C3g Aikido Phono

[Paul Barker]

I like silver mica for EQ

https://www.ebay.com/itm/254730247967?v ... R4a85vq_YQ

That's interesting, I read some fairly polarized views on silver mica in RIAA yesterday. I have some smaller versions of the Russian type in your link.

Polarised opinions? In the DIY audio game of ours? Blimey, how about that

I like them. They're available in 1% or less tolerance at 500v or so. I haven't revisited my choice in the last 20 years. Maybe that's my problem? Maybe they've aged poorly and I don't know it. Anything is possible.

Ive always used them since the first Morgan book recommended them. No complaints or regrets. There is a lot of bull in all forums, and on utube. These days utube is much more stupid, like watching kindergarten kids learn about valve amp and audio technology, more interested in fame than knowledge.

[simon]

YouTube's all about views and subs - the more the more that's monetised.

But yeah, yer pays yer money and yer takes yer chances. Here's a thread from 2002 where Thorsten and John Curl like silver mica
https://www.audioasylum.com/cgi/t.mpl?f=tweaks&m=55308

And here's one from 2003 where Jonathan Carr doesn't like them, post 12
https://www.diyaudio.com/community/thre ... ono.22491/

All "eminent" hi fi industry people. And it was 20 years ago so their views may have changed.

[IslandPink]

I didn't like them in a big size as a coupling cap ( 0.1uF ), I felt they were a bit 'tizzy' in the upper frequencies. However I've used smaller ones to make up RIAA values for the 2nd cap in phonos and they seem fine. I can't remember what I have in my phono in the end - either those or the blue Philips ones.

[Nick]

I used them years ago in the wad clone, I haven't used them since then. IMHO I honestly don't have a view on them either way, or for that matter any cap in a RIAA, having seen how much even a slight change in the response can alter what you hear I have never been able to know with any certainty if what I hear is down the the cap construction or just the cap value.

[Nick]

YouTube's all about views and subs - the more the more that's monetised.

But yeah, yer pays yer money and yer takes yer chances. Here's a thread from 2002 where Thorsten and John Curl like silver mica
https://www.audioasylum.com/cgi/t.mpl?f=tweaks&m=55308

Not even sure if the quotes are consistent with themself. in the first one JC says

You are confusing the issue. I use mica, polystryene, polypropylene, and teflon caps in all my designs. Mica is the worst of the types just mentioned, but not by too much.

Which is certainly damning with faint praise.

[simon]

Yep, beware anything written on t'internet.

Okay I've made some progress with LTspice, the inverse RIAA now loads. When I tried to run the simulation it couldn't find dmtriodep.inc which I located on duncanamps.

Now it can't find tetrode.inc - I've looked around the net but can't find anything that looks suitable. Duncan has a pentodes/beam tetrodes page but only individual models not a general one similar to dmtriodep.inc, that I could find anyway. Any suggestions?

[Nick]

I would check the docs on this site that talk about setting up ltspice.

https://www.audio-talk.co.uk/phpBB3/vie ... php?t=7306

The intact audio forum is now here https://forum.intactaudio.com/viewtopic.php?t=62

[simon]

Yeah I've been using both of these, very helpful. Just can't find the tetrode.inc file, I've even looked inside zips. I'll keep hunting.

[Nick]

Try removing the .inc tetrode.inc from the schematic and see what doesn't work.

[simon]

I dud try that and something else couldn't be found but don't remember what now. I'll try it again in a bit.

[simon]

This is the error message. I'm not sure whether it's because of the missing tetrode.inp or an issue with either the 6N6P or Test B perhaps? I could try to change the Aikido valves to ECC88, but that might be too many variable changes in one go for me to understand what's going on?

Unknown subcircuit.png (123.26 KiB) Viewed 2057 times

[Andrew]

I would guess you don't have the 6N6P model, try something in the standard Duncan amps fileset.

PS It probably makes sense to use whatever valves you have in the circuit.

[IslandPink]

IMHO I honestly don't have a view on them either way, or for that matter any cap in a RIAA, having seen how much even a slight change in the response can alter what you hear I have never been able to know with any certainty if what I hear is down the the cap construction or just the cap value.

Food for thought.

[simon]

Think I'm getting somewhere now. I changed the 6N1P and 6N6P for Duncan's 6DJ8 model and it seems to open fine now. I tried running the simulation but it couldn't find a model for the D3a. I managed to find a file for pentode and triode versions of the C3g on DIYAudio, loaded those as a .inc and edited the C3g_Aikido.asc file to replace the D3a with the C3GP model. And now it looks to work .

Where's the best place to view the sim? The coupling cap immediately after the RIAA filter? The final coupling cap after the second ECC88?

Spice sim 1.png (134.26 KiB) Viewed 2018 times

There appear to be 3 other people who have downloaded the C3g_Aikido model, hope they're managing okay, or can point me in the right direction!

[simon]

The Mundorf ZNs arrived yesterday - I've just measured them and 3 are 99.1nF and the fourth 99.2nF. I've a few of the Russian silver micas of the type Izzy linked to which are nominally 10nF so there's a plan, notwithstanding Nick's comments about importance of overall RIAA accuracy.