• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Carlson-Stromberg ASR-333 modified - by-pass Tone Controls

So to recap for my benefit, as I have an ASR-433, you bypassed the tone controls and used a voltage divider to replace the volume pot feed to the 6AV6. It looks like you have a really good flat frequency response which I was never able to achieve on mine with the tone controls operating. Once you are done please post the component values you have used.
Thank
 
nerdorama said:
So to recap for my benefit, as I have an ASR-433, you bypassed the tone controls and used a voltage divider to replace the volume pot feed to the 6AV6. It looks like you have a really good flat frequency response which I was never able to achieve on mine with the tone controls operating. Once you are done please post the component values you have used.
Thank
Click to expand...
I by-passed the 6AV6 (and removed them) and disconnected the master volume pot from the 6u8.

I ran new coax from the inputs to the voltage divider on the input of the 6u8.
As Gadget73 suggested, I used a fixed voltage divider using a 56k and a 47k to ground.

This gave me the better signal level before clipping, I could only get a maximum of 0.4 vrms before clipping, now it’s 0.8vrms. I suppose I could tweak it a little bit, I might just do that when I have more time.
 
I should also mention that I rebuilt the power supply and changed almost every resistor and capacitor in the entire unit
 
Yes, that is what I really wanted.
I tried to get the unit quiet, but I could not get rid of all the hum, once I by-passed the controls, its quiet as can be.
 
I replaced every resistor in my 433, so many were grossly off value that it honestly took less time than to measure. I think the tone controls are currently bypassed in it too, though I wouldn't mind seeing if I can make them better, and maybe make the bypass switchable. Its got a DC supply for the phono heaters, and a different phono preamp circuit as well at this point, so still basically useful as an integrated amp just with tone controls that don't do anything.

The power amp really is the gem in these units though, nice output iron, good power supply, and a sound basic design.
 
I think S-C used good output transformers. I used a set from an ASR-220. They are small but perform very well.

nerdorama

Thread 'compactron power amp project'

I have a set of transformers from a Stromberg Carlson integrated. It was the ASR220c I think, a 6V6 PP amp with 7199 VA and PI stages. I have a box of 5HA7 compactrons which are a version of the 7247 dissimilar triode. I think it would be fun to build an all compactron 12 pin power amp on a small chassis box. I have a set of 6JB5's coming to use with them and will use a pair of 6CT3 damper diodes. I think it will be a fun little amp project. If anyone has any experience of a similar project or any other ideas to share please let me know.
Thanks,
John
  • Like
 
You must log in or register to reply here.
Back
Top Bottom