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The Un-Official Sadowsky SA200 Thread...

#746
Mine got GT tubes.
front.jpg power amp tube.jpg EL34.jpg
 
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#747
OldogNewTrick said:
I understand TAD invested in another Chinese manufacturer and has control over quality and supply.
TAD Redbase™
https://www.tubeampdoctor.com/media/pdf/f8/c3/fd/TAD_REDBASE_Tubes.pdf
Click to expand...

As far as I've read the TAD tubes are from Psvane. I've generally liked the older TAD product as far as rebranders go, haven't tried the redbase stuff. I got a set of Psvane EL34 for my GT120 build and they were poorly matched from the vendor (>10mA variance at working voltage across four tubes on one bias supply).
 
#748
@coreyfyfe - of course I have no first hand knowledge of this, but they carry Psvane brand tubes and claim that their Redbase tubes are manufactured in an exclusive manufacturing facility. Of course the meaning of "exclusive" in marketing speak might not be the same it implies to me. Anyhow, if I don't forget, I'll call them coming week and ask. They are pretty easy to get hold of on the phone...
 
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#749
Cross post from: https://www.talkbass.com/threads/ch...y-sadowsky-sa200.1596814/page-3#post-28586439

Just installed a sextet of JJ KT88s from AES.

I actually installed the tubes in the wrong amp first, so I got to hear them in both amps. I caught my mistake after digging through my notes and PMs.

Five of the new tubes are matched to about 3%. Unfortunately variance from hottest to coldest tube is about 15.7%, so matching is not great. The variance was 16.1% in the other amp. I swapped the hottest tube with the coldest tube, and the current followed the tube. Current balance across the output transformer is off by 5%. The imbalance doesn't seem to be enough cause any hum problems, so I am not going to bother shuffling the tubes any more.

Both amps sound very good with KT88s. My impression is the tone with the K88 may be a little less organic/bloomy and there is some minor differences in the overall tone and feel. I also got the impression both amps make less power with KT88.

My variac indicates the amp is pulling 1.97A with the current bias settings. Indicated cathode current ranges from 27.3-32.4mA. Factory spec is 25-30mA. I experimented with the bias with the amp drawing between 1.88A to 2.04A. Biasing the tubes a bit warmer seemed to bring the KT88s closer to the sound, feel, and power of the EL34s.

I will have to do some more AB tests to see if my impressions holds. However, perhaps it's important to note both amps did not sound identical running the factory EL34Bs. Probably a good idea to pull out my O'Scope and check the PI balance adjustment as well.
 
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#757
Here's something you probably don't see every day.
1723514677154.png


Finally got around to hooking up the amps in a way that allowed me to quickly switch between them. Both amps have factory preamp tubes. The top amp is running factory Koch EL34B. Pretty sure the EL34Bs are relabeled TADs, which in turn were made by Shuguang.

The bottom amp has a fresh set of JJ KT88s. I pulled out an old set of EL34Bs that had a mix of Koch and TAD labels. The old tubes still sounded great, but would become noisy and occasionally blow the HT fuse if I moved the amp. I am not certain if the problem is because the tubes are too old, or possibly because the pins in the tube sockets needed to be cleaned and tightened.

Even with both amps running EL34B, they had a slightly different sound and feel. This seems to hold with KT88 in one of the amps. The differences are so minor that I am not absolutely certain they are actually there. My impression is the amp running KT88s seems slightly more focused and clean/HiFi.

The amp running EL34B seems to have a slightly more old school sound and feel. It seems looser, bloomier, and woolier. I don't hear any obvious difference in tonal balance, but the mids seem warmer and to have more of a vocal quality. I also think it may be slightly louder and punchier.

IMHO both amps sound great, and as far as I can tell there is not enough of a difference to be concerned about it.

Low light so you can see the fairy dust a bit better:
1723515671580.png

That's not a trick of the camera...the KT88s are noticeably brighter.


Edited to tag @gtirard to see the pretty pictures ;).
 
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#758
Wasnex said:
Here's something you probably don't see every day.
View attachment 7004502

Finally got around to hooking up the amps in a way that allowed me to quickly switch between them. Both amps have factory preamp tubes. The top amp is running factory Koch EL34B. Pretty sure the EL34Bs are relabeled TADs, which in turn were made by Shuguang.

The bottom amp has a fresh set of JJ KT88s. I pulled out an old set of EL34Bs that had a mix of Koch and TAD labels. The old tubes still sounded great, but would become noisy and occasionally blow the HT fuse if I moved the amp. I am not certain if the problem is because the tubes are too old, or possibly because the pins in the tube sockets needed to be cleaned and tightened.

Even with both amps running EL34B, they had a slightly different sound and feel. This seems to hold with KT88 in one of the amps. The differences are so minor that I am not absolutely certain they are actually there. My impression is the amp running KT88s seems slightly more focused and clean/HiFi.

The amp running EL34B seems to have a slightly more old school sound and feel. It seems looser, bloomier, and woolier. I don't hear any obvious difference in tonal balance, but the mids seem warmer and to have more of a vocal quality. I also think it may be slightly louder and punchier.

IMHO both amps sound great, and as far as I can tell there is not enough of a difference to be concerned about it.

Low light so you can see the fairy dust a bit better:
View attachment 7004513
That's not a trick of the camera...the KT88s are noticeably brighter.
Click to expand...

Epic! :bassist: :bassist: :bassist: Thanks for sharing! :thumbsup:
 
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