Dynaco SCA 35  
Integrated Tube Amplifier
fully restored with updates circuit for main amplifier 
with the original Iron ( transformers!) 

New Matched driver and output tubes with Enhanced Fixed Bias or EFB. This method reduces the overall distortion and improves the output power when both channels are driven. Phono section was not modified and still uses the original Telefunken 12AX7 tubes because I do not use MM Phono cartridge 

Read the updates below

Cosmetically this unit is a very clean one retaining the original knobs/face plate etc as i was more interested in getting this amp to perform better.
Includes the assembly manuals etc of the EFB board schematics, user manual for understanding these updates. 

EFB benefits

Innovative way to convert your SCA-35 to fixed bias operation and reveal its full potential. Rated power output will be maintained with both channels driven, and distortion significantly reduced. The *EFB™ feature, when combined with
increased power supply capacity, provides an outstanding upgrade to your SCA-35.

Benefits of *EFB™
- Increased output power with both channels driven
- Reduced distortion
- Reduced bias current for longer tube life


The modified SCA-35 still requires a matched quad of output tubes. This was done on purpose to minimize the extent of changes required, to maintain as much of the original design concept as possible, and because it generates nearly all of the improvement possible. Also, this is always a worthwhile investment in achieving matched performance from both channels
*EFB™ is a trademark of D. Gillespie Designs.


PC-10A board differs from the original Dynaco PC-10 PCB in that it is configured to use either a 6GH8A or 6U8A driver tube in place of the 7199. However, the PC-10A is not just a tube swap with some pin rewiring. Additional components are included to insure stability and low distortion when 6GH8A or 6U8A tubes are employed in place of the 7199. Advantage is easily available Driver tubes and not very expensive like 7199.


The PC-11 PCB is intended as a restoration board, and thus, the circuit configuration, and mounting hole locations, are consistent with the original Dynaco PC-11 circuit
board.

The SCA-35 Capacitor EFB™ Board replaces the original multi section power supply filter capacitors as well as all the associated resistors and high voltage rectifier diodes. Besides larger overall capacitance, additional metalized polypropylene bypass capacitors have also been included. The original cathode bias resistor has been replaced with an innovative Enhanced Fixed Bias feature that allows your SCA-35 to perform to its full potential with both channels driven. Although rated at 17.5W per channel output power, this is really only true if only a single channel is driven. With both channels driven, however, power output is typically closer to 14W per channel (for the original SCA-35), and distortion is significantly higher as well. This is largely due to various compromises related to the use of the simple, but economical, cathode bias system in the original SCA 35 design. Check Tronola.com site

See the comparison in the Picture gallery