Following on from my brash comment on finding this again in this thread, and my single post with links:

darklantern.proboards.com/post/35224/thread    [darklantern.proboards.com/post/35224]

Here's the board. I'll re-cap it. In some places a later version used tantalum for some smaller caps, it seems.

Resistors, hmm. IC, hmm. Nevertheless, what a great start. I have some short silver cable pieces I might use internally.

Install connections, find a 15V PSU. I've found screws for the pcb to the bottom, I may need to fabricate a top.

Wish me luck!  ;=})

Hi RdM - good luck!! - so where did you find a HA10 kit?

Honestly I can't remember! I've probably had it since the early - mid '90s.
Not so much a kit as just the board and bottom case.
I may as well change the 30Ω loading to 20Ω to suit the AT30E.
Then I can compare it with the AT630 SUT when both arrive.

After reading Colin F's post re capacitors, I looked them up.

The two coupling capacitor pairs are 100µF & 47µF, may as well be 50µF. C3, C103. C8, C108.

So I thought I could upgrade those to Audio Note Kaisei caps, I see I can get them from HiFiCollective or PartsConnexion, polar or bipolar.

Presumably those would be good upgrades as coupling caps for this? Polar or bipolar best?

The latter site maybe cheaper. Then, I could also buy Silmic II from them as well, for the 470µF bypass caps.

www.partsconnexion.com/ELNA-72707.html

Those values from the schematic. Would 680µF or even more be 'better'? They're all bypass caps.

And what about the odd one in the incoming power supply, C203, presumably a regulator circuit?

Any use in in increasing that ones value as well?

ISTR reading some chaps opinion that too many µF in power supply or maybe bypass caps could slow things down . . . so I wonder about going too far!

As well, I've ordered already a couple of replacements for the dual transistor LM394,one of each, from Latvia. Just to compare and maybe replace it with.

www.ericasynths.lv/shop/ics/as394-matched-transistors/

www.ericasynths.lv/shop/ics/as194h/

The AT30E stylus has arrived, from France, but the AT630 MC SUT transformer is still stuck in the UK, at a friends workplace.

After a cyber attack, Royal Mail stopped accepting parcels for international delivery for a while.

Then again, there's this sort of nonsense!

www.telegraph.co.uk/news/2023/02/03/royal-mail-make-bizarre-decision-send-stamp-books-compensation/

I spoke with him this morning, he reckons that because of that the commercial couriers are overloaded too, DHL, FedEx, etc.

So maybe I'll just wait, no rush or hurry.

I also received the Empire MC20+ stylus from Denmark. So suddenly I have a surfeit of replaceable MC styli!  ;=})

It's annoying that there's just a single larger hole for "output" on the A&R Cambridge chassis.

I'll have to re-work it somehow to accommodate either output sockets or a stereo cable pair.

So it goes! ;=})

PS: I read recently that Silmic II may be discontinued ... although they seem to be in stock above, and this post was from last year.

www.diyaudio.com/community/threads/elna-silmic-ii-eol-announced.387854/

Regards!

If you’re going to increase the 470u caps to 680u, make sure C202 and C203 are the same value. That’s to avoid excess current at switch-on in Q201. More capacitance isn’t necessarily better, more the quality of cap.
Use a regulated power supply for the 15V input. The regulator on the board could be made to have better PSRR by changing R204 (10k) to two 1N914 diodes in series, to form a more stable voltage reference for the constant current source (Q202).

AMR-iFi R&D

Feb 5, 2023 20:34:07 GMT 12 colinf said:

If you’re going to increase the 470u caps to 680u, make sure C202 and C203 are the same value. That’s to avoid excess current at switch-on in Q201. More capacitance isn’t necessarily better, more the quality of cap.
Use a regulated power supply for the 15V input. The regulator on the board could be made to have better PSRR by changing R204 (10k) to two 1N914 diodes in series, to form a more stable voltage reference for the constant current source (Q202).

Thanks very much for your kind and expert advice Colin.

Of the coupling caps, I'll buy the Audio Note Kaisei bipolar versions. Maybe a spare pair of increased size to test the bass response as noted.

Of the bypass caps, I was going to write that I'll keep them all at 470µF, and might buy a few extra for a chance at matching C202 & C203, thanks.

But it turns out that the pcb is actually populated with Philips 680µF - and also that switch 4's C1/C101 100nF (0.1µF) in schematic actually has 1uF installed!.

That has to be a mistake, surely? I note that this pcb has no serial number, was never soldered to with inputs outputs or psu.

And I'm remembering where I got it from now, Surplustronics when they were in the top end of Queen St, nearby. Where I got my Wharfedale 510.2 drivers from.

In those days they still bought up surplus stuff; in the case of the Wharfedale drivers, they'd been stored in damp, and had some visible external metal corrosion.

Anyway, the Philips caps are 20mm h 12mm dia. There is just 24mm clearance from the pcb to where the underside of the top lid of the case would be, if recreated.

So, if I made a top to fit snugly to it as per the original, that would rule out Elna Silmic & Nichicon KZ Muse at 25mm, although the lesser Nichicon FG Muse 470µF would fit, 10 x 20.

I think it might be better to design and make a higher top lid for it, that can accommodate those and that still looks nice.

Some metal bending! ;=})  I've actually been looking at metal bending possibilities, from in a vice to on a work table.

After all, it's uniquely my own;- I can customise it to suit.

Cheers, kind regards, and thanks again!

Ross

PS: I already have in my junk pile an overkill 15V 4A smps unit, but could buy a smaller one, still plenty. I'll install a socket.

No need to match C202 and C203 exactly. The bipolar Kaisei caps aren’t necessary, polarised ones are fine.
1uF loading!…That’s high and might cause the cartridge to sound strange. 100n would be better, but I’d probably have them out of circuit anyway to avoid ultrasonic peaking.

AMR-iFi R&D

Just a quick update;- I received the replacement transistor pairs some time ago, and have just ordered the Elna Silmics and Audio Note caps from PartsConnexion.
I may end up replacing some resistors as well.
I'm still looking at how to fabricate a top for it, and to connections. I may need to enlarge some holes, or find different connectors to use.

I've even wondered about a full size stereo headphone socket for output. That would fit in the existing hole. Gold plated, quality, etc.?

Apr 28, 2023 20:27:00 GMT 12 RdM said:

Just a quick update;- I received the replacement transistor pairs some time ago, and have just ordered the Elna Silmics and Audio Note caps from PartsConnexion.

I was reminded that I had an uncompleted order, not for the first time.

Initially ordering I got a warning that there was only one polarized 50uF in stock.

So I ordered 2 non-polarized, $1.02 USD more. Then the cheaper of the two expensive FedEx options disappeared.

Looking again in a hurry the other morning, I found the FedEx option back, and pressed Next, confirmed.

Shortly after that I realised that I'd like the 100uF & 50uF Audio Note Kaisei pairs  to be matched.

I emailed them to see if I could swap the 50uF non-polarized back to polarized, the $1.02 each difference would pay their $1/pair matching fee for both.

Emails, okay, sorted. But then news that both Audio Note Kaisei pairs were on back order, expected in ~ 4 weeks.

I've elected to wait until then. It's taken ages to get on to the project anyway.

They're expensive capacitors and the (tracked, signature) freight is even more!

Compared to same values fraction of the price Panasonic Nichicon &or etc. at element14 or similar. Oh well. Gone for the best. Done now.

I see the HA10 schematic specs 2% resistors. I suppose I should check some, look at replacing with obsessively matched 1% as is my wont.

Are there considered opinions or data on the 'quality' of fancy resistors with brand names as opposed to what I might get from say Jaycar, 10-packs to match from cheaply?

Less variable than capacitors? Is there really value in them for small signal stuff like this? I see some touted for SE valve amp builds and the like.

Thanks, cheers!