The Singing Bush Tips 'n' Tricks

The Singing Bush Tips 'n' Tricks, so even Cheerleader Girlie can build it ...

....OK , here it is

ORIGIN THREAD : The Singing Bush


First few posts with graphical info, then I'll write separate posts for both amps, explaining few details


////////

however , most important thing when starting, applicable for both amps:

be sure that trimpot in buffer negative rail (lower JFet group source) is set to max position, prior to first powering up - check that measuring across parallel 39R resistor - reading must be close to 28R

/////////

another thing - remove that silly blue collar from needle wire terminal you got from me - either use heat gun or heat it with solder or lighter ...... then pull it

all wires need to be crimped then soldered in wire terminals, then heatshrinked, to look nice

///////// ( you can see from these slashes that I spent some time recently struggling with Arduino :rofl: )

for 2SK77B - lucky bstrdz having these - all 3W resistors in Mu part of amp - they are still 1R/3W , no change ........... Iq 3A2, output node or SIT Drain (what's easier to reach for measurement) set at approx U/2

///////////

edit 27.07.2020. - SIT Singing Bush startup procedure , post #29
 
Last edited:
The Singing Bush SIT iteration

yup, this one is with THF51/2SK182/2SK180 in lower position

I know that few lucky bstrdz are having 2SK77B , to use there ....

I didn't drew input RCA and twisted pair of thin wires for that , you'll manage
 

Attachments

  • The Singing Bush THF51_2SK180_2SK182 MU schm.png
    The Singing Bush THF51_2SK180_2SK182 MU schm.png
    51.2 KB · Views: 2,859
  • The Singing Bush THF51_2SK180_2SK182 Gain schm.png
    The Singing Bush THF51_2SK180_2SK182 Gain schm.png
    55.9 KB · Views: 3,009
  • SIT-AMP-arrangement.jpg
    SIT-AMP-arrangement.jpg
    271.8 KB · Views: 3,317
  • SIT AMP arrangement.pdf
    120.7 KB · Views: 240
I think I figured out what I need for the THF-51. According to post #97 in the Singing Bush thread, we are trying to create the equivalent of a string of six 0R1 resistors, with the tap point 0R2 from the bottom, and 0R4 from the top.

So my bottom resistors are correct, but the top resistors need to be 3x 1R5 and 1x 2R2 for a total of 0.407 Ohms. Yes?
 

Ben Mah

Member
Paid Member
2012-05-18 6:36 pm
Vancouver
Hi ZM,

In my version of amps (pre - Singing Bush) I recently tried speaker out at the middle of the resistors - THF - 0R3 - speaker - 0R3. With the THF-51S that I have, this gave better distortion results than speaker out at THF - 0R2 - speaker - 0R4.

Do you want to see the results?
 
Hi ZM,

In my version of amps (pre - Singing Bush) I recently tried speaker out at the middle of the resistors - THF - 0R3 - speaker - 0R3. With the THF-51S that I have, this gave better distortion results than speaker out at THF - 0R2 - speaker - 0R4.

Do you want to see the results?

certainly that I want

though , we see that there is no perfect recipe ...... in fact - every recipe is to get in ballpark, and fine tuning is always possible

without NFB and with so broad spread of transfer characteristics of used parts, we are pretty much lucky bstrdz anyway
 

Ben Mah

Member
Paid Member
2012-05-18 6:36 pm
Vancouver
There certainly is variability among the THF-51S. My two pieces are not identical.

My amps are Vds=36.5V Iq=2.3A, same as your spec.

The following are left and right channels, speaker out between 0R2 and 0R4:
 

Attachments

  • Right Vds 36,5V Iq 2,3A Spkr C 8R 30W.jpg
    Right Vds 36,5V Iq 2,3A Spkr C 8R 30W.jpg
    146.5 KB · Views: 123
  • Right Vds 36,5V Iq 2,3A Spkr C 8R 20W.jpg
    Right Vds 36,5V Iq 2,3A Spkr C 8R 20W.jpg
    145 KB · Views: 118
  • Right Vds 36,5V Iq 2,3A Spkr C 8R 10W.jpg
    Right Vds 36,5V Iq 2,3A Spkr C 8R 10W.jpg
    145.5 KB · Views: 120
  • Right Vds 36,5V Iq 2,3A Spkr C 8R 5W.jpg
    Right Vds 36,5V Iq 2,3A Spkr C 8R 5W.jpg
    146 KB · Views: 641
  • Left Vds 36,5V Iq 2,3A Spkr C 8R 30W.jpg
    Left Vds 36,5V Iq 2,3A Spkr C 8R 30W.jpg
    147.4 KB · Views: 636
  • Left Vds 36,5V Iq 2,3A Spkr C 8R 20W.jpg
    Left Vds 36,5V Iq 2,3A Spkr C 8R 20W.jpg
    147.4 KB · Views: 640
  • Left Vds 36,5V Iq 2,3A Spkr C 8R 10W.jpg
    Left Vds 36,5V Iq 2,3A Spkr C 8R 10W.jpg
    145.5 KB · Views: 653
  • Left Vds 36,5V Iq 2,3A Spkr C 8R 5W.jpg
    Left Vds 36,5V Iq 2,3A Spkr C 8R 5W.jpg
    147.2 KB · Views: 702

Ben Mah

Member
Paid Member
2012-05-18 6:36 pm
Vancouver
Here are left and right channels, speaker out between 0R3 and 0R3, Vgs=36.5V, Iq=2.3A:
 

Attachments

  • Right Vds 36,5V Iq 2,3A Spkr D 20W.jpg
    Right Vds 36,5V Iq 2,3A Spkr D 20W.jpg
    146.4 KB · Views: 92
  • Right Vds 36,5V Iq 2,3A Spkr D 10W.jpg
    Right Vds 36,5V Iq 2,3A Spkr D 10W.jpg
    145.4 KB · Views: 102
  • Right Vds 36,5V Iq 2,3A Spkr D 5W.jpg
    Right Vds 36,5V Iq 2,3A Spkr D 5W.jpg
    145.8 KB · Views: 102
  • Left Vds 36,5V Iq 2,3A Spkr D 30W.jpg
    Left Vds 36,5V Iq 2,3A Spkr D 30W.jpg
    146.2 KB · Views: 98
  • Left Vds 36,5V Iq 2,3A Spkr D 20W.jpg
    Left Vds 36,5V Iq 2,3A Spkr D 20W.jpg
    146.8 KB · Views: 103
  • Left Vds 36,5V Iq 2,3A Spkr D 10W.jpg
    Left Vds 36,5V Iq 2,3A Spkr D 10W.jpg
    145.6 KB · Views: 133
  • Left Vds 36,5V Iq 2,3A Spkr D 5W.jpg
    Left Vds 36,5V Iq 2,3A Spkr D 5W.jpg
    147.5 KB · Views: 145
  • Right Vds 36,5V Iq 2,3A Spkr D 30W.jpg
    Right Vds 36,5V Iq 2,3A Spkr D 30W.jpg
    145.6 KB · Views: 105