baronbeehive
Headphoneus Supremus
These are my impressions of the sound after installing 1uF Mundorf SIO metallized polypropylene caps in the WCF position. First it was unfortunate that Foobar decided to alter the order of the tracks that I had previously made some detailed notes on so I have had to listen anew and record my impressions without the notes because I didn't know which tracks they referred to so I had to guess. Fortunately at least the volume remained constant, I had left the volume knob unchanged since the last listening session.
First I have to say I didn't really expect any changes, the sound is already endgame.. but the first thing that hit me was the fuller bodied sound, both instruments and soundstage and the realism was that much greater as a result. I will go in a bit of detail because of the changes. First the bass frequencies as shown by kick drums, drum depth in general and bass guitar, these definately had more impact to the extent that in my notes where I hadn't even mentioned kick drums and bass guitar they were very noticeably more prominent whereas I hadn't noticed before. Another thing that jumped out at me this time was a track where Robben Ford switched pickups in midstream and I clearly heard it this time and the resulting change in tone of his guitar.
IMO this is yet another step up in SQ and I would recommend the change. A similar thing happened when I installed a Brimar tube in my other amp and everything suddenly got that much more powerful sounding and where the frequency band shifted somewhat toward emphasis more on bass. Maybe the cutoff has shifted toward the bass spectrum away from the treble. I would be interested in what CopperFox thinks when he fixes his amp, I know he is a bit of a basshead. The only thing I would say, if you are not so into bass as he is then maybe try an intermediate cap value somewhere between .33uF and 1uF. One thing to say is there is definately no disadvantage in going to 1uF, no oscillation or anything.
Sometime I will do a comparison with my APPJ because that would give a baseline with which to compare any changes, before both amps performed very similarly but this might now have changed.
Next are some cathode bypass Wima's, the reason for the chassis extension. I decided to go for 150uF's, the reason being that I believe the difference between them and the 200uF's that CopperFox has is probably negligable, also they are readily available from Mouser UK.
Going by the cathode bypass calculator the bass roll off starts smoothing out around 150 - 200uF, and the curve from 20hz on is pretty much horizontal anyway. I can't hear anything below 20hz. Then if we say that the equivalent film cap to lytic ratio is 3 - 5 times, if it is 3 times then that is 450 for the 150uF caps and 600 for the 200uF caps. At that capacitance the frequency curve has smoothed out completely and there is no difference between them. Also I have 450uF lytics in currently and I really like the sound atm. If the ratio is 5 times then the frequency curve is pretty much the same as for 3 times so that I believe any gains from the higher ratio capacitance is probably overkill. That means that there is no additional gain from this capacitance, although there is probably no disadvantage either, and CopperFox has not reported any oscillations or any detriment in sound.
That just about takes care of the latest mods except for the PSU. CopperFox has 400uF Wimas in there, but I will probably not change my lytics because they have sufficiently large storage to handle the PSU ripple and any spikes so I don't think there would be any advantage in changing, especially if the cathode bypass Wimas do their job.
First I have to say I didn't really expect any changes, the sound is already endgame.. but the first thing that hit me was the fuller bodied sound, both instruments and soundstage and the realism was that much greater as a result. I will go in a bit of detail because of the changes. First the bass frequencies as shown by kick drums, drum depth in general and bass guitar, these definately had more impact to the extent that in my notes where I hadn't even mentioned kick drums and bass guitar they were very noticeably more prominent whereas I hadn't noticed before. Another thing that jumped out at me this time was a track where Robben Ford switched pickups in midstream and I clearly heard it this time and the resulting change in tone of his guitar.
IMO this is yet another step up in SQ and I would recommend the change. A similar thing happened when I installed a Brimar tube in my other amp and everything suddenly got that much more powerful sounding and where the frequency band shifted somewhat toward emphasis more on bass. Maybe the cutoff has shifted toward the bass spectrum away from the treble. I would be interested in what CopperFox thinks when he fixes his amp, I know he is a bit of a basshead. The only thing I would say, if you are not so into bass as he is then maybe try an intermediate cap value somewhere between .33uF and 1uF. One thing to say is there is definately no disadvantage in going to 1uF, no oscillation or anything.
Sometime I will do a comparison with my APPJ because that would give a baseline with which to compare any changes, before both amps performed very similarly but this might now have changed.
Next are some cathode bypass Wima's, the reason for the chassis extension. I decided to go for 150uF's, the reason being that I believe the difference between them and the 200uF's that CopperFox has is probably negligable, also they are readily available from Mouser UK.
Going by the cathode bypass calculator the bass roll off starts smoothing out around 150 - 200uF, and the curve from 20hz on is pretty much horizontal anyway. I can't hear anything below 20hz. Then if we say that the equivalent film cap to lytic ratio is 3 - 5 times, if it is 3 times then that is 450 for the 150uF caps and 600 for the 200uF caps. At that capacitance the frequency curve has smoothed out completely and there is no difference between them. Also I have 450uF lytics in currently and I really like the sound atm. If the ratio is 5 times then the frequency curve is pretty much the same as for 3 times so that I believe any gains from the higher ratio capacitance is probably overkill. That means that there is no additional gain from this capacitance, although there is probably no disadvantage either, and CopperFox has not reported any oscillations or any detriment in sound.
That just about takes care of the latest mods except for the PSU. CopperFox has 400uF Wimas in there, but I will probably not change my lytics because they have sufficiently large storage to handle the PSU ripple and any spikes so I don't think there would be any advantage in changing, especially if the cathode bypass Wimas do their job.
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