Howdy all, I finally was able to pry loose from a friend an X 202B that I have been looking forward to. A PS rebuild was first conducted with replacement of resistors with low-noise carbon films that were also uprated wattage-wise. I did a comparison with a rebuilt X 202 that I had been using in rotation with a Scott 299B, which in the bass dept. has been really disappointing, not sure what is going on there except that I believe the phono stage must have some built-in roll-off in the bass, just no comparison to the X 202! In comparing the 202 with the 202B, the B just sounds piercing and roll-off in the high frequencies while in the bass it is much better than the Scott but does not have the quantity or quality that the 202 has. Also, the phono stage is hissier than the 202 by a fair amount. The current rebuild did not include rebuilding the bias/DC source yet, nor replacement of the cathode bypass caps or the 1 ufd cathode follower caps. Does anyone have any ideas what may be going on here, do I just need to finish the recapping before getting a clearer picture of the capabilities of the X 202B. Perhaps I should be looking to go with DG's X 202B rebuild article? thanks!
comparing X 202 and X 202B
- Thread starter gkargreen
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G -- The phono preamps are similar if not nearly identical between the two units -- try swapping phono preamp tubes between the units. Some tubes produce far more "hiss" than others.
The low voltage cathode bypass caps are usually the first thing to fail in these amps. It is not uncommon at all to find them with the ends being pushed out due to pressure build up. I'm not saying that there won't be differences between the two units, or that you won't simply have a preference. But comparing them without the bypass caps replaced isn't a fair contest.
Between my own 202 and 202B, the sound is very similar, but I admit to having a soft spot for the X-202. Maybe because it was the first of the series, or uses 12AT7s instead of 7247s in the preamp section and EL84s instead of the 7591s. I'm really just musing, as the design between the two of them is really quite similar. Frankly, the biggest difference is the power supply being SS in the B -- but I would hardly attribute the sonic difference to that. I would get your B right first, including bias and balancing the output stages before you decide.
Dave
The low voltage cathode bypass caps are usually the first thing to fail in these amps. It is not uncommon at all to find them with the ends being pushed out due to pressure build up. I'm not saying that there won't be differences between the two units, or that you won't simply have a preference. But comparing them without the bypass caps replaced isn't a fair contest.
Between my own 202 and 202B, the sound is very similar, but I admit to having a soft spot for the X-202. Maybe because it was the first of the series, or uses 12AT7s instead of 7247s in the preamp section and EL84s instead of the 7591s. I'm really just musing, as the design between the two of them is really quite similar. Frankly, the biggest difference is the power supply being SS in the B -- but I would hardly attribute the sonic difference to that. I would get your B right first, including bias and balancing the output stages before you decide.
Dave
Thanks as always, Dave, your input is most appreciated. I was reading your article (I have been putting together .pdfs of the rebuild articles you have written as they are most informative!) on the "pitiful x202", you had noted doing a bit of work along the lines of EFB and more, but I don't see that you moved forward in that direction as of the last threads I read, is that correct? The X202B article has so much info there about performance enhancements that I would like to try after I get mine to a working baseline, thanks!
This afternoon I replaced the cathode caps per Dave's suggestion, this resulted in less noise with no hum at all, and the sound stage appears to be pushed back into the corners of the speakers. However, I am still noting a good deal of roll-off in the HF as this amp just does not "sparkle" like the X202, as well as not having quite the bass slam the X202 has either, that may be due to the LF "noose" Dave spoke about in his X202B article. I also have not replaced any coupling caps, leaving in the .047 Ero caps which I have heard a quite good and should not be replaced, correct? Also, I have not replaced the big brown CF caps (1 ufd @250v), wondering if they need to go soon and if they may be impacting the sound quality....
