ADA Ampulator

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ADA Ampulator

Postby Yazoo55 » 30 Sep 2016, 17:22

Has anybody got any pictures of the ADA Ampulator circuit boards? I have got the schematics but these do not include a pcb layout. Pcb layouts were included in the documents for the Microcab which I built several years ago and these were really helpful when I did my one channel version.
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Re: ADA Ampulator

Postby okgb » 02 Oct 2016, 23:19

There was a clever Australian fellow who made his one, forgot his name I could post an image of his pcb
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Re: ADA Ampulator

Postby Yazoo55 » 03 Oct 2016, 10:50

Yes please, that would be very helpful.
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Re: ADA Ampulator

Postby Fender3D » 03 Oct 2016, 12:02

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Re: ADA Ampulator

Postby Yazoo55 » 07 Oct 2016, 17:16

Thanks for the link Fender3D. What I am really after is the actual PCB with traces if this exists. I would be really keen to see the version the Australian, I think this is Curtis, built. I have started to try and recreate the original PCB layout using the parts layout and the schematics but this is really tricky.
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Re: ADA Ampulator

Postby Fender3D » 07 Oct 2016, 17:32

The file ADA-Ampulator-loading-chart.pdf contains the PCB layout.
It may be usefull if you're doing it in any CAD with schematic capture and DRC
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Re: ADA Ampulator

Postby Yazoo55 » 29 Oct 2016, 14:21

I have followed your suggestion and I am working through the schematics, using the parts layout as a guide. It will take me a while - I have never really used PCB design software before and I have found that its best to do the routing myself rather than use autoroute.

I won't be able to etch this myself. The board will be too big and it will need vias. Are there any commercial companies you would recommend? I had a quick look and there are several in China. The main board will be about 16" by 3".
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Re: ADA Ampulator

Postby okgb » 13 Nov 2016, 02:34

Yeah it was Curtis , I'll look again
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Re: ADA Ampulator

Postby Yazoo55 » 16 Nov 2016, 18:26

I am laying this out using Kicad. If I upload my work, would anybody be interested in checking it? It will be an ongoing project which will take a while.
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Re: ADA Ampulator

Postby Yazoo55 » 14 Dec 2016, 18:54

OK, I've created schematics and PCB layouts in Kicad. They won't win any prizes for elegance but I'm hoping they will be OK. I have hit one query though. In the power section, there is a 15V bipolar supply for the ICs and a section branches off linked through "MUTE" to transistors linked to the outputs. There is a reference to GND2 which does not appear anywhere else. All other references are to a standard ground (with two references to the chassis ground symbol which are used to provide a special ground for the cable carrying the audio signal between the two boards).

Should GND2 be connected to the main ground?

This is a link to the power section schematic:
Image

I would be happy to share the Kicad files. A second pair of eyes would be very useful!
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Re: ADA Ampulator

Postby okgb » 16 Dec 2016, 17:18

Excuse the delay, I found it , project went down on the cue as I stated using impulses but I found the pcb
can anyone get a hold of Curtis to make sure he's cool with it ?
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Re: ADA Ampulator

Postby Yazoo55 » 16 Dec 2016, 23:23

Great, thanks for this.
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Re: ADA Ampulator

Postby Yazoo55 » 14 Jan 2017, 14:42

I've been working away and done the top board. I used a Chinese fabricator and I am pleased with the results, though there were a couple of mistakes I made. :roll:

I ended up having to add a couple of jumper wires on the back of the board and I had to very carefully enlarge the holes for the power pins which I had set too small. I haven't been able to resolve the issue relating to GND2 and the Mute circuit so I've ducked the issue for the moment and added a jumper to the board so I can come back to this. I've left the components for this off the board. I don't really understand the purpose of the Mute circuit so if anybody can help I would be grateful. If it is optional, I'll just leave it.

I've assembled the board and tested the power supply. I am using a spare ADA MP-1 power transformer I have. This is a photo of the assembled board.

Image

I am planning on doing the main board next but this time I'm going to double-double-check it before I send it off.
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Re: ADA Ampulator

Postby Yazoo55 » 02 Feb 2017, 23:11

I have got the main board ready to send off for manufacture now. I still have a query about the wiring though. I've been through the schematics and layout guides and I can't see a connection from the signal ground to the chassis. There is a bus wire which is soldered to the top of all the pots and this is connected to the chassis but it does not connect to any point on the circuit boards. Is this correct?

As a postscript, I checked out the GND2 issue by recreating the power circuit for the mute function with a spare bipolar supply I have. As I understand it, when powered on, this turns off the mute function to all the outputs by supplying around -14 volts to the base of the three FET transistors. In my test circuit GND2 is connected to tha main ground and it all worked fine. I saw the negative voltage as expected as well as the standard bipolar outputs.
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Re: ADA Ampulator

Postby Yazoo55 » 24 Feb 2017, 19:52

OK, I've done the main board and assembled it for testing and it actually works! I just need to finish putting it into the second-hand KVM rack I bought. I checked the plate voltage to the 12AX7 and it varies from 16 volts up to around 250 volts, depending on how you set it. At 16 volts, it breaks up much quicker. At higher voltages, it stays cleaner.

I did make a couple of mistakes in my Kicad files, the worst being power connectors on the power board and I had to jumper these. :roll: I also got the orientation of a transistor wrong but that was easy enough to sort out when I soldered it in. Definitely a learning experience but well worth the effort.

Image
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Re: ADA Ampulator

Postby Yazoo55 » 04 Mar 2017, 20:06

I've finally got it boxed up in a recycled KVM switch 1U rack - you can get these cheaply off eBay. I never enjoy the boxing stage. It's always the fiddliest bit for me, inevitably involving the use of needle files.

Image

The two big resistors are there to reduce the voltage to the heaters. I used a spare ADA MP-1 transformer I had and the easiest way to get the heater voltage right was to drop the voltage to about 12.6 volts and connect the heaters in series.

I would be happy to share my Kicad files and I have some extra boards.
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