Millett LR + TP Opus + AMB α24 reboot

What people are working on at the moment
User avatar
Nick
Site Admin
Posts: 15707
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#136 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Nick »

Well if it was behaving like an aerial but fine before. To me that still points to there being more noise around for it to pickup. Likewise behaving like a touch switch points to something being off.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
User avatar
Ray P
No idea why I do this anymore
Posts: 6294
Joined: Thu Nov 22, 2007 5:18 pm
Location: Somerset

#137 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Ray P »

Hi Dave. FWIW, I probably wouldn't have selected the Silent Switcher for the phono stage scenario you have, but would likely have gone for very low noise linear regulated supplies and probably with remote transformers but I'm no EE and to some extent I'm just exposing my biases, as we all do. I have just build another BUF-03 based buffer, similar to the one I have used the Silent Switcher in but this time it has a bipolar linear supply using TPS7A4700/TPS7A3301 devices so it'll be interesting if I can detect any difference.

Anyway, the point I was primarily making was about how easily the SilentSwitcher was written off without any apparent meaningful investigation or dialogue with the designer and the easy acceptance of the conclusion that positive commentary about the SilentSwitcher on the internet must be flawed - the internet is no different to any other source of information in that you need to be cautious about the bits you use.

Agree with Nick (Jack) too - change one thing at a time.

Glad you have a way forward now though and the outcome is looking promising.
Sorry, I couldn't resist!
User avatar
Nick
Site Admin
Posts: 15707
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#138 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Nick »

Anyway, the point I was primarily making was about how easily the Silent Switcher was written off without any apparent meaningful investigation or dialogue with the designer and the easy acceptance of the conclusion that positive commentary about the Silent Switcher on the internet must be flawed
I am not sure any of that happened, all I was suggesting was that ones first hand experience is the real reality that you can kick.

Add to add to that. I would point out that I suggested several times that the thing to do is measure so its known what the problem is that needs solving. At no time have I or would I suggest changing more than one thing at once. I made repeated suggestions as to the reset pin (for example), I refuse to be held responsible if my suggestions are not followed (not that they need to be, but don;t then point to me as a source of jumping to conclusions).
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
User avatar
Nick
Site Admin
Posts: 15707
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#139 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Nick »

I had a thought. Given that he silent Switcher seems to have been designed to be powered by a USB supply, it may assume that he source is going to be noisy, and so the focus may be the noise out of the thing, It may be injecting noise back into the source of its power assuming its isolated and doesn't matter. In this case it may be that because there are multiple supplies they are seeing each other and the heard tone may be the result of the various switcher frequency beating with each other via the source.

Have the batteries got any caps across them? There is this odd idea that seems to regard batteries as perfect voltage sources. That may be true if you are powering a bulb and measuring with a constant load.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
User avatar
Thermionic Idler
Old Hand
Posts: 1018
Joined: Sun Apr 22, 2012 8:22 pm
Location: Southsea

#140 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Thermionic Idler »

Nick wrote: Fri Dec 31, 2021 6:37 pm Have the batteries got any caps across them? There is this odd idea that seems to regard batteries as perfect voltage sources. That may be true if you are powering a bulb and measuring with a constant load.
Well, there is a large 4700uF cap across the supply lines from the battery packs to the SilentSwitchers, with a diode/resistor network to reduce inrush current when charging up the cap (see C3 on schematic):

Image

I put that there such that when the batteries deplete and supply to the SilentSwitchers is switched over to the wall wart, the current isn't interrupted during the 3ms that the relay contacts take to switch between one and the other.

I know the battery packs themselves have some basic "last resort" protection circuitry to stop the things from bursting into flames, but whether capacitance forms part of that, I don't know. However, when I was testing the phono stage on the bench, I sourced power for the Silent Switcher from a Duracell PP3 battery of the type that goes into smoke alarms, and still heard some small amount of noise from the board.
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
Speakers: FF225WK Big Mets
User avatar
Thermionic Idler
Old Hand
Posts: 1018
Joined: Sun Apr 22, 2012 8:22 pm
Location: Southsea

#141 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Thermionic Idler »

Placed an order to AMB for the PCB and some of the parts for the sigma22 supply, and Digikey for the rest - where it is currently -32C! :bigsmurf: I specced mostly Nichicon UFW's for the electrolytics, but there are a couple of UKW's in there as well. The board will be configured to put out ±12V.

I'll also be ordering a power transformer from Toroidy - I've decided on 100VA as that matches the maximum amount of power the board is designed to supply. The phono stage draws about 1VA give or take a bit, so overcapacity by a factor of about 100.

Oh and whilst I was at it, I also ordered another programmed processor for the LCDuino, just in case it was operation of the relays without flyback diodes or other farting about that possibly fried the chip - it was only an additional $6 to add it to the order so I figured I may as well have a spare.
Last edited by Thermionic Idler on Sat Jan 01, 2022 7:27 pm, edited 1 time in total.
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
Speakers: FF225WK Big Mets
User avatar
jack
Thermionic Monk Status
Posts: 5493
Joined: Wed Dec 29, 2010 8:58 pm
Location: ɐılɐɹʇsnɐ oʇ ƃuıʌoɯ ƃuıɹǝpısuoɔ
Contact:

#142 Re: Millett LR + TP Opus + AMB α24 reboot

Post by jack »

I'm still not clear-headed after last night, but I'm a bit confused by the behaviour around C3.

Just looking at it (I've not emulated anything), but C3 charges through the 2 x 150R resistors and discharges through the 2 x 1N4148s + the resistors, which means it won't do anything much to the Vcc line unless Vcc is 1.4V (2 x forward bias of a silicon diode, about 0.7V each) below the voltage on C3 (*), so maybe a brown-out, but I can't see what C3 is adding? Then there's there's the power off condition - Vcc drops to zero (I don't know how quickly) and C3 discharges rapidly through the two diodes - they have an Ifsm of 2A (peak forward surge current) so could be damaged... What am I missing? (apart from the ability to concentrate)

Probably need more water. Went to look at the bees on the farm today - very muddy - bouncing & sliding around in the landie was not a great experience...

(*) If Vcc drops or increases, there will some be leakage through the 150Rs, but it seems an odd circuit.
Vivitur ingenio, caetera mortis erunt
User avatar
Thermionic Idler
Old Hand
Posts: 1018
Joined: Sun Apr 22, 2012 8:22 pm
Location: Southsea

#143 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Thermionic Idler »

jack wrote: Sat Jan 01, 2022 5:21 pm I'm still not clear-headed after last night, but I'm a bit confused by the behaviour around C3.

Just looking at it (I've not emulated anything), but C3 charges through the 2 x 150R resistors and discharges through the 2 x 1N4148s + the resistors, which means it won't do anything much to the Vcc line unless Vcc is 1.4V (2 x forward bias of a silicon diode, about 0.7V each) below the voltage on C3 (*), so maybe a brown-out, but I can't see what C3 is adding? Then there's there's the power off condition - Vcc drops to zero (I don't know how quickly) and C3 discharges rapidly through the two diodes - they have an Ifsm of 2A (peak forward surge current) so could be damaged... What am I missing? (apart from the ability to concentrate)

Probably need more water. Went to look at the bees on the farm today - very muddy - bouncing & sliding around in the landie was not a great experience...

(*) If Vcc drops or increases, there will some be leakage through the 150Rs, but it seems an odd circuit.
It's all a bit academic now as the plan is to revert to 'last known working configuration' - i.e. put everything back as it was, with the previous linear supplies. This whole low-voltage DC-DC operation idea just hasn't worked out at all well.

I first had the idea of putting C3 there to maintain the voltage across the supply to the Silentswitchers whilst the relay switches it between the battery and the wall wart (in battery depletion condition). Up to 3ms would elapse where the relay contacts were moving from one to the other, without that cap there, the voltage would drop momentarily to 0v. Was it needed? Probably not.

Then I was looking at the circuit and wondering if it was a good idea to be switching lithium batteries into 4700uF of capacitance without any inrush protection - so I added the two resistors to control the charge-up rate, but the diodes still allow the current to be delivered in the other direction during the relay switch-over. Probably a crap idea (one of a myriad crap ideas infesting this whole project) but it made sense to me at the time.
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
Speakers: FF225WK Big Mets
User avatar
Thermionic Idler
Old Hand
Posts: 1018
Joined: Sun Apr 22, 2012 8:22 pm
Location: Southsea

#144 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Thermionic Idler »

Thinking of upgrading the linestage transformers to Toroidy audio-grade ones when refitting the previous power supplies, as it looks like I *just* have enough space and they seem like good value. I really wish they would indicate phase with their wiring colours though - the dual rail supply needs a centre-tapped input and if the phases are wrongly connected, you end up with half-wave rectification... looks like an oscilloscope and some heatshrink to act as a marker will be required...
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
Speakers: FF225WK Big Mets
User avatar
Nick
Site Admin
Posts: 15707
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#145 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Nick »

I think the order the lead out wires gives a good hint as to the phase. Or at least in the ones I have had they do. Put them in series and measire the voltage across the two ends.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
User avatar
Thermionic Idler
Old Hand
Posts: 1018
Joined: Sun Apr 22, 2012 8:22 pm
Location: Southsea

#146 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Thermionic Idler »

Nick wrote: Sun Jan 02, 2022 2:34 pm I think the order the lead out wires gives a good hint as to the phase. Or at least in the ones I have had they do. Put them in series and measire the voltage across the two ends.
Oh yeah, I don't really need a scope to do that do I... duh! :oops: :lol: Actually, measuring the secondary coil resistances with them connected one way and then the other would probably also do the trick - that way I don't even need to connect the primary to anything.

I R ENGINEER :D
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
Speakers: FF225WK Big Mets
User avatar
Nick
Site Admin
Posts: 15707
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#147 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Nick »

Not sure why measuring the DC resistance would help you any.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
User avatar
Thermionic Idler
Old Hand
Posts: 1018
Joined: Sun Apr 22, 2012 8:22 pm
Location: Southsea

#148 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Thermionic Idler »

Nick wrote: Sun Jan 02, 2022 3:15 pm Not sure why measuring the DC resistance would help you any.
Correct, it wouldn't, because I'm an idiot. I just started responding by writing out the test procedure and then realised in neither case would I be measuring the coils in parallel instead of in series. Even more duh! Maybe I should just go back to bed.

So - sanity check, if I'm measuring the voltage at either end, if the centre tap is connected correctly the voltmeter (set to AC) should read approximately the sum of the two secondary output voltages, whereas if they are not connected correctly, it'll just read 0V (as they'll both be rising and falling by the secondary voltage in phase). In that scenario, one can double check it's actually outputting a voltage by moving one voltmeter lead to the 'centre tap', i.e. the wires that were wrongly connected together.
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
Speakers: FF225WK Big Mets
User avatar
Nick
Site Admin
Posts: 15707
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#149 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Nick »

Yes.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
User avatar
Thermionic Idler
Old Hand
Posts: 1018
Joined: Sun Apr 22, 2012 8:22 pm
Location: Southsea

#150 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Thermionic Idler »

More listening this afternoon - I have to say this phonostage is a keeper, it's starting to bed in now and is sounding more and more musical and detailed - with all the details in their correct place.

I really cannot recommend this highly enough - the PCB is priced reasonably, although with Pete being in the States you're looking at a lot for postage - and the markup that Don Audio place on the inductors is considerable. Then there's the fun and games of getting hold of AD797s if you don't already have them.

But even so, I haven't yet seen an easier or cheaper way into inductor-based stuff, if a phono-stage numpty like me can build it... and this is only the second one I've built, the first was a Bottlehead Seduction in 2006. The rest of the parts are not expensive (notwithstanding stepup transformers if needed), and the power supply only has to provide between ±10 and ±15V so implementation is much easier than it would be with valves (quality of the power supply matters though). With decent step-up iron, I reckon this could see off a lot of commercial stages up to £5k, it's really that good. The Whest will go towards funding Dom Harper's cartridge.
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
Speakers: FF225WK Big Mets
Post Reply