The Audiophoolery Thread.

[Beobloke]

Despite the comedy audiophoolery (and, believe me, there is lots!) I always enjoy the Munich High End Show and had a great time there for two days last week.

I even heard a pair of horn loudspeakers that didn't have me running from the room, crying and covering my ears, which was a first. Mind you, they did cost 800,000 Euro per pair...

The new re-launched Quad 33 and 303 looked quite nice, too.

[Radio Wrangler]

Amplifiers, knobtwiddler? I think those may just be the terminal box at the end of one rather up-market cable. Made from sapient pearwood and supplied by the thaumaturgical engineering department of Unseen University. APC-7 connectors on the other end for those with the most demanding hearing.

David

[Craig Sawyers]

Wow - a new 33/303! I lusted after those so badly it almost hurt as a teenager when the originals were a thing. Of course could never afford them.

Bought a set maybe 10 years ago from the original owner that now grace our kitchen system. FM4, and D-A feeding optical from the TV into the second radio input. Feeding (shock horror) ceiling speakers.

Presumably the new 33 does not rely on 6 transistors per channel!

Craig

[Boulevardier]

Originally Posted by Beobloke

The new re-launched Quad 33 and 303 looked quite nice, too.

Who has relaunched them? Quad?
Mike

[ajgriff]

Quad as owned by IAG:

https://www.quad-hifi.co.uk/quad-33/

Alan

[Radio Wrangler]

Like many hereabouts, I'd love to know what's inside them.

David

[Cobaltblue]

Harvested unicorns I would guess.

Or more likely some mass market parts like virtually all modern consumer goods which actually outperforms the original.

When I say outperforms that's of course in relative terms Hilda's sweat and dodgy soldering will always ace anything from China.

Cheers

Mike T

[chriswood1900]

Originally Posted by Beobloke

Despite the comedy audiophoolery (and, believe me, there is lots!) I always enjoy the Munich High End Show and had a great time there for two days last week.

The new re-launched Quad 33 and 303 looked quite nice, too.

Let’s hope this is the return of sensibly priced decent sounding HiFi gear with a bit of retro style, looking at the launch pictures it does look as though they have dropped the Quad style tone controls for conventional ones with lcd readouts. I would also expect multiple opamps with a discrete output stage to deliver say 100 watts per channel.
Due out this Autumn
What would others like to see or expect!

[Ted Kendall]

Originally Posted by chriswood1900

Let’s hope this is the return of sensibly priced decent sounding HiFi gear with a bit of retro style

I wouldn't hold your breath, judging by the recent "Leak" - neither cheap nor particularly good. The new 33 doesn't have a tape monitor loop, I believe, and the 303 probably won't use the output triples for reasons David has explained at length. Still, electronic instead of mechanical switches on the 33 would be an advance...

[Boulevardier]

Originally Posted by Ted Kendall

I wouldn't hold your breath, judging by the recent "Leak" - neither cheap nor particularly good. The new 33 doesn't have a tape monitor loop, I believe, and the 303 probably won't use the output triples for reasons David has explained at length. Still, electronic instead of mechanical switches on the 33 would be an advance...

But, surely the 303 wouldn't be a 303 at all without those "troublesome triples"...
Mike

[Craig Sawyers]

Given that every non-valved Quad power amp since the 405 has used current dumping, my guess is that the new 303 also uses dumping.

Either that or a total departure, and Class D.

Craig

[chriswood1900]

Quad have started to use some integrated class A/B chips into products like the Vena at 65W Per channel so it is possible they could stick with A/B but would need a minimum of 100W per channel to justify the separate units.

[Trigon.]

Clip below contains sales patter from a QUAD salesman at Munich show (at 41:20):-

https://www.youtube.com/watch?v=hyTZjSUAQqI&t=2457s

Apparently the new 303 will have triples!

Cheers

[Craig Sawyers]

The triples were a Peter Baxandall innovation when he worked as a consultant to Quad. The only bit he did not design was the input circuit, which was designed by Mike Albinson. Both alas RIP.

The other thing that Baxandall said was the 67V regulated supply has nothing to do with audio quality or anything related to that, whatever current thinking is. It was down to this being the first transistor power amp that quad/Baxandall did, and they were paranoid about blowing up power transistors - hence the regulated supply!

Craig

[Boulevardier]

Originally Posted by Trigon.

Clip below contains sales patter from a QUAD salesman at Munich show (at 41:20):-

https://www.youtube.com/watch?v=hyTZjSUAQqI&t=2457s

Apparently the new 303 will have triples!

Cheers

If so, it will be very interesting to see how they design the triples for stability using modern high-FT semiconductors.

But the way things are now, I wonder if schematics/service manuals will ever be easily available. Think Pure!

Mike

[Boulevardier]

Originally Posted by Craig Sawyers

The other thing that Baxandall said was the 67V regulated supply has nothing to do with audio quality or anything related to that, whatever current thinking is. It was down to this being the first transistor power amp that quad/Baxandall did, and they were paranoid about blowing up power transistors - hence the regulated supply!

Craig

Somewhere in his writings, Douglas Self records a discussion with Peter Walker (at least, I think it was Walker) on the regulated power supply issue, which confirms Craig's comment. IIRC, Self was quite passionate in his insistence that a well-designed PA didn't need a regulated power supply.

Mike

[Craig Sawyers]

Well in all the previous power amplifiers (including all current ones bar the 303) they have used dumping, and have managed to adapt the circuit to use modern high fT transistors.

Craig

[Craig Sawyers]

Originally Posted by Boulevardier

Somewhere in his writings, Douglas Self records a discussion with Peter Walker (at least, I think it was Walker) on the regulated power supply issue, which confirms Craig's comment.

It was with Baxandall.

https://www.linearaudio.net/baxandall-self-audio-power

Still available via Amazon for a shade under twenty quid.

Craig

Craig

[Radio Wrangler]

Originally Posted by Boulevardier

If so, it will be very interesting to see how they design the triples for stability using modern high-FT semiconductors.

It isn't that the power transistors have high Ft, rather it's a case that the difference in Ft between the power transistor and the drivers has closed up.

The triples can be made to work again, if fast enough drivers are used to open up the gaps again. Pushing things an order of magnitude or more up-spectrum will mean other details will need attending to. Something more like "VHF style" layout will be needed to avoid inductance in emitter connections, and wires to power transistors on the heatsinks will be right out. I expect the internals will be redesigned to place individual power amp boards right by the power transistors on the heatsinks.

If this sounds silly for audio, it isn't. It's a matter of extending controlled gain and phase characteristics well beyond audio so that things can be wound down in a refined manner without RF instability. The existing 303 quite often exhibits a small tweet in the 7 to 12MHz region somewhere on a sinewave if you're driving it into a resistive load. Hfe and Ft both vary with current, and vary quickly.

So, for a feedback-controlled amplifier above the audio band, you have a band where gain is winding down in a controlled manner without too much phase delay rolling in. For the main feedback loop around a power amp, this roll off band can extend to ten times or more the audio range. For the little three-stage feedback loops of the quad triplets, the roll-off range is even more extreme.

The main loop has deliberate time constants to set its parameters. The Quad triplets just rely on not very well controlled semiconductor parameters to create poles in the right order and with the right spacing.

It can be done, but why bother? There are plenty of fine amplifiers working well without those triplets. They were a tool for getting the best out of the silicon of the day. The device improvements which have given us trouble, also make the triplets unnecessary unless you view them as heritage items there just for the archaeology of it all.

We could also question the benefits of current dumping. Again others get on just fine without it. It helped a bit for getting around semiconductors of the day. Error cancellation techniques can be a bit touchy, where a small error in circuitry creates a disproportionately large error in overall performance. There are some interesting calculations in ensuring the class-A stage can always make up tor the shortcomings in the dumpers, at all frequencies, at all loads and at all combinations of frequencies. There are a few assumptions buried in this area.

Oops.... Phoolery content = 0 Maybe their price will save me!

David

[Boulevardier]

Thanks, David, for your usual excellent explanation.
Mike