The most interesting comment in the article is Nelson’s around the bias circuit —
“The bias circuit that we are using interprets continuous high-power, high-frequency tones as a fault. If you want to do high-power, high-frequency IM test tones, you will need to do them quickly or you will get falsely high readings.”
“The bias circuit that we are using interprets continuous high-power, high-frequency tones as a fault. If you want to do high-power, high-frequency IM test tones, you will need to do them quickly or you will get falsely high readings.”
Historically, high power high frequency test tones are indicative of a major
fault. I simply exploited the difference between rise and fall times of the
sensing circuits to cut off the bias under those conditions.
...or...you are driving a not-very-efficient ribbon tweeter with lots of current and somebody used the "more cowbell" button on the recording.
I think it's safe to say that you are not the target customer for this amplifier.
I think it's safe to say that you are not the target customer for this amplifier.
Guilty as charged.
That said, if the X25 power rails were in the +/- 5v to +/- 10v realm with unlimited peak power and vanishingly low output resistance, I would be tempted. That is what I am working on in the F4 Beast thread.
Thank you mr. Pass for these, what a person you are
He's a real Gentleman.
Papa puts his pants on just like everyone else: one leg at a time. Except, when he puts his pants on, he makes amplifiers!
If you mean the 8 leg critters on the output board, I think those are the TL431. They come in an 8 PDIP and a 3 leg TO92.
After nearly 10 years of following DIYAudio and buying SemiSouth output devices, I had to face that I don't have time to get out the soldering iron. I built my first audio amplifier in 1970. Getting older so I cheated. I invested in a Bryston BCD-3 connected to Pass HPA-1/XA25 connected to Aerial 7s. Stunning. In the coming months I will be auditioning Devore speakers but my old Aerials sound great. The reviews have been written and I can't say more about the sound than what has already been written.
What I can comment upon is my visceral response. For whatever reason, I am able to just listen without picking everything apart and wishing things were different. Rather than getting tense with listening time, I become more relaxed. I often check the thermostat to seek an explanation for my chills. For some reason, over decades of upgrading, I enjoyed fewer and fewer CDs. But with these components, I can enjoy my entire collection. I am so glad that I did not wait longer than I did. When the XA25 design became "known"; I knew I had to have one. I was correct.
What I can comment upon is my visceral response. For whatever reason, I am able to just listen without picking everything apart and wishing things were different. Rather than getting tense with listening time, I become more relaxed. I often check the thermostat to seek an explanation for my chills. For some reason, over decades of upgrading, I enjoyed fewer and fewer CDs. But with these components, I can enjoy my entire collection. I am so glad that I did not wait longer than I did. When the XA25 design became "known"; I knew I had to have one. I was correct.
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