging is far better than ~$1000 solid state amps
of the hafler or adcom category. (I've owned Hafler 220, 500, Adcom 535,
Bryston ?) This is an accurate amplifier, with an excellent dampening
ratio due to the high current capability of the monoblocked
configuration. It will drive speakers that dip into the 4ohm range. I
used it for years as my reference amplifier driving Sound Lab
electrostatics.
The power supply is highly modified- Solid state rectification and
6x600uF photo-flash caps directly supply the el34's B+. Voltages are
held to original level via a zener drop. Bias supply is stiff with over
4000uF of capacitance.
The biasing scheme is very flexible- a 8 position front panel knob
selects each individual tubes bias and routes it to a meter with ±5%
defection from the ideal el34 bias point. Individual bias adjustment is
accomplished via 8 potentiometer mounted in the space of one st70's pc-3
slot. This individual biasing eliminates the need for quad or octet
matching of the tubes, and the potential of damaging a tube should the
other phases tube fail. Note pots and meter on picture below.
Input RCA connectors are gold plated heavy duty, Speaker outputs are
Gold 5 way binding post with large knurled nuts.
Included are the cage covers, a new old stock (not photocopied!) Owners
manual, and a original PCB with high-end components and newish (test
100%) matching 7199 tubes.
For ST-70 value, surf ebay...be careful of as-is buys! See
http://www.audioweb.com/Directory/ModelInfo.asp?modelid=4389
This amp is made from two stereo amplifiers, bolted together sideways,
along the original (ugly) front face. None of the 4 channels of
components have been removed...I simply tied each stereo amps outputs
together "in parallel". Each amplifier is then mono with twice the
power. The factory actually describes this in the manual, and, is a
"common" mod. for all of David Hafler's amplifiers. (Hafler founded Dynaco).
As-is it is not a 4 channel amp because I am using only one stereo
sutherland driver board. One could buy another and make 2 st70's (see
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3079904855&category=50593).
Or, use the two tube driver boards (supplied) that I bought the amps
with. I was in contact with Mr Sutherland...he mailed me the parts to
improve the driver board further, for better bass.
Why do this? 70W tubes is a world stiffer than 35W. The stock 35W st70
gets flabby in the bass real quick on anything but antique speakers
(that have no bass anyway). With this amp you get world class imaging
and tube warmth without weak bass.
The amp is undisputably better than 2 mark4's. More power and most agree
the el34 has more finesse than the mark4 bigger beam tetrodes.
In addition, for the last word in linearity, this amp can/could be
modified to run triode mode, or, switchable between triode and pentode.
See Loading Image...
. I can perform this modfor an additional $100, tested.
I have to charge a $20 packaging fee. Approx 35lbs.
Thanks
-Dan