I got this today and i was told that it is not s real tube preamplifier (edited). There are transistors doing the job, tubes are just for decoration. Is this true? It is powered by a 12V AC transformer.
Also he told me there is no way a 12v AC transformer could power those tubes. They need voltages like 120V or something.
How true are these statements?
Also he told me there is no way a 12v AC transformer could power those tubes. They need voltages like 120V or something.
How true are these statements?
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I have a few of them, they are a tube PREAMP. Not a amplifier. And yes it works ok, not a top of the line but is fine for playing around for tubes. Just hoop up a CD player or even to your computers audio outputs and then plug the rca’s up to any amp you like and then your speakers
Sorry my bad... Preamplifier, i got them to amplify my bluetooth receiver signal which was very weak when connected to the aux of the amplifier. This does a wonderful job of amplifying it to a good volume. Big plus point was the tubes, but when i was told tubes doesn't do anything, it was a let down.
The schematic is for a power supply and bears no relation to the circuit board.
Your acquaintance is probably correct about the device. However, it is possible to obtain a substantial B+ rail by processing 12 VAC. Use a multi-stage voltage multiplier, like that shown. Quite a few tubes will work with an 8 stage multiplier
Your acquaintance is probably correct about the device. However, it is possible to obtain a substantial B+ rail by processing 12 VAC. Use a multi-stage voltage multiplier, like that shown. Quite a few tubes will work with an 8 stage multiplier
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Simple test. Pull the tubes and try it. If you get sound without the tubes, then you know what's happening. If you get no sound without the tubes, then you know that they are at least doing something.
Looks like the board at least has traces to all of the tube pins. Looks to be a double sided board also. Better than something that just has power applied to the tube heaters.
The 12V AC is rectified to +-28V. Effectively it is providing 56V to the 6J1 tube. The circuit is set up as a stereo single stage common cathode triode amplifier. At 56V B+, you will be getting an under-voltage tube amp with good amount of harmonic distortions. If that is what you after, fine. Another issues with a 56V B+ is consistence, meaning your result will vary.
It's a tube preamp augmented by solid state support. My attitude, when doing tubes is, "Revolt against the solid state!".
I normally agree egellings but you can do A LOT for a tube amp if you aren't afraid of adding a little solid state. LEDs for 'fixed' biasing without a separate bias supply, constant current sources/sinks for maximizing gain and linearity, and with a solid state power supply you can significantly reduce size and weight of a tube amp if you are trying to fit it in a small space.
I say as I'm going through the pcb layout for a 13-tube RIAA phono amp that even uses tube regulators in the all-tube regulated power supply...
I say as I'm going through the pcb layout for a 13-tube RIAA phono amp that even uses tube regulators in the all-tube regulated power supply...