The Singing Bush

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#121
The amps have no input buffer. My Luminaria has transformer volume at its input. I measured the Luminaria output impedance the other day and it is 60R in one channel and 70R in the other. So it should be good for frequency response.

Unlike you, I have to sleep now, and will finish my changes tomorrow.🙂
 
#123
Hi Zen Mod,

I modified the other channel today and the amps have been playing music for a few hours now.

The big change soundwise is the lower level of distortion is apparent when playing music at higher volume. Previously the sound would get a bit harsh at higher levels. I don't have a large room so I usually didn't have the volume turned high, so it was not an issue. Now I notice that I can listen at higher volume without the harshness.

Perhaps the sound is also smoother at lower volume.

It does show that there is a point where too much second order harmonic distortion is not good.

Thank you for doing all the work in finding a good operating point for the THF-51S.:cheers:

Ben
 
#134
Zen Mod said:
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

:rofl:

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 shoot 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 :clown:

edit on 13.02.2020: I forgot that all Pa's BAF 2105 Lecture slides, due M. Rothacher's nicety , are available here for download (besides some other interesting things from Mr. MR) :

Articles | AudioMaker
Click to expand...

Choky,

whoz da't guy next to papa who speaks Zemgrish.....


I want to build this amp.....I will be up for some boards.

Cheers,

Greg
 
#136
🙂
 

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#139
Hi Zen Mod,

The revised operating point is definitely a winner. As I mentioned previously, the lower distortion at higher output is definitely noticeable and appreciated.

As for at lower listening level, I really can't say whether I can tell any difference. My memory is not that good. All I can say is that I was quite happy with the sound at lower levels before the change. So perhaps with the initial setup the H2 at lower levels was not high enough to be objectionable.

Ben
 
#140
so , you being practically first being able of making any proper comparisons ..... what are main gains and is there any drawbacks , vs. "regular" FW format amps (those- meaning both lower power and lower dissipation .....and lower THD) ?

I can't comment , hardly being even close to be objective ........ and - didn't had a moment of stereo operation ; did put some tunes with THF51 iteration , but only mono and - my speakers are really too easy ....

resorting to Papa's tricks - connecting adequate load in parallel to speaker , so demands to amp being properly increased ..... one needs to get used to any new procedure , so no go for now
 
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