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FH9HVX - Budget Conscious 100w Class AB for Lean Times

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#21
Vunce and I have the same scope. I am not sure the exact one is still available but it was an Owon SSO8192V 100MHz 1Gsample/sec 1Ms memory depth 2 ch scope with 8in color screen. Nice easy to use scope.

I like it because the button interface is lifted straight from a Tektronix that I used to have at work.
 
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#22
Can you believe that’s all there is to a 100+w Class AB amp? Vunce’s example here with the pre-prototype in an old chassis from another amp with a $25 Abletec SMPS shows how simple and low cost it is to get into the game with this amp.

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#23
xrk971 said:
Can you believe that’s all there is to a 100+w Class AB amp? Vunce’s example here with the pre-prototype in an old chassis from another amp....
Click to expand...

Yup, the title is right on. And it sounds very good! There is plenty of real estate towards the rear of the chassis to add speaker protection and additional CRC if wanted, but this Abletec SMPS I pulled out from mothball storage really does a fine job all on its own. If going with a linear psu, I tried one of the CRC boards from Prasi’s GB and that was also a great option.
This is a fun project 😀
 
#25
kevinr said:
Any suggestions for a substitute for the Abeltec PS ?
Click to expand...

Yeah, it’s unfortunate they are not available any more, I hoarded a few when they went on close-out sale.
If I wasn’t using the Abletec, I would go with a simple linear power supply, it worked excellent. You could use an Antek AN-3236 transformer with CRC psu, should get you about 50vdc.
I’m sure some guys can chime in about other SMPS supplies like Meanwell, there are several different flavors out there. I haven’t used one so no experience with them.
 
#26
You can get these LED SMPS. I have used these before and they are extremely low noise. They are single rail 48v and available in various powers. I got the 800w one, but have not used the smaller 360w version which is only $25. You need two of them so about $50. However, it would probably be of similar construction. The fan is very noisy. You have to add a speed reducer resistor or just disable it and oversized the unit like I do and heat is not an issue. The important fact is that the single rail outputs are galvanically isolated from the mains and earth ground. So you can connect two in series for a +/- power supply with a common 0v at the series connection between the +/- points. Treat the SMPS as a transformer with regards to grounding and isolation. Use a CL60 or 8D-20 NTC between the earth ground and the 0v common point.

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An Antek AN-3236 is $36 plus $8 shipping and the CRC PSU will cost you about another $20 in parts. The SMPS is only nominally less expensive.
 
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#29
Curiosity got the better of me, I had to install the FH9 in the main system to have a listen, even though there is no DC speaker protection onboard.
This little amplifier (size wise) had my FAST TL speakers rockin! Running 140mA bias current at moderate levels for a few hours and it barely broke a sweat, 37°C.
Perfect summertime amp! Looking forward to building the revised layout.
 

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#31
Vunce said:
Curiosity got the better of me, I had to install the FH9 in the main system to have a listen, even though there is no DC speaker protection onboard.
This little amplifier (size wise) had my FAST TL speakers rockin! Running 140mA bias current at moderate levels for a few hours and it barely broke a sweat, 37°C.
Perfect summertime amp! Looking forward to building the revised layout.
Click to expand...

Please let us know the difference of running this amp at 50mA and 140mA bias current provided we have sufficient sinks in terms of sound and almost class A levels I guess?

thanks
 
#33
Hi Manniraj,

At first, I was running it at 80mA bias. There was a bit of an edge to the music. I increased bias by 20mA at a time and gave a listen. The sound got better with each step, smoother and better soundstage. I’m currently at 140mA, and heat is a non factor. 38°C was the highest heatsink temperature I’ve recorded so far.
Each heat sink measures: 210mm x 150mm x 50mm
 
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#34
Vunce said:
Hi Manniraj,

At first, I was running it at 80mA bias. There was a bit of an edge to the music. I increased bias by 20mA at a time and gave a listen. The sound got better with each step, smoother and better soundstage. I’m currently at 140mA, and heat is a non factor. 38°C was the highest heatsink temperature I’ve recorded so far.
Each heat sink measures: 210mm x 150mm x 50mm
Click to expand...

I hope when you say 140mA its referring to setting the bias at 140mV on the DMM side on the bias resistor right?

Thanks
 
#39
You seem to power the SSR from the amp board itself. Taking the + from near the resistor close to the positive power pin and the ground from the psu ground. Not visible from the dark pictures properly, can you please post some well lit pics and also let us know how did you power the SSR boards.

thanks
 
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