Another Super High End Phono Stage! No expense spared...

EngineerNate said:
@absolon - is the 627 a single opamp? Is there room in the PCB version to use a single-family adapter to try that one out?
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Yes, it's a single FET opamp. If you mount them on 2xsingle to dual over/under adapters they will usually fit in a circuit designed for duals. I'm not sure about the Muffsy specifically though.

I built my versions of this circuit on stripboard in both duals and singles configuration. I tried the 49720 and found it was susceptible to noise caused by my wireless router. Don't particularly like the 2134 so didn't even bother. The OPA827 and the AD827 are good, so is the AD825. To my tastes, the OPA627 is the best.

I also got very tight tolerance on the revised RIAA by ordering larger lots of the components, measuring each one and tweaking the RIAA calculator values to find best fit for the actual values of I had. Capacitance was matched to requirement and between channels within about 20pF and resistance within ohms. I think it was worth the trouble. Matched Russian PETP K73-16 on the output and polypropylene for the RIAA ; it's a nice phono stage.

You're right, I was referring to this thread. I get notification of posts to it and the 797 thread so I don't pay attention to the title.
 
ghazzer said:
Engineer Nate: I thought this was the CNC build thread.

It is!

The Muffsy is basically the CNC, with some minor tweaks. The basic design was created by Fasterdamnit based on circuits suggested in Application Notes for some of the popular opamps. Tweaks came in from Big Bill, HypnoToad, Pio1980, shelly_d, and a few others. MANY AKers have made contributions, and meaningful suggestions.

Skrodahl dressed it up a bit and had his own boards built. They were red, not green. He made them available commercially and tagged his product as "Muffsy", but it is basically a CNC.

Anyone is free to add or subtract anything they want to the design, and they can call it whatever they want. Bottom line is that we all owe a heap of thanks to Fasterdamnit & HypnoToad for getting all of this started.
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Judging by the prices I figure skrodahl is doing more of a service to the community than anything else with the kits. :)
 
LME49990 along with Russian Petp caps work very well in CNC. I would love to try OPA627. I have tried OPA2134 and they were too laid back and dull.

Regards
Sachin
 
I was originally recommended to try lme49720 in combo with the opa2134 to get a balanced sound that isn't flavored too heavily towards one opamp or another.
 
Just received 1uf PETP caps fro Romania,to my surprise they are Gold coloured. They are labeled K73- 16B instead of K73-16. They also looks much better made.
s9AiUE7.jpg


Regards
Sachin
 
I've been meaning to right you Sachu.
I'm glad this thread is resurrected.
I was looking for it a while ago.
When I get some time I'll send PM .
My build is several years old .
I'm pretty sure there have been some tweaks since. Also i know there's a MC build I might like to do in the future. I need to pick your brain a bit.:thumbsup:
 
Sachu, please give us your report on the 16b. I have the 16 with Russian Teflon bypass on CNC and it’s amazing!
 
Onebean said:
Sachu, please give us your report on the 16b. I have the 16 with Russian Teflon bypass on CNC and it’s amazing!
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Sure I will. I am currently not using any output caps as my power amp has DC blocking input caps.

Regards
Sachin
 
I am quoting a post from PETP thread in DIY audio

"Some months ago I received a PM from an American commercial loudspeaker producer who was concerned about what he would do when his stock of K73-16 caps (he had around 200) ran out as the value he needed were no longer available.

So, he contacted an American cap manufacturer to see if they could replicate the Russian cap. They told him it was not PEPT but a high Ohmic metallized polypropelene film.

As he said "he has yet to find a cap that equals the K73-16, if the copy falls short, he will continue the search".

I received another email from him telling me that he has a friend who manufactures amps who has done blind tests with listening panels and the K73-16 has been consistently selected as superior to even the most expensive Teflon film caps!

I have a pair of handmade de Graaf (Groningen/Freisland) silver foil caps, they were mega expensive and are bloody good but better than the K73-16s - if only I had known about the Russians I would have saved a load of folding stuff.

Years ago on many forums there were those who were rec. Russian PIOs/Teflon but not one mention of the K73-16s.

linuxguru - if you look at the OPs first or second post he states that 'he has tried all the different variants and there is no meaningful difference between them.

As to their construction, they are superior to almost all other caps I have seen, maybe, just maybe this has a positive effect, producing a neutral cap.

For me they are the cap equivalent of the Vishay Z foils - they simply convey the signal without any interference.

People talk about 'a house sound', with the K73-16s there simply is'nt one.

I am replacing all the caps in my Heybrook Sextet speakers with these, luckily there are plenty of 63V ones left - sometimes you just have to get lucky
biggrin.gif
"

Regards
Sachin
 
I may be an idiot, but just ordered these as potential replacements for the Goodall caps in my Marantz 8 on this recommendation, should that happen.
 
Hey guys! I've started my Muffsy/CNC build and I have a question. Since I'm completely illogically averse to big plastic switches, I picked up a nice metal flip switch from digikey along with some nice rean RCAs to make my back panel from scratch in the 0905 enclosure.

I found an 0905 variant on eBay that had the nice brushed aluminum face plates on both sides so the mounting face is conductive I had a false start with a metal bodied 5.5mm power jack before realizing that duh, AC wall wart, metal body plug = electrified chassis. Fortunately I caught that and I've acquired a decently subtle plastic bodied power jack as a sub. In electrifying the face plate I realized that I need to electrically isolate the RCA jacks from the face plate so that there's no chance of ground loops-I could have just used the face plate as ground but I wanted a dedicated soldered ground connection instead of relying on contact with the chassis for signal. The rean connectors have a nice setup to center them in an oversized hole, (really nice pieces, those) so that's taken care of. I might slip a piece of silicone tubing around each one to be 200% sure they remain isolated.

Which brings me to my last question. My ground lug is currently an 8-32 round head stainless hex bolt threaded through the faceplate from the back combined with a nice brass thumbscrew to hold the lugs. all of the RCA jacks (input and output) are star grounded to the lug. I've seen different grounding strategies on different builds but I'm curious what's considered optimal. Should the chassis be connected to the ground? As it stands it definitely will be.
 
Agreed on that for sure. Should the chassis be included in the ground though? I only ask because the back panel @skrodahl provides as part of his fill kit is FR4 so it's not conductive. So the chassis is isolated.
 
Is there any harm in grounding out the back plate? It's going to be significantly more challenging to not ground the plate. I could make a plastic insert to go into an oversized hole where the ground screw is currently, but it seems like a relatively challenging operation.
 
No, none at all. I'm not familiar with FR4. If the back plate is conductive it should be connected to the chassis. The chassis needs grounding somewhere unless there is only DC coming in.
 
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