JLM 60Watt Power AMP Kit

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Mattsoniclab
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Re: JLM 60Watt Power AMP Kit

Post by Mattsoniclab »

Joe Malone wrote:
Thu Jul 16, 2020 4:15 pm
Mattsoniclab wrote:
Thu Jul 16, 2020 4:09 pm
Hi.
Just curious if there is a way to incorporate a mono sum switch when using two amps, not in bridge mode?

I'm building a stereo amp to run a pair of Grover Notting CR1 speakers in my studio, and it would be great to quickly flick a switch to check it in mono. thanks!
Matt
HI Matt
Yes if you link Vol+ & Vol- with 2 wires between the 2 amps it will make them mono.
OK, awesome thank you!
I appreciate your help ;)

hsy
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Joined: Thu Jan 25, 2024 5:41 pm

Re: JLM 60Watt Power AMP Kit

Post by hsy »

I'm not sure if resurrecting this old thread is the best place to ask this, but:

Has anyone tried running AMP kits from a switching power supply instead of a transformer.

For example this: https://www.aliexpress.com/item/1005005911546916.html

I'm aware that there could be issues , specifically that some SMPS don't like driving large capacitances, and that they won't deliver surge power like a transformer. OTOH that PSU is small, light, and has enough power for several AMP kits.

50hz noise should be minimal to nonexistent - but ultrasonic switching noise might be an issue (?)

does anyone have any practical experience doing this?

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Joe Malone
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Re: JLM 60Watt Power AMP Kit

Post by Joe Malone »

hsy wrote:
Fri Jan 26, 2024 10:38 pm
I'm not sure if resurrecting this old thread is the best place to ask this, but:

Has anyone tried running AMP kits from a switching power supply instead of a transformer.

For example this: https://www.aliexpress.com/item/1005005911546916.html

I'm aware that there could be issues , specifically that some SMPS don't like driving large capacitances, and that they won't deliver surge power like a transformer. OTOH that PSU is small, light, and has enough power for several AMP kits.

50hz noise should be minimal to nonexistent - but ultrasonic switching noise might be an issue (?)

does anyone have any practical experience doing this?
Each power supply type is different so you have to try them to see if there are any noise issues and usually need more Amps SMPS than you will use to handle transients or large-cap bank with soft start circuit so the power supply can charge up the cap bank and then let the cap bank handle the transients

I have run 2 x 60w amp kit from 2 x 100W 24v cage SMPS. Turned trimpots up to +/-27.5v (max) Wired as +27.5v - 0v - 27.5v.

Also I have run 12pakamp kit from 2 x 500w SMPS

I also have a 50w amp pcb 50mm x 50mm & 2 x 70w or 1 x 140w amp + DSP pcb 100mm x 100mm that are made to run on single 48v smps directly.
See below (not currently on the JLM Audio webshop) The AMP ICs are clamped under the pcb to the heatsink.
AMP 48v.png
AMP 48v HP.png
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Joe :-)
JLM Audio
Capturing Audio without Injury

hsy
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Joined: Thu Jan 25, 2024 5:41 pm

Re: JLM 60Watt Power AMP Kit

Post by hsy »

Thanks!

That sounds like it should work. I want to run 2 or 3 AMP kits from that 300W PSU.

Any suggestions how to implement a soft start or delayed start if that proves necessary?

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Joe Malone
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Re: JLM 60Watt Power AMP Kit

Post by Joe Malone »

hsy wrote:
Sat Jan 27, 2024 8:25 am
Thanks!

That sounds like it should work. I want to run 2 or 3 AMP kits from that 300W PSU.

Any suggestions how to implement a soft start or delayed start if that proves necessary?
Start with no soft start and see if the SMPS can start the amp without going into hiccup mode.

Soft start is easy but you have to work out the values that work. Basically a resistor in series with each power rail. Like 1 to 10ohm 5w. The relay coil is best at 5v or 12v and run a zener in series with the coil and wire across the amp cap bank. So if 35v unreg dc across the amp cap bank then a 5v relay with 30v 1w zener so the relay will not operate until about 33v shorting out the soft start resistors.
Joe :-)
JLM Audio
Capturing Audio without Injury

Rawsky
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Joined: Tue Jan 23, 2024 10:33 am

Re: JLM 60Watt Power AMP Kit

Post by Rawsky »

Hi Joe
I have built the amp I got from your shop last Monday morning and it is going very well. Thanks for all your help. I believe there is a 'mod' I can do "With no volume control fitted the +/-vol pins can be used to do EQ like low end extension by adding a resistor and capacitor" What resistor and capacitor (in series) would I use to do this. The amp is used as power amp for my ADA MP1 guitar preamp (Schematics at https://adadepot.com/index.php?topic=148.0). Using 2 8 ohm speakers in series and playing jazz standards on my hollowbody. I am trying to decrease treble. Cheers

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Joe Malone
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Re: JLM 60Watt Power AMP Kit

Post by Joe Malone »

Rawsky wrote:
Mon Jan 29, 2024 2:23 pm
Hi Joe
I have built the amp I got from your shop last Monday morning and it is going very well. Thanks for all your help. I believe there is a 'mod' I can do "With no volume control fitted the +/-vol pins can be used to do EQ like low end extension by adding a resistor and capacitor" What resistor and capacitor (in series) would I use to do this. The amp is used as power amp for my ADA MP1 guitar preamp (Schematics at https://adadepot.com/index.php?topic=148.0). Using 2 8 ohm speakers in series and playing jazz standards on my hollowbody. I am trying to decrease treble. Cheers
Adding a small cap across the unused vol+/- will atten the high frequency. Use an online RC filter calc with 20k for the resistor value you can see what cap size will attenuate at what frequency.

So cap value of 1nF would be 8k low pass filter. And by adding in a series resistor you can make the filter only attenuate above 8k a certain amount of dB. Normal guitar amp speakers peak at about 5k and then roll off sharply. So if the speaker peak is too harsh then. Maybe 2n2 cap to roll at 4k and add series resistor if it is then you dull or try a smaller cap value.
Joe :-)
JLM Audio
Capturing Audio without Injury

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