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Inexpensive IC based phono preamp for LOMC
http://www.diyaudioprojects.com/Forum/viewtopic.php?f=10&t=4441
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Author:  Hawkeye [ 10 Aug 2019, 14:13 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

Hello, you have developed a nice Phono amp,
but I've got a Question,
is there a way to record in Nab EQ ?
I'm not so much into electronics.

I'm sorry for my englisch I'm not an native speaker.
Have a nice day.

Author:  gofar99 [ 11 Aug 2019, 21:33 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

Hi, Yes indeed. I use a NAB compensated one on an Akai R-R. It is designed for 7.5 IPS, but is close enough for 3.75 IPS. Mid band gain is about 60db. The preamp is designed to take the signal directly from the play back head. Use the high gain mode for most heads.

Good listening
Bruce
Attachment:
LOMC IC Phono NAB Preamp April 2017.jpg

Author:  Felix [ 14 Aug 2019, 04:56 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

G'day all, I've just done a quick repair on my first point to point 'ugly' construction version of this excellent phono preamp, and just listening to some Dave Brubeck album on vinyl, I just can't believe how good and 'musical' this simple phono preamp sounds! 'None' of my many other phono stages (as good as they are), sound as musical as this one. This simple DIY phono stage is stunningly good! Regards, Felix.

Author:  mwhouston [ 14 Aug 2019, 05:22 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

Felix wrote:
G'day all, I've just done a quick repair on my first point to point 'ugly' construction version of this excellent phono preamp, and just listening to some Dave Brubeck album on vinyl, I just can't believe how good and 'musical' this simple phono preamp sounds! 'None' of my many other phono stages (as good as they are), sound as musical as this one. This simple DIY phono stage is stunningly good! Regards, Felix.

If it ain’t me mate from QLD. This guy knows his OPAMPs. And of course this chip based phono pre is all chip. I’ve built a dozen of these and they have all been great.

Author:  Felix [ 14 Aug 2019, 05:43 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

G'day mate. Qld? Yes but please don't hold that against me! I'm not really sure why this phono stage sounds so good. Is it the OPA2134 or the RIAA curve? I don't know, but it does! Regards, Felix.

Author:  mwhouston [ 14 Aug 2019, 06:20 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

Felix wrote:
G'day mate. Qld? Yes but please don't hold that against me! I'm not really sure why this phono stage sounds so good. Is it the OPA2134 or the RIAA curve? I don't know, but it does! Regards, Felix.

I’ve built and sold many with Bruce’s blessing. Everyone I’ve sold has had a great rap. Now a few are being traded on SNA. The new owners are contacting me and saying they are stunning. I repaired one for nix the other. With all the time it had spend in transit a big output cap came loose. Fixed it and now he says it’s one of his fav. MM stages.

Mimic Carbon II is the latest iteration of the Mimic line.

http://retro-thermionic.blogspot.com/2018/03/mimic-carbon-ii.html

Bruce’s finest hour!

Author:  gofar99 [ 14 Aug 2019, 21:10 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

I just love happy folks. I have sold a few as well. Mine have AC supplies with sophisticated filtering. I figure between the time to build and cost of materials I lose $$ on every one. But it does make some vinyl lovers really happy. I probably should market them from the company, but....we do tube stuff. The design was really an accident...I needed another phono preamp one day and cooked it up. It is similar to many others, but seems to have hit the sweet spot on that sort of design. While I use only tube gear in my main system one of these modded for NAB is used for play back in my Akai R-R. Far better than what came with it.

Good listening
Bruce

Author:  mwhouston [ 14 Aug 2019, 22:17 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

All of mine run on two or three 9V. One guy did ask me to make a PS for his which I did. He was happy with it on batteries but doubly happy with the PS I made and retro-fitted.

Author:  vdljev [ 03 Jan 2020, 18:08 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

Hi there! This is gonna be my first audio project ever and a gift, summer fun here in southern hemisphere!
Since the person using it has a cheap MM catridge and i don´t think that´s going to change in a while, i simply omitted the switches, do someone think the input impedance switch from +in is imperative for adjusting normal MM catridges?
Also, has some doubts on the layout and i atacched a photo for if anyone has any suggestions wich would be highly welcomed. Is it ok for the input signal (Catridge out) to come from the bottom passing through both sides (at a certain distance?) of the psu?
You can see 2.2K output series resistor included some posts ago is missing, is this a prob? what´s it´s function?
And lastly, Only found some 32mm long 4.7 non polarized cap film, should the foil be connected to the op-amp or the output conectors?

Those are many questions i know, just want to simplify things to improve success chances.
Happy new year to all!

Author:  gofar99 [ 24 Jan 2020, 21:50 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

Hi, The layout seems OK, I just use perf board on mine. The location for the inputs should not be an issue. You can use a single 47K resistor for the input to ground load. The others are for low output moving coil cartridges. The 2.2K on the output is to prevent interactions with the cable capacitance between the preamp and the phono preamp. Often it can be omitted in budget builds. The gain switch can be omitted use just the 300 ohm resistor (some variations have a 330 ohm one and either is fine). The foil on the caps...if they are marked should go to the phono preamp side as it will be the lower impedance to ground. The main preamp will probably be 10 time higher (or much more). The parts in the versions with tape head equalization components are not needed for phono operation only. I don't see a power supply and it really is important for low noise performance. Mark uses batteries which is fine. I prefer plug in ones so the ones in the actual project are considerably more complicated.

This is a pretty easy build and is an excellent performer. Easily equal to much more costly preamps. I believe you will be surprised and happy with it.

EDIT: do not omit the 1M resistor after the output capacitor. Omitting it will cause problems if you connect the phono preamp to an amplifier that has blocking input capacitors. Not all that common anymore, but you can never tell.

Good listening
Bruce

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