I found a giant heatsink. ISO Simple <2W class A projects?

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#21
#24
Anyone have experience with the JLH 1969 mini boards?

This one I’m looking at appears to have slightly better parts:

US $2.79 | Mini 1969 TIP41C Mono Channel DC 12V High Power Digital Audio Amplifier Assemble Board 40W
https://a.aliexpress.com/_mPaCO5k

Im trying to figure out how to determine the amount of gain with this type of amp. My preamp can do 12Vrms so I’d like to configure a tiny amp like the JLH mini to work with minimal gain- since I only need ~2W to 4ohm. This would mean less overall power, less heat too?
 
#27
OldDIY said:
Class A (HOOD1969) generates a lot of heat. With an output power of 2W, a constant consumption of more than 10W. At 12V, the current consumption will be about 0.8-0.9A.
Input voltage 0.2V.
Click to expand...
The lowest I can set the output from the preamp is 0.775Vrms, that seems too high still. Also are there special considerations for a 4ohm load? I can't find much discussion around that.

I'm ok with moving the heat, I have plenty of experience in that area.

Might be time to punt on the class-A until I learn a lot more EE. 🙁
 
#29
ericwestpheling said:
The lowest I can set the output from the preamp is 0.775Vrms, that seems too high still. Also are there special considerations for a 4ohm load? I can't find much discussion around that.

I'm ok with moving the heat, I have plenty of experience in that area.

Might be time to punt on the class-A until I learn a lot more EE. 🙁
Click to expand...
If you have volume pot in your preamp, the lowest output is 0 volts. If you do not have volume pot on pre, install it, its very useful thing.
 
#30
adason said:
If you have volume pot in your preamp, the lowest output is 0 volts. If you do not have volume pot on pre, install it, its very useful thing.
Click to expand...
ok so the "preamp" i'm referring to is my DSP box, which can scale the maximum voltage applied to the analog output. It can do 0.0218V, 0.775V, 1.54V, 3.08V, 6.15V, 12.2V.

My ES100 Bluetooth receiver outputs to the DSP at line-level, and can be attenuated down to whatever signal level wanted. I've been doing my volume control by trimming the output there (they have a great remote control app).

I guess I could attenuate the output from the DSP box, just always seemed like something I probably avoid.
 
#31
Do some Forum searches (and also use your Google Advanced Search kungfu, filling in Google's box "site or domain" with diyaudio.com) for the acronym FAOW.

Nelson Pass showed an amplifier which has First And Only Watt , and other contributors offered tweaks, improvements, and alternatives.
 
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#32
ericwestpheling said:
output from the preamp is 0.775Vrms
Click to expand...
The signal level at the amplifier input can be easily lowered using a resistive divider (two resistors).
You can change the feedback resistors. This will change the gain and reduce distortion. But stability issues may arise. Use TIP, not 5198.
An interesting option is to send a signal through a resistor to the emitter of the first transistor.
 

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#33
ericwestpheling said:
Anyone have experience with the JLH 1969 mini boards?

This one I’m looking at appears to have slightly better parts:

US $2.79 | Mini 1969 TIP41C Mono Channel DC 12V High Power Digital Audio Amplifier Assemble Board 40W
https://a.aliexpress.com/_mPaCO5k

Im trying to figure out how to determine the amount of gain with this type of amp. My preamp can do 12Vrms so I’d like to configure a tiny amp like the JLH mini to work with minimal gain- since I only need ~2W to 4ohm. This would mean less overall power, less heat too?
Click to expand...
I'm finding those to be really useful and versatile little amps. I'm getting superb results (-98dB THD) from a couple of them set up for 2.7X gain and tuned to drive low-impedance headphones with just a 12VDC regulated supply. Most of the parts get tossed (only the output transistors and a few of the resistors remain), but the layout is pretty good (only one trace mod required) and they're cheap as chips.

PS - I'm using this version. https://www.aliexpress.com/item/2251832849809698.html
 
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#34
jbau said:
I'm finding those to be really useful and versatile little amps. I'm getting superb results (-98dB THD) from a couple of them set up for 2.7X gain and tuned to drive low-impedance headphones with just a 12VDC regulated supply. Most of the parts get tossed (only the output transistors and a few of the resistors remain), but the layout is pretty good (only one trace mod required) and they're cheap as chips.

PS - I'm using this version. https://www.aliexpress.com/item/2251832849809698.html
Click to expand...
thats good to know. thanks. the versions like your link are significantly cheaper than the one I was looking at, especially if they'll need some rework. Not loving the idea of reworking 24 boards though.

I have my PAM8406 class AB board almost done. Trying to go surface mount except for the input caps. Its taking a while to put a good BOM together using EasyEDA/JLCPCB parts catalog- so they can do the assembly, just a frustrating interface with EasyEDA.

After sleeping on it for a few nights I'm thinking it makes most sense to use PAM8406 x 12 for the array amp and then build my understanding of discrete circuits up to where I can actually understand making a good class-A.

Also the idea of managing a 30W max draw for the entire array is much more palatable right now. Going to waste some power going from 24V to 5V but it will be super super clean by then!
 
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