Just a little more data on the amp. The peak clean power output is 1.3 watts RMS per channel (as determined from watching an oscilloscope). The 3dB frequency response is ≈48 Hz to 30 KHz. A plot of the end to end frequency response is included below with the lines indication the stated bandwidth of just the Edcor output transformers.
Attachment:
Frequency Response.png
This plot is from measured data taken with a signal generator (Zout=600Ω) and a fixed resistive load of 8Ω. The test setup is pictured in the first post. Below is the as built schematic (nearly).
Attachment:
Schematic - as built (small).jpg
I say nearly because after finishing the amp and checking the plate dissipations, I found that the B+ voltages were running a little high. As such I added an appropriate dropping resistor in each B+ line to get the plate dissipations back under the maximum of 5.5 watts each. You can see the modification in this picture.
Attachment:
6CY7 Amp Resistors.jpg
They may not be in the most optimal position in the power supply, but with a nice constant current SET stage it works out just fine.
I still can't get over how good and how loud this amp sounds. It handles everything from classical, to blues, to choral music equally well. And the sound stage is awesome. I will never go back to building common power supply filters for both channels ever again.
Login
Register
FAQ
It's one of those "tube things" that either you care about or you don't. These are all small base 9 pin miniature tubes. The heaters for these tubes are 6.3W for the 6CA4 and 4.7W each for the 6CY7s, for a total of 15.7W. This is compared to 1.9W for a typical 12A*7. What this means is that this amp REALLY GLOWS! In a dim room the glow from the amp really stands out.
