DIY Audio Projects Forum
http://diyaudioprojects.com/Forum/

Inexpensive IC based phono preamp for LOMC
http://diyaudioprojects.com/Forum/viewtopic.php?f=10&t=4441
Page 4 of 20

Author:  mwhouston [ 01 Nov 2013, 21:33 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

A little off topic but inline with small caps, can anyone tell ma what dielectric Ducon used in these old small value caps. Is it Polystyrene, Polypropylene, Mylar, Polyester ??? I think it may be Polystyrene. The vales are 0.0033 and smaller.

And I see mustards are getting big prices on eBay. I have a few NOS and slightly used. What was the make-up of the mustards?

Author:  gofar99 [ 10 Nov 2013, 20:51 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

Hi Everyone, An update....I discovered that the equalization for audio tape players is rather easy to implement with this preamp. So I have attached a modified schematic that ought to work. I plan to try it tomorrow on a old Sony recorder that has really sick amps.

Good listening
Bruce
Attachment:
LOMC IC Phono NAB Preamp November 10 2013.jpg

Author:  mwhouston [ 10 Nov 2013, 22:31 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

Lets try that again with the images this time:

A little off topic but inline with small caps, can anyone tell me what dielectric Ducon used in these old small value caps. Is it Polystyrene, Polypropylene, Mylar, Polyester ??? I think it may be Polystyrene. The vales are 0.0033 and smaller.

And I see mustards are getting big prices on eBay. I have a few NOS and slightly used. What was the make-up of the mustards?
Attachment:
PB022525.JPG

Author:  gofar99 [ 11 Nov 2013, 11:14 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

Catsup? No clue. way back though many used paper.

Good listening
Bruce

Author:  mwhouston [ 13 Nov 2013, 06:58 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

Here is my take on Bruce's phono pre. On\off switch at the front left with yellow led below and battery test point on the right. On the rear two sets of RCAs for two TT with the selector switch between the two pairs. One set of output RCAs near 50\100ohm load selector for MC carts. and bottom switch is for MM or MC selection. The enclosure is heavy die-cast Al.This build is at enclosure only stage though I have all the parts to complete the project.

I intend to run the preamp on 4 X 9V batteries which will be held internally to provide +/-18V. OK lets talk about the colour. Firstly it is not yellow but according to the spray can it is Sunburst Gold. I will accept Lambogini Yellow. Stop laughing I'm serious!!
Attachment:
AssembledI.jpg
Attachment:
AssembledII.jpg
Attachment:
AssembledIII.jpg

Author:  gofar99 [ 13 Nov 2013, 08:29 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

Mustard?
Did you not the possible mod to use it for NAB tape head play back? It works great at that.

good listening
Bruce

Author:  mwhouston [ 13 Nov 2013, 15:49 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

gofar99 wrote:
Mustard?
Did you not the possible mod to use it for NAB tape head play back? It works great at that.

good listening
Bruce

Mustard? Is that as good as you can do? How about puss? No tape EQ just some flexibility with inputs and MC loading. I don't have a huge amount of room once the four 9V batteries go in.

Author:  mwhouston [ 16 Nov 2013, 19:00 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

Cct. brd. is near completion just one or two components to go to drive the "on" LED. The prototype brd is only 1.75" square. I was going to use higher quality components but that would have made brd. assembly even harder. I chose small components which would fit on the brd. for a neat build. On board is the differential power supply resistive network. This will give me +/- 18V (from 4 X 9V batteries). The PS caps are LOW ESR 220uf\25V and output caps NPs. The resistors are metal film and other caps MKT and Mylar\polyester. Not supper high grade components but these will allow me to build a neat and compact unit complete with its own PS. With real estate being tight I go 3D and place components underneath the brd. Wire links (4 of) are all solid pure silver and silver solder used.

I have included a switch to switch between 50 and 100ohms loading for the MC stage which better suits my Ortofon Rondo Blue cart. I have added split soft rubber grommets to the sticky stand-offs and bituminous heavy Al foil to the lid and bottom of the cast Al enclosure to control resonance and vibration. Hope to have it up and going in the next day or so.
Attachment:
Isolation.jpg
Attachment:
CctBrd.jpg
Attachment:
CctBrdII.jpg

Author:  gofar99 [ 16 Nov 2013, 22:24 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

Hi Mark, You have to love those mini boards. Here they are sold by Radio Shack. I use them and "surf" boards rather often. If you normally use SUTs, the combination of SUT and preamp seem to sound better to me. Without the SUT mine reminds me of the Moon LP3 I have. Clean and accurate but not as lush as I would expect.

Good listening
Bruce

Author:  mwhouston [ 17 Nov 2013, 03:18 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

Dick Smith here use to sell the but they got out of components etc. I have a stack of them. What is a SUT?

Page 4 of 20 All times are UTC - 6 hours [ DST ]
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/