Hello, I am looking to build a small bookshelf setup for my room. I'm on a tight budget since I am a college student. So I was looking to build an amp for around $150. So I have two questions which amp is better the Amp Camp or the JLH 1969. Also what chassis would you recommend? I also want to use a proper power supply, not a laptop one.
Find out where to get the parts for both and how much they cost. Hobby electronics shops should have all the parts for the JLH. The semiconductor lineup won't cost much as the types used have been in production for decades.
The bulk of your costs would be for the chassis, heat sinks, and power supply components.
The 1st question i have is what is the outpu timpedance of the JHL?
From the JHL article: Output impedance: 0.03ohm (at 1kHz).
This is significantly different than the ACA which has a highish output impedance which means that ACA is much more sensitive to the effects of loudspeaker impedance on end performance.
The JHL will fall into the 99% and the ACAs fall as shown. Anything in the fringe really requires careful consideration of loudspeakers.
So these amps may both be about 10w, and Class A, but beyond that…
So, what speakers do you plan on?
More to come...
dave
From the JHL article: Output impedance: 0.03ohm (at 1kHz).
This is significantly different than the ACA which has a highish output impedance which means that ACA is much more sensitive to the effects of loudspeaker impedance on end performance.
The JHL will fall into the 99% and the ACAs fall as shown. Anything in the fringe really requires careful consideration of loudspeakers.
So these amps may both be about 10w, and Class A, but beyond that…
So, what speakers do you plan on?
More to come...
dave
JLH recommended two heat sinks one per channel 12.5 cm H by 10 cm W with a pair of output transistors mounted on each. The ones I used for my build over 40 years ago were 15 cm H by 10 cm wide.
I had no output transistor failures however I had some problems with the quality of the transformers I bought. One of these was a nominal 150 VA for 10 W per channel into 8R. Today for reliability and cool running of the transformer I would use a quality toroid of at least that rating.
The output stage dissipation was quoted as 17 W per transistor = 34 W per heat sink. I would aim at selecting ones with a thermal rating (degrees C or K per Watt) with a view to limit the heat sink temperature to 50 degrees C.
With an indoor temperature that could rise to say 35C, a limitation of 50C on the heat sinks means a substantial pair - better than about 0.5K/Watt if possible. Unless they are also augmented by attaching to a thick aluminium chassis or your air conditioning is up to the task of holding the air temperature to a nominal 22C, fans are fitted etc, you would need something with deep fins, about 20cm x 7.5cm x 4.5cm to cope with warmer climates than JLH designed for.
A JLH can be built from common/industrial parts. Then there's always the option of running it first from a laptop supply and saving up/collecting the proper power-supply parts in the meantime.
JLH can sound great with laptop supplies!
Remember proper capacitance is needed on the output cap, usually the ones with the kits are too small for good bass. It's likely a benefit with a big capacitance on the supply side too. If you have a sound card setup to measure distortion spectrum, you can also do some tuning on current (and more) to get low distortion.
Use it with 8ohm speakers for best distortion performance, as with most amplifiers.
Remember proper capacitance is needed on the output cap, usually the ones with the kits are too small for good bass. It's likely a benefit with a big capacitance on the supply side too. If you have a sound card setup to measure distortion spectrum, you can also do some tuning on current (and more) to get low distortion.
Use it with 8ohm speakers for best distortion performance, as with most amplifiers.
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