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Re: Phono Transfer System Construction Information

Posted: Thu Jun 11, 2020 11:23 am
by Audio1Man
Hi Brian

If you have access to an Audio precision the RIAA curves & tests are part of the software tests.
Duke

Re: Phono Transfer System Construction Information

Posted: Thu Jun 11, 2020 11:55 am
by JR.
I suspect he is looking for a piece of hardware that can sit in line to facilitate monitoring the RIAA equalized feed going to the cutting head.

He just needs a typical riaa playback circuit without the 40 dB of gain at 1kHz....

JR

Re: Phono Transfer System Construction Information

Posted: Thu Jun 11, 2020 6:48 pm
by brianroth
JR. wrote:
Thu Jun 11, 2020 11:55 am
I suspect he is looking for a piece of hardware that can sit in line to facilitate monitoring the RIAA equalized feed going to the cutting head.

He just needs a typical riaa playback circuit without the 40 dB of gain at 1kHz....

JR
Indeed, my goal is a tidy, already designed solution. As mentioned in an earlier post, adding a big-ass pad in front of a conventional phono preamp seems silly since Wayne designed a line input device with the RIAA playback curve. I've been slowly re-reading this thread to verify the deemphasis curve is very accurate, although the primary reason for this app is to ensure the cutting amp isn't farting <g> or otherwise acting up. You cannot playback the lacquer if it's destined to go through the plating and pressing steps.

Bri

Re: Phono Transfer System Construction Information

Posted: Thu Jun 11, 2020 9:07 pm
by mediatechnology
Brian -

All you need to do is pad the cutterhead drive level and feed it into the RIAA EQ portion of the EQ Monitor board at J4.

You'd need to populate IC6, IC7 and if you want a balanced output to drive the monitor, add the THAT1646s at IC10/11.
You don't really need IC7 either but it will give you a gain trim.

See: https://proaudiodesignforum.com/images/ ... 092719.pdf

Feedback monitoring is something a little different - the RIAA is applied to the output of the feedback coil preamp.

The PTS is being used by a number of facilities for cutting.
The FLAT MM preamp is used as a feedback coil amp, the EQ Monitor board to provide Inverse RIAA and then using IC7 to sum modulation and feedback. A second RIAA board is then used to EQ the feedback path.

Gus Elg at Sky Onion is using it this way and he would be a good contact for you for any questions you might have on this project.

I just had a client tell me that it used to be that about 1 in 10 projects were mastered for vinyl - now its 1 in 2 or 3.

Re: Phono Transfer System Construction Information

Posted: Wed Jul 01, 2020 4:15 am
by billshurv
There is a scary chance I will get my build running by the end of the week! Watch this space.

Re: Phono Transfer System Construction Information

Posted: Thu Jul 02, 2020 3:45 pm
by mediatechnology
Glad you're getting closer!

Re: Phono Transfer System Construction Information

Posted: Wed Jul 08, 2020 9:56 pm
by grufti
No way! One down [nearly] ... n+1 to go. I know the feeling

Re: Phono Transfer System Construction Information

Posted: Sat Jul 11, 2020 6:39 pm
by billshurv
Having to work from home with two under 5s has not been conducive to working on projects. Work has been particularly manic as well, which is a good thing in the grand scheme of things. If I can get the test cables I need finished final visual inspection of the soldering and I can start testing.

Re: Phono Transfer System Construction Information

Posted: Sat Jul 11, 2020 7:50 pm
by mediatechnology
Last November I got a puppy - a Spaniel/Border Collie mix.
Very high energy dog...
It's been hard for me to build boards to replace what I've sold.