Smaller Leach Amp V1

[loek]

So i can go another 4 weeks for vacation...
I am back in town and got wet eyes from reading all the posts from the past 3 weeks. But at the end there is not so much news except that the boards are not made in europe.....
Hope it is the same quality as Jens boards.
Greetings, Loek

[gengis]

Loek,

Jacco V. is going to have your boards, better be nice to him until you get the boards.

2oz boards.

[AJT]

gengis,

i am committed, payment made! now i wait! thanks

[loek]

Thanks for the warning, i will give him some tobacco products if the boards are here.
Loek

[ble0t]

Speaking of those CD 15000uF/80V caps, here's what I'm planning to use...



I picked up 12 of these from JEA as well...they should make a nice CRCRC for the boards

[AJT]

these caps are waiting for action!

[gengis]

ble0t,

Got any spare boards as in the picture?

[jondoe]

Hello everybody.

I was wondering how many of you would use separate regulated suply for the frontend of the amp.
I was thinking that the reason the frontend had a smaller supply voltage was in order to not "latch" the power transistors when clipping occurs because only the VAS would clip. Of course this reduces available voltage swing therefore efficiency.
If R2R is the target that means the frontend voltage would have to be raised in order to reach VCEsat in the output transistors. This could lead to latching in these transistors.

The frontend could be suplied by such a voltage that it wouldn't quite reach VCEsat and therefore not latch the output to +/- rail and provide optimum voltage swing/rail voltage at the same time. Of course this depends ont the PSU ability to maintain rails under various loads.
(if one would seek only the benefits of regulated supply, then the frontend voltage should be smaller by some amount than the rail voltage under the worst load possible).

I guess the frontend voltage should be only 3-5 volts larger than power section voltage. This can easily be done experimentally.

Any thoughts ?
PS. sorry if this was discussed somewhere else

Cheers

[jacco vermeulen]

Originally posted by jondoe
sorry if this was discussed somewhere else

Sigh!

If the locomotive of a train brakes i'd think everything behind it does too.
I do not see the need to put loudspeakers on an amplifier that can drive it into clipping.
Even if it does, i'd favor it if only the last wagon hits the brakes.
If its you, you could add a clipping indicator led.

Here's the circuit of the classis Accuphase P102, again.
B1 voltage rails for the front end and the driver is 45vdc
B2 for the output is 20vdc.

Though this one uses Mosfets, J76/K213 for the drivers, and K389 for the entrance, they only need a few volts extra to open up.
Notice that the driver gets the full 25 volts difference.
FTR: regulation need not mean putting higher voltage on the front end.

[jondoe]

OK. Thanks.
Sorry for putting it like that
This was more like a hypotethical situation. Clipping is clipping, no matter where it comes from.
I have some small trafos and will use them for frontend regulation.
I just wanted to hear some opinions.

Again, i'm

Jonny