Passive Preamp

Overview  Circuit description  Protocol  Parts/PCB
I have built the circuit on a PCB. The assembled board can be seen below. The actual size of the PCB is 160x100mm (a Eurocard).
Assembled board
Click on the picture for a larger view
PCB Drawing
As you can see, I have used PCB-mounted phono sockets. I know a lot of people don't like those, but I like the easy assembly and lack of wiring :-). If you want to use better connectors, you can just install them on the backpanel and connect them to the PCB using short pieces of wire.

The preamp is made for the box as you can see. The PCB size is a standard size (in Europe at least), and the box is made to fit that PCB size. As both the front panel buttons and the phono connectors are fitted on the PCB, a box with the specific depth (104mm) is needed. I'm working on a different PCB layout that separates the control panel from the "audio" section, so they can be installed separately.

Apart from the parts on the PCB, the following parts are needed:
  1. A remote control transmitter. You can use almost any "universal" remote. Or you can use just about any Philips remote - doesn't matter if it's for a TV, a VCR or something completely different. If anybody's interested in a DIY remote just ask. It won't be cheaper, but may look better depending on your skills :-)
    I have drawn up a schematic for a transmitter based on a Philips app. note, and also designed a PCB. The result can be seen here and here. That design should work with 1 to 32 buttons, and can control other RC5 equipment also.
  2. A power source. 6-12V AC or 7-15V DC. 5V AC can also be used, if you use an LDO regulator instead of the 7805. A cheap standard wall-wart can be used. Or if you have a power amp that can supply power for a preamp (such as Dynaco power amps), you can probably use that. But if you want the preamp to switch the power for power amp, a separate supply is a good idea ;-)
  3. Relays for the power switching function if you want to use it. Just use a small 5 or 6V relay. The relay should be approved by whatever authority rules your country...

And now the bad part - the cost. The cost depends a lot on where you buy the parts, what quantity you buy and how lucky you are. The total cost including PCB, box and motorpot is around DKR 1000 (about US$ 160) when the parts are bought in Denmark (Farnell/RS). If lots of people want to buy kits, I could probably get the parts at better prices... If you buy surplus parts, you can probably save a lot of money.

The Alps pot is a big part of the cost BTW - about a third! It costs more than the box and factory-made PCB combined...

I can supply parts if anybody's interested. I can also sell PCBs and pre-programmed controller chips, if you already have the other parts. Or you could make the PCB yourself if you're a masochist ;-)

New!

Kits are now available from Dantimax in Denmark


Overview  Circuit description  Protocol  Parts/PCB


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Comments? Questions? Just send me an e-mail!

MailMail: mcs@post5.tele.dk