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

Hi, everyone

This is a great thread!! I am going to get my first turntable this X'mas and therefore need a phono stage. I first found Muffsy website from where I was led to here. Based on many posted in this thread, it seemed that this CNC phono stage is not a complicated build. Just curious what is the difference between Muffsy's version and the one described in this thread? I was going to buy Muffsy's kit but then decided to give myself extra challenge to source the parts (I prefer some parts that are not used in the kit). I have downloaded the Digikey BOM that HypnoToad posted in post 193 (thanks!) and the schematic. Just curious where can I get the PCB (Muffsy no longer sell PCB only). Thank you very much in advance for the help!

Regards,
 
The main differences are that the Muffsy has more input impedance choices (these can be used directly on the CNC as well), lower input resistor value (can also be changed directly on the CNC), variable gain and a redesigned RIAA-filter with less resistance and components from the E24-series. It is also much smaller, which will limit your component choices.

Gerber files for a version with larger component footprints are available here, and can be ordered from the fab house of your choice.
 
My friend and AK member also designed a new version for ops power supply based on lm317/337. It's a double sided board with adjustable output. It can be run on AC Wall wart as well as transformer


Regards
Sachin
 
skrodahl said:
The main differences are that the Muffsy has more input impedance choices (these can be used directly on the CNC as well), lower input resistor value (can also be changed directly on the CNC), variable gain and a redesigned RIAA-filter with less resistance and components from the E24-series. It is also much smaller, which will limit your component choices.

Gerber files for a version with larger component footprints are available here, and can be ordered from the fab house of your choice.
Click to expand...

Thank you very much for the info. Much appreciate!!

Regards,
 
Seriously?
My post where I gave away the design files to a suitable power supply for the CNC has been silently deleted.

Well, they're attached to this post for anyone who wants them just because it's Christmas soon. I'll find somewhere else to build my karma from now on, this is just silly.

PSU-2D-cu.png

PSU-AK-render.png
 

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skrodahl said:
CNC Gerbers :)



Some info:

* It has my values for input impedance and RIAA equalization, all within the E24-series
* It has variable gain
* There's space for input capacitors
* Input, output and power in has 5 mm pin spacing for terminal blocks
*
Here are pictures of the PCB, routing and component placement:

23424877804_ee7efa3d99_c.jpg


23424877854_1280389753_c.jpg


23945326332_3244a6827e_c.jpg



-skrodahl
Click to expand...

Very nice! I can hardly wait to get my board.

Question, though. I dug out my Denon DP-52F turntable from the closet and discovered it had a Grace F8 cartridge that I bought 30 years ago. I attempted to measure the capacitance of the built-in phono leads (after disconnecting the cartridge from one lead), and although the measurement jumped around a bit, it did seem to center on ~ 100 pF. So I'll use that as a starting point and leave off the optional input capacitors initially.

Does anyone know (based on a cartridge that hasn't been made in years) what I should use for the input impedance? Or should I just start with 47k and see what happens?

Thanks.

Edit: Using my signal generator, 47K resistor and this procedure: http://sound.whsites.net/articles/cartridge-loading.html I measured the coil inductance of the Grace F8 at 231 mH.

Using the value of 100 pF for the capacitance, then the optimum shunt resistor according to http://www.hagtech.com/loading.html is 48K ohm.

So it looks like I answered my own question, i.e., stick with the 47k
 
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Could some one explain the reasons behind mixing opamps in the CNC ? At first I thought the two op amps were one for each channel but now I realise that they are two separate gain stages ? And if that is so then mixing them is ok but what would be the reason and the thought process ? Would you put the faster dual op amp in the first stage or second and a single one in the other, or is it all about which op amp gives the most gain ? You can tell I know zilch about the theory here but I did manage to build a sweet sounding CNC, now looking at playing with it a bit.

Rog
 
Rog,

According to others, if you use the OPA 2134 in position 1 and the 4562 in position 2 it sounds better than if both were the same.

No theory, it's just what sounds better . . .
 
Hi Roger
Its just matter of taste or depends on your system. I have found LME49990 suit my system most, followed by LME49720. Most Burr Brown sounds very laid back and people having bright sounding system or cart can take benefit.

Regards
Sachin
 
YMMV! That is what it is all about. Hopefully you have access to a parts store (or friends) and can try a number of different opamps in your CNC and find a combo(s) that you like. Each of us has a different environment in our listening area and our ears are all different, so it is no wonder that a given set of opamps does not sound the same to everyone.

Enjoy - - -
 
That kind of goes against the tongue-in-cheek title to this thread but I wondered the very same thing yesterday. Imagine a pair of those sticking out the top of the nice component boxes they have been put into.
 
Enter this string in a Google search and you will get 9 hits: "site:audiokarma.org burson CNC"

You may find other posts where they used different combinations of words.
 
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