JLM 60Watt Power AMP Kit

Support for JLM Audio Kits

Moderator: Joe Malone

kevanatkins
Posts: 4
Joined: Fri Aug 25, 2017 6:14 pm

Re: JLM 60Watt Power AMP Kit

Postby kevanatkins » Tue Aug 29, 2017 7:54 pm

kevanatkins wrote:
Joe Malone wrote:
kevanatkins wrote:Yikes. I didn't get a notification about your reply. Anyway...

I haven't made much headway since. There's no link on the mute terminal. I've attached some photos.


You must fit the link between mute and -V to turn the amp ON. Without the link you will be in mute so will never get anything out of the amp.

Also for full gain NO resistor should be fitted to the volume terminals. Shorting the vol +/- turns the volume right down.


Fitted the link and removed the resistor. Still nothing.


Oops. Nevermind. My fumbling about putting the link in and taking out the resistor loosened the power connection. PEBCAC! Everything works now.

Thanks Joe!

User avatar
Joe Malone
Site Admin
Posts: 1572
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: JLM 60Watt Power AMP Kit

Postby Joe Malone » Tue Aug 29, 2017 8:01 pm

kevanatkins wrote:
kevanatkins wrote:
Joe Malone wrote:
You must fit the link between mute and -V to turn the amp ON. Without the link you will be in mute so will never get anything out of the amp.

Also for full gain NO resistor should be fitted to the volume terminals. Shorting the vol +/- turns the volume right down.


Fitted the link and removed the resistor. Still nothing.


Oops. Nevermind. My fumbling about putting the link in and taking out the resistor loosened the power connection. PEBCAC! Everything works now.

Thanks Joe!


Cool great to hear :-)
Joe :-)
JLM Audio
Capturing Audio without Injury

rtchau
Posts: 7
Joined: Thu Nov 03, 2016 12:22 pm

Re: JLM 60Watt Power AMP Kit

Postby rtchau » Thu Sep 07, 2017 10:14 am

Joe Malone wrote:
rtchau wrote:
Joe Malone wrote:
HI Richard
If the volume pot is turned fully down does the amp motorboat?


Hi Joe,

No - it only seems to go bananas after the volume pot is turned up past 50%, prior to that it starts to hum after 10-20%, and nothing at 0%.


OK what value is the volume pot? If 10k log connect a 4.7k resistor between the center wiper and 0v and retest to see if pot can get to 100% with only hum.


Hi Joe,

Sorry for the huge delay - we've moved house and I've changed jobs, so it's been busy times.

I did what you suggested and connected a 4.7k resistor between the centre wiper and 0v - however for simplicity of testing, I connected it directly to the terminals on the PCB on 0v and where the centre wiper joins the PCB (+in).

The motorboating is gone, but replaced with a hum that seems to change from low to high pass depending on volume (higher freq passing at low volume, lower frequency passing at high volume) - it seems I've created a sort of Franken-EQ shaper with the 10k pot :P

Cheers,

Richard

rtchau
Posts: 7
Joined: Thu Nov 03, 2016 12:22 pm

Re: JLM 60Watt Power AMP Kit

Postby rtchau » Thu Sep 07, 2017 12:23 pm

One other thing I've noticed is trouble with clearance between the capacitors on either side of the LM3886 and the heatsink that it's bolted to... is there a trick to mounting the LM3886 on the board that I missed, so that it has better clearance and the capacitors aren't making contact with the heatsink? I saw another build on this thread where the plastic on one of those caps had worn through.

frazzman
Posts: 8
Joined: Wed Jan 25, 2017 1:01 pm

Re: JLM 60Watt Power AMP Kit

Postby frazzman » Mon Jul 09, 2018 4:46 pm

Hi Joe,

I have 2 of these power amps running happily in bridged mode using a 2x18 160VA toroid.

I’d now like to use this power amp to drive 2 passive speakers.

So my question is, are there any issues with “converting” this to dual mono, but leaving the toroid as is (2x18)?

As I understand it, a 2x25 is what your spec calls for when running 2 independent channels / unbridged?

Cheers

User avatar
Joe Malone
Site Admin
Posts: 1572
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: JLM 60Watt Power AMP Kit

Postby Joe Malone » Tue Jul 10, 2018 10:30 am

frazzman wrote:Hi Joe,

I have 2 of these power amps running happily in bridged mode using a 2x18 160VA toroid.

I’d now like to use this power amp to drive 2 passive speakers.

So my question is, are there any issues with “converting” this to dual mono, but leaving the toroid as is (2x18)?

As I understand it, a 2x25 is what your spec calls for when running 2 independent channels / unbridged?

Cheers


Using the 2 x 18vac into 8ohm speakers will just limit the power to some like 40w.
If using 4ohm speaker you will still get the 68w with the 2 x 18vac transformer.
Joe :-)

JLM Audio

Capturing Audio without Injury

Return to “JLM Audio Kits”

Who is online

Users browsing this forum: No registered users and 3 guests