3-4 years ago I bought this 35 watt amp kit.
https://store.qkits.com/electronic-kits/audio-kits/35w-mono-power-amplifier-kit.html
The circuit shown is stock except the filter caps.
I wasn't satisfied with it just barely doing 35 watts and the heatsinks getting real hot, so with the help of a solid state amp builders group on Facebook I modded it to produce 93 watts into 4 ohms.
I used one of the Legacy car audio amps that cram a maybe 30WPC or less amp into a thick rather large aluminum chassis with VU meters and a fan that due to the chassis design didn't blow air out of the chassis.
One amp channel installed.
Part of heatsink cut so that the fan would actually blow air out of the chassis.
Here's the modified amplifier.
The filter caps are 20,000uF not 40,000uF. I know there's some things that aren't exactly right.
The interesting thing about thick film resistors is when they get overloaded they simply go open circuit which is what happened to the amp when I was testing it at full output. Speaker leads briefly shorted and all four thick film 50 watt emitter resistors went open circuit.
Question is do I keep this amp and build a second channel or do I go with this 100 watt kit amp?
https://store.qkits.com/electronic-kits/audio-kits/100-watt-mono-power-amplifier-kit.html
Schematic
http://www.funnykit.co.kr/bemarket/shin/menual/fk666.pdf
Two issues.
1. The amp requires +/- 50V versus the +/- 35V the current amp uses.
2. Only one pair of output transistors are used.
https://store.qkits.com/electronic-kits/audio-kits/35w-mono-power-amplifier-kit.html
The circuit shown is stock except the filter caps.
I wasn't satisfied with it just barely doing 35 watts and the heatsinks getting real hot, so with the help of a solid state amp builders group on Facebook I modded it to produce 93 watts into 4 ohms.
I used one of the Legacy car audio amps that cram a maybe 30WPC or less amp into a thick rather large aluminum chassis with VU meters and a fan that due to the chassis design didn't blow air out of the chassis.
One amp channel installed.
Part of heatsink cut so that the fan would actually blow air out of the chassis.
Here's the modified amplifier.
The filter caps are 20,000uF not 40,000uF. I know there's some things that aren't exactly right.
The interesting thing about thick film resistors is when they get overloaded they simply go open circuit which is what happened to the amp when I was testing it at full output. Speaker leads briefly shorted and all four thick film 50 watt emitter resistors went open circuit.
Question is do I keep this amp and build a second channel or do I go with this 100 watt kit amp?
https://store.qkits.com/electronic-kits/audio-kits/100-watt-mono-power-amplifier-kit.html
Schematic
http://www.funnykit.co.kr/bemarket/shin/menual/fk666.pdf
Two issues.
1. The amp requires +/- 50V versus the +/- 35V the current amp uses.
2. Only one pair of output transistors are used.
Attachments
Indeed they are. The 35W heatsinks were a joke as well.
I think the TIP41 and TIP42 on the 35 watt amp were also a joke.
The nice thing about the 100 watt kit is it looks like the transistor that sets the bias is attached to the heatsink which provides thermal compensation.
With the 35 watt kit, that transistor was mounted in free air and made bias rather unstable. When I modded it to 93 watts, the transistor got mounted to the heatsink.
I think the TIP41 and TIP42 on the 35 watt amp were also a joke.
The nice thing about the 100 watt kit is it looks like the transistor that sets the bias is attached to the heatsink which provides thermal compensation.
With the 35 watt kit, that transistor was mounted in free air and made bias rather unstable. When I modded it to 93 watts, the transistor got mounted to the heatsink.
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There should be better kits around, with larger heat sinks, and so they'd be more expensive.
If you can scrounge up some decent heat sinks, there are good, reasonable price amp boards in the store here.
https://diyaudiostore.com/collections/power-amplifier
If you can scrounge up some decent heat sinks, there are good, reasonable price amp boards in the store here.
https://diyaudiostore.com/collections/power-amplifier
That old car amp chassis won't work so well, you need fins.
Class D amps don't need big heat sinks, have you considered one of those?
Working boards/amps from China are inexpensive. Typical example:
https://www.amazon.com/BT20A-Bluetooth-Audio-Amplifier-Integrated/dp/B07BQC7GNL/ref=sr_1_5
Class D amps don't need big heat sinks, have you considered one of those?
Working boards/amps from China are inexpensive. Typical example:
https://www.amazon.com/BT20A-Bluetooth-Audio-Amplifier-Integrated/dp/B07BQC7GNL/ref=sr_1_5
Scaling up from 35 watts can work but asking for 100 watts or more really needs a better more substantial design.
The amp itself I would run it at maximum power into 4 ohms at 400Hz for 6-7 hours a day while at work. I did that maybe 10 days.
Amp seemed to work fine.
Now if I kept the amp design that makes 92 watts into 4 ohms, how do I modify the current limit circuit of the 35 watt amp to allow the amp to do 92 watts into 4 ohms?
Amp seemed to work fine.
Now if I kept the amp design that makes 92 watts into 4 ohms, how do I modify the current limit circuit of the 35 watt amp to allow the amp to do 92 watts into 4 ohms?
I don't actually need another amplifier at the moment.
This is moreso just a project that I want to finish.
This is moreso just a project that I want to finish.
Concerning the amp, I may fix the one channel then get some proper audio test equipment so that I can measure things like THD, frequency response and whatever else should be measured on an audio amp.
What I may do is ditch the amp kit completely and build a honey-badger.
https://diyaudiostore.com/collections/power-amplifier/products/honey-badger
Not sure if it will fit in the existing chassis or if I'll need a new chassis.
https://diyaudiostore.com/collections/power-amplifier/products/honey-badger
Not sure if it will fit in the existing chassis or if I'll need a new chassis.