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?
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?
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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.
Thanks, I may give these a try. The electronorgtechnica tubes were an improvement as well. Found a matched pair on ebay for $12.
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.
Using starving tubes you can add the former, but the latter can't be added.
You can try 6Ж9П, 6Ж10П, 6Ж11П, 6Ж49П, 6Ж51П, 6Ж52П.
> 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.)
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.
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