[ttan98]

Hi,

I notice you use Toshiba 2SC5200&1943 as output transistors, I have a few questions:

1. What drivers transistors are you using, TIP41/42 or BD139/140?
2. Do you normally match your o/p transistors to give best performance, I suspect not?

thanks.

[AKSA]

Hi Ttan98,

Thank you for your post.

Drivers are 2SC4793 and 2SA1837.  These are the recommended Toshiba drivers for the 5200/1943, and they are very very good.

I carefully match like transistors in the 100W version of the amp;  beta within 2% and Vbe within 1mV.  On the single pair amp, the 55, there is no requirement to match the outputs.  In any event, NPN and PNP are very different to each other.

Hope this helps,

Cheers,

Hugh

[ttan98]

I tried to source these components from Farnell and RS components however both of them did not stock some of them. Furthermore, I don't trust the quality from Ebay even though I can get them there(my last resort)

I wonder whether you can sell me 2 pairs of these to make a stereo pair, ie
2SC5200 - 2
2SA1943 - 2
2SC4793 - 2
2SA1837 - 2

If you don't want to sell them for one reason or another please direct me to a local distributor in Melb./Sydney who stock them and willing to sell me in small quantity. I am from Melb. Thank you for your time.

[AKSA]

Tean,

Call me on 9457 5591 to arrange a time.  I have the original Toshibas, can supply at low cost.

Cheers,

Hugh

[rabbitz]

FYI, I get mine from WES Components. If you get stuck you can always find them there but from Hugh is even easier.

[ttan98]

Hugh,

Thanks for selling me the drivers and power transistors.

A follow-up question, if I were to drive the 2SA5200/2SC1943 combo using the CFP driver combo, what master and slave drivers do you recommend to achieve good linearity.

What I have in mind is something similar to what Roender is doing to his amp.

Thanks.

[AKSA]

Hi Tean,

My pleasure to meet you on Saturday!

That would be a good option;  I've experimented with this approach and it works well.  You can also contact Mihai Rauta in Bucharest - he is happy to chat about it and highly articulate in English.

For the CFP master I recommend something like 2SC3423/2SA1360, while for the CFP slave the C4973/A1837 is just fine, though the slave should be a tad slower and the MJE15030/31 series is very good too.

You will need to keep the resistor between the drivers very low, around 18R, to ensure that the CFP driver never turns off when that side of the output stage is inactive.  This is very important to proper control of the output devices, and it will avoid the instability at switch off/on which plagues CFPs.  But it will reduce efficiency very considerably, since this resistor passes around 70mA at idle, more than a complementary output pair passes!  Heatsinking the slaves is essential, and the cooling should be rated to the same level as the outputs themselves.

Cheers,

Hugh

[ttan98]

Hugh,

Sorry to bother you, do you any MJE15030/31 that I can buy from you? I need a pair of each. Total of 4.

thanks.

[AKSA]

Hi Tean,

Yes, no problem, call me when you want them!!

Hugh