CNC Phonostage completed

[Anil kumar]

Well, i finally completed my CNC phono stage build after a long gap.

I must thank Sachin, Raghu, Omishra & Sreekanth for their great assistance in building this beautifully sounding phonostage.

The face plate has been cut out from an Aluminum rectangular tube, i wanted no screws visible on the front panel. I really enjoyed making this unique cabinet as its a combination of aluminum & wood chassis. Working with the thin front & back aluminum panel was very difficult particularly edges, but well worth the effort. Did lot of running around to get the right kind of material for the project.
Using LME49990 opamp, cartridge loading resistance is 62K. In comparison to Technics, Yamahas & Sansui, i find CNC "more everything" bass is adequate, vocals are bit more forward and top end is sweet and musical after 40 hours of burn in. Background is dead silent, no hum or hiss without the record playing.

This is indeed a amazing sounding phonostage. Honestly, a huge applause to Sachin and Raghu :clapping:

Here are some building pictures.

 

[manniraj]

The cabinet build looks great :clapping:

 

[santnai]

Congratulations Anil !!! This one of the best cabinet. Appreciate your DIY spirit.

 

[techiecal]

Lovely DIY job. Where did you get the kit for the preamp and power supply?

 

[jmascreen]

Great cabinet Anil..

 

[karthi1000]

fantastic cabinet :clapping::clapping:

 

[nraghunadh]

Congrats Anil,
Neat build and It is looking very beautiful.
:thumbsup:

Raghu

 

[omishra]

Wonderful build!
No words, amazing.

 

[Hiten]

Superb Build.
Regards

 

[sachu888]

Very nice, excellent :thumbsup: How does it sound?

Regards
Sachin

 

[dheerajin]

I know it will sound good after some burn in....even i have CNC phonostage with power supply....nowadays i am using MC cartridge ..so no longer required this...if anyone wants the phonostage , then contact me...will give this with reasonable price...

 

[kuruvilajacob]

Congrats Anil. What cartridge are you using? How does it compare with the inbuilt phono of your Yamaha or Sansui ?. Most Sansui amps have very good phono stages.

 

[Anil kumar]

Thanks to all for the response.

Dear Sachin & kuruvila, phonostage is sounding very sweet with superior detail (initial 50 hours of impression). Earlier i had trouble with hum & background noise, it was terrible, may be due to CAT cable. Later replacing them with 2 core teflon shielded wire. Now sounds far superior than other amps which i have but Pioneer SA 9100 sounds different may be due to it's broad frequency response (7Hz to 80KHz). It is the best sounding amp in my vintage collection SA-9100 is Pioneer's one of the finest professional stereo amplifier built in 1973.

I am quite happy with the build, :signthankspin: Sachin & Om

Regards,
Anil

 

[manniraj]

Thanks to all for the response.

Dear Sachin & kuruvila, phonostage is sounding very sweet with superior detail (initial 50 hours of impression). Earlier i had trouble with hum & background noise, it was terrible, may be due to CAT cable. Later replacing them with 2 core teflon shielded wire. Now sounds far superior than other amps which i have but Pioneer SA 9100 sounds different may be due to it's broad frequency response (7Hz to 80KHz). It is the best sounding amp in my vintage collection SA-9100 is Pioneer's one of the finest professional stereo amplifier built in 1973.

I am quite happy with the build, :signthankspin: Sachin & Om

Regards,
Anil

Congrats and happy listening
Where did you get the 2 core teflon shielded wire in Bangalore? I need some for my upcoming builds.

 

[Anil kumar]

manniraj
Where did you get the 2 core teflon shielded wire in Bangalore?

Bought them from cable craft on SP road last year.

 

[Selvin]

Yesterday evening I got an opportunity to meet Mr. Anil Kumar and listen his system. Nice set up with Vintage amplifiers and DIY speaker. Auditioned his recently build CNC Phono stage also. Professional kind of build. Sound.. Yes.. there are many better sounding Phono stages around. But this Phono amp is much better than many Integrated amps inbuilt phono stages and even challenges separate phono stages below 10k. Congrats Mr. Anil.:clapping:

 

[Fantastic]

I'm surprised that the preamp didn't sound exceptional. Passive RIAA is the way to go and gives superb sound. With a good opamp I don't see what could be significantly wrong with it.
However you might need to check on the following.
1. Use polypropylene film capacitors for the RIAA components. If you ask if it is so important, I'd say that in 'many' situations the polypropylene makes an audible difference. However some polyester film caps also did sound good. So how do you 'really' know if it will matter here ? You have to TRY it ...no other way!
2. Measure the capacitance value ! If it isn't the optimum value or even way off , the simple solution ( in a passive RIAA) is to just alter the resistor. You can make up any value you want easily ! The RxC value must be the same.
3. MEASURE the total capacitance of your phono system. Disconnect the cartridge and measure what the capacitance is at the RCA plug that plugs into your preamp. So you can only have the balance on your preamp. More will kill the HF sound !
If the cartridge requires 250 pF and your capacitance measured at the RCA plug is ( typically ) 150 pF then your preamp must not have more than 100 pF on it. That is the total capacitance of the RCA socket on the chassis ( 4pF) , the shielded cable 10pF, stray capacitances and the cap on the board. So that cap should probably be 82pF or less.
4. Use a metal film resistor at the input of the preamp. Supposedly sounds brighter than carbon film ( I can't confirm that as I really didn't find a diff). But just do it ...just in case it matters !

Also note that the 47K load and 250pF capacitance is a "recommended" value for your cartridge. If you have a test vinyl disc you can 'fine tune' it for YOUR cartridge which will have parameters slightly different from the published specs. Without a test disc you can just play music and vary them separately till it sounds 'right' ! Start with impedances higher than recomended like 82K or 62K and go down and capacitance not more than 470 pF ( TOTAL) and go down.

Sit with some friends , bring out your hooch and have a great time experimenting !

 

[murali_n]

Hi Anilkumar,

Congrats for the build. I suggest you also use a SSP Pre-amp after the Phono section, and feed into the Vintage Power amp section, this should give a better sound imho.

N.Murali

 

[linuxguru]

Using LME49990 opamp, cartridge loading resistance is 62K. In comparison to Technics, Yamahas & Sansui, i find CNC "more everything" bass is adequate, vocals are bit more forward and top end is sweet and musical after 40 hours of burn in. Background is dead silent, no hum or hiss without the record playing.

Anil - good work, and very nice-looking build!

FWIW, TI is discontinuing the LME49990 opamp wef Sep 2016, hence those who wish to build projects that use the LME49990 (and several other TI/NatSemi analog parts) may want to buy and retain a few spares over the next year, before availability becomes scarce.

 

[sachu888]

They are actually discounting may other opamps as well(mostly DIP). I don't know what is the reason behind this.

Regards
Sachin