I need help with this amplifier...

[viktor1986]

Hi

Original schematic use Toshiba two pair's 2SC5200&2SA1943 output transistor.I want too use TWO pair's of IRFP240&9240.

I am not sure in value of R23 and R24.Voltage on this two resistor schoud be 7.8V.This is OK,but what is with currrnet in two resistor's?

Explanation please....

[ilimzn]

It would help if you posted the unmodified schematic. Basically the current you want depends on the slew rate you want. A good ballpark figure would be aboout 10mA per pair of IRFP240/9240.

BTW what happened with the amp you designed and said would build in another thread?

[viktor1986]

Originally posted by ilimzn
It would help if you posted the unmodified schematic. Basically the current you want depends on the slew rate you want. A good ballpark figure would be aboout 10mA per pair of IRFP240/9240.

BTW what happened with the amp you designed and said would build in another thread?

Here is original schematic.Boraomega is the designer.

[viktor1986]

Originally posted by ilimzn
It would help if you posted the unmodified schematic. Basically the current you want depends on the slew rate you want. A good ballpark figure would be aboout 10mA per pair of IRFP240/9240.

BTW what happened with the amp you designed and said would build in another thread?

Here is picture of that amplifier(Legend-MK2).

Mozes i na hrvatskom na mail da mi napises nesto za doradu.

[bogdan_borko]

Hi VICTOR!

Replace R23 and R24 with one resistor 390 Ohms and set 20mA trough Q11 and Q12.

MY proposition:

1. make the amplifier but don`t connect output mosfets
2. Replace R23 and R24 with one resistor 390 Ohms
3. try to adjust bias with R19 and see if you can adjust 20mA trough Q11 and Q12, and if you can`t , replace R18 with some other value to acheve this.

POZDRAV!

[AndrewT]

Hi,
if you decide to go with FETs then add a gate resistor to each FET and add a zener from each gate to source.

Increase the output FET Iq to 100mA for each FET and allow your sink size to let you experiment with upto Iq=250mA per FET. This will get hot.

Move the base connection of Q8 to next to R18 and connect the wiper of VR19 back to R20.

[MikeB]

You have to be careful with this design, "mlaen" had built it and ran into stability problems as it is a bit undercompensated...
You need to add an input filter at least. I guess when changing to mosfets you have really to readjust the feedbackcompensation.

Mike

[viktor1986]

Originally posted by MikeB
You have to be careful with this design, "mlaen" had built it and ran into stability problems as it is a bit undercompensated...
You need to add an input filter at least. I guess when changing to mosfets you have really to readjust the feedbackcompensation.

Mike

MikeB,Techo is very very good and stable amplifier."Mlaen" had built Techno and he had problem's with him because he mistake too much.Mlaen has change some transistor's(they are not used in original schematic) and because that he had problem's with Techno.His Techno now work's fine because boraomega saw were is "MLAEN" mistake.

In my country,one guy has built Techno two month's ago are his amplifier work's perfect.

[viktor1986]

MikeB,why are you tell me that is Techno unstable amlplifier?!People must know that TECHNO is very good and stable amplifier!Look on the schematic!You know that is good schematic!Maybe you are jealouse on boraomega amplifier's because they are better than yourse ?!

[MikeB]

That's quite ridiculous... A single 10pf millercap in a high gain amp is not much. Mlaen did only substitute the output stage with even slower transistors...
And, i don't know which one is better... I did not intend to measure sizes now, maybe you want ? You say boraomega's amps are better, have you compared ? If not,

Mike...