FX Audio 6j1 tube preamp - a $31 wonder

As good as the FX sounded with it's tiny wall wart I was skeptical there was any room for further improvement using a better power supply. Wrong!

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Hello!
As a complete novice in terms of amplification and high - end devices, I can hardly understand how much sound can be improved by changing the power supply. Reading your comments I am inclined to believe it, and change the original power source. However, I would like to be able to hear the difference of the sound using the original power supply and another like the pyramid that you use.

Would it be too much to ask that you show us a comparative video?
Excuse me if I have exceeded the request.
Thank you very much for your comments and advice.
 
Audio is all about building to an established price point. The only way FX Audio can sell a tube preamp for $31 and realize any profit is by using a cheap wall wart. Few if any high end preamps or amps are powered by wall warts because companies budget for a better power supply. If you look at the Pyramid insides you can see that it uses a transformer like you would expect to find in more expensive amps. Cheap wall warts are notoriously noisy and that is what you want to avoid with a preamp. I've replaced wall warts with linear power supplies on amps, preamps, and DAC's and all have benefitted. You don't need a video, just do the research and read what others have to say. The caveat here is that with some low to mid fi systems the improvement of the FX may not be nearly so apparent.

th
 
Right, the FX pre is a price point wonder. If it had input selection it might be a giant killer of sorts, with comparatively limited output power. Adding this and that could cut value for price and move it into a more crowded category, so, for what it is as-is, it appears to be a real bargain as an active component for cheap pickup cartridge money.
 
the consensus is that a linear power supply is the way to go, but what about the internal power supply that supplies the voltage to the tubes?

has anyone tried removing that & replacing it with a linear one?

obviously. the linear power supplies will cost way more than the pre amp, but maybe it's worth it?

also, does anyone know how high we can go above the 12v? 14.5 maybe?
 
the consensus is that a linear power supply is the way to go, but what about the internal power supply that supplies the voltage to the tubes?

has anyone tried removing that & replacing it with a linear one?

obviously. the linear power supplies will cost way more than the pre amp, but maybe it's worth it?

also, does anyone know how high we can go above the 12v? 14.5 maybe?
Keep it as close to the 12.6 V rating of the two tube heaters in series as possible. Running it substantially higher will shift operating points away from design parameters and shorten tube life. Also, some possible negative effects for the on-board voltage convertor.
 
The reason it's worth splurging on a linear supply is because you will probably own it longer than the pre. You can use it with whatever component you want as long as it meets the specs.

I own several of the above supplies in the video. They are decent if you don't overtax them. They do get hot.
 
Also if it has not been mentioned you can adjust Astron voltage down as low as 11.8v or so and up to about 14.5. It's not hard but does require multimeter and opening the case. Obligatory mains voltage cautions apply.
 
I dont know my way around a tube preamp circuit... and the trial and error might be expensive.
Does anyone here know how to drop the gain on this Tube 01 board ?
 
This seems a bit like the Little Bear P5 thing I've got. It also uses 6J1s but has it's own DC supply; you simply feed it AC. Originally mine came with some really small 110v/18v transformer that wasn't up to the task. The unit *did* work with it and it worked for quite some time; but I eventually replaced it with a 20-0-20 transformer and just used one side and center-tap. This actually brought all my voltages up to where they were supposed to be.

On the subject of linears vs. switchers:

If the switcher is designed and built properly; you don't really hear much difference. It is entirely possible to produce a SMPS supply that has a very clean DC output for audible use. My DAC came with a small switching brick; I swapped that out to a linear wall-wart; but I also powered it from the Alinco SMPS I *normally* use for my ham radio equipment. It's technically a 13.8v 32A supply...but the voltage is adjustable from 0 up to 16. Anyway, I ran the DAC on the Alinco supply and couldn't hear a difference between it and the wall-wart. If anything I think the SMPS made things sound a little bit better due to the more stable voltage supply on current demand.
 
If the switcher is designed and built properly; you don't really hear much difference. It is entirely possible to produce a SMPS supply that has a very clean DC output for audible use. My DAC came with a small switching brick; I swapped that out to a linear wall-wart; but I also powered it from the Alinco SMPS I *normally* use for my ham radio equipment. It's technically a 13.8v 32A supply...but the voltage is adjustable from 0 up to 16. Anyway, I ran the DAC on the Alinco supply and couldn't hear a difference between it and the wall-wart. If anything I think the SMPS made things sound a little bit better due to the more stable voltage supply on current demand.

A linear wall-wart for instance can mean anything, but is typically a cheap bare-bones effort that may be regulated or unregulated and as you pointed out may not have a stable voltage. It doesn't take much to beat a linear wall-wart. Just like it doesn't take much to beat a laptop smps. I'm betting that Alinco SMPS cost a lot more than either. SMPS's have gotten much better over the past few years and can be just as good or even better than some linear options - but it won't be cheap. If you couldn't hear a difference between the Alinco and the wall-wart, that sounds like a win for the wall-wart.
 
found a dilvpoetry pre-amp that uses the same board as the fx-audio the main difference is that instead of +/- 30 volts to the tubes, it has a different internal power supply that is +/- 45 volts

i tried to create an album so that i could show some pics, but was unsuccessful

some of the components on the board are different values, but i think that is due to the different voltages that the 6j1 is running at, & the film caps are different & the dilvpoetry doesn't have the ferrite on the bottom that the fx does

need to do some head to head comparisons to determine how the sound compares between the 2

i picked the dilvpoetry up used on amazon for about $20 :) ordered another :)
 
you can upload photos directly from your computer to a post.
If your photos are hosted someplace (e.g., Flikr), they're also easily displayed using ["img"] tags (no quotes) -- Flikr and Photobucket generate the syntax for images they host.
 
found a dilvpoetry pre-amp that uses the same board as the fx-audio the main difference is that instead of +/- 30 volts to the tubes, it has a different internal power supply that is +/- 45 volts

i tried to create an album so that i could show some pics, but was unsuccessful

some of the components on the board are different values, but i think that is due to the different voltages that the 6j1 is running at, & the film caps are different & the dilvpoetry doesn't have the ferrite on the bottom that the fx does

need to do some head to head comparisons to determine how the sound compares between the 2

i picked the dilvpoetry up used on amazon for about $20 :) ordered another :)
how do you know it is 45v?
 
found a dilvpoetry pre-amp that uses the same board as the fx-audio the main difference is that instead of +/- 30 volts to the tubes, it has a different internal power supply that is +/- 45 volts

i tried to create an album so that i could show some pics, but was unsuccessful

some of the components on the board are different values, but i think that is due to the different voltages that the 6j1 is running at, & the film caps are different & the dilvpoetry doesn't have the ferrite on the bottom that the fx does

need to do some head to head comparisons to determine how the sound compares between the 2

i picked the dilvpoetry up used on amazon for about $20 :) ordered another :)

.. i'll try linking borrowed pics of the 2 boards.
51kkBor7pJL.jpg

The dilvpoety above...
New-TUBE-01-DC12V-1A-Tube-Preamp-Buffer-6J1-HIFI-Audio-Preamplifier-Used-with-Digital-Amplifier.jpg

The tube 01.
 
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