Dieselpunk Preamp of Doom and the Beast with Two Backs

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

Post by Thermionic Idler »

Nick wrote: Thu Mar 16, 2017 4:45 pm Make sure the iron is hot enough. That way it only needs to be in contact for a second.
I have an OKI induction iron - got it when I built the Son of Beast back in 2012, got fed up with the Maplin cheapo thing I was using. I got it with a variety of tips so hopefully there should be one suitable.

Also just this minute ordered an antistatic mat and wrist strap - a large number of parts came in antistatic bags, not only are those op amps delicate but also the various logic controllers that manage the attenuator relay boards...
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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#32 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Thermionic Idler »

So over the last week or two, boxes have been arriving from various establishments - from a 7+ acre establishment in Texas (Mouser) to a house on a residential estate in Newport Pagnell (HiFi Collective). The only outstanding bits now are some back ordered Molex connectors from RS.

Most of today was spent sorting the disparate deliveries into bags earmarked for the various circuit boards and different parts of the builds. Taking longer than I was expecting - as always - but the idea is when I come to populate the PCB's, I'm not ferreting about trying to find parts.

By the way, I'm aware that all the picture links have broken thanks to Dropbox's service improvements. Meredith has recommended Imgur so will be using that in future - both pre and power amps are currently being redesigned so will pop more pics up when they're done.
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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#33 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by IslandPink »

Or you could just reduce the pics to 256kB with Gimp and put them on the forum...
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Irene Idler
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#34 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Irene Idler »

Dave started wiring up circuit boards Thursday morning and is making good progress. However, we seem to have hit a snag... he got the analog meters set up and kludged them into his main system to test them, and he's been in the living room raptly watching the needles moving for at least 20 minutes now. Totally mesmerised. :D
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#35 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Mike H »

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

Post by Andrew »

Irene Idler wrote: Sat Apr 01, 2017 12:24 pm Dave started wiring up circuit boards Thursday morning and is making good progress. However, we seem to have hit a snag... he got the analog meters set up and kludged them into his main system to test them, and he's been in the living room raptly watching the needles moving for at least 20 minutes now. Totally mesmerised. :D
Probably much better than the rubbish on telly.
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Thermionic Idler
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#37 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Thermionic Idler »

More pics will follow when I've managed to get Imgur installed on my iPhone - and to do that I need to first upgrade to the latest iOS - which requires the usual merry dance trying to release enough storage on the bastard thing to enable the upgrade to happen in the first place.

One thing I have managed to do is upload a video to Youtube for the first time ever. Here are the SIFAM meters that will go on the front of the preamp being tested with the JLM buffer. I think I need to configure the buffer for more gain - the gain pots are up to max and the X-DAC is sending quite a healthy level into the kit, but I'm getting nowhere near full deflection.

The other thing I want to do is replace the white LED backlights with incandescents, but I'm still figuring out how to kludge them in.

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

Post by Mike H »

What are the meters indicating, input to the pre-amp or output from it?

If they are meant to show true 0dB at '0' position on the scale then level should be 1 Volt peak at that point. Think that's right.

Could be they are already able to do that though. An eternal problem with these kind of meters is that while they indicate as expected from a constant sine wave, they read much lower for actual audio, because it consists mostly of transients.
 
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
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#39 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Thermionic Idler »

Mike H wrote: Sun Apr 02, 2017 5:37 pm What are the meters indicating, input to the pre-amp or output from it?

If they are meant to show true 0dB at '0' position on the scale then level should be 1 Volt peak at that point. Think that's right.

Could be they are already able to do that though. An eternal problem with these kind of meters is that while they indicate as expected from a constant sine wave, they read much lower for actual audio, because it consists mostly of transients.
This is true, so far I've only tested them on music. The idea eventually will be to have them on the preamp outputs, to read 0dB at the point that the power amps are putting out 30 watts or so, which is the max 'music power' rating of the Fostexes in the Mets (though they can peak at 100W). I don't know at this stage precisely what that will equate to in terms of input voltage to the Beasts so I'm leaving things alone right now.

The good thing about the buffer is that it should allow this kind of adjustability, along with the obvious benefits of not having a dirty great set of meter rectifiers directly across the signal.
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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#40 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Mike H »

Where are the Vol pots, in the pre-amp or the power amps?
 
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
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Thermionic Idler
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#41 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Thermionic Idler »

Mike H wrote: Sun Apr 02, 2017 8:38 pm Where are the Vol pots, in the pre-amp or the power amps?
Volume control is in the preamp. No pots as such - it's one of these: http://www.amb.org/audio/delta1/
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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#42 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Thermionic Idler »

Up until today I've been working on the power supply board and the VU meter buffer.

This morning was the designated time to steel myself and solder the surface mount OPA1612AID, OPA1632D and OPA1611AID op amps to the Alpha 24 circuit boards. Probably the most tricky soldering job I've ever taken on, I really wasn't looking forward to this.

Aside from a couple of instances of the chip sliding out of kilter when trying to tack down the first leg, I think it went reasonably well. The solder has flowed around the joints okay from what I can see under a magnifier, and the joints proved solid when tested with a multimeter. I tried to keep the contact time to about a second for each of the legs, so hopefully I've not cooked anything.

Anyway, here's a pic of the A24 circuit boards as they are right now (right) and their regulated power supply board (left) - as you can see there are still bits left to be populated. The penny is for scale. Resistors are all Vishays - CPF for 2 watt, CMF series on the A24 boards and RN series on the power supply.

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

Post by Thermionic Idler »

I should probably re-post what the preamp is eventually going to look like. I've tweaked the design a bit since the dropbox links died.

Front view:

Image

Internal layout:

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

Post by Mike H »

Thermionic Idler wrote: Sun Apr 02, 2017 9:12 pm
Mike H wrote: Sun Apr 02, 2017 8:38 pm Where are the Vol pots, in the pre-amp or the power amps?
Volume control is in the preamp. No pots as such - it's one of these: http://www.amb.org/audio/delta1/
OK so, for levels significantly less than full up, the needles will hardly move. This is the other problem with using meters...
 
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
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#45 Re: Dieselpunk Preamp of Doom and the Beast with Two Backs

Post by Thermionic Idler »

Mike H wrote: Sun Apr 02, 2017 9:59 pm
Thermionic Idler wrote: Sun Apr 02, 2017 9:12 pm
Mike H wrote: Sun Apr 02, 2017 8:38 pm Where are the Vol pots, in the pre-amp or the power amps?
Volume control is in the preamp. No pots as such - it's one of these: http://www.amb.org/audio/delta1/
OK so, for levels significantly less than full up, the needles will hardly move. This is the other problem with using meters...
Yeah, I wish I'd been able to find a wider range meter of the same design (40dB or so). I could patch them between selector and attenuator boards but that would defeat their purpose really.
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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