Embedded Files
The picture below shows the integreted SCA35... or rather what is left of the original Dynaco SCA35 amplifier....
The important thing connected to the remains of the SCA35 was the buy of the famous outputtransformers and the mains powertransformer.
A smaller but equally exciting DIY task.
To change the remains of a Dynaco SCA35 that was purchased from a small island in DK, and rebuild the pieces into a brilliant version of Dynaco's ST35.
And why do you try to rebuild such old electronics remnants from the sixties into a "new" good-sounding amplifier?....
You like to make that attempt because you know, that Dynaco's engineers succeeded in producing some of the best output transformers, which included two extra patented taps from OP's called "Ultra-Linear".
This Dynaco patent gave an excellent result with a frequency response and excellent linearity from 20 Hz ~ 20,000 Hz - 1.5dB and a distortion down to around 0.5%. Fantastic data at the time!
These data came as a previously unheard great result from David Hafler and Herbert Keroes in the sixties, and the success continued until 1974 when the "Ultra-Linear" patent expired.
The original ST35 schematic:
The new ST35. Version:
Both pictures above are available as PDF files.
The basic PCB for the ST35 REV. Version has been made on CadInt:
Approx. Size 38,7 cm x 29,3 cm
The PCB incl. transformers and mains power capacitors
Next the Pcb seen from the solder side (copper side).
The pre-drilled 6mm holes for the two noval sockets.
There are no difference at hookup wiring from the SCA35 to the ST35 output transformers
The visual thin guide-lines need to be connected
Important:
The new shown PCB uses one ECC83 and one ECC82.
The original design by Dynaco included the use of the 12DW7 input/driver tube. The 12DW7 houses one ½ ECC83 and one ½ ECC82.
The sales prices of 12DW7 has increased during the last decade, and the layout of the Dynaco ST35 REV. version has been changed to the standard tubes ECC83 and ECC82
Besides the change of valves the bias regulation has now two single cathode resistors (one for each EL84) and multiturn trimpot’s to adkust the negative voltage.
This layout allows the users to find better bias-balance for the EL84 valves in the outputstage .
The estimated size of the amplifier to be seen on the picture above
The bottom view of the ”new” Dynaco ST35:
The power capacitors moved to the sidepanels for more space.
With dust and all.......
The backside of the Dynaco ST35 with a four pole switch to be used together with bias testing for each EL84.
On the front of the amplifier four 3 mm holes located to house the LED’s for test of each valve. The idea is that the correct bias adjustment shall ligt up one LED at the time which indicates the wanted 24 mA per output valve.
My ”personal” version of the famous Dynaco ST35 standing on the top of the
1963 Bang & Olufsen’s ”Grand Prix Moderne” .
This is the author’s Dynaco ST35 design....small , tight and able to deliver great sound....
A bit blurry photo...but it's what's left of the old pictures....
Brass top plate with wooden sides made of varnished teak wood
The Dynaco ST35 circuit is worth all the work
The ST35 sounds beautifully
Page updated
Google Sites
Report abuse