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Hello,
I am interested in a project to take a stereo signal from a record needle cartridge and split the signal into a stereo amp and also a mono amp to be used at the same time (and independently with some switching). I have tried a couple of simple methods that negatively effected the stereo signal. I am thinking op amps might be a way to do this but I am unable to design this. Regardless of what method is used sharing your knowledge would be so greatly appreciated.
- Tom
Hi TC,
Want to try a parallel suggestion?
Michael's op amp method will likely be a lot better since the WW article is old.
I had some time and simulated the luxury version WW circuit, but I'm limited because (a) I don't know how to simulate a ceramic cartridge, and (b) I was hitting a component license limit with the software.
Also, (c) I don't have audio experience whereas Michael does, so it's best to go with any recommendation from Michael.
Anyway, you could try both circuits if you like, if you have the parts.
From the simulation, it seems pretty reasonable (I subjected what I thought was a large signal, 200mVp-p, and the output was around 2.6Vp-p, and the distortion was 0.1% at 100Hz, 1kHz, and 10 kHz. At 100mVp-p, the distortion dropped to 0.06% at these frequencies. I subjected the input to C1 in the simulated circuit below. The response was good across the entire audio range, and the tone controls functioned. However none of this matters if the input isn't the same, and I can't add much to the simulation since I'm at exactly 50 components (the limit) unless I split up and test portions.
Anyway, if you think it's worth a gamble, I'm happy to put this into a CAD package and generate a simple circuit board CAD files (it's only a few tens of $ including postage, if you give the files to any PCB manufacturer to get the board printed).
If you do get it printed and you have spares (usually they give 5-10 boards) then if I could make a request, I wouldn't mind one to experiment with (and perhaps Michael would like one too).
It took a bit longer than expected, there's a lot of BC109's!
The image below shows just the left channel, I will copy-paste it to make the right channel once this one is reviewed. There is a PDF version of the circuit which may be easier to see.
I wanted to highlight/ask these things:
1. I've only used through-hole parts, so the board might end up being perhaps eurocard-sized, but as I understand there is room for that.
2. I've added a Line input too, since it's low-hanging fruit. If it's not needed, then the footprint for the relay contacts can be easily jumpered with wire, since then the relays (one for each channel since they are inexpensive and will simplify the layout) are not required.
3. The mono output is perhaps a few hundred mVp-p when the main output is say 2V p-p, since the mono input will be expecting a low amplitude, but I don't know the precise value, so there are trimmers for that, labelled VR6 on the left channel.
3. It needs an approx 24V supply, I'm thinking I could add a bridge rectifier if desired so that it can connect to a transformer. What's the opinion on that?
4. Considering adding a couple of small solder-in fuses on the mono output connections (both signal and ground) in case some problem occurs with the vintage equipment; is this a good idea, or not necessary?
