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High gain opamp based preamp for low output MC cartridges.

There will be two boards- the preamp (including buffer) and the filter for the SMPS.
This is just so I can get an idea how many to order in the initial build.
I will buy a few, check them out for functionality and correctness (test then build into my preamp) then order more if necessary.
No defective boards will be sent out.
Orders should specify what boards are required.
The latest (and presumably final) parts lists and LTspice schematics are attached.
Next I will post a spec sheet and a design description, to be followed by layout views when they are complete.
Once the layout views are complete I will be able to price the boards.
 

Attachments

I will want two boards for sure. Do you have dimensions for the pre pcb yet Wyn? Just looking at existing cases I have . Also do you know the max current consumption of the pre? Off topic but I watched an interview with John Siau and Laurie Fincham where they stated the AHB2 was all discrete . I know the DAC3/ LA4 use op amps .
 
raymondo said:
I will want two boards for sure. Do you have dimensions for the pre pcb yet Wyn? Just looking at existing cases I have . Also do you know the max current consumption of the pre? Off topic but I watched an interview with John Siau and Laurie Fincham where they stated the AHB2 was all discrete . I know the DAC3/ LA4 use op amps .
Click to expand...
Thank you. Well, I know for sure that the Quad used 301s, and I opened up my AHB2 and I thought that there were a pair of TI opamps on the main board- which is very complex I might add.
I just assumed that as the THX patent and the old expired Quad patent are basically identical and the circuit descriptions are the same that the opamp was being used in the same way. However, if they state otherwise then it must be so.
In any case thank you for the information, and my interest in the design has grown even more!
 
raymondo said:
I will want two boards for sure. Do you have dimensions for the pre pcb yet Wyn? Just looking at existing cases I have . Also do you know the max current consumption of the pre? Off topic but I watched an interview with John Siau and Laurie Fincham where they stated the AHB2 was all discrete . I know the DAC3/ LA4 use op amps .
Click to expand...
Dimensions not quite fixed as some jumpers are still to be placed, but the upper lower/upper bound is 145mmx100mm/ 150mmx100mm.

The latest 3D image, including the input load components and jumpers.
latestboard.jpg
I've started investigating PC board fab houses...
 
wyn palmer said:
Dimensions not quite fixed as some jumpers are still to be placed, but the upper lower/upper bound is 145mmx100mm/ 150mmx100mm.

The latest 3D image, including the input load components and jumpers.
View attachment 1586455
I've started investigating PC board fab houses...
Click to expand...
It looks like a preamp board will likely be $11 each plus shipping. The cost for me to purchase a minimum order of 5 boards of the maximum dimension is $55.
 
wyn palmer said:
It looks like a preamp board will likely be $11 each plus shipping. The cost for me to purchase a minimum order of 5 boards of the maximum dimension is $55.
Click to expand...
Wyn, please, count me in for 2. I will paypal the amount as soon as I get a firm quote on boards plus shipping.
 
latestboardview.jpg
Latest board view- almost complete, with red board and white lettering. Just some clean up to make the layout more symmetric and "pretty" and rewiring of the single ended/balanced "jumpers" remaining.
Note that the "jumpers", although spaced to be the real jumpers as shown, can be replaced by short wires- which is what I will be doing.
I also received a request for a MM version, with 20dB less gain- so a sensitivity of c. 2.5mv.
This can be done with the change of three resistors per channel, so it is possible to make it switchable. The equivalent input noise degrades by about 1dB- so the SN ratio increases by about 19dB- ignoring the source resistance noise.
The nominal RIAA compliance degrades slightly to about +/-15mdB from +/-10. The overload characteristic should remain unchanged at 28-29dB at all frequencies up to about 1.5MHz.
 
radelius said:
I would like two of each Wyn. Great job!
Click to expand...
Without @HalfApt this would not have been possible.
As of now there are orders for almost 15 boards, so the price will come down. The latest estimate is $6, plus shipping from me, for the preamp board.
Shipping will include only the cost of a bubble shipper plus postage.
I'll post an estimate for the filter board ASAP.
 
As the numbers of orders has increased the preamp board PLUS the PSU filter board is now seemingly down to $5 each, plus shipping.
This will be confirmed when the board size is finalized.
We are combining both boards in a single Gerber file as this is the most efficient/most cost effective way to get the boards built.
The boards can be separated with a minimum amount of work. In effect the filter boards come virtually for free.
The board is now green rather than red- believe it or not it's cheaper!
 
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