PMA, I think we are measuring the same thing, but at low levels like 10-20W with the A-21, higher order distortion can be exaggerated by NOT having 15mV-22mV across Re at idle. Your amp is doing as expected. I must admit that at higher output powers, a bipolar transistor output is never perfect, and includes higher order harmonics, without a great deal more negative feedback. What I always try to concentrate on is the linearity of the transfer function over the transition between Class A and Class A-B, which is usually optimum around 22mV bias across the emitter resistor.
Back to the original problem: Why does the A21 not like 4 ohm loads, compared to some other power amps?
Back to the original problem: Why does the A21 not like 4 ohm loads, compared to some other power amps?
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Beautiful work Pavel!
It looks from the pictures that you created mirror image boards for the two output PCBs instead of using the same one for both? Are you really that much of a tweak?
I really like the design, I wish this amp was available for radio station use, RF immunity is so much better with FET inputs, especially without LP filtering on the inputs greater than the 1st order you included.
Cheers!
Howie
What made you start collecting vinyl so late, 25 years ago they were being dumped en masse?
I agree with PMA that fets in both the input and the driver in this topology are better. However, Parasound engineers designing the cheaper models, invariably find better thd specs and more efficiency by using bipolars in the driver stages, so the A21 uses bipolars after the first stage instead of fets. My JC series amps use fets throughout, for example:
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I knew a guy once that collected old milk bottles, he had them all shelved and cataloged in his basement and travelled miles to swap meets.
Amazing what some people collect. The problem is that when you die it's all just junk for the wife to dispose of.
My wife has said that my vintage audio will be at the bottom of the drive before the undertakers arrive.
Amazing what some people collect. The problem is that when you die it's all just junk for the wife to dispose of.
My wife has said that my vintage audio will be at the bottom of the drive before the undertakers arrive.
Amen!
Another good example was the (also now gone) Jazz Record Mart in Chicago.
Sigh ...
mlloyd1
Another good example was the (also now gone) Jazz Record Mart in Chicago.
Sigh ...
mlloyd1
I would LOOOOOOOOOOOOOVE that. It's true, it's sad. Thank Jesus Christ Lord Mary Willington that Discogs exists.
I don't share this opinion at all. For me it's really annoying to go to thrift stores and sift through garbage 95% of the time, and just have smelly hands afterwards. If someone else wants to do that to find a gem that I then pay them $10-15 for, WORKS FOR ME. I have plenty of fun going through bins at record stores where it's not 50% Jim Reeves or classical mail subscription garbage.
The truth is almost all the good stuff goes directly to the record stores anyways, because people know they have value and that's where they take them to sell them (from a deceased loved one or they just need $). But if you want to see bad prices, check out Craigslist... Fools are like "all my records are worth $30 a piece because I like the bands, got 175 of them barely scratched to hell with almost legible lettering on them fancy graphics on them sleeves"
That'd be nice, but I think it's a reflection of people listing more. Go look at something rare and tell me it's going down... ya right! Median sale price $20, only thing listed for 2 years $175. But I would say maybe some classical has reduced in value.
Mine told me I will be at the bottom of the drive before the undertakers arrive - shes keeping the audio equipment
Having had a pleasant evening of Joe Bonamassa followed by some Saint Seans violin concerts sitting with the wife and lots of gin I can say music is more enjoyable with 2.
Just have to get the headphones working for when she is in bed and I want to get eclectic.
YouTube recorded in the Fort Worden Cistern which has a 45 second reverb time.
Just have to get the headphones working for when she is in bed and I want to get eclectic.
YouTube recorded in the Fort Worden Cistern which has a 45 second reverb time.
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