6J1 Tube Preamplifier u$s35.

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Tube Preamplifier 6J1.

Hi , someone know how is the performance of this cheap preamplifier ?

Some time i listened that changing the tubes chinese 6J1 for 6AK5 or 5654 good quality tubes , the sound is good enough..

Is a good option for limited budget ?

Santiago
 

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ICG

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Joined 2007
I have a similar one, it's okay. It would profit from a higher anode voltage but you'd have to change a lot of the parts to do that though. The case is ugly but that's probably just my opinion but I'd take out the blue LEDs which illuminate the tubes. To do that you have to desolder the sockets, at least on mine it was.

The price is quite high though, the cheaper ones got the same parts tolerance and quality. You can get it with a really nice metal case for ~28$ or without case for 12$ (shipped from China).
 

ICG

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Joined 2007
Is this it? Tube buffer with 5532 output?
I kept a screen capture of the circuit as a reminder NOT to fall prey to its siren sounds.

I've now seen the video. It's a headphone amp (not a preamp) and the tube is not a 6J1, it's a E180F, on similar amps it's a 6J9P. And I don't think the 5532 OPs are appropriate as headphone output stages, that's asking for distortion.
 

ICG

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Joined 2007
That would be ideal, the rise of the anode voltage got a great potential sound quality improvement. To change the board to 100V would practically mean to build a completely new one.

I've found the FX-Audio Tube-03 on ebay but I'd appreciate it very much if you could help with an Aliexpress link. I get excellent search results on google, ebay, amazon etc but I seem to fail on Aliexpress a lot. I get always tons of irrelevant search results and dozends of them (if not hundreds) are duplicate results. :(

Thank you for your suggestion!
 
I'll try that one without tone control :
2018 New TIANCOOLKEI TUBE 01 bile preamp tube amplifier preamp bile buffer 6J1 MINI HIFI preamplifier DC12V-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group

Search for" fx-audio tube-03 " you'll find a lot, i got mine from eBay.

Edit // tube-03 is perfectly biased, 100v, Pentode working as triode with 120R cathode and 3.3k anode (7.5ma bias).
Just the pot volume is unusual, just a variable resistor in an inverting opamp stage (ne5532) with 22k fixed input resistor and pot acting as a 0 to 50k variable resistor.
 
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ICG

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Joined 2007
The page doesn't work for me, it says article not found. Maybe they don't want it to show in Germany?

As for the capacitors, there are several possibilities. The most logical would be to create the 150V with a cascade/voltage doubler or more in series. The capacitors are in series and therefore lower the capacity/current but increase the voltage rating and the effective voltage. The cascade needs a bunch of diodes and capacitors and AC voltage.

Another possible expaination would be they use film capacitors for the anode voltage, which have usually a much higher voltage rating and the electrolyte caps are. I can't tell though because I can't see the article.

They could also have a buck converter on the board and the low rating capacitors are just there to buffer the input or the voltages for the control ICs. because of high frequency of the converter a small film capacitor might be enough.

To make fake claims is ofcourse still a possibility though. That happens a lot on chinese sellers unfortunately. They usually don't just straight out lie but increase the numbers in the specification slightly.
 
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