My bad! Just a loose connection on the positive rail of the left channel. Weird.
Offsets now perfect ~4mV both channels.
Yes, you can bias as hard as you like. Just change the bias trimmer value for something larger.
It's pointless though - The improvement in performance is naff-all, and all you'll do is heat up the room.
This amplifier, with it's fast high open loop gain, is designed with reasonably low bias, to be one of the more efficient LatFET amplifiers.
A shorted Mica cap? As we used to say "Murphy was an optimist: He thought only things that could fail would fail." We came to understand that things that couldn't possibly fail will also fail! Or as a mentor of mine said "No, you won't see it in the units you build in the lab, you won't see it in a pilot run, but you will probably see it in the first 100K units, and you will certainly see it when you build a million of them!"
https://www.worldradiohistory.com/AUSTRALIA/Australian-Electronics-Monthly.htm
Here's something you're looking for...
Here's something you're looking for...
You can look bob cordell lsk389 desing note for preamp, but lsk389 is not good for this amp, because input capacitance little high and it is mean low slew rate… Lsk489 jfe2140 or sst402 could be nice. Jensen 990c or skulptor sk99 discrete opamp could be nice. also my favorite opa1641-42 or opa1655-56 for simple preamp…But if you have dac thats been vout 2vrms, you do t need to preamp. If your sources have vout 250mv like phone stage you need to preamp…. I started to desing new discrete preamp class a (balance and se input direct input or 8x gain, mc mm phone input.)i can share whrn it finish. Definitely i have started to use cap bank on my amplifier. 5x4700-3300 or 2200uf. Cheaper but super fast and good perfermons with Low esr caps.
Attachments
I have just finished a build using a Hammond 1182F30 transformer for each channel. This should result in a bit over 60 watts, rather than 50W. The schematic of the supply circuit I used is attached. Note that the fuses are after the bulk caps. This would match the power amp layout that added caps to the board. If you build with the amp design that does not have bulk caps I think most would argue for placing the fuses ahead of the bulk caps
of course no... because aem 6000 isnt a class a.... you need to use low esr cap and hıgh ripple... 10k uf low esr could be expensive. you can try build cap bank... look my cap bank....
i have started listening to the amp, taking the place of a Yamaha B2 in the audio system associated with the flatscreen. Listening to Youtube videos of Joe Bonamassa/Beth Hart, Larkin Poe and Mark Knopfler/Emmylou Harris and the like. It sounds great! The Yamaha needs to go on the bench to have its input switches cleaned, but I am certainly not thinking I need to get that done quickly. Again, the amp sounds great!
In the environment we have it in now, where we sit 8 feet or so from the speakers that flank the tv, I can't say that I really hear a difference. Slide guitars are still crisp and clean, the female singers’ voices are still beautiful, and the base is clear and tight. The speakers are reasonably high quality mini-monitors with Scan Speak dome tweeters and Morel woofers, so they should not be masking anything. The setup was designed to make speech more comprehensible, particularly when we watch English murder mysteries with Scottish actors (no offense intended). We discovered during the pandemic that system was very good for music videos as well.
The amount of power it requires for comfortable listening in this space is probably less than 10watts. Both this amp and the Yamaha are specified to have distortion in the range of 0.00x at this level, so not hearing a difference maybe isn’t surprising?
The amount of power it requires for comfortable listening in this space is probably less than 10watts. Both this amp and the Yamaha are specified to have distortion in the range of 0.00x at this level, so not hearing a difference maybe isn’t surprising?