Phono Transfer System Construction Information

Construction information for DIY projects, including the MS Mid Side Matrix, Elliptic Equalizer, Mastering Console, Phono Transfer System, Insert Switcher and the Dual Class-A Amplifier. You can post your baby pictures here.
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jimwnyc
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Re: Phono Transfer System

Post by jimwnyc » Tue Feb 23, 2016 8:38 pm

Hey Guys

Thought I would write a new post now that I've had some time with Wayne's phono transfer system. It has really been terrific. I'm SOOO glad I stumbled upon it on eBay and then reached out to Wayne to get the ball rolling. He's been incredibly helpful throughout the ENTIRE process of getting me up and running.

And now that I'm up and running, the setup sounds terrific. Doing RIAA correction digitally is GREAT and I highly recommend folks to try it out. Playback at 24/96 or 24/192 is so incredibly transparent, I don't feel like this is any less of an analog experience. Plus, the ability to use VSTs to do real-time de-clicking is a god-send if you have crappy vinyl that you want to listen to NOW.

Anyway, if folks have questions - please post them! I've run some of my friends through my set up but their eyes generally glaze over...so its not that much fun for me to discuss with them. :mrgreen:

Thank you so much, Wayne!!!

-Jim

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mediatechnology
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Re: Phono Transfer System

Post by mediatechnology » Tue Feb 23, 2016 9:52 pm

Thanks for the update Jim!

Is it quieter than what you had?
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jimwnyc
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Re: Phono Transfer System

Post by jimwnyc » Wed Feb 24, 2016 8:52 pm

mediatechnology wrote:Thanks for the update Jim!

Is it quieter than what you had?
Thanks for bringing this up, Wayne, as I completely forgot to mention this point. And its a big one.... this thing is QUIET! Way quieter than my previous (non-balanced) setup, which was RCA->8ft TRS cables into the instrument inputs on my Impact Twin.

Now I run the balanced output of the Phone Transfer System via 10ft XLR to TRS cables into the line input of the Impact Twin. It is very much silent!

-Jim

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squarewaveind
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Re: Phono Transfer System

Post by squarewaveind » Thu Aug 04, 2016 11:18 am

Here's a recent build I did for Adam Gonsalvez over at Telegraph Mastering. Unbalanced input, switchable MM/MC, variable input impedance for MC, variable capacitive load, variable gain in 3dB steps, and +/-1.5dB L/R trim. The raw stereo gain goes from 27dB to 52dB, and with the trim the full range is 26.5 - 53.5. The MC transformer is wired for +18dB (1:8), so the MC range is 45 - 70. Noise specs are below. The cartridge load is my cheapo Audio Technica AT-LP60.

Un-weighted, 22Hz - 22kHz bandwidth.

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Gold
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Re: Phono Transfer System

Post by Gold » Thu Aug 04, 2016 12:33 pm

Cool build. I had bad luck trying to bring the preamp gain out to the front panel. I got frequency response and phase response errors. Did you run frequency sweeps? I also wasn't able to get more than 6dB or so out of the front end gain on the other board without running into impedance/frequency response problems. Wima makes a 2.2uF that will fit there and let you get more gain without low roll off.

Is there a reason you didn't remote the preamp? I consider that a major feature. Especially with a lathe where the preamp is usually mounted at least six feet away. Real world noise figures with long cables will probably be different.

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mediatechnology
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Re: Phono Transfer System

Post by mediatechnology » Thu Aug 04, 2016 1:34 pm

Nice-looking build Sam!
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squarewaveind
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Re: Phono Transfer System

Post by squarewaveind » Wed Aug 10, 2016 12:38 pm

Adam has had the preamp for a little while now and it's been working great so far. He has it mounted in a rack very close to the lathe so I believe the cable run is only about 4-5 ft. He says it's dead quiet even with everything cranked.

Paul, how long was the cable run for the preamp gain when you were having issues? Did you shield the wires?

For this build I ditched the balanced send and receive between the preamp and EQ boards (for obvious reasons). The full instrumentation amp wasn't really necessary in this case, but I populated it on the off chance that Adam ever wanted to convert it to balanced input. The signal goes directly from IC3 on the pre to IC5 on the EQ. I redesigned the gain stage around IC5 for the +/- 1.5dB trim utilizing a linear 1k pot. The input impedance to this stage is 2.43k, so I increased C33/34 to 4.7uF for a low roll off at 14Hz.

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mediatechnology
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Re: Phono Transfer System

Post by mediatechnology » Wed Aug 10, 2016 2:21 pm

Adam has had the preamp for a little while now and it's been working great so far. He has it mounted in a rack very close to the lathe so I believe the cable run is only about 4-5 ft. He says it's dead quiet even with everything cranked.
Cool!
The full instrumentation amp wasn't really necessary in this case, but I populated it on the off chance that Adam ever wanted to convert it to balanced input.
It's a good thing you did since it still is a balanced input and it realizes common mode rejection even if it is connected using an RCA.

The balance of co-axial cables isn't as good as true STP but apparently quite a few modern "co-axial" RCA cables are internally STP so the only unbalanced portion of the interconnect is the RCA where "-" ties to the outer conductor.
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Gold
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Re: Phono Transfer System

Post by Gold » Wed Aug 10, 2016 3:12 pm

squarewaveind wrote: Paul, how long was the cable run for the preamp gain when you were having issues? Did you shield the wires?
I think you are talking about the gain on the preamp card. I guess the wires were three to six inches. Twisted but not shielded. I got excessive crosstalk, peaky frequency response and more noise. I'm not a big fan of shielded cable to front panel controls. The few times I've tried it I've gotten HF roll off from capacitive coupling.

I never tried it unbalanced. Only balanced with twisted pair. With a balanced front end cable length isn't too important. I tried a 25ft cable between remote box and tonearm without any measurable difference. I think there might have been a slight audible difference but I wouldn't swear to it. I have the remote box located directly under the tonearm with a short cable.

The noise floor with about 65dB of overall gain is about -78dBu. RIAA EQ in no weighting. There is a 30ft cable between the remote box and the base station.

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JR.
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Re: Phono Transfer System

Post by JR. » Fri Aug 12, 2016 11:12 am

Gold wrote:
squarewaveind wrote: Paul, how long was the cable run for the preamp gain when you were having issues? Did you shield the wires?
I think you are talking about the gain on the preamp card. I guess the wires were three to six inches. Twisted but not shielded. I got excessive crosstalk, peaky frequency response and more noise. I'm not a big fan of shielded cable to front panel controls. The few times I've tried it I've gotten HF roll off from capacitive coupling.
If the gain trim being talked about is the 50K pot in the NF leg from op amp (IC5?) output to negative input, using single conductor shielded cable, with shield connected to op amp output will provide shielding to a low Z node, and any cable capacitance will look like a small cap across the feedback R. Even at max gain the LPF pole should be higher than audio.

JR
I never tried it unbalanced. Only balanced with twisted pair. With a balanced front end cable length isn't too important. I tried a 25ft cable between remote box and tonearm without any measurable difference. I think there might have been a slight audible difference but I wouldn't swear to it. I have the remote box located directly under the tonearm with a short cable.

The noise floor with about 65dB of overall gain is about -78dBu. RIAA EQ in no weighting. There is a 30ft cable between the remote box and the base station.
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