Any experiences with the sonic quality of replacing the mains with
a switching supply like a Coldamp SPS30? It can also be ordered
with -/+ 15VDC to power the opamps in the 405/clones.
I have to switch out a noisy transformer in my unit and
am considering this as an option.
a switching supply like a Coldamp SPS30? It can also be ordered
with -/+ 15VDC to power the opamps in the 405/clones.
I have to switch out a noisy transformer in my unit and
am considering this as an option.
I have discovered over the past two weeks that contrary to popular belief an SMPS works and sound far better than conventional large transformer based supplies.
Chord Electronics seem to make a bit of high-end money out of switching supply amplifiers. among other gear.
Interviews with the designer showed earthing arrangements to be bigger than normal issues. Well, he would say that to promote his approach but the argument looked reasonable.
Hi-Fi and Home Audio, music systems, components, home cinema
Otherwise, have you exhausted the options of conventional, R-Core, C-core H-Core transformers which may fit the space available better?
It may be worth considering that 2 stacked toroids paralleled or seriesed can work just as well as a large one, Assuming the original transformer was probably under 200VA, why not a couple of say, 80VA size on the same mounting bolt? There are more ways than one to skin a PSU!
Interviews with the designer showed earthing arrangements to be bigger than normal issues. Well, he would say that to promote his approach but the argument looked reasonable.
Hi-Fi and Home Audio, music systems, components, home cinema
Otherwise, have you exhausted the options of conventional, R-Core, C-core H-Core transformers which may fit the space available better?
It may be worth considering that 2 stacked toroids paralleled or seriesed can work just as well as a large one, Assuming the original transformer was probably under 200VA, why not a couple of say, 80VA size on the same mounting bolt? There are more ways than one to skin a PSU!
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I think there are good technical reasons why this should be the case. Just connect a scope to one of the rails of an amp under load, fed by an SMPS and then by a linear power supply. SMPS typically shows some switching fuzz above the audio frequency, but that is about it. Linear power supply sags under load, but not just that, it starts to produce a cross between a sawtooth and a sine wave at the net frequency. This produces a lot of harmonics, right in the audio band. In short, it makes a lot of sense to move the frequency at which the net voltage is transformed to outside the audio band.
vac
I would say this knocks the nail on the head. Conventional 50/60Hz transformer supply hum and harmonics lie inside the audio band.
We make transformers for all kinds of applications and I have tried most types and configurations. All my amps except for the class A I made in the last two weeks are big transformer driven until the SMPS arrived (US$50). The SMPS is from Mean Well Type S-350-27 adjusted to 30VDC/13Amp
My brother and I did some extensive listening over the past four days to evaluate the two set-ups and we both concur without any doubt, there is no comparison, SMPS is tonally far superior to conventional power supplies besides there is zero hum.
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Nico,
This is good news.
Is there any sonic benefit from additional capacitor banking
of the mains rail voltages?
Did you do any listening tests with and without the cap bank
attached to each channel?
This is good news.
Is there any sonic benefit from additional capacitor banking
of the mains rail voltages?
Did you do any listening tests with and without the cap bank
attached to each channel?
This is a single rail, fairly large device and obviously 2 will be needed for the QUAD. MEANWELL offer multi output supplies but they seem to all be low power affairs and of the same polarity. Competing Chinese manufacturers seem to offer similar products, so perhaps this is not a suitable solution.
Does anyone know of such an affordable supply with dual, opposite polarity outputs or more compact types that could safely be stacked for the same purpose?
I was going to get
SMPS500R with +/- 50VDC and +/- 15VDC aux. It can maintain 500W continously
and peak at 650W which is more current than the 2 x Q405 boards need.
It is 100mm x 100mm. Should be an easy fit to replace the factory transformer
and leave room for caps too if needed.
Google SMPS500R from (connexelctronic.com).
The unit is roughly $80USD. Which is about the cost of as replacement toroid.
I want to restore the 405 (stock as possible) to drive some ESL 63 so I get
some insight into Quad/Peter Walker's notions of acceptable sonics.
SMPS500R with +/- 50VDC and +/- 15VDC aux. It can maintain 500W continously
and peak at 650W which is more current than the 2 x Q405 boards need.
It is 100mm x 100mm. Should be an easy fit to replace the factory transformer
and leave room for caps too if needed.
Google SMPS500R from (connexelctronic.com).
The unit is roughly $80USD. Which is about the cost of as replacement toroid.
I want to restore the 405 (stock as possible) to drive some ESL 63 so I get
some insight into Quad/Peter Walker's notions of acceptable sonics.
I want to restore the 405 (stock as possible) to drive some ESL 63 so I get
some insight into Quad/Peter Walker's notions of acceptable sonics.
I think that is an insult to Quad and Peter.
In their day they were not " acceptable"
they were state of the art!!!!!!!!!
There were many other talented designers working at the same time either still with valves or with transistors, differences in tastes and hearing gave rise to many now famous brands.
No one then or now makes "Acceptable" HiFi!!!
some insight into Quad/Peter Walker's notions of acceptable sonics.
I think that is an insult to Quad and Peter.
In their day they were not " acceptable"
they were state of the art!!!!!!!!!
There were many other talented designers working at the same time either still with valves or with transistors, differences in tastes and hearing gave rise to many now famous brands.
No one then or now makes "Acceptable" HiFi!!!
I don't think that's what the OP meant - If you read it as what P.Walker thought "acceptable", it is quite respectful of the designer who assuredly, according to his papers, had his eye on the instruments and measurements and not on "sonics".I want to restore the 405 (stock as possible) to drive some ESL 63 so I get
some insight into Quad/Peter Walker's notions of acceptable sonics.
....No one then or now makes "Acceptable" HiFi!!!
However, the real matter is that it refers to long ago when Audio generally sucked due to technical shortcomings. I know because I DIY'ed then too. 😉
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I wasn't trying to insult Quad or Walker's legacy. I'm interested in hearing the
sonic signature offered by Quad/Walker for late 70s.
sonic signature offered by Quad/Walker for late 70s.
The SMPS from Connexelectronics seems brilliantly efficient, thanks errcl65.
However, as a basic board assembly, you'll need to add a few things as it has some issues with PSRR of the amplifier and it requires shielding for safe low-emission use. You need to add at least a line filter socket to keep noise off the mains. These are pictured and rated also.
I'd be interested to know what the seller meant by its unregulated design, where other types are regulated and whether it's really relevant.
However, as a basic board assembly, you'll need to add a few things as it has some issues with PSRR of the amplifier and it requires shielding for safe low-emission use. You need to add at least a line filter socket to keep noise off the mains. These are pictured and rated also.
I'd be interested to know what the seller meant by its unregulated design, where other types are regulated and whether it's really relevant.
Two power supplies wired pos to neg which would be the zero volts.
Edit: The output of this model is completely floating so it can be connected in series for Pos- 0 - Neg supply.
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Good news, thanks Nico,
A floating supply wasn't clear in the spec. I read and I've seen a shower of sparks when an acquaintance just assumed it without checking.
That must be one mighty JLH amplifier there...😎
A floating supply wasn't clear in the spec. I read and I've seen a shower of sparks when an acquaintance just assumed it without checking.
That must be one mighty JLH amplifier there...😎
Hi Ian, it sounds pretty loud but the power is only around 24 watt peak into 8 ohms before the onset of clipping. I am now hi-jacking this thread with irrelevant stuff. Sorry guys.
It is not a good idea to add additional capacitors from rails to ground. The SMPS has some capacitance on board, usually exact the needed amount to shave off switching peaks. Adding more capacitance may make it more difficult for the SMPS to correct the effects of loading, so it may actually make it worse.
What then are the effects of cross channel isolation if you
supply both sides with the same SMPS without reserves/filtering
dedicated to each channel?
Should we be looking at one SMPS for each channel?
supply both sides with the same SMPS without reserves/filtering
dedicated to each channel?
Should we be looking at one SMPS for each channel?
Not sure what you]re aiming at here, errcl65. The original supply was connected to both amplifiers and you say you want to keep the amplifier as close as possible to original so that you can evaluate the sonics.
Since the sound of an amplifier is often characterised by the PSU as much as the amplifier, I wonder what you mean to achieve with SMPS and/or separate supplies. I'll venture that it will have a different character to the original. Not that it won't sound better and all kinds of high-end speak but if you just want to upgrade it there are a myriad options qnd the usual things modders do to follow trends. It's revealing that such amps are worth less than those in original condition.
Another issue is that separate supplies offer most benefit to the cross-talk of simple designs with poor PSRR. You could say that most early designs were like this and the QUAD 405 might be a candidate for improvement but it is not a conventional design, having a small signal class A amplifier driving the load with the assistance of a normal sized amplifier in class B, via the balance of a clever LR bridge circuit and CR compensation at the input.
Of course, you are free to do things as you please and others will flock to support any modifications for the fun of it but I would be cautious messing with the original arrangements if my aim was to evaluate what the designer heard. 😉
Since the sound of an amplifier is often characterised by the PSU as much as the amplifier, I wonder what you mean to achieve with SMPS and/or separate supplies. I'll venture that it will have a different character to the original. Not that it won't sound better and all kinds of high-end speak but if you just want to upgrade it there are a myriad options qnd the usual things modders do to follow trends. It's revealing that such amps are worth less than those in original condition.
Another issue is that separate supplies offer most benefit to the cross-talk of simple designs with poor PSRR. You could say that most early designs were like this and the QUAD 405 might be a candidate for improvement but it is not a conventional design, having a small signal class A amplifier driving the load with the assistance of a normal sized amplifier in class B, via the balance of a clever LR bridge circuit and CR compensation at the input.
Of course, you are free to do things as you please and others will flock to support any modifications for the fun of it but I would be cautious messing with the original arrangements if my aim was to evaluate what the designer heard. 😉
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