C3g Aikido Phono

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IslandPink
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#16 Re: C3g Aikido Phono

Post by IslandPink »

I believe that the ZN's are typically very close tolerance, I can check a few if you like.
My RIAA uses a 0.1uF 'ZN' in the first leg to ground.
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#17 Re: C3g Aikido Phono

Post by simon »

If you get chance that would be useful
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#18 Re: C3g Aikido Phono

Post by IslandPink »

You might want to check this out - looks like a bargain, the 250V is enough for your circuit, and not available from HiFiColl any more.
Ask what accuracy they are matched to.
https://www.ebay.co.uk/itm/266082947995
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#19 Re: C3g Aikido Phono

Post by IslandPink »

These blue Philips ones are one of the few film/foil ones available in small values.
I think my phono uses a teflon 0.022 plus a couple of this sort, to make up the 0.0345 I needed.
There seem to be a few values around on EBay at the moment, might get some myself.
https://www.ebay.co.uk/itm/175019404344
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#20 Re: C3g Aikido Phono

Post by IslandPink »

I tested some Mundorf ZN's from my stash.
These were al bought from HiFi Collective without request for matching.
Measured with Voltcraft LCR meter, with two readings on each cap.

1.5u/250 : 1.523 , 1.516
1.8u/250 : 1.823 , 1.823
1.0u/630 : 1.006 , 0.999
0.22u/630 : 0.219 , 0.219
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#21 Re: C3g Aikido Phono

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#22 Re: C3g Aikido Phono

Post by Andrew »

Nick wrote: Sun Jan 29, 2023 3:36 pm I would also consider the Mundorf ZN ones.

Exactly what load is that c3g going to be driving, it looks a bit harsh over 10kHz (<1k I would guess). Did you ever do a THD against frequency sweep for it?
It was quite low Z RIAA, Nick, if I recall.

It was designed in the days when I was working my way up to successfully driving LCRs.

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#23 Re: C3g Aikido Phono

Post by Nick »

Andrew wrote: Mon Jan 30, 2023 9:50 am
Nick wrote: Sun Jan 29, 2023 3:36 pm I would also consider the Mundorf ZN ones.

Exactly what load is that c3g going to be driving, it looks a bit harsh over 10kHz (<1k I would guess). Did you ever do a THD against frequency sweep for it?
It was quite low Z RIAA, Nick, if I recall.

It was designed in the days when I was working my way up to successfully driving LCRs.

Andrew
Yep, I assumed that, and as such, its a solution for a problem that that circuit doesn't have to have. It could just as well have a 10k RC RIAA and I am not sure there are any negatives from it.

Don't get me wrong, I was part of the plot in the days of trying to drive low impedance RIAA's, because "reason".
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#24 Re: C3g Aikido Phono

Post by IslandPink »

It looks low because the first cap to ground is a 0.47 . in mine which uses 20k input resistor, i have 0.1uF as the cap.
The RIAA is interesting, a subtle variation on the normal all-in-one . Was that developed on Spice or was there an existing example like that ?
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#25 Re: C3g Aikido Phono

Post by Nick »

It looks low because the first cap to ground is a 0.47
I would say it looks low because that cap is in series with a 680R resistor.
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#26 Re: C3g Aikido Phono

Post by IslandPink »

Yes but also the 5k6 on the anode of the C3g, so it's about 5 or 6 k, which ties in with the cap size ( ? )
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#27 Re: C3g Aikido Phono

Post by Nick »

IslandPink wrote: Mon Jan 30, 2023 11:48 am Yes but also the 5k6 on the anode of the C3g, so it's about 5 or 6 k, which ties in with the cap size ( ? )
Oh, I agree, the values in use with that RIAA all make sense and are self consistent, that wasn't my point. My point was because of the choices in that RIAA the valve is going to be asked to drive into less than 680R, and just because it can I am suggesting is not a reason to want to make it so it does.

If I remember that circuit is a combination of the low is better idea taken to the extreme by Andrew wanting to get to where he could drive a 600R LCR network. But because its not actually having to drive a 600R network I think with hindsight it could have been done differently.
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#28 Re: C3g Aikido Phono

Post by IslandPink »

Yes, i agree, it should sound nicer with a higher impedance.
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#29 Re: C3g Aikido Phono

Post by Andrew »

It is a nominal 5k6, if memory serves, it was done in Spice, but the values will scale up, or down, according to requirements.

We did, at the time, think low Z had other advantages, so it was about striking a balance, but that's where my memory goes hazy.
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#30 Re: C3g Aikido Phono

Post by simon »

IslandPink wrote: Sun Jan 29, 2023 9:38 pm I tested some Mundorf ZN's from my stash.
These were al bought from HiFi Collective without request for matching.
Measured with Voltcraft LCR meter, with two readings on each cap.

1.5u/250 : 1.523 , 1.516
1.8u/250 : 1.823 , 1.823
1.0u/630 : 1.006 , 0.999
0.22u/630 : 0.219 , 0.219
Thanks, that's pretty good. I've bought four 0.1uF in your link. Should be good for coupling if not used in RIAA.
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