Would the mk3 benefit from more bias ...?
Simulations here: http://www.diyaudio.com/forums/soli...mkiii-hx-builders-thread-146.html#post3270977
Remember?
The "silencing the lifted ground" operation makes a heck of a difference. It's now dead silent. I recommend.
What did you do then?
I completed the same mods and also have I hum free amp now. However, mine does not use a ground lift resistor on the board or bridge rectifier between the line cord ground wire and case. I have the line cord ground going directly to the case and ground wires from that point to the input RCA connector grounds. I was able to see the difference that this last connection made on the Arta spectrum analyser display. It produced about a 10 db drop in 60 hz content on the output.The "silencing the lifted ground" operation makes a heck of a difference. It's now dead silent. I recommend.
Leach discusses this option in Lo Tim.I have the line cord ground ......... to the input RCA connector grounds. I was able to see the difference that this last connection made on the Arta spectrum analyser display. It produced about a 10 db drop in 60 hz content on the output.
Leach discusses this option in Lo Tim.
Yup it's also recommended in Self's book.
As the Mk3 flies ..
Any improvement on the clipping characteristics ....?
The Baker clamp does eliminate the rail sticking and removing the bootstrap capacitor renders the clipping symetrical. The bootstrap cap is part of this amp's soul, I won't remove it.
Martin tell us more.
Refer to post 2015... too much stuff "lift grounded"
Martin.
Here is Carnival time .... a moment to have fun...but i do like to do electronics
Producing transmission line speakers....audio quality result if fine.
Some books says overshot is fine!
regards,
Carlos
Producing transmission line speakers....audio quality result if fine.
Some books says overshot is fine!
regards,
Carlos
Attachments
The Baker clamp does eliminate the rail sticking and removing the bootstrap capacitor renders the clipping symetrical. The bootstrap cap is part of this amp's soul, I won't remove it.
You prefer the sonics with bootstrap cap ...?
Hi Wayne,
I had to pull the tops of and measure. I have the Super A set at 192mA per rail and +-38.6V. The MKIII is set at 80mA and +-75.5V. They really are just too close to call on my system. Both are crystal clear with great bass.
The mod is not difficult. The most time consuming part is pulling the boards out so you can get to it. I am attaching a pic of how I did R8A. I just drilled a small hole through the board to the trace below and swung the end of R8. Sorry, I didn't take any pics of the bottom of the board. I cut the traces just where I show in the other attachment and the jumpers are easy since the traces have exposed copper.
Blessings, Terry
Hi Terry,
I tried to follow your mod last night but R17 (1K) burns out ...
Please clarify did you really include R17 to the main ground??
I'm confuse between these two mods of you and martin on post 2015 as he keep the R17 on the lifted ground.
Regards,
Willy
Attachments
Hi Terry,
I tried to follow your mod last night but R17 (1K) burns out ...
Please clarify did you really include R17 to the main ground??
I'm confuse between these two mods of you and martin on post 2015 as he keep the R17 on the lifted ground.
Regards,
Willy
Hi Willy-
I made this mod also and had no problem with R17. It doesn't make sense that moving that end of R17 from the lifted signal ground to main ground could cause the problem. You are only reducing the resistance from collector to ground by 10 ohms (1%). I think you must have a wiring error or short somewhere. Are you sure you cut the correct trace?
Steve
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