A viewer sent me one of these higher end made in China tube pre-amps to check out. After he purchased it, he freaked out after he saw the scathing results of this unit at Audio Science Review, but was confused because it sounded OK to him. I was ready for the worst, and saw possibly a long mod and repair service needed to make something decent out of it after reading the same review.
I'm not exactly sure what is going on but the "upgrade" model I was sent, with an extra power supply board, Mundorf caps and Philips 6DJ8 tubes, tested fine. I saw nothing other than some slight weirdness with the tone defeat button not totally defeating the tone controls, and that can be compensated for by just turning both the treble and bass all the way up to get a flat response curve. For how most people would use a device like this, it seems to perform well and is a VERY solidly build unit, that looks very nice.
I also was testing it using the unbalanced RCA jacks, so maybe the XLR jacks as used by Amirm in their test have issues? There is a separate board and some transformers etc. related to their operation. I know changing the coupling caps doesn't account for the wildly different results I got, so maybe the tubes in the unit he tested had issues?
Anyway, this is the first piece of made in China audio gear I see nothing that really needs any attention, and for what it was designed to do, seems to work well.
I'm not exactly sure what is going on but the "upgrade" model I was sent, with an extra power supply board, Mundorf caps and Philips 6DJ8 tubes, tested fine. I saw nothing other than some slight weirdness with the tone defeat button not totally defeating the tone controls, and that can be compensated for by just turning both the treble and bass all the way up to get a flat response curve. For how most people would use a device like this, it seems to perform well and is a VERY solidly build unit, that looks very nice.
I also was testing it using the unbalanced RCA jacks, so maybe the XLR jacks as used by Amirm in their test have issues? There is a separate board and some transformers etc. related to their operation. I know changing the coupling caps doesn't account for the wildly different results I got, so maybe the tubes in the unit he tested had issues?
Anyway, this is the first piece of made in China audio gear I see nothing that really needs any attention, and for what it was designed to do, seems to work well.
The circuit doesn't seem to have feedback, I would assume that the performance is heavily dependent on the quality of the tubes and their selection/matching
I still don't get the point of replicating a preamplifier that, in my opinion, was a bit "flawed" by default and soon replaced by the LS25 (barely 2 years later) where they replaced the 2 stages in cascade with just one and used a current sink for the input stage and CCS load for the output cathode followers.
Anyway the original LS22 performance claim was 2V rms at 0.01% THD. I might understand that higher distortion of the replica is on purpose to get some tube distortion while driving a SS amp but that's the only possible use. In my opinion it is not a good approach because the result is always a bit random (not every SS amp will like it) but, as always, everyone does what he/she likes.....
You have been very kind Stephe in your verdict. Mine is more in line with the other website....🙂
I still don't get the point of replicating a preamplifier that, in my opinion, was a bit "flawed" by default and soon replaced by the LS25 (barely 2 years later) where they replaced the 2 stages in cascade with just one and used a current sink for the input stage and CCS load for the output cathode followers.
Anyway the original LS22 performance claim was 2V rms at 0.01% THD. I might understand that higher distortion of the replica is on purpose to get some tube distortion while driving a SS amp but that's the only possible use. In my opinion it is not a good approach because the result is always a bit random (not every SS amp will like it) but, as always, everyone does what he/she likes.....
You have been very kind Stephe in your verdict. Mine is more in line with the other website....🙂
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I feel there was something wrong with the unit tested on "the other website". The sine wave at 20hz in their review was insanely distorted, this unit I tested looked fine. Their test showed distortion that was off the chain, I didn't see that. No, it's not "perfect" but it's far from being a decorative door stop. I think "Pretty good" is an accurate description of the unit I tested.
I personally don't get the obsession with pre-amps and why people want to insert them in the signal path of a system that doesn't need one. As I said in my review, if someone gave me one for free, I wouldn't use it because my system doesn't need a pre-amp. It also seems very overly complex with a lot of stuff in the signal path, as you said why does it need 2 stages for how little gain it has?
But like I always say, if you are looking for 0.01% THD or less, just use SS gear. There is no reason to bother with tube gear if you don't want to hear the tube gear 🙂 There are much cheaper/smaller clean pre-amps if you actually just need a pre-amp and aren't looking for a device to round the edges off of a overly sterile sounding system. I think that is what this device might be useful for.
I personally don't get the obsession with pre-amps and why people want to insert them in the signal path of a system that doesn't need one. As I said in my review, if someone gave me one for free, I wouldn't use it because my system doesn't need a pre-amp. It also seems very overly complex with a lot of stuff in the signal path, as you said why does it need 2 stages for how little gain it has?
But like I always say, if you are looking for 0.01% THD or less, just use SS gear. There is no reason to bother with tube gear if you don't want to hear the tube gear 🙂 There are much cheaper/smaller clean pre-amps if you actually just need a pre-amp and aren't looking for a device to round the edges off of a overly sterile sounding system. I think that is what this device might be useful for.
ASR only tested the balanced input as stated by this post (possibly output too). Clearly you can see in the innards the balanced inputs use 10K:10K bridging transformers and outputs use 600R:600R transformers. More likely those audio transformers are poor quality units, possibly not enough inductance for bass. You tested unbalanced signal which bypasses those transformers that possibly resulted in a different performance. Just an observation. If I own the preamp, I would not use the balanced jacks or replaced those transformers with known quality pieces.
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