Dieselpunk Preamp of Doom and the Beast with Two Backs

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Thermionic Idler
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#46 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Thermionic Idler »

Here's where we are after 4 days effort:

Completed A24 linestage boards:

Image

Regulated power supply for the A24 linestage supplying +/- 10V (two diodes still need populating as both Farnell and Maplin appeared incapable of supplying the correct part):

Image

And two power supply boards configured for 5V and 12V - the 5V is an 'always on' supply for the logic control, the 12V supply is for the meter buffer, meter backlighting and a trigger for switching the Beast power amps on and off.

Image
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
Speakers: FF225WK Big Mets
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Mike H
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#47 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Mike H »

Shoddy.



:D
 
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#48 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Cressy Snr »

Mike H wrote: Tue Apr 04, 2017 7:17 pm Shoddy.



:D
+1 :mrgreen:
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#49 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by IslandPink »

Ooh, crisp !
Very smart !
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#50 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Thermionic Idler »

The SIFAM vintage-style meters came with pure white LED backlighting. Despite the buff colour of the dials this still didn't look right to me, so this morning I unsoldered the LED and series resistor and kludged in E10 bulb holders and 100mA 12V incandescent bulbs. The bulbs get their power from the buffer board which has inline 10R resistors in the lamp circuit for soft start - I understand that this is to help extend the life of the bulbs. A pleasing side-effect is that they run a bit dimmer than full bright, in fact the glass barely gets warm.

They are going to be a bit of a sod to replace but hopefully not impossible:

Image

Testing with the JLM meter buffer:

Image

The result is very pleasing, exactly the kind of light you'd get from a 1930's wireless, which is what I wanted:

Image
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
Speakers: FF225WK Big Mets
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#51 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Cressy Snr »

Those are dead cool Dave.
I love retro and those meters now look the biz: right bang in the style of the '30s. :D
For me, it's those sorts of details that count when building convincing casework.

Looking forward to seeing and hearing these creations. :)
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#52 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Mike H »

Yep very good. :thumbleft:
 
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#53 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Ali Tait »

Like it,look like mini AVO meters.
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#54 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by pre65 »

Looks really nice, I'm envious. :)
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#55 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by IslandPink »

Velvet Underground 'VU' !
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#56 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by simon »

Yeah they're the dogs Dave. They'd look great with GM70s :-)
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#57 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Thermionic Idler »

Thanks everyone. I guess I came up with the look based on the Garrard 301 that the thing would be sitting under. I think the two will complement each other in the rack very nicely.

I had no option but to go DIY for this. I wanted old fashioned glowy meters, full remote control and balanced operation. Nobody makes a linestage with all those things in it.
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
Speakers: FF225WK Big Mets
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Thermionic Idler
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#58 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Thermionic Idler »

Next update - well not much of an update I'm afraid. I did have plans to continue with the remaining circuit boards over the Easter weekend but I got struck down by the cough from hell and decided breathing in solder fumes was not a good thing.

Right now I just don't know if I'm going to get either of these things completed in time for this year's Owston - sorry guys, I'll try, the focus is on the preamp as we have ongoing irritating issues with the Modwright - but it's all about finding the time, energy and budget for the last few bits.
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
Speakers: FF225WK Big Mets
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Thermionic Idler
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#59 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Thermionic Idler »

I've been doing some more work on the chassis design and layout - I wasn't happy with the way it was coming together and decided to re-engineer it to have a 4mm front panel separate to the 'u-tray', and perspex 'window' to protect the LCD display and remote sensor. No more exposed screw heads on the front panel now (except for the ones securing the meters).

Whilst I was about it I also reorientated the circuit boards internally - the AC wiring to the power supply boards is now much shorter than before.

Here's the updated view of what it'll look like:

Image

and the wireframe view showing internal layout:

Image

I still have to model the fastening between the U tray and top panel but nearly there, I think.
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
Speakers: FF225WK Big Mets
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Thermionic Idler
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#60 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Thermionic Idler »

About done with the preamp chassis design, now at the point of investigating getting it actually made. Here's the final look, hopefully a more high-rez image than I've posted before - the brown is a wooden end cheek:

Image

I've also done some re-engineering on the Beast power amps - by increasing the width 3cm I was able to put the toroids back to horizontal orientation per the Bruce originals, and drop the height of the top cover. Now quite a handsome Beast, methinks. The third, smallest toroid, goes inside the chassis directly underneath the big one, all secured with the same bolt and removing the need for a separate bracket. It supplies HT to the input stage with barely any current going through it, so should be okay heat-wise. Going to incorporate some brass mesh in the top for ventilation - hopefully this is close to how the final amps will look but need to get the pre-amp built first:

Image
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
Speakers: FF225WK Big Mets
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