• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

DSP-Based Phono Preamp/ADC with Digital Out?

jdubs

Member
Forum Donor
Joined
Mar 12, 2018
Messages
97
Likes
19
Re-wiring isn't a big deal, though...and you can just do it with adapters. Can't really do that for MM cartridges, as those tie the ground at the cartridge to the L channel (floating with an MC cartridge).

For an MM cartridge, you would use the Instrument input, not the Mic or Line inputs.
 

scott wurcer

Major Contributor
Audio Luminary
Technical Expert
Joined
Apr 24, 2019
Messages
1,501
Likes
2,821
Re-wiring isn't a big deal, though...and you can just do it with adapters. Can't really do that for MM cartridges, as those tie the ground at the cartridge to the L channel (floating with an MC cartridge).

For an MM cartridge, you would use the Instrument input, not the Mic or Line inputs.

The grounding clip can be cut at the cartridge if there is one (Grado's have none). Most TT's/arms can be modified for differential, the Jelco for instance uses a 5pin DIN so no mod is necessary. The Thorens is a trivial rewire inside the plinth as was my current TT. I don't know what you mean by doing it with adapters both Thorens and my TT had the ground inside the plinth with RCA outputs (not differential). A true differential cart has 5 outputs.

If you want to properly terminate a cartridge for resistance and capacitance there is no way but to do it externally or live with the inaccuracy.
 
Last edited:

jdubs

Member
Forum Donor
Joined
Mar 12, 2018
Messages
97
Likes
19
The grounding clip can be cut at the cartridge if there is one (Grado's have none). Most TT's/arms can be modified for differential, the Jelco for instance uses a 5pin DIN so no mod is necessary. The Thorens is a trivial rewire inside the plinth as was my current TT. I don't know what you mean by doing it with adapters both Thorens and my TT had the ground inside the plinth with RCA outputs (not differential). A true differential cart has 5 outputs.

If you want to properly terminate a cartridge for resistance and capacitance there is no way but to do it externally or live with the inaccuracy.

100%. Dealing with it is just very easy to do if you have any sort of diy'er in you. I think Channel-D sells adapters, too, for folks uninterested in making their own. In the case of an MC catridge, the ground wire goes to the ground in both XLRs...the hot side of each the L and R channels goes to the + side in the XLR and the return goes to the - side in the XLR.
 

scott wurcer

Major Contributor
Audio Luminary
Technical Expert
Joined
Apr 24, 2019
Messages
1,501
Likes
2,821
I haven't checked Channel-D's site in years, what I see there is hard to take plenty of borderline audiofoolery. A 20MHz phono stage makes no sense, does this mean in "flat" mode all the AM/HAM EMI/RFI gets amplified by 40dB? I also see they offer hardware RIAA (even though their raison d'etre was software RIAA) so they can do the audio grade capacitor dance. MAC only is a non-starter for me, but that's another issue (silly now that Intel is everywhere).
 

jdubs

Member
Forum Donor
Joined
Mar 12, 2018
Messages
97
Likes
19
They've been around for a long time...but (I think) mistakenly went down the mac path, initially. I'm sure development for the PC would be a huge undertaking, financially, plus there are a bunch of other solutions there, now. I do have to say, though, that they have been very helpful whenever I've had questions.

Btw, just pulled down your article and am looking forward to reading it!
 

Wombat

Master Contributor
Joined
Nov 5, 2017
Messages
6,722
Likes
6,459
Location
Australia
Hi Scott,
The OP asked about DSP EQ, but the OP's problem statement was "I’ve found phono stages that A/D to do RIAA EQ in DSP, then D/A right back to output, and I can find phono stages that have a digital output, but I can’t find confirmation of a phono stage that does both "

This unit does indeed support both digi and analog outputs, according to the manual. It also doesn't circumvent using EQ in the digital domain to make fine tuned adjustments given that one loading doesn't work for all cartridges and that post EQ allows a broader adjustment range for VTA.

I appreciate that not everyone will find this interesting or helpful but I hope some do, and that was my only intent.



Hi jdubs,
At this price, expectations are not high, but NE5532's can easily be used and are good enough for the Benchmark DAC1. There are many examples of LM833 based phono eqs going back to the 80s. There's no inherent reason it has to be junk so I'd be interested in any test results, please share if you know of any. Users aren't reporting the usual issues that would be seen at this price: pot mistracking, ground loops, noise, obvious distortion.

I went with the ESI mainly because of 3rd party test results verifying its performance, its 24 bits (reducing windows dither on spdif input), and I already have a nice phono pre


Here's one:

https://www.audiosciencereview.com/...rn-pluto-and-art-djpre-ii-phono-preamps.3457/
 

Jaimo

Active Member
Joined
Feb 16, 2018
Messages
198
Likes
179
Location
Toronto, Canada
From your link...

Most mic pre-amps have 1k - 2k input impedance and of course will work but mis-terminate a MM cart badly and have a large effect on the frequency response, an MI cart like a Grado fares better. You don't need a balanced input since balanced connected TT's are very rare unless you re-wire them yourself.

EDIT - I don't know why they recommend the TC Impact Twin, from the specs neither the line or mic inputs can offer the correct load to a MM cart. I'll try to find my old drawings.

Pls do share your schematic. With all the superb low cost DAC’s and services like Tidal/Roon, I’m past the days of spending thousands of dollars on phono preamps so the PV phono box is out of the question.

I’m just looking to maintain my “weekend” vinyl rig and not invest too much here.
 

jdubs

Member
Forum Donor
Joined
Mar 12, 2018
Messages
97
Likes
19
On most audio interfaces (like the TC Impact Twin), there are instrument inputs. Those inputs are 1 MOhm....so they can be easily padded down (with a single resister) to the 47 KOhm that most cartridges like to see.

-Jim
 

scott wurcer

Major Contributor
Audio Luminary
Technical Expert
Joined
Apr 24, 2019
Messages
1,501
Likes
2,821
Hi Scott,
The OP asked about DSP EQ, but the OP's problem statement was "I’ve found phono stages that A/D to do RIAA EQ in DSP, then D/A right back to output, and I can find phono stages that have a digital output, but I can’t find confirmation of a phono stage that does both "

This unit does indeed support both digi and analog outputs, according to the manual. It also doesn't circumvent using EQ in the digital domain to make fine tuned adjustments given that one loading doesn't work for all cartridges and that post EQ allows a broader adjustment range for VTA.

I appreciate that not everyone will find this interesting or helpful but I hope some do, and that was my only intent.

Sorry we got a little off track especially with the TT modifications for differential output. There are many ways to do this and it matters if you are just archiving or want real time listening. I'm realistic about vinyl, the surface noise (not just ticks and pops) and distortion makes most of the extreme fussing look rather silly. I've gone back to an RIAA phono pre (of unique design) and a headphone amp for listening. The latest Scarlett 2i2 drivers work for simultaneous play/record at 24/96 if I feel like recording (in Audacity).
 

Hephaestus

Active Member
Joined
Jun 2, 2019
Messages
233
Likes
495
Location
Rapture
Linn Selekt DSM has MM and MC inputs. It applies RIAA in digital domain and has SPDIF output. Expensive piece of audio jewellery but as far as I am aware Linn electronics measure pretty well and have 5 year warranty and extremely long software support...
 

pozz

Слава Україні
Forum Donor
Editor
Joined
May 21, 2019
Messages
4,036
Likes
6,827

jdubs

Member
Forum Donor
Joined
Mar 12, 2018
Messages
97
Likes
19
I don't understand why it can't output at 24bit / 96khz. That would make it much more interesting.
 

scott wurcer

Major Contributor
Audio Luminary
Technical Expert
Joined
Apr 24, 2019
Messages
1,501
Likes
2,821
On most audio interfaces (like the TC Impact Twin), there are instrument inputs. Those inputs are 1 MOhm....so they can be easily padded down (with a single resister) to the 47 KOhm that most cartridges like to see.

-Jim

SNR is a little worse probably not a problem, does the combo input stay differential if you use a stereo 1/4" jack or is only the XLR differential?
 

jdubs

Member
Forum Donor
Joined
Mar 12, 2018
Messages
97
Likes
19
SNR is a little worse probably not a problem, does the combo input stay differential if you use a stereo 1/4" jack or is only the XLR differential?

Pretty sure only the Mic inputs (via XLR) are differential. I think instruments, by nature, are unbalanced (could be wrong).

-Jim
 

scott wurcer

Major Contributor
Audio Luminary
Technical Expert
Joined
Apr 24, 2019
Messages
1,501
Likes
2,821
Pretty sure only the Mic inputs (via XLR) are differential. I think instruments, by nature, are unbalanced (could be wrong).
-Jim

Since a mono jack shorts the minus input to ground wiring it that way works fine. That how I modded my current TT. I took short pieces of Mogami miniature microphone cable and threaded them through the RCA female connectors on the back and soldered stereo female 3.5mm sockets to them. Then simply using a mono 3.5mm to RCA adapter turns the output into single ended with the shield ground in both cases.
 
Top Bottom