FX Audio 6j1 tube preamp - a $31 wonder

Thank you everyone for your help and suggestions. I figured this out and it was the wireless router.

The router was originally located something like 50 cm from the pre-amp, on the same plane so that the unshielded tubes saw the router across the amp. In this photo the white router is on the right and pre-amp on the left on top of the amp:

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Now, turning off the router removed the crackling completely (even with the barely audible crackling w/ stock tubes). Then when I turned the router on, the crackling started exactly and only when the router started 2.8 GHz wifi (i.e. not when it was negotiating the base cable connectivity). So nothing wrong with the tubes.

Moving the pre-amp to the left, and the router on the floor, removes the crackling even with the Voshkod's, giving enough shielding and distance:

20190315_083121.jpg

Interestingly 2.8GHz and 5 GHz are in the 6cm to 11cm wavelength range, i.e. in the ball park of the physical dimensions of these unshielded tubes. And seemingly Voshkod's are more sensitive to the interference. I have not measured, but I think they are a bit taller than the default ones, being closer to the wifi wavelengths.
 
My initial impression of the Voshkod 6J1P-EV's is that the bass is certainly more emphasized and fuller, but somehow I feel that mids and highs are not as rich as with the default Chinese tubes (that come w/ the Dilvpoetry). Perhaps burning them a bit more will change things, we'll see. I like the visuals though, they are a bit taller, and the heat glow is more pronounced at the top compared to the default tubes. The search continues...
 
Well, inspired by this thread, and seeing one on the local Facebook marketplace, I got one. I'm still using the stock power supply and stock tubes, but I like it. I miss the remote volume control of the Luxman A-007 I was using, but no biggie. I plan to upgrade the power supply, and place my tube buffer between the pre and power amps. I do like the way it sounds, but the biggest surprise was how cool the tubes run.
 
I tried one of these. Sounded good but too much gain for my system. 3 clicks = too quiet...4 clicks = too loud! Just need something with more fine volume adjustments in my setup.
 
I tried one of these. Sounded good but too much gain for my system. 3 clicks = too quiet...4 clicks = too loud! Just need something with more fine volume adjustments in my setup.

This is my main complaint too. The Dilvpoetry has 5x gain according to manual. In daily listening only the range from 6PM to 8PM is usable.
 
This is my main complaint too. The Dilvpoetry has 5x gain according to manual. In daily listening only the range from 6PM to 8PM is usable.
Just more gain to throw away, it should ideally replace the line stage, not be added to it. Using it as a tube sound "filter" in a functioning system will have the consequence of excess gain.
 
With the $99 APPJ/Miniwatt the FX is a perfect gain match.

Max the Miniwatt and 9 o'clock on the FX is just right for late night listening.

With the FX at 12 o'clock I get room filling sound at normal listening levels.

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Our systems are so different it's hard to generalize about the FX's gain.

If your source is a DAC rather than a CD player you may need the extra gain of the FX.

That can be especially true if you use a flea watt amp driving efficient speakers.
 
I put in a pair of NOS RCA 6AK5’s in my FX preamp and they seem awfully microphonic - I get a “ding” if I tap them. I didn’t notice this with the original 6J1 tubes.
Is this to be expected or indicative of faulty tubes?

Not really s big deal as I don’t plan on taping the tubes and it’s positioned far from the speakers.
 
I put in a pair of NOS RCA 6AK5’s in my FX preamp and they seem awfully microphonic - I get a “ding” if I tap them. I didn’t notice this with the original 6J1 tubes.
Is this to be expected or indicative of faulty tubes?

Not really s big deal as I don’t plan on taping the tubes and it’s positioned far from the speakers.
Not necessarily a fault, more a quirk that may or may not be tolerable, depending.
 
Just more gain to throw away, it should ideally replace the line stage, not be added to it. Using it as a tube sound "filter" in a functioning system will have the consequence of excess gain.

I was using the FX unit to replace my linestage. I was using it like this:

Rega RP1 (Denon DL-160 cartridge) -> Hagerman Bugle 3 phono preamp (lowest gain setting, 40 dB) -> FX Audio preamp -> RCA switcher box -> Quicksilver mono tube amps (90 wpc) -> Tannoy Arden (93 dB efficiency).

I also used the FX in my office like this:

PC (volume set to 15-20 out of 100 out of the PC) -> FX Audio tube preamp -> McCormack amp -> MIrage M3si speakers

In both cases, I could only turn the FX to around 3 or 4 clicks (7:30 position). By the next click (8:00 position), things were getting a bit loud. I mean, personally I could deal with the 8:00 loudness setting, but at that level, the sound travels up to my upstairs (open stairway) and my wife complains. I need about 5 "in-between" steps between clicks 3 and 4 on the FX.

In fairness, my Sainsmart 6N3 is the same way, but there are no "steps"/clicks...it's more of a smooth adjustment...so I can kind of "feather" it to a more precise volume level.

I did think it sounded quite nice though. I would have kept it to just mess around with it, but could use the $40 right now more than the preamp (yikes). I'm not ruling out buying another one later, just not right now when I already have the Sainsmart.
 
I was using the FX unit to replace my linestage. I was using it like this:

Rega RP1 (Denon DL-160 cartridge) -> Hagerman Bugle 3 phono preamp (lowest gain setting, 40 dB) -> FX Audio preamp -> RCA switcher box -> Quicksilver mono tube amps (90 wpc) -> Tannoy Arden (93 dB efficiency).

I also used the FX in my office like this:

PC (volume set to 15-20 out of 100 out of the PC) -> FX Audio tube preamp -> McCormack amp -> MIrage M3si speakers

In both cases, I could only turn the FX to around 3 or 4 clicks (7:30 position). By the next click (8:00 position), things were getting a bit loud. I mean, personally I could deal with the 8:00 loudness setting, but at that level, the sound travels up to my upstairs (open stairway) and my wife complains. I need about 5 "in-between" steps between clicks 3 and 4 on the FX.

In fairness, my Sainsmart 6N3 is the same way, but there are no "steps"/clicks...it's more of a smooth adjustment...so I can kind of "feather" it to a more precise volume level.

I did think it sounded quite nice though. I would have kept it to just mess around with it, but could use the $40 right now more than the preamp (yikes). I'm not ruling out buying another one later, just not right now when I already have the Sainsmart.
Ok, understood.
In this case, a passive controller may be a better option, one with a better grade continuous pot.
 
Out of interest,using say Audacity has anyone done an A/B test comparing recordings made with and without this device?
I'm asking as I have the equipment but I wouldn't know how to analyze the findings.
I'm very happy with this in its stock form though I intend to add a better power supply and valves in stages and it would be informative if I could compare results in a graphic form.
 
Out of interest,using say Audacity has anyone done an A/B test comparing recordings made with and without this device?
I'm asking as I have the equipment but I wouldn't know how to analyze the findings.
I'm very happy with this in its stock form though I intend to add a better power supply and valves in stages and it would be informative if I could compare results in a graphic form.

Trust your ears as they're all you need to please.
 
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