DIY CNC MM Phonstage

[sachu888]

Hi,
don't get fooled by its cost.It was not made for commercial purpose so it costs less.Its a very simple but high end design.You will be surprised how good it sounds.s

Regards,
Sachin

[sachu888]

Hi all,
Please find below pics for battery connection for +9/-9


By sachu888 at 2012-02-12

Regards,
Sachin

[wizardofoz]

I received my boards from Sachin thismorning...and by the afternoon had it all put together and in a decent looking box ( I have 7 like this with everything from dacs to gainclones to lighternotes and b1 pass pre too, now a CNC MM phono pre. Works without any mistakes... Using opa2134's with +/-15v regulators.

[sachu888]

I received my boards from Sachin thismorning...and by the afternoon had it all put together and in a decent looking box ( I have 7 like this with everything from dacs to gainclones to lighternotes and b1 pass pre too, now a CNC MM phono pre. Works without any mistakes... Using opa2134's with +/-15v regulators.

Sir your build is very neat,very professionally built  :thumbsup:How did you like the sound?

Regards,
Sachin

[richard]

Sachin,

I'm interested in your preamp. How can I learn more about it?
I like the concept of placing a very small preamp as close as possible (electrically) to the cartridge. I have a few questions, but I think that I'll wait for your answer, first.

Thanks.

[ropie]

Very nice build, Wizard

[zwarte-romantiek]

Yeah...really nice build.

Is it possible to amplify the signal in this MM phono stage?

Sachin - i'm interested too. Do you still have boards left?

Niels

[sachu888]

Sachin,

I'm interested in your preamp. How can I learn more about it?
I like the concept of placing a very small preamp as close as possible (electrically) to the cartridge. I have a few questions, but I think that I'll wait for your answer, first.

Thanks.

Hi Richard,
Thanks you like my build.This was my first DIY.The board size is only 4X3,so you can use very simple box for that.This is a very high end deign,modified by some Audiokarma members.It has a variable resistive loading.You can compare it with any high priced Phonostages of big brands and it will not disappoint you.It is very easy to build all part values have given on PCB,you just need to do proper soldering.There is a long thread on Audiokarma about this Phonostage http://www.audiokarma.org/forums/showthread.php?t=371889
There are 200+ built on Audiokarma alone and everyone is using this in main system.I have also made few more preamps/Phonostage/ etc.I will start new threads about them sometimes later.Few designs which I have built:
SSP: http://audiokarma.org/forums/showthread.php?t=401521
Hypnotoad's Moving Coil Phono Stage(HTMCPS): http://www.audiokarma.org/forums/showthread.php?t=418308
Pass B1 with LDR Volume control and DIY OPS(Omishra's Power Supply) http://audiokarma.org/forums/showthread.php?t=395040

Regards,
Sachin

[willbewill]

Has the circuit been modified much from the original?


Do you have an updated schematic?

[sachu888]

Hi malcom,
You can see latest here http://www.audiokarma.org/forums/showthread.php?t=371889&page=39
BTW : I have seen your DIY Phono projects here they are top class

Regards,
Sachin

[willbewill]

Thanks Sachin

I will check my parts to see if I have the right components to build one although I know I definitely don't have LME49720 chips

[wizardofoz]

Thanks guys...

I actually got 3 boards from Sachin and the 2nd will probably be built up and placed in a box under the tt with the tone arm wiring connected into it directly and a set of line level RCA outputs. I haven't decided yet if it will be 2x9v battery powered or if I will have external power as an option too...maybe on the other side of the DPDT switch.

[sachu888]

Thanks Sachin

I will check my parts to see if I have the right components to build one although I know I definitely don't have LME49720 chips

Hi Malcom,
Here is the BOM with Element14 as well as Manufacturer part no.I am tried Opa 2134,AD823 and LME49990 and all sounded very good in this PS.

   CNC BOM      
Quantity   Element14 Part No   Mfg Part no   Description
2   1854822   ECQV1H273JL   CAP .027UF 50V STACK METAL FILM / RIAA Capacitor
2   1854824   ECQV1H333JL   CAP .033UF 50V STACK METAL FILM / RIAA Capacitor
2   1744826   ECQV1H473JL   CAP .047UF 50V STACK METAL FILM / RIAA Capacitor
2   1744833   ECQV1H105JL   CAP 1UF 50V STACK METAL FILM / DC Blocking
4   4830799   K104K15X7RF5TL2   CAP .10UF 50V CERAMIC X7R 10% / Power Supply Filter
4   9693637   ECA1VM100   Cap 10uf 35V
2   1438582   AD823ANZ   IC OPAMP JFET R-R DUAL LN 8DIP / AD823 Op Amps
2   4675952   RN60C1000FB14   RES METAL FILM 100 OHM 1/4W 1% / Gain Resistor - Increased
2   1126936   MCMF0W4FF1500A50   RES METAL FILM 150 OHM 1/4W 1% / Gain Resistor - Std
2   9341447   MF25 18K   RES METAL FILM 18.0K OHM 1/4W 1% / Input Loading Resistor
2   9341536   MF25 2K2   RES METAL FILM 2.20K OHM 1/4W 1% / Noise Blocking Resistor
2   1126948   MCMF0W4FF2000A50   RES METAL FILM 200 OHM 1/4W 1% / RIAA Resistor
2   9341650   MF25 27K   2 X P27.0KCACT-ND / RES METAL FILM 27.0K OHM 1/4W 1% / RIAA Resistor
2   9341757   MF25 33K   2 X P33.0KCACT-ND / RES METAL FILM 33.0K OHM 1/4W 1% / Input Loading Resistor
2   9341960   MF25 47K   2 X P47.0KCACT-ND / RES METAL FILM 47.0K OHM 1/4W 1% / Input Loading Resistor
2   9342125   MF25 62K   2 X P62.0KCACT-ND / RES METAL FILM 62.0K OHM 1/4W 1% / Input Loading Resistor
2   1129162   MCMF0W4FF7500A50   2 X P750CACT-ND / RES METAL FILM 750 OHM 1/4W 1% / RIAA Resistor
4   1854081   CMF503K3200FHEB   4 X RNF14FTD3K32CT-ND / RES MF 1/4W 3.32K OHM 1% AXIAL / Feedback Resistor
2   1878814   CMF503K8300FHEB   4 X 3.83KXBK-ND / RES 3.83K OHM 1/4W 1% METAL FILM / RIAA Resistor
2   http://www.ebay.com/itm/4P-4-Position-DIP-Switch-Side-Style-2-54mm-Pitch-Through-Hole-DIY-Good-New-/160748538313?pt=LH_DefaultDomain_2&hash=item256d5c09c9      2 X CT2064-ND / SWITCH SPST GOLD 4 SEC / Input Loading Dip Switch
2   4528359   237   2 X 235K-ND / STRAP BATT ECON 9V T STYLE 4"LD / 9v Battery Connectors
1   Toggle switch      1 X S114-ND / SW TOGGLE DPST 5A SOLDER LUG / On Off Switch

Regards,
Sachin

[sachu888]

Thanks Sachin

I will check my parts to see if I have the right components to build one although I know I definitely don't have LME49720 chips

Hi Paul,
I have built DIY regulated Power supply for this.I am using one Power supply board with an R core trafo to power my B1,SSP,LDR and CNC Phonostage.Power supply is modified by my friend Omishra,so we call it OPS on AK.You can see some pics here http://www.audiokarma.org/forums/showthread.php?t=456732

Regards,
Sachin

[williamsunique]

I have recently completed the build of the CNC phono stage.  This is not an expensive build and with the first class printed circuit that Sachin sent to me it is very easy to construct.  The BOM is available and what is very useful the manufacturer’s part numbers of components are listed in this.  I stuck rigidly to the listed parts knowing that other constructors had previously tried and tested them with excellent results.
This phono stage uses passive equalisation to correct the RIAA curve.  There is some debate as to whether passive is better than active or vice versa.  I understand the theory behind this, but I think the proof of whether something is any good is when you listen to the results.  I therefore am not one to be put off by circuit design.  I had read good things about this phono and as it was easy to obtain all that was required to build it, I did not hesitate in going ahead.  The CNC is based around two dual opamps.
The power supply I used to run the CNC consists of two 12 volt sealed lead acid accumulators.  This supplies the required plus and minus volts.  I have not tried it with a mains derived power supply yet.  The rest of my system is pretty revealing and if something is not quiet right it soon becomes noticeable.
Recently I have been swapping between my Boozehound Labs phono and my Elliott Sounds P06 phono, both these stages are homebrew.  Neither of these phonos have been upgraded in anyway.  I realise that both can be improved by using superior components.
The Boozehound Lab phono is Jfet based, whereas the Elliott Sounds is opamp based.
Interestingly the Elliott Sounds phono uses a mixture of active (bass) and split passive (treble) RIAA correction..  IMO both these phono stages are excellent, far better than my previous valve based phono of Chinese origin and far far better than the phono stages integrated in the various different amps that have passed through my hands.
The CNC worked first time and the first LP side I listened to was pretty impressive.  After a few more sides I started to move my head around to find the sweet spot, it gave the impression that this sweet spot was varying.  I had carefully checked the tolerances of the RIAA components before installing them and they were matched left and right.  Further listening and yes there was definitely something not right here, although the vocals seemed to be in the middle of the soundstage, the left side appeared to be a lot stronger than the right.  I should point out here that my speakers are Quad ESL57s and these have a very precise sweet spot, this can be somewhat frustrating at times.  In order to prove that it was the CNC at fault here, I disconnected it and installed my P06.  This was much better with a far more defined soundstage.  The CNC was re-installed and I was back with an undefined soundstage, stronger on the left, than the right.  The opamps (AD823) I was using were those that were recommended by other constructors.  These I had purchased from a reputable supplier, RS components and they were definitely pukka.  Anyway as these were easy to change for something else I did just that.  I had previously had good results with the LM833 in my P06, in fact these were my choice over some other more well thought of opamps.  I had tried OPA2134, AD 823, OPA627 and a couple of other lesser thought of opamps TLO72 and NE5532.  In my opinion the LM833 was clearly the winner.  I plugged a pair of LM833s into the sockets on the CNC and voila that was it, wonderful.  Left and right equilibrium was restored, the sweet spot was in it’s correct spot, I think it is so important to have this balance correct, without it the soundstage is just not as it should be.  The depth and spaciousness with the CNC was excellent.  I have a sub woofer and super tweeters connected through an active crossover to enhance and extend the frequency range.  Lower bass and upper highs were to my ears excellent.  The middle range also was superb.  I am delighted with the results I am obtaining with this phono stage.  I feel it is unfair to compare it with my Boozehound Lab and Elliott sound phonos, which are both excellent.  The build of my CNC has been achieved using the recommended components as mentioned previously.  I know that my other two phono stages can be improved by using better components.  The great thing about this diy hobby of ours is that you think you have reached your sonic goal, until something even better comes along, but yes for the moment, the CNC will be staying in my main system.  I just need to house it in a box, I like it that much.
I am unsure why the LM833 sounds better than some other opamps in both my P06 and CNC.  The input of the LM833 uses PNP transistors, where as some other opamps tried use FET input.  I tried various different cartridges with these opamp based phonos and always I returned the same result, the LM833 being the winner.  The output of my phono stage feeds an optical selector, which feeds an optical V/C which connects to an LM3886 based amp.  The power plus and minus for these phonos’ is derived from two 12 volt batteries.  Could it be that the AD823 require plus and minus 15 volts in order to perform better, or maybe a different voltage.  It just seems strange to me that the cheaper lower specification LM833 is the better.
Paul.