HE-569 pre/eq 500 series

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I'm late coming to the party! are there any more kits available ?

Some companies use a switch to reverse the transformers for line input, that maybe an option?
Anyone have a schematic of the transformer switching ? [ reversing the i/o ] I think hairball uses it, not sure who else!
 
Does anyone know which of the resistors on the BOM sheets are the 6 values for the 22113 fb resistors? The main board schematic shows these as between 820R and 22k, but the gain resistors BOM don't show 820R but show extra, non-original resistors outside of this range.
 
I actually joined GroupDIY because of this project. I would visit every day to see the progress, getting more and more excited about building four of these preamps to get closer to the sound of the album that blew my mind when it came out, Led Zeppelin IV. It's so sad to see such a beautifully laid out board and panel just fade away.... Hopefully Pahstah will either offer these commercially (hopefully for a little less than the H2 guys charge ($2000)) or finish the kit and offer it in the White or Black market. I'm still hopeful!
 
I have 19 of my Lustraphone transformers in stock having just completed a batch. I also designed a small mic amp with the voltage follower attached. the whole board is the width of the 8 pin socket, the board having gold plated figures as per Helios designs.
Cyril
 
I have 19 of my Lustraphone transformers in stock having just completed a batch. I also designed a small mic amp with the voltage follower attached. the whole board is the width of the 8 pin socket, the board having gold plated figures as per Helios designs.
Cyril

Nice one Cyril,
Can you please post photos of your PCB?

thank you so much
 
Very nice Cyril,
it's really small the pcb.

What is the Voltage Follower circuit? What is it for?

Thanks
Early Helios channels used the 2180 pre-amp,, followed by the switched passive bass filter which requires a high impedance follower, the EQ section requires a low impedance drive., the voltage follower provides both. Later modules incorporated the VF on large circuit boards using a 16 way connector. I have reduced to this design and thus lessen the cramped nature of components behind the front panel.
Here is a plea, for those constructing the early modules please use a small relay adjacent to the input transformer to change the microphone phase or move the phase switch to the top of the module. The module could be more stable at high gains if the microphone input cables and switching remain at the top of the channel away from high level signal levels..
Cyril
 
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