6J1 Valve Preamp, Vacuum Electrom Tube Preamp Valve Preamp Amplifier Board Audio Amp Assortment Musical Fidelity Kit

Trying to avoid using terms like "warm," this little circuit produces all the transparency and clarity one would expect from a tube amp. After all, most of the tube amp magic happens in the preamp stage. Every element within the mix is more audible, without being overly dominant or blaring. Yes it's counterintuitive for inherently noisy tubes to sound more clear than transistors. But CD quality digital audio must be dithered. The intentional injection of noise.Clearing up any confusion surrounding capacitor polarity: inside the silkscreened circles marking where the electrolytic caps are placed, the negative lead should ALWAYS go in the hole marked with the series of stripes. No doubt those of you ohming out the solder pads will say, "Hold on! Half the pads without the stripes are connected to ground." That's because this board uses both positive and negative voltage. The caps receiving negative voltage will see the ground as positive voltage. Positive compared to the negative voltage on the negative lead. So connecting the positive lead to ground is in fact proper. If anybody is unclear, a polarized electrolytic capacitor connected backward will in fact explode. As at least one reviewer has reported.If anyone is having trouble finding a 12VAC power adapter, a DC adapter can be fairly easily converted to AC. Provided it has a transformer. Most modern power adapters are no longer built around transformers. They simply rectify the voltage to DC, and regulate it down to the desired output voltage. The trick in conversion is to disconnect and bypass the rectifier circuitry. Connecting the output cable directly to the transformer output.

This kit is good if you have some circuit board experience under your belt. No instructions, but a few other kits taught me you go small to large in order of soldering, Diodes, Resistors, Small caps, tube carraige, In/Out, DC in, then finally your big caps. As far as sound quality, it works best at 50%. It starts to break up when dimed. Which is what you want for guitar amplification, so I'm going to do that with mine.

Just a bag of components. Nothing else. Not one shred of information on the assembly aspect. No schematics, no website, nothing but a bag of frustration and disappointment if you buy it for learning purposes.

Putting the kit together was fun. It was a pretty easy build. The PCB was clearly labeled and easy to follow.Installing all the components was straightforward with basic soldering skills needed. However, I'm not sure how to properly use this preamp.I've tried using it as a headphone amp, a preamp for my turntable, and as a preamp for a small guitar amp and in all scenarios, the sound is barely audible even when maxing the gain knob.On top of that, the sound is lacking low-end and warmth. It's very unsatisfactory as a preamp...If anyone has any ideas on the input/output impedance needed to get this preamp to preamp, let me know...

Actually a clone of Musical Fidelity X10D-Tube Buffer Pre-Amplifier. Great tone from cheap record player that sounded so flat. It acts like a great buffer. Was confused that I had an extra part (diode) and it was on the list of sent components. I contacted the seller and got a Chinese manual with schematic and found I didn't need it. Also saw they don't use negative feedback loop or cathode bypass capacitors so I will be modding mine after I get all the data I need from "stock" I'll swap all the cheap caps and do some mods. Most likely will use this for my record player but will add a switch and jack for a tube gain guitar pedal.

This unit requires an A/C power source of 12 volts ac as the amplifier also requires a different A/C source of 18vac which I would have to invert with a voltage divider just to bench test it.

I purchased this and put it together, was going to use it for as a preamp for my old rca r-190 45 player that I installed a magnetic phono cartridge but it didn’t boost the signal to the amplifier. I guess so have to check all of the soder joints it has low volume amp is transistorized

Was easy to assemble and was not missing any parts.