AB100 Class AB Power Amplifier

[Skylar88]

Hi Jan

In the BOM, those caps are rated 50V.

Try TRX Electronics in Pretoria for hard to find components. They import from Mouser, etc.

Good luck
Christo

PS I'll send you the BOM if you send your email by PM.

 

[Vrystaat]

Thanks Christo, I have sent you a PM.
Regards
Jan

 

[osscar]

Hi,

Yes BD140/139 can be used with lower rail voltages... MJE340/340 will give slightly higher THD readings...As outputs i used Mj11015/16 in TO3 cans - because i had to3 pre-drilled heat-sinks.

 

[Vrystaat]

Thanks osscar, what voltage casps did you use for C5,C6,C7,C8 and C12 ? My rail voltage will less than +-50Vdc.

 

[osscar]

hi,
C5 and C6 should be 63V (as filter caps ) for +-50V to be on safe side

C7 and C8 can be as low as 16V. I used film cap as c7 (2uf2 or so) .for c8 i used bipolar(non-polar) el.cap- 25 or 50V because i had them.
c12 also can be 16 or 25 V or higher...across C7, C8, C12 there are now high voltage during normal conditions. Higher voltage caps are usually bigger..so its depend on PCB pad size.

 

[Vrystaat]

osscar, just a last question, I will be using Prasi's layout. In the original circuit R3 were 1k, you changed it to 100R to lower the gain. I will be using 1R emitter resistors , would it be better to keep R3 at 100R ? Why did you decide to lower it initially, oscillation ?
Regards
Jan

 

[osscar]

no I have never had a stability problem AB100, 36db (x63 times) original gain is too high for me - it might fit if you connect mobile phone vith lov voltage output directly to amplifier...for me approx. 26db gain is ok, and distortion figures are little less..

 

[osscar]

with 1R emitter resistors you can use even lower bias ..according to D.Self book - around 20mA per device

 

[Vrystaat]

Thank you sir, I think I'm sorted, I shouldn't bother you soon !

Now just to wait for the rest of the ordered spares to arrive ! I wonder how the sound would compare to a Slewmaster with a CFA frontend, well, lets wait and see.

Regards
Jan

 

[osscar]

Good luck with your project, I also like Prasi PCB design - you will be able to compare the sound soon i hope !

 

[Vrystaat]

Thanks osscar, much appreciated, delivery dates changed again apparently due to Corona, lets hope for the best.
DARLINGTON PNP 100V 10A 125W TO247
Stock no.:7743666
Qty:8New delivery date:
11/09/2020Choose alternativeTRANS GP BJT NPN 45V 0.1A 3-PIN TO-92
Stock no.:6711113
Qty:50New delivery date:
29/07/2020Choose alternativeDARLINGTON NPN 100V 10A 125W TO247
Stock no.:7743662
Qty:8New delivery date:
16/10/2020Choose alternative

 

[Vrystaat]

Finished with boards, now waiting for spares in this dark Africa ! Prasi, thank you very much, boards came out beautiful, well done !

 

[osscar]

nice diy boards!

 

[prasi]

Beautifully done Jan!. I like seeing diy boards

 

[osscar]

it's your pcb design after all

 

[Vrystaat]

Thanks Prasi, you are the man ! ! Allway's willing to help the guy's with a nice layout.

 

[Vrystaat]

Good day all,
Just a question, a few of the resistors have weird values, eg 4.75K, 33.1R, would it cause a problem if I used standard values like 4.7K and 33R ? Will it cause symmetry problems with DC offset or perhaps instability ?Help appreciated.

Regards
Jan

 

[osscar]

I use standard values without any problems...

 

[Vrystaat]

Thanks osscar, much appreciated !

 

[Vrystaat]

Gooday osscar, can you please affirm, I know you used a smaller input cap and lower emitter resistors. The feedback resistor of 100R as well. What are all the changed values that you have used, info appreciated.Perhaps a schematic with all the changes would be nice !
Regards
Jan