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6j9 replacement
6j9 replacement
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Old 17th August 2019, 12:18 AM   #1
rich1051414 is offline rich1051414
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Default 6j9 replacement

Lots of tube preamps(low voltage with buffer) are coming out lately, but I don't like the chinese tubes in them, those tubes aren't really good for the job, so the amps end up being underwhelming. Many have buffers with triple zero distortion at high impedance, so the tube is really the only thing that does anything to the signal if used at line level as a preamp.

Is there a good replacement out there for these? I spotted a russian military electronorgtechnica listing in 6j9n, and seems to be a viable replacement, but I don't know if it is worth it, if those aren't actually great tubes to begin with.

Anyone went down the rabbit hole yet and want to share what they have figured out?

Last edited by rich1051414; 17th August 2019 at 12:26 AM.
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Old 17th August 2019, 02:43 AM   #2
lavane is offline lavane  United States
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I think the 6688 or E180F. I saw NOS 6688's being sold as replacements for the 6J9 Around $20 each for Philips. Hopefully someone else will chime in to be sure. The add I saw was for replacing 6J9's in Douk Audio equipment.
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Old 17th August 2019, 05:36 AM   #3
Alllensoncanon is offline Alllensoncanon  United States
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6j9 replacement
Quote:
Originally Posted by rich1051414 View Post
Lots of tube preamps(low voltage with buffer) are coming out lately, but I don't like the chinese tubes in them, those tubes aren't really good for the job, so the amps end up being underwhelming.

Anyone went down the rabbit hole yet and want to share what they have figured out?

If you open one up and trace out the circuit, you likely will find a 24V B+ (+-12V really) triode connected cathode follower circuit driving an Op Amp. The short pole is the under voltage 6J9P circuit, not the brand name of the 6J9P. If you have to change something, change the Op-Amp. It is doing most of the heavy lifting. After that, you can get a bagful of low cost 6J9P and find a pair that you like the most. Low voltage B+ tube rolling does work to a certain degree. Tube to tube variation can be large at those low B+ voltages.
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Old 20th August 2019, 06:42 AM   #4
rich1051414 is offline rich1051414
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Originally Posted by lavane View Post
I think the 6688 or E180F. I saw NOS 6688's being sold as replacements for the 6J9 Around $20 each for Philips. Hopefully someone else will chime in to be sure. The add I saw was for replacing 6J9's in Douk Audio equipment.
Thanks, I may give these a try. The electronorgtechnica tubes were an improvement as well. Found a matched pair on ebay for $12.
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Old 20th August 2019, 08:06 AM   #5
Junm is offline Junm  Philippines
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You can try a cheaper russian 6J9P, (6Ж9П) or 6J11P. they are better than chinese 6J9.
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Old 20th August 2019, 12:19 PM   #6
DF96 is offline DF96  England
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Some low voltage 'tube buffers' can be improved by bypassing them i.e. removing them from the system. They are not designed to simply pass on the signal unmolested; if this was the aim they would use higher supply rail voltages and more appropriate valves.
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Old 20th August 2019, 04:07 PM   #7
Cookj is offline Cookj  Belgium
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DF96 is correct! Their is nothing wrong with these tubes. The grossly stupid application, often marketed by charlatans, and bought by the gullible! But! Hey there's a valve somewhere in there.
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Old 21st August 2019, 12:03 AM   #8
Wavebourn is offline Wavebourn  United States
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6j9 replacement
One of advantages of tube amplifiers is soft saturation that sounds less nasty than hard clipping. Another advantage, especially of single ended amplifiers, is distortions go down to zero and their order decreases when sounds decay, it preserves "an air" in sound reproduction.
Using starving tubes you can add the former, but the latter can't be added.

You can try 6Ж9П, 6Ж10П, 6Ж11П, 6Ж49П, 6Ж51П, 6Ж52П.
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Old 21st August 2019, 06:19 AM   #9
PRR is online now PRR  United States
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> Some low voltage 'tube buffers' can be improved by bypassing them i.e. removing them from the system.

I bought a pair of very good studio microphone channels with all frills including "tube". I started bypassing parts I did not need. One mod really improved the sound, "clearer", "wider". I shut-down and later powered-up, I noticed it came "live" in 1 second instead of 13 seconds. I had bypassed the tube! (Which actually was my intent, but I got distracted and forgot.)
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Old 31st August 2019, 11:39 AM   #10
rich1051414 is offline rich1051414
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Originally Posted by PRR View Post
> Some low voltage 'tube buffers' can be improved by bypassing them i.e. removing them from the system.

I bought a pair of very good studio microphone channels with all frills including "tube". I started bypassing parts I did not need. One mod really improved the sound, "clearer", "wider". I shut-down and later powered-up, I noticed it came "live" in 1 second instead of 13 seconds. I had bypassed the tube! (Which actually was my intent, but I got distracted and forgot.)
That's interesting, but I blind tested myself with a switch that bypassed the tube preamp at exactly the same volume, which then goes through a solid state headphone amp with VERY low distortion(hand built whammy).

Config 1: Fiio Q1 MK II -> Sabaj Tube Preamp -> Whammy -> Headphones
Config 2: Fiio Q1 MK II -> Whammy -> Headphones

With the electronorgtechnica tubes, the only difference is stereo separation widens, as well as something I can't quite put my finger on(I assume 2nd harmonics). With the original chinese tubes, the signal was much warmer, and less detailed, I assume because of excessive harmonics.

To me that sounds like what it is doing is causing a slight negative phase shift as well as introducing a small amount of second harmonics(with the electronorgtechnica tubes, a lot with the chinese tubes).

These two things(a slight negative phase shift and a bit of second harmonics) have been shown to be positive improvements to most people.

After testing and blindly shuffling the inputs about 5 times, every single time I preferred music when played through the tube preamp.

Not all tube amps are created equal though, so I don't doubt your experience.

Last edited by rich1051414; 31st August 2019 at 11:51 AM.
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