JLH Shunt feedback phono amp construction

[EssB]

I found it - it was in ETI mag as part of his modular preamp in April 1992. It's here:
https://www.americanradiohistory.com/Archive-Electronics-Today/90s/Electronics-Today-1992-04.pdf

If you don't want to wade through that, here's the original schematic

 

[jamesfeline]

Hello EssB.. well done, that's a great find
greatly appreciated

 

[epicyclic]

Yes the sensitivities should read ... 3.7mV (mm), 340uV (mc).


The gain numbers are correct .


I have recently encountered this in the thread started by... Anthony.taylor1967...( Gain resistors on JLH phono ) over in analogue source.

Just looked at the overload voltages and the typos persist they should read .... 67mV (mm) , 6mV (mc) .

 

[jamesfeline]

Hello

little update .. mounted the power transformer today onto the PCB, for some reason took me ages to find the best fit and configuration of fitment that I was happy with, I did not want loads of flying leads all over the place .... so on the whole am happy with this for now ..

 

[jamesfeline]

one picture flip side of the pcb ...

 

[jamesfeline]

sorry picture attached

 

[jamesfeline]

Beautiful work!

Many thanks for the kind comment

 

[jamesfeline]

Hello

This was the psu I was going to use but was to big for the case .. so decided to put this on the shelf for the Class A head phone amplifier for a later date .. pics just for info

 

[jamesfeline]

Hello quick update .. pcb's all mounted and PSU tested all OK

 

[jamesfeline]

A few pictures as a quick update .. just need to mount the transistors and a few resistors
.. now need to start looking at turntables for purchase

 

[jamesfeline]

ok .. nice Sunday afternoon task

going to match all the transistors, not sure if the design needs this also never done this before . hey, what the heck worth a go

 

[jamesfeline]

OK a little update as lost some interest in this project but going to give another push to get completed .. so a few pics from over the weekend.

 

[jamesfeline]

the power supply is up and running and fully tested

 

[jamesfeline]

just waiting for the front panel to come back from the engravers .. and waiting for a few components to complete the phone pre amp

 

[jamesfeline]

there will be a aluminium separator fitted between the PSU and preamp this is my next job

 

[StevenCrook]

Interesting.

I couldn't find any JLH pcbs so decided to make it my 'learning about KiCad' project and based on the schematic on Paul Kemble's site.

I've been trying to finish the PCB layout this week. At current rate of progress I might actually have something assembled early next year. Or later

 

[jamesfeline]

Hello Steven

Thanks for the response .. as been a lonely post, I have a few original PCB's available and have just commissioned another 20 boards as per the original as I have the gerber files

 

[StevenCrook]

You have gerbers? I though all of that was lost when Hart closed. Did you manage to buy up all their remaining boards and docs?

I might be interested in a board, but only if my KiCad efforts crash and burn... Having got this far, I really want to try mine to see if it works. Planned to be powered by a silent switcher and a board per channel. Still thinking about component choices for some of the capacitors.

I'm also toying with a KiCad layout for an earlier design JLH did for HFN/RR. I'd intended to make it when the article was published but producing a board turned out to be too difficult. I still have the transistors I ordered at the time (1979) so I thought why not...

 

[jamesfeline]

Hello Steven

I have always been a fan of JLH and HART kits ... so have been purchasing their PCB's for years ... but when no longer available I made clones of all the PCB's with some minor improvements and made my own PCB's with updated Gerber files 99% same as the originals but with more robust PCB tracks and better connections etc
I have the whole range for my own use

 

[jamesfeline]

well I have done it
Made my own original PCB