Dieselpunk Preamp of Doom and the Beast with Two Backs

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Thermionic Idler
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Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Thermionic Idler » Sat Dec 10, 2016 6:51 pm

So the only DIY I've ever done up to this point has been building gear from kits, the first of which was the WAD 2A3PSE over a decade ago. After this came two Transcendent OTL kits (T16 and Son of Beast, the latter of which is still in use) and I think there was a Bottlehead phono stage in there somewhere as well.

This new project moves on from that, the layout and chassis are my own design, but in some ways it's still a 'kit' build, in that the circuit designs are not my own. However, I'm hoping the build log will still be of interest.

For the preamp, I wanted to go balanced along with full remote control, so I have decided on a solid state design from Ti Kan of AMB labs. His 'kits' are very well regarded but also quite demanding, in that he pretty much only supplies the circuit boards and the 'Volumaster' software chip for running the relay-based attenuator and input selector - the upside of that is that the boards are very flexible and configurable to what you want. I will be building the α24 fully-differential line amplifier, to be fed by the LCDuino-1 / δ1 / δ2 relay based attenuator and source selection system. This will give a true balanced output to the power amps to be located near the speakers, in addition it will supply a 12V 'turn on' voltage to power relays in the power amps, enabling the whole system to be powered on and off remotely.

I've designed the preamp with quite a 'retro' style to match my much-prized 301 turntable. Here are a couple of CAD pics of the planned layout:

This one shows the front panel:

Image

And this shows the internal layout plan:

Image

Top right is the α24 preamp circuit boards, to the left of those are the stack of δ1 / δ2 attenuator and source selection boards for balanced operation. There are 3 toroids along the left - one to supply 5V 'always on' to the control system and solid state relay (orange), one switched 12V to supply the VU meter driver circuit, backlights and power amp switching relays (blue) and one to supply +/-10V regulated to the preamp boards. The associated power supply boards are along the front, rightmost near the pot is the buffer for the VU meters, fed by the unbalanced output from the preamp. The idea being to align the 0dB point on the meters with 30W or so output, so that we can easily see how close we are to clipping / speaker overdrive.

Sifam VU meters and RCA control knob have been purchased:

Image

The VU meter buffer comes from JLM Audio in Oz:

Image

And here are the AMB circuit boards that arrived this week, beautifully made:

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Moving on to the power amps, a hell of a lot of thought has been taking place around where I wanted to go with these, but in the end I have decided to build the Transcendent 'Beast' amps, although with 12 EL509's per side rather than 16. After having heard my 'Son of Beast' give a pretty good account of itself at Owston, and later demonstrate a wonderful synergy with Steve's Metronomes (we're planning to get our own pair of those as well), I decided that I didn't want to lose the unique clarity and transparency that OTL's have (plus it removes the requirement to get all spendy on OPT's). The EL509 output stage of the full on 'Beast' is very similar to the 'Son', just with more valves in parallel, and a meatier driver stage. Bruce sells the PCB's and plans for a very reasonable price, and I now have them - again, very well made:

Image

The full 16 valver occupies a chassis of 17" by 17" and that was too deep to fit on a bookshelf. However there is the option to run it with fewer output valves, and I worked out that if I rotated Bruce's layout around by 90 degrees and limited the build to 12 valves (still good for 75 watts which is plenty), the chassis depth could be reduced to a shade over a foot. So they'll look like this:

Image

Meredith quite rightly pointed out that they should be mirror-imaged, and it took me some time to work out how to do that when the circuit boards, and therefore the placement of the B9A input/driver stage valves, were *not* mirror imaged. It then occurred to me that I could cover the (pretty ugly) power toroids, B9A valves and fuse holders / status LED's to achieve the desired effect. The curve on the top was inspired by the Atma-Sphere amps. Here's a picture with the covers transparent:

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And the internal layout showing the smallest toriod inside the case:

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There will need to be an input / isolating transformer to handle the balanced line feed, and a power relay for remote on/off switching.

Currently I have a spreadsheet with all the parts listed out (there are lots), which I'll use to build orders from various suppliers based on the best price. When will the actual build start? Dunno, but soon-ish I hope!
Deck: Garrard 301
Audio Origami PU7
Van Den Hul Black Beauty
Phono: Whest PS30RDT
Pre-amp - Scratch built AMB α24/LCDuino
Amp - Transcendent "Son of Beast" 15W OTL
Speakers - FF225WK Metronomes

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Irene Idler
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Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Irene Idler » Sun Dec 11, 2016 1:08 pm

What Dave hasn't included is the trim we'd talked about. Bear with me, now, because as a nerdgeek *and* a wife, having admired both Steve's lovely Mets and Nick's (?) 300B design (among many others), I saw no reason that Dave couldn't build something both functional *and* beautiful. Mostly because I want to see my American audiophile friends drool.

Dave said he wanted to use Fender jewel power indicators, and I suggested we look for a trim design that could incorporate those and somehow find a way to mirror the amps. He wasn't sure it would be possible to mirror them due to the circuit board layout. I just kept asking "why not?" and brainstorming ideas until he sat down and tried modelling it, at which point he determined that he *could* mirror them with a little creative rerouting of bits.

Thus it was time to consider trim designs. Dave was very keen on the idea of something that would be a little art deco-ish and a little dieselpunk, echoing the design ethos of the 30s and 40s where everything was streamlined and trimmed like a locomotive or a big shiny car. A bit of Google-fu turned up this:

Image

Dave wanted to use the indicators as the circular bit, but they're only 18mm and I thought that would make the trim too small in proportion to the size of the amp chassis. I suggested a design in which the jewels would be the center of the circle, but that we could create a wider border, increasing the size of the trim to be more proportional with the size of the amps, by using a polished brass washer behind the jewel bezels; the combination of narrow silver bezel and brass border would be striking and different, as well as allowing for the other bits of the trim to be less delicate (and thus difficult to manufacture). The rest of the trim would also be brass-colored with amber-colored jewels that would echo that color, giving the thin ring of silver from the bezels.

A quick round of GIMPery got me to this:

Image

Forgive the poor quality of the artwork; I didn't think the extra work to make it all look perfect was worth the hassle, as this gets the idea across just fine. Against the planned black Hammerite finish I think it's just what he wanted, and he seems pretty pleased with the look as well. I have no idea whether he'll use it or not (we have no idea where we'd get the trim made), but I think it looks pretty sweet.
Last edited by Irene Idler on Sun Dec 11, 2016 1:28 pm, edited 4 times in total.
"Hey, you know the rules, baby. If you wanna PLAY funky, you gotta SMELL funky." -- Mike Troutman

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pre65
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Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by pre65 » Sun Dec 11, 2016 1:19 pm

That's a good idea, I hope you can make it like you want. :)
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Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by cressy » Sun Dec 11, 2016 1:51 pm

Why not use transfers for the lines? I did that with the last motorbike I had on one of the side panels.
A friend who has a signwriting business made the faux pinstripe lines from vinyl that was on a backer.
I positioned them, stuck them on along with a sticker for a chain company I wanted to add then clearcoated over the lot so they wouldn't come off with a satin clearcoat.

Just an idea
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Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Irene Idler » Sun Dec 11, 2016 2:25 pm

cressy wrote:Why not use transfers for the lines? I did that with the last motorbike I had on one of the side panels.
A friend who has a signwriting business made the faux pinstripe lines from vinyl that was on a backer.
I positioned them, stuck them on along with a sticker for a chain company I wanted to add then clearcoated over the lot so they wouldn't come off with a satin clearcoat.
That would be the easiest way, but I asked Dave if there's such a thing as half-round brass rods and he discovered there are, in rather suitable 4mm and 6mm sizes -- then it would just be a matter of finding a washer of the right thickness and circumference, expanding the center hole if needed, and paying someone with a machine shop to trim and polish everything up just right. That's the expensive way, of course, but Dave is a man who likes things done properly.

...or we could buy some adhesive-backed plastic trim from China, but I'm afraid once I mentioned using real brass it was all over. He is now down the rabbit hole, Googling like a madman.
"Hey, you know the rules, baby. If you wanna PLAY funky, you gotta SMELL funky." -- Mike Troutman

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

Post by Mike H » Sun Dec 11, 2016 4:59 pm

Irene Idler wrote:Against the planned black Hammerite finish I think it's just what he wanted,
The satin black Hammerite is nice, however Hammerite these days is pretty thin so doesn't 'cover' too well, so if you go with that make sure it's good and black underneath first.

If on aluminium, suggest start with an acidic grey primer.
 
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Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Mike H » Sun Dec 11, 2016 5:05 pm

Luv the title BTW :lol:
 
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Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Cressy Snr » Sun Dec 11, 2016 8:10 pm

That looks soooo cool, it's liquid nitrogen. :D
And I've been on the pale ale...and I feel like a pinball.

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

Post by Irene Idler » Mon Dec 12, 2016 4:13 pm

Cressy Snr wrote:That looks soooo cool, it's liquid nitrogen. :D
Plus it will double as a space heater.
"Hey, you know the rules, baby. If you wanna PLAY funky, you gotta SMELL funky." -- Mike Troutman

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

Post by Dave the bass » Mon Dec 12, 2016 5:38 pm

Aaaah..... but Space is big.... I mean.... really big!
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Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Mike H » Mon Dec 12, 2016 5:49 pm

Yes, you may think it's a long way down the road to the chemist :D
 
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Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Dave the bass » Mon Dec 12, 2016 5:53 pm

Top marks to MikeH :)
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Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Ray P » Mon Dec 12, 2016 6:47 pm

Dave the bass wrote:Aaaah..... but Space is big.... I mean.... really big!
it might be relatively small...

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

Post by Thermionic Idler » Tue Dec 13, 2016 7:43 pm

Oh dear.

So I've just been looking over my CAD models of the Beast monoblocks, looking at where I'm going to add things like mains IEC connectors and power relays and tag boards to manage the connections from the 3 mains transformers onto the circuit board.

From the positions of the three input valves, I think I've modelled them with the circuit boards upside down!

D'oh!

Well, easily fixed...
Deck: Garrard 301
Audio Origami PU7
Van Den Hul Black Beauty
Phono: Whest PS30RDT
Pre-amp - Scratch built AMB α24/LCDuino
Amp - Transcendent "Son of Beast" 15W OTL
Speakers - FF225WK Metronomes

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

Post by Thermionic Idler » Fri Feb 03, 2017 5:17 pm

News just in - looks like Rozenblit is discontinuing the Beast. Quite relieved I bought the circuit boards when I did, the new Beast Junior is only going to be made available as a complete kit.

http://tubehifi.websitetoolbox.com/post ... nd-8400302
Deck: Garrard 301
Audio Origami PU7
Van Den Hul Black Beauty
Phono: Whest PS30RDT
Pre-amp - Scratch built AMB α24/LCDuino
Amp - Transcendent "Son of Beast" 15W OTL
Speakers - FF225WK Metronomes

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