10-12-2019, 06:15 AM
Made some progress on this - see pics. First I decided to split the RIAA phono stage and put it on a separate chassis with the PSU and line stage in the case as shown in tother threads. The circuit I used is a simple one but slightly odd in that it's a CCDA = constant current draw amplifier, more info here - https://www.tubecad.com/2009/03/blog0161.htm and see attcahed schematic. I made a few changes subbing 470r for the Rk's and 310r for the grid stoppers.
The two valves at the back are VR150/30's, there to clamp final HT at 309v as I killed a 820u 400v cap as HT is 450v, not ideal but I used what I had to hand.
Andy.
The two valves at the back are VR150/30's, there to clamp final HT at 309v as I killed a 820u 400v cap as HT is 450v, not ideal but I used what I had to hand.
Andy.
