Slewmaster - CFA vs. VFA "Rumble"

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#10,702
OPS

Referencing the Attached schematic;

Does the transistor of q107/108 need to be the same as the OPS transistors q109-q114?

Example, if I use MJL4302 / MJL4281 BJTs for the OPS, would I need them for the q107/108 as well?

I currently have enough on hand to do a 3 pair OPS (6 each) only, and they appear to be non procurable for a while.

Thanks!
 

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#10,703
No, but keep in mind Q15 needs to be on the same heatsink as Q107 and Q108. Also Q104 needs to be on the same heatsink as Q109-Q114 for temperature tracking. For example you could use the njw0281/0302 as drivers and mjl4281/4302 as outputs.
 
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#10,705
ostripper said:
I would build this one.

Keentoken and some new (cool - JJS) member helped me figure out
how to iron out the "blameless" overload/diode issue. Clipping is
officially tamed in this design. Diodeless self - clamping VAS.

This is a cascoded "blameless" similar to the badger/wolverine designs.
Some things were simplified , some were added (new).

Was able to get this one down to 1-2 ppm / 20khz without TMC. Just
simple CMC , even at 56-68pf is enough to get single digit PPM.

I will officially offer this to the forum as it's new "Badger" store design.
If me (and others) procede with this gift , it will be endowed with protection
and a servo. It will be made with few options as a well tested , rock solid
WORLD CLASS design - that can match ANY OEM golden/ audiophile
offering.

OS
Click to expand...

Hi OS

I do like this 2020 badger... principally the vas arrangement.

I see it as a buffered Hcascode vas.

I got even better harmonic distribution and lower overall THD by placing an extra transistor between the leds and the emitter of the vas transistor.

Please let me know what you think.

Best
 

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#10,707
Would the Sanken 2SC3858/2SA1494 be suitable OP devices for one of these amps, or are they perhaps too slow? They have an fT of 20MHz. It seems the other commonly used MT-200s are 2SC3264/2SA1295 which have fT of 60/35MHz, but are otherwise pretty close in spec.

They're not not listed in post #9489, even though I understand this isn't supposed to be an exhaustive list. These OPs seem to be reasonably readily available in contrast to other MT-200s.
 
#10,710
MT200...

andrensairr said:
Would the Sanken 2SC3858/2SA1494 be suitable OP devices for one of these amps, or are they perhaps too slow? They have an fT of 20MHz. It seems the other commonly used MT-200s are 2SC3264/2SA1295 which have fT of 60/35MHz, but are otherwise pretty close in spec.

They're not not listed in post #9489, even though I understand this isn't supposed to be an exhaustive list. These OPs seem to be reasonably readily available in contrast to other MT-200s.
Click to expand...

Any genuine Sanken mt-200 transistors are good. If you can get them, you should. They are pretty much gone here in the US, except for gouging resellers and fakes.
 
#10,718
Hello, Os_stripper fans. I've been reading the posts for several months. I admit I'm a little lost with all the versions. I have a broken HK 990. Suddenly, I did a study. Just for Laughs. I still have to check and verify. Hello aspirin !!!
 

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