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😀
😎
steenoe said:
should I replace it with 2SK369 ?
naah .... I'll see what I can expect with 2SK170 there......
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:
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:
you didn't made recently major overhauling/repair of habibi 25 ?
(btw, rust never sleeps ..... )
Indeed ...
"Who cares what we love so long as we know what happened.." Mark Twain said or Helmut Schmidt, dunno exactly ...
But thats the reason anyway ...
So lets return to HK drekk ...
Manu
"Who cares what we love so long as we know what happened.." Mark Twain said or Helmut Schmidt, dunno exactly ...
But thats the reason anyway ...
So lets return to HK drekk ...
Manu
I cannot presume to know anything about this, but often times I see a CCS on the input JFETs to inprove their performance. Would this be something you could add and use to control the DC offset?
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)....
juma said:
well - dissmantling CFPs ..... OK , but changing outputs .........
completely out of any previous intention hehe
but - who knows ....
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.... 😕
Zen Mod said:
Collector resistors on drivers (Q420/Q422) are not needed any more and R506 might need a bit of experimenting, but you know that already
Don't forget to report back on results 😉
juma said:
Collector resistors on drivers (Q420/Q422) are not needed any more and R506 might need a bit of experimenting, but you know that already
Don't forget to report back on results 😉
yeah ...... in few months
- Status
- Not open for further replies.