FX Audio 6j1 tube preamp - a $31 wonder

petemcfc said:
https://www.audiocheck.net/audiotests_polaritycheck.php

I have confirmed that by switching speaker leads around I have positive polarity,previously it was negative.
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Not sure I follow all that. That test link talks about having one speaker out of phase, which obviously is audible if things get wired up that way. It also says absolute polarity is not audible.

Call me a cynic - absolute polarity is something IMO most if no one would ever even notice, and far down the chain of other audible things that matter more in any playback system.

Would love to see a link where one could hear the difference when both channels are reversed in polarity.
 
Finally have the FX tube 01 back in the system. I had to wait to get -20 db attenuators as my amp has a .5V sensitivity. I will have to give it a bit more time, but the overall effect seems to be a better bass response compared to a straight passive pre. Overall the impression I get is more fullness with ever so slightly less clarity.
 
Im using Mullards very bass heavy but great sound seperation.
Just playing a 12" by The Notwist, a German band they have hit the Radiohead Kid A groove.

 
I bought an FX-Audio TUBE-03 preamp with bass and treble controls, unit is labled NFJ&FXAUDIO on the front. My unit shipped with Shuguang 6K4 tubes (printed 6K4 inside a star, number 802 underneath) instead of the expected 6J1 tubes. I don't read Chinese, but from some Shuguang datasheets found on the web, they look to be very different tubes (same pinouts). See images below.

They sound great to me, but I really can't guess if they could be improved. All components here add up to sounding fabulous. Is it the pre, the tubes, the Allo Volt+ TPA3116, or the newly recapped and retweetered 96 dB Klipsh 8" two way speakers? (Volt + powered by 12V 3 Amps, FX-Audio 19V from an old SMSL Q-something).

Anyone out there with 6K4 tubes and any opinions of them?

Very few 6K4 seen on that auction site, almost all are Soviet 6K4 glass. After reading about happy folks with JAN Sylvania 6AK5 and 5654, or Voskod 6J1P-EV, I'm thinking this might sound even better, though my guess is it might be the law of diminishing audio returns and tail-chasing perhaps. I may not need to chase upgrades, but I do like to have a spare pair for favorite gear.

And, big thanks to PG for all this new fascination, fits my wallet and sounds outstanding. A tip o' the hat and a toast of the glass!

So, 6K4 opinions, or favorite tube rolls for acoustic jazz, female vocals, solo cello, and modern obsessions like Brian Eno and Laurie Anderson?

Thanks!!
 

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SanJoseMichael said:
I bought an FX-Audio TUBE-03 preamp with bass and treble controls, unit is labled NFJ&FXAUDIO on the front. My unit shipped with Shuguang 6K4 tubes (printed 6K4 inside a star, number 802 underneath) instead of the expected 6J1 tubes. I don't read Chinese, but from some Shuguang datasheets found on the web, they look to be very different tubes (same pinouts). See images below.

They sound great to me, but I really can't guess if they could be improved. All components here add up to sounding fabulous. Is it the pre, the tubes, the Allo Volt+ TPA3116, or the newly recapped and retweetered 96 dB Klipsh 8" two way speakers? (Volt + powered by 12V 3 Amps, FX-Audio 19V from an old SMSL Q-something).

Anyone out there with 6K4 tubes and any opinions of them?

Very few 6K4 seen on that auction site, almost all are Soviet 6K4 glass. After reading about happy folks with JAN Sylvania 6AK5 and 5654, or Voskod 6J1P-EV, I'm thinking this might sound even better, though my guess is it might be the law of diminishing audio returns and tail-chasing perhaps. I may not need to chase upgrades, but I do like to have a spare pair for favorite gear.

And, big thanks to PG for all this new fascination, fits my wallet and sounds outstanding. A tip o' the hat and a toast of the glass!

So, 6K4 opinions, or favorite tube rolls for acoustic jazz, female vocals, solo cello, and modern obsessions like Brian Eno and Laurie Anderson?

Thanks!!
Click to expand...

Thanks for the kind words. Shuguangs came in my FX and they sound excellent.
 
SanJoseMichael said:
I bought an FX-Audio TUBE-03 preamp with bass and treble controls, unit is labled NFJ&FXAUDIO on the front. My unit shipped with Shuguang 6K4 tubes (printed 6K4 inside a star, number 802 underneath) instead of the expected 6J1 tubes. I don't read Chinese, but from some Shuguang datasheets found on the web, they look to be very different tubes (same pinouts). See images below.

They sound great to me, but I really can't guess if they could be improved. All components here add up to sounding fabulous. Is it the pre, the tubes, the Allo Volt+ TPA3116, or the newly recapped and retweetered 96 dB Klipsh 8" two way speakers? (Volt + powered by 12V 3 Amps, FX-Audio 19V from an old SMSL Q-something).

Anyone out there with 6K4 tubes and any opinions of them?

Very few 6K4 seen on that auction site, almost all are Soviet 6K4 glass. After reading about happy folks with JAN Sylvania 6AK5 and 5654, or Voskod 6J1P-EV, I'm thinking this might sound even better, though my guess is it might be the law of diminishing audio returns and tail-chasing perhaps. I may not need to chase upgrades, but I do like to have a spare pair for favorite gear.

And, big thanks to PG for all this new fascination, fits my wallet and sounds outstanding. A tip o' the hat and a toast of the glass!

So, 6K4 opinions, or favorite tube rolls for acoustic jazz, female vocals, solo cello, and modern obsessions like Brian Eno and Laurie Anderson?

Thanks!!
Click to expand...
6K4/6BA6 is not at first glance a good linear audio tube choice, 6J4/6AU6 would make more sense and a choice for tuberolling, but not my fave for audio either. Maybe they work better in triode mode?
 
P1030982.jpg P1030983.jpg
SanJoseMichael said:
I bought an FX-Audio TUBE-03 preamp with bass and treble controls, unit is labled NFJ&FXAUDIO on the front. My unit shipped with Shuguang 6K4 tubes (printed 6K4 inside a star, number 802 underneath) instead of the expected 6J1 tubes. I don't read Chinese, but from some Shuguang datasheets found on the web, they look to be very different tubes (same pinouts). See images below.

They sound great to me, but I really can't guess if they could be improved. All components here add up to sounding fabulous. Is it the pre, the tubes, the Allo Volt+ TPA3116, or the newly recapped and retweetered 96 dB Klipsh 8" two way speakers? (Volt + powered by 12V 3 Amps, FX-Audio 19V from an old SMSL Q-something).

Anyone out there with 6K4 tubes and any opinions of them?

Very few 6K4 seen on that auction site, almost all are Soviet 6K4 glass. After reading about happy folks with JAN Sylvania 6AK5 and 5654, or Voskod 6J1P-EV, I'm thinking this might sound even better, though my guess is it might be the law of diminishing audio returns and tail-chasing perhaps. I may not need to chase upgrades, but I do like to have a spare pair for favorite gear.

And, big thanks to PG for all this new fascination, fits my wallet and sounds outstanding. A tip o' the hat and a toast of the glass!

So, 6K4 opinions, or favorite tube rolls for acoustic jazz, female vocals, solo cello, and modern obsessions like Brian Eno and Laurie Anderson?

Thanks!!
Click to expand...
:):banana::)
 
petemcfc said:
That cd is in my collection.
In the back ground what has the meters?,Because I dont have one of them.
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For fun i connected the FX to a little amp with the Yamaha YDA138 chip.
The results are involving with a much smoother sound than the YJ amp used previously.:)
 
SanJoseMichael said:
The production of tubes appears to require a great deal of hands-on human labor... Some pretty fascinating photos.

Shuguang Vacuum Tube Factory Tour:
http://www.enjoythemusic.com/china_2009/shuguang/
Click to expand...

The box of gold pin Shuguang tubes on the second page are the 2a3-c which are very affordable compared to most big bottle direct heated triode tubes. I think mine cost $50 each and they sound better than my high dollar vintage RCA's.
 
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https://psvanetube.com/wordpress/psvane-tubes-factory-tour/


Shuguang was originally established on Dec 26, 1965. It started as a numbered factory (# 770) providing supplies to the Chinese military – of course, vacuum tubes. At that time all factories supplying to military were numbered by the government and usually the factory did not have a sign at the address and was heavily guarded by military personnel. After 1980s when China opened up to the rest of the world, many of those factories were finally allowed to use their official name and no longer have military guards but regular security guards.

Shuguang, in English it means “dawn”, indicates the new start of the Red China. ( if I ever the term of ‘red China’ 20 years ago in China, I probably will get myself into some serious trouble. but nowadays nobody cares – everyone in China seems to be too busy in making a good living so politics is barely a central piece for average person’s life.) Shuguang was one of the very few electronics manufacturer in China at that time and probably the only one that has survived 50 years of ups and downs.

Shuguang is located just north of Guangdong province (if you don’t know where Guangdong is, it is at the very southern tip of mainland China. The city Shuguang is located in is also the birth city of Chairman Mao Zedong so the way people do business there is more conservative than the Chinese reform pioneers in Guangdong. Shuguang is a group company, including 5 plants, 14 subsidiaries, 3 joint-ventures, 5 property holding companies plus a hospital, school, and of course kindergarten as well. The group employs over 6,000 employees and currently is still state owned. However, today’s state-owned-entities (SOE) are quite different from what they were 25 years ago – now management is westernized but still comes with a blend of central control and political influence. Shuguang manufacturered vacuum tubes only up to 1983. After then, as the tube demand dropped substantially, the group started joint venture with LG to manufacturer color TV tubes etc. and later ventured into real estate development and other business. Of course in the 1990s when high end audio regains its life worldwide, demand for audio tubes have bring many production back online again.

Satistics shows that by 2005, Shuguang had deveoped over 120 types of vacuums tubes and manufacturered over 70 million tubes over 40 years.
 
State owned!!!!!!!!!!!!!!
I do hope those tubes arn't listening in and reporting back,Im relieved that as a matter of course I swapped mine out and replaced them with some good old British made ones.
My pair of FX units are situated rather close to a router for my liking,(Though that's Chinese made as well).
 
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