Millett LR + TP Opus + AMB α24 reboot

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Thermionic Idler
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#91 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Thermionic Idler »

Here's the PCB design for holding the Lundahl step-up transformers, currently being fabricated at JLPCB. The inputs / outputs will use Phoenix Contact 1725*** terminal blocks. I used a set on my power management PCB and was very impressed with their quality.

This gives me a way to configure it for MM or MC operation without having switches in the signal path. It then occurred to me that if I routed the MC output to 6-way connectors rather than 2 way ones, that would also give me an easy way to add exactly the right resistive (and possibly capacitive) loading to the secondaries.

Image
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
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Thermionic Idler
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#92 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Thermionic Idler »

Crossing my fingers that the LR phono will actually be a Christmas project and not a January 2022 project.

The standoffs and screws have arrived from Accu.

Yay.

Some bits of PTFE hookup wire have arrived from Modulus.

Yay.

And I've even got a nice new soldering sponge that isn't all grey and disintegrating.

Yay.

The Lundahl MC stepup PCB has shipped from China - expected on the 17th.

Hopefully.

I should have received the Mouser order yesterday but for some reason it's still at Stansted - it now just says Delayed with no scheduled delivery date.

Thank you Fedex. SLA? What SLA?.

As for the small Schaeffer panel for the input sockets to mount into - that shipped on Wednesday, and was returned back to Schaeffer today (head-desk). The tracking info suggests some issue with the export paperwork.

Brexit - the gift that keeps on giving.
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
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Ray P
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#93 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Ray P »

I'm in a similar situation, a Schaeffer panel that is taking forever to be delivered (UPS) and a Mouser order stuck at Stansted (Fedex).
Sorry, I couldn't resist!
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#94 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Thermionic Idler »

My Mouser order was delivered today (2 working days late) so hopefully yours won't be far behind, Ray. The PCB's have already arrived at Stansted from China, even though they're not due here till the 17th.

Schaeffer have re-sent my small panel today, I know I'll need to pay UPS some money for ripoff import fees (god I miss the single market) but haven't seen anything requesting that yet.
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
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#95 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Thermionic Idler »

PCB's actually arrived early - delivered yesterday. Just waiting for the small panel from Schaeffer now.

After the LR phono is done, I've decided to completely re-do the power supply board in the AMB, as I've been having ongoing issues with software glitches and power supply trip-outs on first power-up. Right now it's just not working reliably.

The Arduino board used to be powered from its own regulated 5V supply and performed entirely without fault, all this trouble started after the low-voltage conversion, so I need to go back to the drawing board. I think the problem is that the 5V supply is shared across several things (relays, battery chargers) with no isolation at all. I also want to include an option (set via software) to continue to supply power to the low-voltage stuff when the system is shut down.
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
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#96 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Nick »

What's the brownout voltage settings on the processor?
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#97 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Thermionic Idler »

Nick wrote: Wed Dec 15, 2021 12:12 pm What's the brownout voltage settings on the processor?
Good question - unless I'm missing something due to sheer ignorance, I don't think anything like that has been set. Can't find any reference to it in the code, and there's nothing on the schematic that I can see. That said, I think during software re-flashes when I have the TTL-232R-3V3 lead connected, it's operating on 3.3V rather than 5V, so it ought to be able to cope with a degree of voltage drop.

Image
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
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#98 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Nick »

That circuit suggests 5v rails
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#99 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Nick »

Also why no small caps on the xtal. Also why is the reset line connected to RTS on the 232 interface? Is it to do with the programming interface. I would worry about noise on that line triggering reset.
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#100 Re: Millett LR + TP Opus + AMB α24 reboot

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Nick wrote: Wed Dec 15, 2021 7:00 pm Also why is the reset line connected to RTS on the 232 interface? Is it to do with the programming interface. I would worry about noise on that line triggering reset.
I believe it is - in normal operation, J3 only has pins 1 - 3 connected to provide power to the board (pins 1+2 ground, pin 3 +5V). The track from RTS to pin 1 is pretty short - about half an inch at the most I think.
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
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#101 Re: Millett LR + TP Opus + AMB α24 reboot

Post by jack »

I have a general issue with the robustness of the Arduino design WRT /Reset , especially if there's noise about.

Years ago (*), I found a whole bunch of inconsistencies in the atmel docs regarding the reset pin in general.

See https://www.avrfreaks.net/forum/avr40-a ... protection

The key docs are
AVR040
and AVR042 (** it would be '42') - I put in a whole load of errata notes to Atmel about this but can't remember whether they made the changes - my previous experience with them is that they were pretty good about that sort of stuff.

If your uP is having reset issue, the above thread is a good read.

(*) Blimey! 11 years ago!
(**) The link to AVR042 is correct but it seems to have gone from Atmel/Microchip's site...
Last edited by jack on Thu Dec 16, 2021 10:46 am, edited 5 times in total.
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#102 Re: Millett LR + TP Opus + AMB α24 reboot

Post by ed »

Nick wrote: Wed Dec 15, 2021 12:12 pm What's the brownout voltage settings on the processor?
just caught up with this....I think the moment has passed, but trigger level is set by fuses, not sure what the default is. I think 5v is tested at 4.1 but best check datasheet.

edit:
post overlapped with Jack......without going back over whole thread is this arduino or native 328? some things are not as they seem between the two.
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#103 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Nick »

ed wrote: Thu Dec 16, 2021 10:30 am
Nick wrote: Wed Dec 15, 2021 12:12 pm What's the brownout voltage settings on the processor?
just caught up with this....I think the moment has passed, but trigger level is set by fuses, not sure what the default is. I think 5v is tested at 4.1 but best check datasheet.
Yep I was asking what it was set to, not how was it set.
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#104 Re: Millett LR + TP Opus + AMB α24 reboot

Post by jack »

Nick wrote: Wed Dec 15, 2021 7:00 pm Also why no small caps on the xtal. Also why is the reset line connected to RTS on the 232 interface? Is it to do with the programming interface. I would worry about noise on that line triggering reset.
X1 - Not a crystal - it's a ceramic resonator - no caps needed.
X2 - The DS1302 is designed for watch crystals with a specific loading requirement - 6pF, which is built into the device, so no external caps needed there either.

The noise on reset is exactly why I posted the links to the thread on AVRfreaks - it's a poorly understood part of AVRs and years ago I had real problems with it (albeit in a very noisy environment, but that just highlighted how poor the documentation was).

SDA & SCL don't have pull-up resistors - I'd have expected to see a 4K7 to Vcc on each.
Last edited by jack on Thu Dec 16, 2021 11:58 am, edited 1 time in total.
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#105 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Thermionic Idler »

Well, I'll give a bit more detail of the issues so far. I thought I'd posted before about it but it looks like I only posted to the AMB forums on this occasion.

A couple of times, I've taken it out of standby (so a normal 'power-up') to be greeted by this:

Image

The 300B amps came on so I knew it had sent the 'power-on' signal to the relays, but after that it was completely unresponsive - could only be cured by re-flashing the software.

Just before the second time that happened, it stopped responding properly to inputs from the volume control - if I adjusted it, it would instantly go to minimum volume (thank god it didn't go the other way!).

Another time more recently, after taking it out of standby, the display looked weird, like it had been shifted halfway over, but it still worked. It was later that day that we had all that trouble with the RCD tripping, and the resulting enforced power cycles ended up resolving that display issue.

So not sure if that would be a reset issue as nothing has really changed in that space? Since then it's been working fine (fingers crossed) but given it worked faultlessly for 4 years prior to me mucking about with it, I'm inclined to put back the regulated supply that I had previously (it will work with a DC supply provided it's at least 5V higher than the output).
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
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