The Singing Bush

[Zen Mod]

Well , we all know funny Laws of Life .......... to achieve Plethora of Pinjatas , one must find The Singing Bush , and fathom real role, place and importance of said Phenomena in search for Greater Pastures



so , let's refresh a memory ........ The Singing Bush

as you probably know , I was on Pilgrimage (end of last year) to Sea Ranch .... to have few walks by the Open Ocean , collect some wood flown to shore ..... and to remind Pa that life isn't serious thing at all

who sez that patience and good eye are not things good to have ?

good eye spotted that Pa is not having a Loo in ( or by) his workshop;

patience is needed to catch a moment when Pa must go to Loo ( in da House) , while forgetting to shoo me outa Workshop and lock ..........

so - result is - I came back home with pair of 2SK77B Tokins , being so damn lucky that Pa didn't count them in da Shoe-box , prior to packing me in Variac's car .... ( he drove me to Snoopy Airport)

anyway , what to do with just a pair of them ...... I can't make just one Digital Domain channel ...... still using stereo in my systems ; have no money left for another Pilgrimage so fast and , besides , Pa would say "we are not home!!" even without counting what's left of Tokins in shoe-box...

so , must be some SE ........

luckily , eye and patience again - I recollect watching funny vid , Pa's Lecture at BAF 2015 , where he presented ZM's 50W SE Amp , and also Peasant (rest of Greedy Boyz) iteration , where he cheated , forcing one vulgar mos puck to behave SIT-like ,, with help of some Schade feedback , obtained with nice input xformer

coincidentally - we recently had some fun in 2sk77b

I already posted some pics and back'o'napkin sketches there , but here we go again , posting everything here , to have it complete in one place

to start with, for your amusement, picture of Alcatraz Federal Penitentiary

edit on 13.02.2020: I forgot that all Pa's BAF 2015 Lecture slides, due M. Rothacher's nicety , are available here for download (besides some other interesting things from Mr. MR) :

Articles | AudioMaker

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The Singing Bush Tips 'n' Tricks


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[Zen Mod]

see , ZM's 50W SE Amp , as Papa kindly constructed it ......

it's clever to watch entire vid I linked in previous post ....... you can learn few things , especially about heat

 

[Zen Mod]

making amps simply by schematic ( even drawn by Papa ) is boring ....... while making it absolutely and utterly unnecessary more complicated is ......fun ; besides , there is just one M2 amp , which (we all know) is best amp ever made and sole one which is sacrilege to change

so , what I concocted is something as this (broken in two halves, upper and lower , so easier to combine common upper Mu-block with different lower halves)

so , Mu first

 

[Zen Mod]

then, ZM's half

 

[Zen Mod]

then Peasant half


as already habit - when using nice signal repeater coil , I'm putting footprints for all 3 usual suspects - Edcor, Jensen, Cinemag

 

[Zen Mod]

I started populating pcbs probably a week ago

 

[Zen Mod]

then few days ago , finally did first thing - testing in vivo Mu block

it behaves , Iq set at 30V (half of rail in amp) , steady 3A , behaving nicely .... no hiccups and surprises

10K trimpot enabling fine setting of Iq

observe fuse holder 🙂

T4A , keeper of good mood

 

[twitchie]

Fugly!!!

 

[twitchie]

3.2A * 28V = 89.6W on the lower device, minimum 180W Tdp or is this only for hockey pucks?

Did you have the upper half connection to OUT fixed at the middle point or is it still possible to connect at different points in the resistor string?

 

[Zen Mod]

Patience ,my dear Watson ........ and Courage!!

🙂

that's what's needed when playing with rare and precious toobz

yesterday I followed connecting ZM's half to Mu , enabling full 60V rail , and testing how entire shebang behaves in DC domain

can't be more satisfied .......

voltage potential at output node ( inner side of output cap) ramps up to some 17V nicely fast , then hesitates a little , and goes smoothly to 31V (where I decided to set it) , as Mu starts conducting

3m3 across Opto- Governor is seriously slow to be charged , exactly as intended

 

[Zen Mod]

now , show time !!

ZM's half pcb removed from my Preciousssss, made some security cover for same , took random THF51ES and connected with short wires , so Poor Man's ZM's amp ( you can call it Vienna Boy's Choir amp , if you like )

was lazy to organize isolator sheet for THF , so entire heatsink is sorta live , at SIT drain potential - approx 30Vdc

 

[Zen Mod]

now, sole pic - explanation later

see - 35Vdc , set at output node ........ so THF Ugs is a smidge lower (3A x 0R2)

DVMs showing - 60Vdc rail , 600mV across 0R2 , output node potential

 

[Zen Mod]

The Singing Bush - THF51ES - yelling!!! at 8R

night was young ........... ok , it wasn't even night yet 🙂

so , why not inducing few Greedy Boyz smiling tonight ..... simply because I know that Regular Greedy Boy expects daily dose of graphs , to sleep peacefully

see few things :

- Singing Bush THF thinks ........ no - it's convinced that he is Toob amp!! (10% THD at full power is normal thing)

-THD ( 1W@8R) , keeping 30V5-31Vdc at output node is nearly doubled , comparing to where I moved it - at 35Vdc

-visible clip at scope starts at 32W/8R

- good to have ballsy buffer - it shows in FR , also in THD vs. Freq. graph

 

[Zen Mod]

The Singing Bush -THF51ES - yelling!!!!!! cheerfully at 4R

I have no intention to pursue finer tuning than this ( 60V/3A/35VUds) , I'm happy as is

from these graphs you can see:


- Singing Bush THF is convinced that he's Toob amp with Big Cojones , and 4R tap , besides

-slipping is around 40W , and I wasn't in the mood to eek my eyes at that softness ..... nice and easy soft rounding of sine crest .... who cares

 

[hirscwi]

I'm afraid if I tried this, it would be "burning bush" without Moses...

 

[Zen Mod]

Tomorrow I'll repeat same battery of tests with random 2SK182ES ( now I'm confused - is ES with 182 , or is it with THF51 ....... or is it with both ? .... lazy to check on pics)

will post that , and then maybe day later , will repeat same battery of tests with Schade Mos Puck .......... and then maybe day later , will repeat same battery of tests with My Preciousssssssssssss




time for some reading and nap

.......

 

[Ben Mah]

Muy Bueno, Amigo!!

 

[Zen Mod]

I forgot some numbers ......... THF51 down:

rail 61Vdc

output node set to 35V

Iq 3A

8R clip at 16V2rms= 32W

4R clip approx 40W

gain for 5Vrms out :

4R - 468mVrms ; 10.68V/V , 20.57db

8R- 355mVrms ; 14.08V/V , 22.97db

 

[cubicincher]

to Zen Mod

Clapping hands!


Greets
Dirk


p.s.: my 50W- SE- Schade- amp is also alive....

 

[Nelson Pass]