I think I understand from where. If I have the trimmer(for setting the offset) set in the middle(all circled in red resistors set to 2.5k) I get the fft on the left with lower 2nd. If I alter the trimmer position to lower the offset I get higher 2nd.
If I bypass the trimmer the position counts less getting the 2nd lower and higher overall thd.
In the sim files you sent you have the trimmer bypassed but in the shared schematic it isn`t.
Attachments
well, can I make mistake sometimes?
these 100K resistors need to be inside of course, just connecting wiper with pot ends, sorta safety parts in case of wiper ever loosing contact
will correct mistake in both Boo and Poo and re-post necessary files
these 100K resistors need to be inside of course, just connecting wiper with pot ends, sorta safety parts in case of wiper ever loosing contact
will correct mistake in both Boo and Poo and re-post necessary files
if that unfortunate mistake ended on your pcbs, remedy is easy
put 0R in place of 100K resistors, cut trace between caps and upper end of trimpot, cut trace between caps and lower end of trimpot
those 100K resistors are anyway just result of my Chicken OCD, even if I never had multiturn trimpot gone dead, when I use it with minuscule currents
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The thing is that if you don’t bypass the trimmer you get 3x lower thd at 1W and from here my confusion. Did you noticed that?
It’s a learning experience here, if you don’t do mistakes you don’t learn! At least in my case☺️
I didn't even think of that - you can't count on unpredictable things as positives; biasing voltage must be stable, as much is possible
thus, complete R string between gates must be covered with cap bank
I corrected one of the two channels yesterday and mounted the pads also.
When I tried to do the thd testing my focusrite card couldn’t be found by the Windows. Hmm..
I changed the connector on a few usb ports on the same pc but still nothing then I changed the pc and ended opening the soundcard.
What I found was one blown internal dcdc converter.
Replacing that with a ldo the card started again but now it has a bit of mains noise, I will replace with the correct part when ordering next time from mouser.
I am attaching some measurements done with IP as preamp, now I can get higher power for the same 1% thd.
When I tried to do the thd testing my focusrite card couldn’t be found by the Windows. Hmm..
I changed the connector on a few usb ports on the same pc but still nothing then I changed the pc and ended opening the soundcard.
What I found was one blown internal dcdc converter.
Replacing that with a ldo the card started again but now it has a bit of mains noise, I will replace with the correct part when ordering next time from mouser.
I am attaching some measurements done with IP as preamp, now I can get higher power for the same 1% thd.
Attachments
Yes, running stereo now. I managed to modify the second channel today and after I lost myself into the music.
The heatsinks have the same temp as before but now the mosfets have only 4-5c more than the heatsink ao I put the top lids on and closed the enclosures.
I was thinking to increase a bit the bias but once I seen that now I can get 22w instead of 14w at 1% thd I think will leave it as it is. The aleph was plenty loud at max so I imagine the boo will go more louder if needed.
Now I am not sure about the phase of the 2nd harmonic. Rew says it’s positive, shouldn’t it be negative? I have the irfp150 on the negative phase.
Maybe Rew it’s not showing it ok?
I said earlier that I am not interested to increase the bias because I am ok with the thd levels that I get but I was thinking that maybe a certain bias brings the negative 2nd?
The heatsinks have the same temp as before but now the mosfets have only 4-5c more than the heatsink ao I put the top lids on and closed the enclosures.
I was thinking to increase a bit the bias but once I seen that now I can get 22w instead of 14w at 1% thd I think will leave it as it is. The aleph was plenty loud at max so I imagine the boo will go more louder if needed.
Now I am not sure about the phase of the 2nd harmonic. Rew says it’s positive, shouldn’t it be negative? I have the irfp150 on the negative phase.
Maybe Rew it’s not showing it ok?
I said earlier that I am not interested to increase the bias because I am ok with the thd levels that I get but I was thinking that maybe a certain bias brings the negative 2nd?
no other way than to play with variables and measure with DIANA ( able to show polarity of harmonics)
I can't predict much - I mean - I can predict what will happen with OS only when changing things, but you're using it with one or the other FE, and at least for BBA3 I can't tell anything - it really depends how you set it
no much use of predicting in usage with Iron Pre Bal - with just 6db of gain, it's working pretty hard ......
in short - any FE will dominate with its own THD Spectra, OS practically having Chameleon nature - not showing much of itself
what's most important - hope that you're already foot-tapping .......
I can't predict much - I mean - I can predict what will happen with OS only when changing things, but you're using it with one or the other FE, and at least for BBA3 I can't tell anything - it really depends how you set it
no much use of predicting in usage with Iron Pre Bal - with just 6db of gain, it's working pretty hard ......
in short - any FE will dominate with its own THD Spectra, OS practically having Chameleon nature - not showing much of itself
what's most important - hope that you're already foot-tapping .......
Rew is able too but I was not sure if what it shows up is true. I will try Diana too.
the thd doesn’t change much when changing the FE. In the attachements I have BBA3 running
I started already the music... I think some things I had to do today will get delayed.
Thanks again!
Attachments
I’ve been thinking at this since you mentioned from the beginning about creating a bit of asymmetry to get 2nd hd.
I want to use on the positive phase the 2sk182es and on the negative one the thf51s. I already have 2 pairs of 2sk182es since a long time ago and was thinking to trade one pair for a pair of thf51s.
What do you think about this? Are there any ltspice models around for the 2 sits?
I want to use on the positive phase the 2sk182es and on the negative one the thf51s. I already have 2 pairs of 2sk182es since a long time ago and was thinking to trade one pair for a pair of thf51s.
What do you think about this? Are there any ltspice models around for the 2 sits?
my models aren't good enough for that level of nitpicking ...... my advice - build it and measure, every permutation you can think of, then decide what you like most