I'll pass on the ion curtain. I'm not a fan of ionizing radiation or loose ions. I only turn on the static eliminator when I need it.
The Quads would respond well to a hepa filtered air curtain. It would probably extend the life longer than the dust covers but would need to be active all the time.
Do you think the laminar flow would be a problem? Probably better to live in a class 10 clean room for a number of reasons.
I figure that as long as the pressure is positive and the flow isn't so fast that its noisy it would be a great solution. I'm just not motivated enought to implement it. My quads are approaching 20 years without failure and I don't want to disturb them until I need to.
Douglas Self, in his Power Amplifier book pontificates at length.
This applies to the usual case where the VAS with Miller capacitor set the OL bandwidth of the amp before the Class B follower. There is an optimum bias when that is driven at low Z.
However, other configurations are possible which do not suffer this 'feature' including the Wurcer SupaDupa, AD797 and my poor efforts at making a 990 type perform SupaDupa.
It is not 'hfe doubling' but a change in voltage gain.
Damn!
I've waited >30yrs for someone to try this. Peter Walker has passed on so maybe even no one alive at QUAD has heard this.
I must agree that the Quad without dust covers is exceptional. I have special .00025 mil mylar dust covers which really help but are not completely transparent. The stock ones are not good and I don't think they have explored better solutions (even an amorphous film would be better).
The problem is that the bias attracts dust pretty aggressively and California is pretty dusty so for now the dust covers stay.
The problem is that the bias attracts dust pretty aggressively and California is pretty dusty so for now the dust covers stay.
I am not sure it is correlated with bandwidth (outrageous anyway)or current. No miller cap and OL bandwidth >20 000. All precautions had been taken that any stage never run out of current up to 6Mhz.
I believe more in a question of optimal temp variation with signal and associated changes of Rdson. I have noticed this same optimum bias current with different power FETs on different topologies. Need to try a true error correction topology to validate (but i'm lazy).
I also wonder if an amp, running at class A on average levels, and at class B at peaks, does not give a subjective impression of increased dynamic, see what i mean.
Contrary to many, i tend to prefer good class B to pure class A for power amps.
All that, with measuring distortions so low that i don't know what i could notice ;-)
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Similarly, class AB amps shake chairs, while class A is standing in the corner, waiting for cold winter nights...
So true.
My next amp, if any, will be class D.
And just to worry about triangle, comparator and filter. (emoticon here)
The "gruntiest" amplifier I've come across recently was Bryston's 28BSST -- boring class AB, you can download the schematic from the manufacturer. There's "magic" in some of the implementation, which are key to making it happen, but it demonstrates that just doing things conventionally in an overall sense is sufficient ...
Frank
Frank
I've listened to 40 years of Bryston amplifier evolution. Compared to Pass, Ayre, Parasound, Audio Research and other well regarded competition i find them grainy, lacking resolution, and even harsh souding on a variety of speakers. Bryston's seemingly overly positive reviews may have more to do with the size of their advertising budget than their technical and audible accomplishments.
Bryston's famed "discrete " preamp topology is a 3 stage simple discrete opamp coupled through 4 to 6 aluminim caps per channel, an entire preamp is powered by a single pair of fixed voltage three terminal regulators from an unsophisticated raw supply.
Bryston's famed "discrete " preamp topology is a 3 stage simple discrete opamp coupled through 4 to 6 aluminim caps per channel, an entire preamp is powered by a single pair of fixed voltage three terminal regulators from an unsophisticated raw supply.
Perhaps you can teach an old dog new ..... have you actually listened to these units? Bryston of late seems to have learnt a few tricks, there's been a marked turnaround of opinion recently -- check out the 6moons review.
Those adjectives you use can be ascribed to virtually any amplifier not fully optimised in a setup; I listened in agony to Audio Research M600 Reference amps on one very ambitious setup, they were drilling holes through my skull ...
I heard a decent drum solo workout on the Brystons, the genuine bite and raw impact of the real thing on a casual playback was impressive...
Frank
Tough customers. In all my years here Bryston is the only audio amp maker that inquired about licensing one of our patents. We do/did some custom branding for others to hide part numbers. None now, but at least one CD maker (re-boxer) added some quite expensive op-amps more than 20yr. ago.
Andrew Lakner had just finished to provide his very very nice SSA for a recording studio. (Current feedback symmetrical)35 years ago I thought that class A is the history. May be it is the time now?
Then, for some reasons, build a Hypex NC400 and was in the same studio to compare them.
This guy is a very good designer, use to listen carefully at each steps of his work and had proven he owns clever ears.
That's what he said, despite one of them was his baby:
"...can say firmly the amps are similar in character and musical presentation in general. From there on, subtle differences are noticeable, some in a favor to NC400, some to SSA, have to be fair and honest."
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