Looking for transistor subs for a couple of transistors in the pre-driver part of the circuit, Q31/33 the originals are 2sa564a, this is a pnp to-92, 150mhz part with max -7 Vebo, Hfe 180-360
A close subs i've found was ksa1381 a to-126 part no big deal with that but the Vebo is only -5 volts max, would I ever see over -5 volts here?
Or the Ksa1220A, differences larger value cob at 26pf, original 3.5pf and again Vebo at -5
Any other subs I should be looking at
A close subs i've found was ksa1381 a to-126 part no big deal with that but the Vebo is only -5 volts max, would I ever see over -5 volts here?
Or the Ksa1220A, differences larger value cob at 26pf, original 3.5pf and again Vebo at -5
Any other subs I should be looking at
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You do notice the difference in the Hfe bias =10ma as opposed to 2ma and the 1381 is a TV BJT not a designed for audio one like the 2SA564A
The 1220 needs 300ma Hfe bias .
Your in the UK why don't you pick a well known and used in the UK a BC range one you have a wide choice of audio BJT,s of that range to chose from that are nearer the 2SA564A ?
The 1220 needs 300ma Hfe bias .
Your in the UK why don't you pick a well known and used in the UK a BC range one you have a wide choice of audio BJT,s of that range to chose from that are nearer the 2SA564A ?
the original q31, 33 are 2sa1127 or 2sa999.Given the fact that they are safely cascoded you can go with 2n3906 with no problem at all.Even bc327 will work there. I think you were talking aboutthye cascode itself, q35, 37 which were either 2sa912 or 2sa1124. For that ones you should look for scraped modern Onkyo, pioneer... 5+1 systems which are using equivalent modern transistors.Most of the kenwood transistors were damn fast and are now unobtainium so you can hardly expect to find something identical.
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Yep, you thought right, wrong part number and position wrote down, I think I'll try one of the above transistors rather than scavenge at the moment, space is pretty tight as well, could accommodate at to-126 nothing larger.
R.e using bc parts the pin outs aren't the same and don't really like crossing legs to fit.
i'd urge you to check the tone defeat (on/off switch) before firing it on along with all the sigma drive wiring and traces through the tone eq switches...cold solder...it's acommon problem for this model.The IC5(input fet transistors) don't have a straight dc bias path outside the tone defeat switch for the feedback input and that can cause huge problems.people put that on the sigma drive feedback which is again problematic but no dc path outside the switch is really dangerous.If you really want to make this amp a star, check the kenwood ka-9x or kenwood l-02 schematic and how they solved all the problems .I had one 8 years ago and i know what is worth.Basicaly the best amp i ever heard and i heard some 40 k priced amps that didn't even came close to this kenwood in terms of pure sound quality.
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Thanks for the tip, I'll make sure I rework the solder on that switch. Did you make any mods to this amp? And when you say best amp, the ka-1000 of l-02?
you should also measure the switch in the 20 ohm scale ohm meter.l-02 is just another league as it solved all the ka-1000 reliability problems and has the best phono preamp ever built into a commercial unit, but k-1000 can be modded into l-02 at least with the sigma and feedback wirings.the rest minimalist stile relies on very high quality transistors and a smart topology.
do what l-02 does and you can't go wrong, but you need to take into the account the Tone stack embedded in the feedback network.On that ka-9x has a different idea.You might consider removing it altogether and simply canceling the tone defeat switch using an external eq if needed, but then the phono preamp might need some equalisation with some vinyls...I'd probably just wire a 1 megohm resistor in parallel with the switch just to make sure that i have some dc there.
So with the l02 schematic, sigma drive feedback goes to ic1. Amplifier feedback through? Have you done this mod before?