Batery powered DIY CNC phono stage

[sachu888]

Thanks guys.I had connected only one 9 volt battery.Will show the diagram to my friend.I hope he can make sense of it.

Did you able to solve your problem?

Regards,
Sachin

 

[sivasarjun]

Thanks guys.I had connected only one 9 volt battery.Will show the diagram to my friend.I hope he can make sense of it.

No.Yet to take it to my friend.Hope to do it this weekend.If the problem is solved /persists will report here.

 

[jls001]

I had been using my DIY CNC MM Phono stage for quite some time without a proper cabinet. I finally gave it a proper shelter.

1) The bare (el cheapo) cabinet populated with the RCA rear connectors for inputs and outputs:

2) Here's a view of the board with the cab:

3) Input and Output cables connected. Earth wire also connected. Input and output wires are a thin coax cable. RCA connectors are gold-plated Neutriks.

4) The rear - earthing terminal is actually one half of an MX gold plated speaker binding post

5) Battery terminal is a 5-Pin connector.

6) All wired up, including the front panel mounted DPDT switch.

Question 1: I have not used any capacitance loading across the output terminals. Last night I tried it with a Shure Mx97E cartridge and it sounded fine.

I plan to give this pre to a friend who will be using it with the Ortofon OM5e cartridge. Is it a good idea to fit capacitor of appropriate value across the output terminals? Will it improve the sonics?

Question 2: If I can get hold of two variable voltage AC to DC adaptors of about 1A rating whose DC outputs can be selected to 9, 12, 15, etc Volts, can we treat the two AC-to-DC adapters like the two 9V batteries used for powering this circuit? The idea being that when rolling opamps, +9V/0V/-9V may not be the best Vcc for certain opamps.

Question 3: the gain of this phono stage is fairly low. I need to jack up my preamp gain by 5-6 dBs. Is there any value I can change that will increase the gain of the CNC by some dBs? I am guessing the current gain is below 40 dB.

 

[sachu888]

Hi Joshua,
Build looks very good.
Wall wart adapters will add unwanted noise and thus not recommended.
Ortofon recommends load capacitance 200-600 pF for OM5e.If your friend is using stock interconnects on TT(high Capacitance)then you will not need any loading.You can always try 50pf and see if it makes any difference.
You can replace 150 Ohms resisters with lower values like 100 ohms.It will give you approx 5db more gain than the stock CNC.You can even integrate it with SSP for gain.It is very nice sounding preamp.

Regards,
Sachin

 

[sachu888]

Hi Joshua,
Which caps did you put at 1uf?They look little different.

Regards,
Sachin

 

[jls001]

Hi Joshua,
Build looks very good.
Wall wart adapters will add unwanted noise and thus not recommended.
Ortofon OM5e Recommends load capacitance 200-600 pF.If your friend is using stock interconnects on TT(high Capacitance)then you will not need any loading.You can always try 50pf and see if it makes any difference.
You can replace 150 Ohms resisters with lower values like 100 ohms.It will give you approx 5db more gain than the stock CNC.You can even integrate it with SSP for gain.It is very nice sounding preamp.

Regards,
Sachin

Thanks, Sachin for the quick replies.

My friend uses a ProJect Debut III turntable. The interconnect is stock. I will give it to him without capacitance loading. He can run it out for some time and may be later we can add 50 pF loading.

I will definitely change the 150 Ohm to 100. The gain is way too low to my liking.

My friend will eventually use it to replace the built-in phono stage of his Marantz PM6004 integrated. I am hoping that it will be a substantial improvement - as he hopes - to the the in-built phono stage. After listening to it last night, I re-appreciated how good this phono stage actually is, so I have a feeling he won't be disappointed.

Addendum: I first listened to it with the stock OPA2134 opamp. Cartridge is Shure Mx97E. I was amazed to hear very nice imaging and fairly balanced sound, though the upper highs sounded veiled and constricted. Later I swapped out the OPA2134 for the LME49990 and the highs opened up very well. Resistive loading used was 62 KOhms. The LME49990 definitely does highs better than the OPA2134.

 

[jls001]

Hi Joshua,
Which caps did you put at 1uf?They look little different.

The cap is what you included in the kit

 

[murali_n]

Hi all,

There are some mixed reactions to the CNC MM Phono pre-amp's performance from some people, I request them to use either the 4562 or the 49990 opamps and select the correct resistance loading and give their opinion, after a detailed audition.

N.Murali

 

[omishra]

The cap is what you included in the kit

Those are same film caps, we previously used 63V rating (smaller footprint) now its 250V rating.

With Shure 97xe, I am used standard loading 47K? and 62K? was to bright HF. 62K? bumps HF but rolloff low. 47K? loading gives near flat response. First OPAMP is LME49990 and second one is AD823 near output. This was well balanced and highs are clear and not too harsh. Using both places LME49990 was very bright, but now since I changed to GR Research speakers I will try to put back LME49990 in place of AD823 and report back.

 

[sachu888]

Those are same film caps, we previously used 63V rating (smaller footprint) now its 250V rating.

With Shure 97xe, I am used standard loading 47K? and 62K? was to bright HF. 62K? bumps HF but rolloff low. 47K? loading gives near flat response. First OPAMP is LME49990 and second one is AD823 near output. This was well balanced and highs are clear and not too harsh. Using both places LME49990 was very bright, but now since I changed to GR Research speakers I will try to put back LME49990 in place of AD823 and report back.

Hi Om,
those 1uf caps do look little different.250V caps won't fit on CNC.We have used only 50v and 63 V 1 uf caps on CNC.They look like HTMCPS .1uf caps.
Joshua can you post a close pic.Do your 1 uf caps look same like pic below

Regards,
Sachin

 

[jls001]

Hi Om,
those 1uf caps do look little different.250V caps won't fit on CNC.We have used only 50v and 63 V 1 uf caps on CNC.They look like HTMCPS .1uf caps.
Joshua can you post a close pic.Do your 1 uf caps look same like pic below

Will take the glamour shots tonight

Will shoot the HTMCPS too.

 

[omishra]

Those are same film caps, we previously used 63V rating (smaller footprint) now its 250V rating.

With Shure 97xe, I am used standard loading 47K? and 62K? was to bright HF. 62K? bumps HF but rolloff low. 47K? loading gives near flat response. First OPAMP is LME49990 and second one is AD823 near output. This was well balanced and highs are clear and not too harsh. Using both places LME49990 was very bright, but now since I changed to GR Research speakers I will try to put back LME49990 in place of AD823 and report back.

Continuing earlier post - I changed second AD823 to LME49990. Now both are LME49990 and it sounds amazing. But same time dirty record pops up more.

So both places LME49990 make sound very open and natural.

 

[sachu888]

Continuing earlier post - I changed second AD823 to LME49990. Now both are LME49990 and it sounds amazing. But same time dirty record pops up more.

So both places LME49990 make sound very open and natural.

Hi Om,
I found the same. LME49990 work best in pairs.

Regards,
Sachin

 

[jls001]

Will take the glamour shots tonight

Here's the innards of the CNC MM Phono stage showing the capacitors in question:

Notice the LME49990 opamps proudly doing duty in their Dual SOIC to DIP adaptors


And here's a top view:

Addendum: For those who intend to drill holes for RCA sockets, the best drill bit size is 21/64" (=8.33mm) if you use Neutriks. I am guessing MX or similar brands will also have very similar diameters.

 

[omishra]

^^ correct they are 1 uF caps.

 

[jls001]

Those are same film caps, we previously used 63V rating (smaller footprint) now its 250V rating.

With Shure 97xe, I am used standard loading 47K? and 62K? was to bright HF. 62K? bumps HF but rolloff low. 47K? loading gives near flat response. First OPAMP is LME49990 and second one is AD823 near output. This was well balanced and highs are clear and not too harsh. Using both places LME49990 was very bright, but now since I changed to GR Research speakers I will try to put back LME49990 in place of AD823 and report back.

I guess 62kOhms is too high a value for the M97xE. The glare in treble that I heard on most records is bad. It is fatiguing. Will try 47 kOhms again. I am beginning to guess that either my cartridge is a bit defective or M97xE has fairly rolled off highs. Or there is something wrong with my VTA or tracking force. I just don't like the treble I am hearing.

Question: has anyone tried the Jico SAS stylus for the M97xE? Of course, at about twice the price of a brand new cartridge, it is hardly cheap.

Also two very interesting options for V15/III owners:

Regular: VN35, JICO stylus @ US$ 78


Super Analogue Stylus (SAS): VN35 SAS, JICO stylus @ US$ 133


Hyper Elliptical (HE): VN35HE, JICO stylus @ US$ 106



Hyper Elliptical SAS: VN35HE SAS, JICO stylus @ US$ 133

The last one looks yummy and hopefully someday will grace one of my V15/III.

And for those interested in Shure cartridges, here's a new online retailer:

Shure M97xE:
Buy Online | Lowest Price | Free Shipping| Shure M97XE High Accuracy, Low Mass Turntable Cartridge - Buy online at the guaranteed lowest price in India - BAJAAO - Buy online and Review Musical Instruments, Pro Audio, Studio, P.A. Audio Equipment in I


Shure M92E:
Buy Online | Lowest Price | Free Shipping| Shure M92E Turntable Cartridge for DJ and Traditional Use - Buy online at the guaranteed lowest price in India - BAJAAO - Buy online and Review Musical Instruments, Pro Audio, Studio, P.A. Audio Equipment in


Shure M78S:
Buy Online | Lowest Price | Free Shipping| Shure M78S Phono Cartridge - Buy online at the guaranteed lowest price in India - BAJAAO - Buy online and Review Musical Instruments, Pro Audio, Studio, P.A. Audio Equipment in India


Shure M44-7:
Buy Online | Lowest Price | Free Shipping| Shure M44-7 Competition DJ Cartridge - March Deal - Buy online at the guaranteed lowest price in India - BAJAAO - Buy online and Review Musical Instruments, Pro Audio, Studio, P.A. Audio Equipment in India


Shure M44G:
Buy Online | Lowest Price | Free Shipping| Shure M44G DJ Record Needle - Buy online at the guaranteed lowest price in India - BAJAAO - Buy online and Review Musical Instruments, Pro Audio, Studio, P.A. Audio Equipment in India


Shure WHLB:
Buy Online | Lowest Price | Free Shipping| Shure WHLB White Label DJ Turntable Cartridge - Buy online at the guaranteed lowest price in India - BAJAAO - Buy online and Review Musical Instruments, Pro Audio, Studio, P.A. Audio Equipment in India


Shure SC35C:
Buy Online | Lowest Price | Free Shipping| Shure SC35C General Purpose DJ Cartidge - Buy online at the guaranteed lowest price in India - BAJAAO - Buy online and Review Musical Instruments, Pro Audio, Studio, P.A. Audio Equipment in India

etc. They also stock replacement stylii.

PS: I have no affiliations to these retailers.

 

[sachu888]

I guess 62kOhms is too high a value for the M97xE. The glare in treble that I heard on most records is bad. It is fatiguing. Will try 47 kOhms again. I am beginning to guess that either my cartridge is a bit defective or M97xE has fairly rolled off highs. Or there is something wrong with my VTA or tracking force. I just don't like the treble I am hearing.

Question: has anyone tried the Jico SAS stylus for the M97xE? Of course, at about twice the price of a brand new cartridge, it is hardly cheap.

Hi Joshua,
Shure M97xe has rolled off highs that is why recommended loading is 62k.If you are using LME49990/49720 or LM4562 opamps you may feel 62k loading too bright,so keep it 47k.62k May perform better with laid back Opamps like OPA2132/2134.
FM Bhaskar is using JICO SAS for M97xe.You can PM him for more details.
Very nice build BTW

Regards,
Sachin

 

[john_k_antony]

Hi all,

Just finished my first DIY project successfully. Battery powered CNC phono stage :yahoo:. First of all I would really like to thank Sachin (sachu888) for the kit and all the help in getting this done. I am so glad that it worked in the first try. I am spinning some LPs with the CNC now. Here is rest of my gear

TT : ProJect Debut III with OM 30 stylus, Speed Box and AcrylIt platter upgrade

Existing Phono : Project MM Phono Box

Pre Amp - Denon 2310

Power Amp - Acoustic Portrait NJ1 ( Just bought it yesterday from a FM )

Speakers - Kef iQ7.

I am in the run in period now. As Sachin said it needs minimum of 30 hours of run in. However let me share some very initial impressions with CNC compared to Project MM Phono Box

1. The frequency response seems very controlled. Earlier with the same LP, MM Phono Box used to let go some high frequencies that used to cause some irritation. But CNC seems to control that pretty well. No sudden "shout" or high frequency over shoot.

2. Mids and Low end is good. I would say similar to Phono Box. But I am waiting for the run in time to complete and watch out for differences.

3. The crack and pop sounds seems to have reduced a bit. I am not able to believe that CNC could reduce the crack and pop .

4. The gain seems to be little less than Phono box. I just need to increase the volume in the pre amp a little more than Phono box.

Over all very excited about the first DIY project and the outcome of the effort. I update more details as the phono stage runs in.

I also did some "in efficient" connections between RCA jack and the PCB. Need to fix that once I get the cabinet for this.

I just notices some thing now. I accidentaly switched off the CNC phono while it was playing. It tripped my Denon AVR!. But Denon came back after switching it on again.

Here are some pictures

Thanks,
John.

 

[sachu888]

Hi John,
Soldering looks good,one suggestion please keep the input output wires length as short as required.Sound will improve after 25-30 hrs.
You can increase its gain by swapping 150 Ohm resisters with 100 Ohm without any ill effect.
Which resistive loading did you select on DIP switches?

Regards,
Sachin

 

[omishra]

Nice! The way you bent the resistance leads and laid on PCB, it says everything. It must be a success.