PhonoCard (Chipbased Phono pre)

[Tazzy]

I just found Maartens design for a Chipbased phono pre

http://www.euronet.nl/~mgw/diy/preamps/uk_phonocard_1.html


His project got me thinking about building one... Maarten had run into some problems it seems though.

Anyway, a chip phono pre seems like a nice change opposed to chip amps.

[analog_sa]

His project got me thinking about building one... Maarten had run into some problems it seems though.

No wonder he's having probs- one of his design goals seems to be the use of a blue LED

Seriously, I don't think building a PhonoCard, as musically satisfying as a Gaincard is going to be so trivial, or indeed possible. After an extended divorce with the opamp family (20years?) i recently tried to build a few phono stages with modern opamps and confirmed my suspicion that although much more refined than 5534, the 627/637 chips retain a similar musical character. Depending on sound priorities it may appeal. The sound has low subjective distortion, excellent controlled bass, prat can be really good in some topologies and the sound stage is stable and reasonably deep. At the same time low level detail retrieval is limited, the soundstage has very low height, images are generally small, voices are all a bit pale, depressed and even choked and the sense of space and airiness is mediocre. The best sounding phono topologies with opamps IMO are still inverting stages, split passive RIAA, separate regulators (or much better - batteries) for each stage and dc coupling if possible. It may be good enough for some but cannot really compete with good discrete or valve circuits.

[platenspeler]

Originally posted by analog_sa


No wonder he's having probs- one of his design goals seems to be the use of a blue LED

hehe

Working on a different project right now, the phonocard will have to wait until I finish another gainclone project with blue LEDs .

I'm planning on a passive RIAA filter design. The last project I built sounds really good (phonoclone) and although I still like the tube amps better, the opamp version is probably faster.

Maarten

[Tazzy]

Got any preliminary info I could read about your new project?

[Squalish]

The Grado PH-1's schematics are available somewhere on here, and it's even simpler than this. It's merely a single opamp gainstage using the NJM4556 opamp with two filters in the feedback and switched ground resistors for different gains.

[tporreco]

Anyone ever heard of, or tried Radio Shack "little rat" phone RIAA eq. Costs $25 and runs off 9V battery. I've seen this get good reviews on other forums. I usually only listen to vinyl. I am working on completing my first DIY GC. This seemed like a good solution to me for phono RIAA, in keeping with the GC theme of simplicity and low cost. Got one in the mail yesterday. Haven't got it all working yet. But, if anyones interested I'll let you know how it sounds.

[PauSim]

I tried it some time ago, after finding the schematic here: http://www.audioxpress.com/reviews/media/AE300GG.pdf

Did the usual stuff, I think. Got rid of almost all psu components and fitted a single 9v battery inside the box; replaced the power plug with an on-off switch; changed all electrolytics for Elnas; all 100n caps for LCR polypropilenes (big ones these), all smaller value caps for polystirene caps, matched all resistors and tried other op-amps . These made the most significant difference to the overall sound. Didn´t like the NE5532 much, really: coherent, but dirty sound. Tried the BB OPA2132 (or was it 2134?) and found it cleaner but the resident chip ended to be a TL 072 or 074 (anyway it´s the dual-op-amp, like the BB): a bit noisier than the BB´s but better bass.
Oh, and switched the green LED for a shiny blue one. This was an important mod too, very Krellish

Today I would add a second battery in series for a true dual-rail supply and maibe remove the output electrolytics, etc.

A friend of mine used to listen through an unmodded one next to an all-AudioNote setup and said mine was far superior sounding than his (right, given the cheap nature of the PP-1 it shouldn´t be too difficult ).

It was worth , educative and great fun.

Cheers

[Ropie]

But, if anyones interested I'll let you know how it sounds.

Yes, I'd be very interested, and some pictures would be good too

[platenspeler]

I more or less finished the PhonoCard. It's running for a couple of days now without problems. Only the box needs some additional work and I'm working on a battery powersupply.

The black wire is for the ground connection until I give it a separate connector.

The sound is not bad at all, but I'll wait with my final verdict until everything is connected properly and the amp has got time to break in a little.

Maarten

PS. More info on http://www.platenspeler.com/diy/prea...onocard_2.html

[analog_sa]

Hi Maarten

I am really curious to know how your 'clone' plays. Can you compare it to other projects/commercial phonos? It certainly is very different topologically and i am sure has unique sonic character.

Please tell me about the function of Ri - it's a real resistor, not the internal resistance of your cart, right? Have you tried current mode? It will obviously require to recalculate the first NFb network.