Conclusions ........
I'm going to make a little pause here ... to let things settle in my head and to re-check graphs little more
in case that's easier for you to grasp things , find complete measurements in one rar file here : Dropbox - Singing Bush measurements.rar - Simplify your life
I know that I didn't took gain measurements in latest tests , was lazy , but that data is of secondary importance here
anyway , first and most important conclusion is - if you have any of those SITs , and you have way of measuring THD spectra ( if I can , everybody can) , The World is your Oyster - no reason that you can't build it and squeeze last ounce of performance , whatever value of Ugs your SITs have .....
even if it's preferable to have that pair close by Ugs
I'm going to make a little pause here ... to let things settle in my head and to re-check graphs little more
in case that's easier for you to grasp things , find complete measurements in one rar file here : Dropbox - Singing Bush measurements.rar - Simplify your life
I know that I didn't took gain measurements in latest tests , was lazy , but that data is of secondary importance here
anyway , first and most important conclusion is - if you have any of those SITs , and you have way of measuring THD spectra ( if I can , everybody can) , The World is your Oyster - no reason that you can't build it and squeeze last ounce of performance , whatever value of Ugs your SITs have .....
even if it's preferable to have that pair close by Ugs
to Zen Mod
Very interesting measurements! You have been busy!
Most interesting for me: different Vgs and their results
And I take it back: no little afternoon comatose nap....
Greets
Dirk
Very interesting measurements! You have been busy!
Most interesting for me: different Vgs and their results
And I take it back: no little afternoon comatose nap....
Greets
Dirk
Thanks for all of the work, Zen Mod.
I have 62.5V available so I will increase my string from 4 x 0.1R to 5 x 0.1R and decrease Vds of the THF and give it a try with lower H2. I have quite high H2 right now. Who knows which operating point I will prefer.
I have already tried in in LTSpice and there was a substantial drop in H2.
I have 62.5V available so I will increase my string from 4 x 0.1R to 5 x 0.1R and decrease Vds of the THF and give it a try with lower H2. I have quite high H2 right now. Who knows which operating point I will prefer.
I have already tried in in LTSpice and there was a substantial drop in H2.
ook Spice , in this phase
you need to alter model to represent your exact SIT , as lhquam did show in his thread ...... and as you can see here , by measurements
luckily , due to Mu above , rail voltage is not so influential as SIT Uds voltage is ; so , vary Uds and Iq and Mu take-out point ..... good thing is - rail will go up , with decrease of Iq
you need to alter model to represent your exact SIT , as lhquam did show in his thread ...... and as you can see here , by measurements
luckily , due to Mu above , rail voltage is not so influential as SIT Uds voltage is ; so , vary Uds and Iq and Mu take-out point ..... good thing is - rail will go up , with decrease of Iq
ZM - you are truly prolific
My head is hurting but I am learning - understand the basics but may need a "tutorial" on fine points 🙂
Also I will need to look into how to take these measurements with a Mac.
Thank you for all the info
Bob
My head is hurting but I am learning - understand the basics but may need a "tutorial" on fine points 🙂
Also I will need to look into how to take these measurements with a Mac.
Thank you for all the info
Bob
I have modified my THF-51S right channel, which has the higher distortion. I added one 0R1 resistor in the string between the IXFN and THF and took the output at 0R2 above the THF ( total 5 x 0R1 ).
8R load at output
V+=63.2V (at 2W, did not check at other output levels), original was 62.5V
Iq=2.54A at 2W, dropping to 2.39A at 50W, original was 3.25A
THF Vds=35.5V, varying slightly at output levels, original was 29.0V
Measured distortion levels are similar to Zen Mod's measurements.
Below is measured distortion at 2W for original operating point, followed by revised operating point measurements at 2W, 5W, 10W, 20W, 30W, 40W, and 50W.
The original had 2.33% THD and the revised has 1.00% THD at 2W into 8R - quite a difference.
Now to revise the left channel and do some listening.
Edit: Typo in titles of measurements - should be Vds, not Vgs
8R load at output
V+=63.2V (at 2W, did not check at other output levels), original was 62.5V
Iq=2.54A at 2W, dropping to 2.39A at 50W, original was 3.25A
THF Vds=35.5V, varying slightly at output levels, original was 29.0V
Measured distortion levels are similar to Zen Mod's measurements.
Below is measured distortion at 2W for original operating point, followed by revised operating point measurements at 2W, 5W, 10W, 20W, 30W, 40W, and 50W.
The original had 2.33% THD and the revised has 1.00% THD at 2W into 8R - quite a difference.
Now to revise the left channel and do some listening.
Edit: Typo in titles of measurements - should be Vds, not Vgs
Attachments
-
Right Iq 2,41 Vgs 5,9V 8R 40W.jpg -
Right Iq 2,44 Vgs 36,2V 8R 30W.jpg -
Right Iq 2,48 Vgs 36,1V 8R 20W.jpg -
Right Iq 2,51A Vgs 35,8V 8R 10W.jpg -
Right Iq 2,52A Vgs 35,6V 8R 5W.jpg -
Right Iq 2,54A Vgs 35,5V 8R 2W.jpg -
BAF2015 THF-51S Right Ch 62,5V 3,25A Vds=29,0V Sp out C 8R 2W.jpg -
Right Iq 2,39 Vgs 35,1V 8R 50W.jpg
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Verdict?
you probably wrote about , but my head full ...... what you have upstream and downstream of amp?
you probably wrote about , but my head full ...... what you have upstream and downstream of amp?
No verdict yet. I have only one channel revised. A SissySIT is providing power right now.
Because my amps were already finished, and built in a compact package, it took me quite a bit of time to take it apart, make the change, and put it back together, and also make sure that I didn't make any mistakes. Then the tests took a bit of time. I will make the change to the second channel tomorrow and then do some listening.
For preamp I have a Michael Rothacher designed Luminaria with 2SK82 and my speakers are Avantgarde Uno Series 2 (about 20 years old).
Because my amps were already finished, and built in a compact package, it took me quite a bit of time to take it apart, make the change, and put it back together, and also make sure that I didn't make any mistakes. Then the tests took a bit of time. I will make the change to the second channel tomorrow and then do some listening.
For preamp I have a Michael Rothacher designed Luminaria with 2SK82 and my speakers are Avantgarde Uno Series 2 (about 20 years old).
..... though , can't remember do you have implemented buffer in front of THF51 , so - take care of having output volume of Luminaria all the way up , that way having least Rout
do your Voluming
with input Volume control
do your Voluming
with input Volume control