AB100 Class AB Power Amplifier

[DaveFred]

Here is another version, with less expensive parts.

Any feedback would be appreciated.

View attachment Prelim much cheaper DaveFred Prasi NP AB100 BOMS.zip

 

[DaveFred]

I have several Prasi boards for sale if anyone is interested.



They are 2mm boards, 2oz copper, ENIG.

Two boards plus shipping to the USA would be $35.00 USD paid via Paypal.

Two boards plus shipping to Canada would be $40.00 CDN paid via Paypal.

PM me if interested.

Thank you,

David.

 

[Vrystaat]

"pragtig". Probably all I can remember from the time I lived in the Vaal. Really well executed build Jan, glad to hear it sounds as good..dB

Thank you sir, just spotted your comment Your Afrikaans is still superbbb !

 

[RS232]

Small questions
How much heatsink does this amp needs?
How about power supply 50/0/50Vdc ?
Just asking because I have a few heatsinks and transformers taking space and this looks a nice simple(?) project

 

[osscar]

+ -50V DC is also mentioned in the original NP mini article.So this is exactly what is needed for this amp. Higher voltage will not work without changes in the circuit - lower voltages will work.
Heat sinks should be quite large if there is a + - 50 VDC power supply ..... As with any serious 100W-120W (8 ohms) or 200W (4 ohms) AB class amplifier.

 

[alexcp]

Small questions
How about power supply 50/0/50Vdc ?

Cannot use TIP142/TIP147 with +/-50V rails. These are only good for 100V between collector and emitter, and they will see the full voltage between the + and - rails. With +/-50V they will fail. Either lower the rails or select higher voltage Darlingtons.

 

[Nelson Pass]

They are rated to 100V, and looking at the SOA, I think they would be OK, although
you would be pushing it...

 

[RS232]

Well I do have a couple of 30/030Vac transformers that I was saving for an Aleph30 that will do the trick (30*1.4=42) so bellow the max rating of the 142/147.
Now for the heatsink I have seen a few pictures here from members that build it and it ranges from small (osscar) to Class A size from another builder (Vrystaat)
I don't need all the power from the amp but is good to have some headroom for those heavy and difficult part in some music (listen from classic to heavy metal (depending on mood)).

 

[DaveFred]

Cannot use TIP142/TIP147 with +/-50V rails. These are only good for 100V between collector and emitter, and they will see the full voltage between the + and - rails. With +/-50V they will fail. Either lower the rails or select higher voltage Darlingtons.

Has anyone built the amp with TIP142/TIP147 and +/-50V?

 

[osscar]

I would not call my heat sinks small - they have a thick base and the overall size is large. They have never even been really warm (only when I put in a 100Khz full signal square wave accidentally )
White one running at 38 V and black one at 43 V

 

[RS232]

Compared with the ones we use on the F series they are

 

[osscar]

My F5 with heat sinks like white (approx.) ... works for years - temp. about 50 degrees Celsius.

 

[prasi]

Has anyone built the amp with TIP142/TIP147 and +/-50V?

You could use a crc psu or a cmx like the Mark Johnson cmx..

 

[Nelson Pass]

Well I do have a couple of 30/030Vac transformers that I was saving for an Aleph30 that will do the trick (30*1.4=42)

The actual value is more like 1.3 X for about 40V, so you're extra safe.

 

[DaveFred]

The actual value is more like 1.3 X for about 40V, so you're extra safe.

The transformer I ordered is 35v.

If using Prasi's LT4320 based active rectifier wouldn't it be closer to 50v (1.4 vs. 1.3)?

 

[RS232]

It depends on the transformer manufacturer and how good the under load regulation is but I'm no expert

 

[DaveFred]

It depends on the transformer manufacturer and how good the under load regulation is but I'm no expert

TOROIDY from Poland.

 

[ZUM911]

Has anyone built the amp with TIP142/TIP147 and +/-50V?

I have built it with 49V rails and TIP142/47. I ran it for about 2 weeks after I built it with no problems.

 

[alexcp]

Has anyone built the amp with TIP142/TIP147 and +/-50V?

I did. One pair failed during testing.

I have built it with 49V rails and TIP142/47. I ran it for about 2 weeks after I built it with no problems.

That's not surprising. The Darligtons see the difference between the supply rail and the output. If you run your amp at a low output level - which most people do at home - nothing bad happens, because the output is not far from zero volts, and the voltage across output transistors is not much higher than a single supply rail. However, if you run the amp into clipping intentionally or accidentally (say your preamp sends a transient down to AB100, or you connect a cable while the amp is on), there may be a problem.

 

[alexcp]

Here is my build on a test heatsink. Works fine Just in case, I have a couple of spare boards left.