stay at home type 69 project

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TwentyTrees

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I've got two underway (the "M" version with the output buffer). It'll be a little while until I finish them, I'm waiting on the Jensen input transformers and I'm not getting much time for DIY at the moment, but I'm pretty excited to try them out and will report back once I do.
 

vizcities

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Just commenting on this thread to follow it! I'm a massive fan of the Helios Type 69 sound & look forward to seeing where this project goes.
 

vizcities

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Anyone finish this? Also: the Dropbox w/gerbers, etc. seems to have disappeared...
 

blackart777

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Hi,
Thanks a lot for sharing this!!!!! I have ordered the PCBs....  ;D
Great work!!!
Best
Hugh
 

TwentyTrees

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Hey Blackart, I've built a few of these now (the first version of the H9M, with buffer and no output transformer) - they're GREAT preamps, really top class, and I'm sure you'll be happy with them. There are a couple of things you'll want to know relating to the version I built, which might or might not apply to the PCB version you've ordered. None of this reflects on Matt's design, I ordered the boards immediately knowing it was a V1 and there may be some prototyping needed and Matt was really supportive in helping me pull things together.

Voltages: I couldn't get the H9M version to run happily off +/-16V. The various sections of the circuit all have coupling caps between, so in the end I replaced the diode on the -16V rail with a KA7908 regulator (plus caps from the datasheet) to bring the negative rail down to -8V (24V rail to rail). That did the job! The pinout of the KA7908 meant some very careful lead-bending and cap-soldering was required, so it might make more sense to substitute the diode on the +16V rail for a positive 8V regulator instead. I didn't need a heatsink, as there's not a whole load of current drawn.

Rotary switch: on the PCB version I built, the low frequency EQ rotary switch was slightly out of line with the other switches, around 1mm or so forward of the PCB edge. Easily compensated with a small cavity on the back of the front panel / bracket.

Phantom power: I ran an LED off the +48V switch - which meant that the reservoir cap didn't fully discharge when phantom was turned off, and phantom discharged very slowly indeed. The original might not have that issue as designed! Anyway, I used the info in this thread to address it.

Pots and toggle switches: there's a lot going on with a Helios front panel, so I ended up using Alpha 9mm pots and the smallest ultraminiature toggle switches I could find to fit everything in there. I'm sure that's due in part to my front panel layout and knob choice though!

Hope this all helps. As I say, much of this may be particular to the V1.0 boards I was working with. Either way, it's well worth it - they're fantastic units and I see them becoming my studio workhorses. Huge thanks to Matt for his generosity in sharing these designs!

IMG_20210416_145433_574.jpg

IMG_20210416_145433_584.jpg

IMG_20210416_145433_596.jpg

IMG_20201026_211620~2.jpg

IMG_20201026_211628~2.jpg
 
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TwentyTrees

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Here's a diagram of the back of my phantom power switch, as it ended up. If I was to do it again I wouldn't bother with the LED as that really complicated assembly - it was a huge pain to put together!

Ignoring the LED side of the switch, it's basically an SPDT switch with the 6k81 resistors etc on the wiper, +48V supply point on one throw, and ground via a 10k 1/2W resistor on the other throw. That will ensure the reservoir cap discharges nicely (though as I say, that might not be an issue if you don't complicate things with an LED. I always complicate things.)

H9M phantom power switching (bleeder - LED).jpg
 

ruffrecords

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I really like your front panel layout. Neat, clear and attractive. Am I right in thinking the front panel has recesses milled on the rear face to accommodate the nuts for the pots and switches?

Cheers

Ian
 

TwentyTrees

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I really like your front panel layout. Neat, clear and attractive. Am I right in thinking the front panel has recesses milled on the rear face to accommodate the nuts for the pots and switches?

Cheers

Ian
Thanks Ian! I really appreciate that. I always found the original Helios panel design to be a little unintuitive so I spent quite some time on this one. This is probably version 20 or 30! You're absolutely right about the nuts, the switches and pots mount on the bracket and the (very thick) panel has recesses as you say. The front panel is then held on by the nuts on the Greyhills, hence the nut covers. A panel could definitely be realised more cheaply and easily, but I'm a sucker for a nut-free panel!

As a slight aside, this particular panel was done by Frank at NRG and is UV printed black on anodised aluminium. I also had a few done by Meface following your recommendation, to test out their products, and I have to say they also did an absolutely excellent job - they're the black ones in the picture below. They can't print white of course, so the legend is just unprinted alu. Beautifully machined though.

IMG_20210416_145433_348.jpg
 

vizcities

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TwentyTrees - Those front panels are stunning. Would it be possible to get the layout files?
 

TwentyTrees

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TwentyTrees - Those front panels are stunning. Would it be possible to get the layout files?
Thank you! I'll work up a version that has all the mounting holes on the panel so an L-bracket isn't required, and share here. They're specific to the version I built of course, so anyone who wants to reuse will need to do their due diligence to make sure it will work for their version.

I updated the later ones to include the regulator, as I also couldn’t get them stable at +/-16.
I hadn't clocked that - great! Is the rotary switch position and spacing the same across all these TH versions?
 

TwentyTrees

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By the way, if anyone's curious about how these sound then I did a short video a little while back running a bunch of stems through them. It's not level-matched or particularly scientific, but you can find it here:

 

TwentyTrees

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Attached is a simplified version of my front panel. Standard caveats apply - this is designed for the v1.0 PCBs I built, using these switches and these pots, so please double check and measure everything before using these for your own builds! I couldn't upload an FPD file, so had to change the extension to PDF - just rename to ".fpd" when downloaded to use with Front Panel Designer.

H9M front panel - GDIY version.png

Notes on this version:
  • Simplified design to give more space for different knob choices
  • Redesigned so that bracket isn't needed - all controls mount on front panel
  • Removed +48V LED to simplify construction
  • Included a 1.2mm cavity on the rear of the panel for the LF rotary switch - but check whether your version needs this, as it may not
  • Main legend design is a PDF imported from Inkscape - font chosen to work with "Helvetica" family in Front Panel Designer, for further customisation (the "H9" is an engraving in Front Panel Designer - set to print mode - so can be freely edited)
  • Mid band frequency points are the stock ones in Matt's design
 

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  • H9M front panel - GDIY version.pdf
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blackart777

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Hey Blackart, I've built a few of these now (the first version of the H9M, with buffer and no output transformer) - they're GREAT preamps, really top class, and I'm sure you'll be happy with them. There are a couple of things you'll want to know relating to the version I built, which might or might not apply to the PCB version you've ordered. None of this reflects on Matt's design, I ordered the boards immediately knowing it was a V1 and there may be some prototyping needed and Matt was really supportive in helping me pull things together.
hi twentyTrees
thanks a lot for the information and your feedback on these preamps
A huge thank you for sharing your front panel version.
I have twelve weeks to wait for the sowter transformers.....
so a lot of time to study all this....;
you did a great job!!!!
Bravo!
 

TwentyTrees

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hi twentyTrees
thanks a lot for the information and your feedback on these preamps
A huge thank you for sharing your front panel version.
I have twelve weeks to wait for the sowter transformers.....
so a lot of time to study all this....;
you did a great job!!!!
Bravo!
You're welcome, and thanks for the feedback!
 

Cyril Jones

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Dec 22, 2011
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Excellent module, love the front panel layout. be warned transistor TR5 could do with a 4K7 in the base lead. In the past have found under certain output fault conditions the transistor fails and passes that onto the output transistors causing those to fail.

RAINDIRK AUDIO DESIGN LUSTRAPHONE equivalent mic. transformers available on mail, cyril_jones@sky.com .
Original size Mu-metal cans 32mm dia. x 47mm long.

Cyril
 

Whoops

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RAINDIRK AUDIO DESIGN LUSTRAPHONE equivalent mic. transformers available on mail, cyril_jones@sky.com .
Original size Mu-metal cans 32mm dia. x 47mm long.

Cyril

Hello Cyril,
I recommended your transformers to many people in this forum and everyone has the same complaint, no one can get in touch with you by email, you don't reply to the emails.
So people that wanted to buy transformers from you end up giving up, in the end I put my reputation in the line to have recommended you.

I think your transformers are really good but if you will not reply to your emails then why even advertising it?

and yes they used the cyril_jones@sky.com email
 

Cyril Jones

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My sincere apologies to all who attempted contact. I have experienced a good deal problems recently with Emails and hope they are behind me now.
Of course I am upset by the situation.
cyril_jones.com and info@raindirk.com a both not active for some reason and will be corrected shortly.
My apologies once more.

Cyril Jones
 

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