Zen Mod said:
Manu will tell how his HK sounds (ditto from box , untouched , with all these years on shoulders , without any tweak ) comparing to his A5
I didn't fired up my yet , except on the bench ;
anyway - I tested ( repaired ) one combo few years ago - that's why I had idea to pursuing them
for testing purposes , I tried it in clipping too ;
you can imaging how heavy clip is - 80Vpp , with enough sine input (at 440Hz) that looks almost as perfect square
OK - I cheated - without load on output
edit :
plan is - to exchange all resistors to MF , tweak input resistance , check dissipation of predrivers , change input cap , decrease Iq ( to burning hand point ~ 40-50W/channel) tweak value of 1uF cap across Vbe multiplier ( bias xistor) ;
after that - preamp - HK725 ; it's in fact very nice discrete OP with Jfet input ;
maybe I'll call it DOSNS10 - Death Of Steen's NS10 .......
Sounds like a great plan. Did you find a datasheet for those 2SK106's? Making a quikky search didnt return one. I only found a spec. sheet.
That is a terrific name for it
Zen Mod said:
should I replace it with 2SK369 ?
naah .... I'll see what I can expect with 2SK170 there......
He-he, there are some spec's listed in the previous pdf
The output transistors of the poweramp are way cool
They look like Sanken's SB705/SD745
steenoe said:
He-he, there are some spec's listed in the previous pdf
The output transistors of the poweramp are way cool
SB705/SD745
tnx mate
I have all datasheets , no worry ;
I'm just lazy - in fact leaving things for later ..... I'm at least trying to do one thing then the other ........
after many moons - I have some conclusions :
preamp is hopeless piece of junk - in stock form
what's needed - better PSU , decreasing really excessive gain , changing all resistors to plain MF vanilla ( even if for just few criticall ones ) , getting rid of caps in signal path , adjusting output offset .....
amp - even with decent zero gain pre , decent block cap instead of crummy elco on input - it' also over sensitive on input;
what's needed ........ except changing resistors , and decreasing overall gain ...... is something like this ( just rough sketch ) :
preamp is hopeless piece of junk - in stock form
what's needed - better PSU , decreasing really excessive gain , changing all resistors to plain MF vanilla ( even if for just few criticall ones ) , getting rid of caps in signal path , adjusting output offset .....
amp - even with decent zero gain pre , decent block cap instead of crummy elco on input - it' also over sensitive on input;
what's needed ........ except changing resistors , and decreasing overall gain ...... is something like this ( just rough sketch ) :
Attachments
Zen Mod said:after many moons - I have some conclusions :
preamp is hopeless piece of junk - in stock form
what's needed - better PSU , decreasing really excessive gain , changing all resistors to plain MF vanilla ( even if for just few criticall ones ) , getting rid of caps in signal path , adjusting output offset .....
amp - even with decent zero gain pre , decent block cap instead of crummy elco on input - it' also over sensitive on input;
what's needed ........ except changing resistors , and decreasing overall gain ...... is something like this ( just rough sketch ) :
Well ... you never sleep...
Mebbe I should open this piece of junk ...
BTW : What is better than Junk ... The most ordinary, common place, and humble object of our daily dissmissal.
Speaking of junk ... I am just somewhat grumpy today ... just changed my habibi Renault 25 against hugly (beurk-green) Citroen Xsara (the name alone ...) imagine my mood ..
Manu
Manu said:
Well ... you never sleep...
Mebbe I should open this piece of junk ...
BTW : What is better than Junk ... The most ordinary, common place, and humble object of our daily dissmissal.
Speaking of junk ... I am just somewhat grumpy today ... just changed my habibi Renault 25 against hugly (beurk-green) Citroen Xsara (the name alone ...) imagine my mood ..
Manu
you didn't made recently major overhauling/repair of habibi 25 ?
(btw, rust never sleeps ..... )
ZM, I would try to (referring to sch. from post #48 of this thread) remove CFP pairs (Q422/Q426 and Q420/Q424) and put nice simple emitter followers to drive the output BJTs.
I never liked the sonics of CFP, it always sounds limited, tightened, lifeless, EF is a better choice to me...
Also, I would take out output BJTs and use IRFP240/9140 (in EF topology) which could be driven directly from Q414/Q416 (with, let's say, 10 mA running through them). That way you don't need pre-drivers at all (gain from cascoded JC-2 is more than enough)....
I never liked the sonics of CFP, it always sounds limited, tightened, lifeless, EF is a better choice to me...
Also, I would take out output BJTs and use IRFP240/9140 (in EF topology) which could be driven directly from Q414/Q416 (with, let's say, 10 mA running through them). That way you don't need pre-drivers at all (gain from cascoded JC-2 is more than enough)....
Originally posted by Zen Mod
well - dissmantling CFPs ..... OK , but changing outputs .........
completely out of any previous intention hehe
but - who knows ....
Yeah, you are right - too much work, it will be OK with BJTs, it's just that I have a full beg of IRFPs and crazy notion to minimize component count....
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