I recently picked up one of these, mildly moded by the PO. The pre sounds wonderful throughout the mids, very 3d. But the line section seems a little wimpy on bass. The phono section sounds just fine compared to other good phono sections.
I think the only mod that the PO did was to substitute 1 microfarad Mundorf caps for the C9/C109 ooutput coupling caps that should be 3.3uF per the schematic.
Wondering if I should put some 3.3uF caps back in? Line stage tubes are Amperex bugle boy 6DJ8s, those should be good. I could roll in some other tubes, or maybe test them on my Eico?
Would appreciate any input.
I think the only mod that the PO did was to substitute 1 microfarad Mundorf caps for the C9/C109 ooutput coupling caps that should be 3.3uF per the schematic.
Wondering if I should put some 3.3uF caps back in? Line stage tubes are Amperex bugle boy 6DJ8s, those should be good. I could roll in some other tubes, or maybe test them on my Eico?
Would appreciate any input.
Looking at the Dynaco-PAS-4 circuit diagram it shows -
C9/C109 as =1uF- polypropylene,
this is shown also in the parts list.
Dynaco PAS-4 - Manual - Vacuum Tube Preamplifier - HiFi Engine
There is no sign of =3.3uF capacitors.
C9/C109 as =1uF- polypropylene,
this is shown also in the parts list.
Dynaco PAS-4 - Manual - Vacuum Tube Preamplifier - HiFi Engine
There is no sign of =3.3uF capacitors.
Thank you, Ducnan.
Interesting, the online diagram I found elsewhere indicated a 3.3uF in that position.
I found that I had some 6DJ8 tubes on hand, rolled them in. I think they helped the high level section bass response. They tested a little stronger in my Eico 667.
Interesting, the online diagram I found elsewhere indicated a 3.3uF in that position.
I found that I had some 6DJ8 tubes on hand, rolled them in. I think they helped the high level section bass response. They tested a little stronger in my Eico 667.
That preamp wants to see a high-impedance load, for sure, like ≥100KΩ. If your load is less, you may see some performance losses. Putting in a higher-value cap certainly won't hurt anything, and may improve bass response into a lower impedance load.