|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
24.140.98.34
Bandwidth sweep 20-20KHz.
Hammond 125ESE OPT.
So far I have found 3 things that seem to affect ARTA THD% measurement :
1) 2A3 types - monoplate vs. biplate.
I also was able to detect a defective tube.
2) plate load and biasing of 2A3 finals
3) external vs. internal signal generator - this was most evident at lower power levels.
The ESI Juli@ has performed well since I removed anti-virus program from PC running XP SP3.
Follow Ups:
The effect of changing impedance and inductance.
I hooked up some Optimus Pro LX5's as a load for the OPT secondary.
Just ran the signal into 10:1 attenuator probes to the soundcard.
A microphone would probably have a different looking graph because of the room acoustics or whatever.
The sweep is not razor flat, but I was not expecting it to be with a speaker load.
This is the best I can do until I get a bit more familiar with FFT measurements.
That would get back to a 5k load .
Keep it up, doing a great job.
The measurement was taken on 5K primary tap w/8 ohm speaker.
Were you able to hear anything that could be correlated to what you measured? Just curious about the threshold of audibility.
There was a subjectively veiled characteristic to the right channel, the one that had the defective 2A3 with twice the THD%.
The tube measured fine on the DMM, so it was not an easy thing to diagnose.
It might have been more evident if I had driven the amp closer to clipping.
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: