About a year and a half ago, I overhauled a Dynaco SCA-35 using Dave Gillespie's EFB/power supply and power amplifier boards. I have been very pleased with the result, and have been using it for a small system fed by a computer and DAC, where I find the preamplifier controls to be quite useful.
But, I kept reading that the ST-35 was even better, and wondered what that would sound like in my system with better speakers. Although the original ST-35 can now be recreated using the Dynakitparts kit, I thought it would be fun to try something different, starting with another SCA-35 and taking advantage of the extra space to add a power supply choke and selectable inputs. I originally intended to also add a volume control, but Dave warned me that this would wreak havoc with the impedance the ST-35 sees. Dave also suggested adding a small cooling fan.
I've now finished this project and am, again, very pleased. Since it's a bit offbeat, I thought that there might be interested here, where I have been lurking and learning for the past two years.
Rather than drilling a big new hole in the case, I mounted a 50 mm fan over the openings used in the SCA-35 for the low-level inputs. The fan is powered by a small encapsulated 5 V switching power supply (sort of a wall wart without the wall). This supply is also used to drive an LED behind the original pilot light jewel. As a rough estimate, the fan seems to lower the temperatures (measured with an IR thermometer) of the heat-generating components by about 10 C, making the unit notably cooler.
Using the SCA-35 EFB/power supply board provides a bit more capacitance than either the original ST-35 supply or Daves ST-35 EFB board, but the dropping resistor values had to be slightly modified.
As you can see in the pictures below, I've tried to maintain the classic Dynaco look, as if it might have been an original product.
David
But, I kept reading that the ST-35 was even better, and wondered what that would sound like in my system with better speakers. Although the original ST-35 can now be recreated using the Dynakitparts kit, I thought it would be fun to try something different, starting with another SCA-35 and taking advantage of the extra space to add a power supply choke and selectable inputs. I originally intended to also add a volume control, but Dave warned me that this would wreak havoc with the impedance the ST-35 sees. Dave also suggested adding a small cooling fan.
I've now finished this project and am, again, very pleased. Since it's a bit offbeat, I thought that there might be interested here, where I have been lurking and learning for the past two years.
Rather than drilling a big new hole in the case, I mounted a 50 mm fan over the openings used in the SCA-35 for the low-level inputs. The fan is powered by a small encapsulated 5 V switching power supply (sort of a wall wart without the wall). This supply is also used to drive an LED behind the original pilot light jewel. As a rough estimate, the fan seems to lower the temperatures (measured with an IR thermometer) of the heat-generating components by about 10 C, making the unit notably cooler.
Using the SCA-35 EFB/power supply board provides a bit more capacitance than either the original ST-35 supply or Daves ST-35 EFB board, but the dropping resistor values had to be slightly modified.
As you can see in the pictures below, I've tried to maintain the classic Dynaco look, as if it might have been an original product.
David
Is there a significant sound improvement in comparison with your SCA-35?
