Ok, so here are my first impressions. Purely subjective opinions.
After removing IC 309, 310 (the filters) there was an immediate improvement in mids and highs. BUT. I didn't need to turn the volume up as much to get the sale loudness, and there was a little bit of harshness present. Total guess was that without the filter present that IC313, 314 (the last op-amps in the chain) were providing gain that was no longer needed. I actually only listened to a few songs before I stopped and pulled those op-amps and replaced them with the jumpered empty plugs. And then I swapped the "tin can" HA/NOPB 49720's into positions into IC 311, 312.
This is much better. I need a little more volume to get the same loudness as before now. But there is more overall clarity, especially in the mids and highs. Vocals are clearer. I like this.
I think that I've effectively showed that at the very least those 2 op-amps per channel are unnecessary, and that removing them can be an improvement. I can say this, there's no way that I will be putting those 4 op-amps back in the player.
From here I'm going to concentrate on the power supply for a while. I've been reading a lot of talk about the benefits of replacing the bridge rectifier diodes in the analog section (1SR35-200) with Schottky diodes or fast/soft recovery diodes. The 11DQ10 Schottky seems to have been a favorite but is no longer being made. As it happens I do have 4x Vishay SBH100-E3/54 diodes on hand, which are supposed to be a good sub for the 11DQ10's. These will probably be going into my player in the near future. And whenever I make my next Mouser order I'll be ordering what I need to do a voltage regulator upgrade. Then I'll start measuring what it would take to make a torroidal transformer or 2 fit. This is proving to be a lot of fun.
Cheers,
James
http://www.mouser.de/ProductDetail/.../SB1H100-E3-54/?qs=u91jd7aysvMXltu%2bMMJLmQ==
After removing IC 309, 310 (the filters) there was an immediate improvement in mids and highs. BUT. I didn't need to turn the volume up as much to get the sale loudness, and there was a little bit of harshness present. Total guess was that without the filter present that IC313, 314 (the last op-amps in the chain) were providing gain that was no longer needed. I actually only listened to a few songs before I stopped and pulled those op-amps and replaced them with the jumpered empty plugs. And then I swapped the "tin can" HA/NOPB 49720's into positions into IC 311, 312.
This is much better. I need a little more volume to get the same loudness as before now. But there is more overall clarity, especially in the mids and highs. Vocals are clearer. I like this.
I think that I've effectively showed that at the very least those 2 op-amps per channel are unnecessary, and that removing them can be an improvement. I can say this, there's no way that I will be putting those 4 op-amps back in the player.
From here I'm going to concentrate on the power supply for a while. I've been reading a lot of talk about the benefits of replacing the bridge rectifier diodes in the analog section (1SR35-200) with Schottky diodes or fast/soft recovery diodes. The 11DQ10 Schottky seems to have been a favorite but is no longer being made. As it happens I do have 4x Vishay SBH100-E3/54 diodes on hand, which are supposed to be a good sub for the 11DQ10's. These will probably be going into my player in the near future. And whenever I make my next Mouser order I'll be ordering what I need to do a voltage regulator upgrade. Then I'll start measuring what it would take to make a torroidal transformer or 2 fit. This is proving to be a lot of fun.
Cheers,
James
http://www.mouser.de/ProductDetail/.../SB1H100-E3-54/?qs=u91jd7aysvMXltu%2bMMJLmQ==
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