120 Watt Power Amp build thread.

Support for JLM Audio Kits

Moderator: Joe Malone

User avatar
Mick@ITC
Posts: 32
Joined: Fri Aug 24, 2007 1:20 pm
Location: Melbourne
Contact:

120 Watt Power Amp build thread.

Post by Mick@ITC »

Hi all

Following my earlier threads I have now started the 120 Watt power amp build. The kit arrived from Joe last night and as I eagerly shreaded the packing material :) I thought I would start the process of logging this adventure on this forum for the benefit of others who might venture down this track.
So the contents were...
- One 2 unit rack case...Ikea style :D
- two bags containing the two power amp kits;
- One Transformer; and
- One recitifier.

Basically the layout of the case is drawn but I don't know how to put it up on this forum :oops: Anyone help me there?

I'll take photos as I go and hopefully be able to share them with you.

Regards

Mick

User avatar
Mick@ITC
Posts: 32
Joined: Fri Aug 24, 2007 1:20 pm
Location: Melbourne
Contact:

Post by Mick@ITC »

So here we go with the questions.... :o :P

First of all, the LEDs. They are connected to the appropriate trem but I think from what I have read that they can be put in backwards. So just want to check my logic with you guys. The Anode (longer leg) is connected to the LED term (third from left). The Cathode (shorter, figured that out all on my own!! :P ) is connected to the 0V term (forth along. Can someone that has put in an LED and it didn't blow up :D confirm this.

Second one is the MUTE switch. Does a momentry switch (see part SP0700 in JAYCAR) suit this application. Also, I'm putting it on the second amp ONLY. Is this appropriate????? :?

Third one is something to give back to the group is a drawing of the bridging wiring. Once I figure how to get JPEGS up here I'll post that. This was drawn folloing instructions from Joe, so its likely to work!! :P Ahhh but did I draw it right??? :P

Forth one is ...does anyone have a photo of the mounting of the heatsink in the Power Amp application? Where does it go?

Lastly, mounting the doughnut Transformer, do the two washers ...one metal, one plastic/rubber go on the top of the transformer with nothing between the bottom and the case floor???

Looking forward to hearing from you.

Regards
Mick :D :D :D

chrisp
Posts: 184
Joined: Sun Mar 04, 2007 11:46 am
Location: Sydney, Australia

Post by chrisp »

Hi Mick

(1) LED - you've got it right.

(2) No, not a momentary switch as that will only mute for so long as you hold it down. You want a simple SPST toggle switch.

(3) + (4) + (5) I've sent you a PM. Call me and I'll talk you through what you need to do.
Chris P
---------------------------------------------------------
I do lots of things. I believe eclectic skills are best.

User avatar
Mick@ITC
Posts: 32
Joined: Fri Aug 24, 2007 1:20 pm
Location: Melbourne
Contact:

Help with 2 x 50v Bi Polar caps

Post by Mick@ITC »

Hi all

I need some help with the installation of the 2 x 50v Bi polar caps (the black ones in the kit.

All the other caps have the required polarity marked on the PCB. This one does not and I'm guessing...!!! :oops: Not real clever thing to do with a PCB!!! :lol:

So can someone enlighten me regards the polarity of these??? :?:

Build is going along nicely, have a log of pictures in stages. My 17 year old son actually SMILED...I think :wink:

Mick

PS Thanks CHRISP for the chat and the directions....

User avatar
Joe Malone
Site Admin
Posts: 2070
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Post by Joe Malone »

HI Mick
Bi polar or Non polar electro caps can go in either way around since they have no polarity.

The Mute switch needs to be closed for the amp to NOT be muted. Also you can wire both mute wires together and switch them to one -V.

Thanks Chris for helping Mick 8) Did you ever get to try out the RC network in place of the LCR in your powered speaker design?
Joe :-)
JLM Audio
Capturing Audio without Injury

chrisp
Posts: 184
Joined: Sun Mar 04, 2007 11:46 am
Location: Sydney, Australia

Post by chrisp »

Rick wrote: Did you ever get to try out the RC network in place of the LCR in your powered speaker design?
No, or at least, not yet. I had bought and installed the LCR components before your suggestion, and as the whole thing worked like a dream I have been reluctant to open them up again. If I do open them up for whatever reason in the future, I plan on doing the RC thing across the vol terminals, but right now I'm still getting a surge of delight with every new song I listen to.

Plus, I'm spending my time lately drawing up a JLM inspired 12 channel, 4 bus mixer: channels being 99V BADs plus a 1073 style EQ section (HPF, low, presence, high shelf), stereo busses being class A/B hybrid BADs with a PEQ1A type EQ (something like the EQ 500 card) and a VCA compressor section. Balanced send/return and transformer outs on each channel and bus, plus a firewire DAW interface to and from each channel.

Once I get it further developed I might post a few drawings, but that will be another thread. I'll stop highjacking Mick's guitar amp build story now.
Chris P
---------------------------------------------------------
I do lots of things. I believe eclectic skills are best.

User avatar
Mick@ITC
Posts: 32
Joined: Fri Aug 24, 2007 1:20 pm
Location: Melbourne
Contact:

Post by Mick@ITC »

Thanks guys...nearly done got lots of photos of progress.

Regards
Mick

chrisp
Posts: 184
Joined: Sun Mar 04, 2007 11:46 am
Location: Sydney, Australia

Post by chrisp »

Its funny, Mick, that first time you actually switch your DIY on at the mains and wait for something to go bang, pop or start smoking.

LEDs make a nice sizzling sound as they burn out.

May your project go better than some of mine!
Chris P
---------------------------------------------------------
I do lots of things. I believe eclectic skills are best.

User avatar
Mick@ITC
Posts: 32
Joined: Fri Aug 24, 2007 1:20 pm
Location: Melbourne
Contact:

Post by Mick@ITC »

chrisp wrote:Its funny, Mick, that first time you actually switch your DIY on at the mains and wait for something to go bang, pop or start smoking.

LEDs make a nice sizzling sound as they burn out.

May your project go better than some of mine!

:P I would type a smart-assc reply but the tips of my fingers are burned off right now :D :D

Me

User avatar
Mick@ITC
Posts: 32
Joined: Fri Aug 24, 2007 1:20 pm
Location: Melbourne
Contact:

Post by Mick@ITC »

Hi all

Sorry for not replying before this but life is somewhat hectic. Well the amp is complete and running really well. We got a 4X10 bass box from Lorenz and running the Presonus Eureka as the pre-amp. All sounds beaut.
Had a few teething problems which were simple wiring errors that Joe fixed in an email, as usual the JLM service shines through. Sean's mates dont believe him that we built it as it is all packaged up nicely in a 3U rack case.
I wrote a log/manual thing as I went and it is all but finished. I am not able to attach it here so if anyone wants a copy just email me at Mick.Connolly@BlueScopeSteel.com and I will send it.

Finally a big thanks to Joe for the combination of a fantastic kit and fantastic service and also to Chris(p)and Barney for the help and encouragement.

So now its saving time for a couple of BA pres!!!

Regards
Mick

PS. Joe, how many of the poweramp cards can be bridged together? 2 = 120Watts, can more be bridged to give bigger wattage?

chrisp
Posts: 184
Joined: Sun Mar 04, 2007 11:46 am
Location: Sydney, Australia

Post by chrisp »

Mick@ITC wrote:Well the amp is complete and running really well .... Sean's mates dont believe him that we built it as it is all packaged up nicely in a 3U rack case.
And that's what DIY is about - that point of joy when you have something functional that you've actually sweated over yourself.

Well done, Mick & Sean.
Chris P
---------------------------------------------------------
I do lots of things. I believe eclectic skills are best.

Mihaly
Posts: 2
Joined: Thu Nov 01, 2007 2:52 pm
Location: Melbourne

Re: 120 Watt Power Amp build thread.

Post by Mihaly »

Just completed a 120W stereo amp (4kits). It sounds great.

Thanks to Mick for sending his manual for the build, it was very useful. and of course to Joe for the excellent support and a superb kit. Very impressed with how well thought out it was.


A few learnings:
Joe recommended a 150mm heatsink for each pair. However, the amps are a little wider than the heatsink. As I was interfacing to some PA speakers, I used speakon connectors. With these, XLR connections and power connection, there is only just room for 300mm of heatsink. It meant I had to angle the amps in the box. Better solution: put the XLR inputs on the front (for this application)

The metalwork took way longer than building 4 amp kits. (Good boxes from Altronics, 2U is big enough)

Read all the information on the website - I overlooked the need to connect the mute to 0V. Hence on power up, although there was no smoke (very pleased with that), there was no sound either (very worried at that).

The 300VA transformer has different wiring colours to the 160VA and its not easy to get information. If anyone needs it, I have it (but do not remember it). In the end I worked it out using a voltmeter and Joe confirmed the info. The mains leads are obvious (orange).

Can buy complete XLR cables for less than one of the connectors at JAYCAR. 2m cable ~ $10, one XLR connector the same. (2m is enough for a patch cable from graphic EQ to amp...).

Next project a BA2 - once I work out which configuration to build....

Cheers,
Mihaly.

User avatar
Mick@ITC
Posts: 32
Joined: Fri Aug 24, 2007 1:20 pm
Location: Melbourne
Contact:

Re: 120 Watt Power Amp build thread.

Post by Mick@ITC »

Well done...its a great feeling... :mrgreen:

chrisp
Posts: 184
Joined: Sun Mar 04, 2007 11:46 am
Location: Sydney, Australia

Re: 120 Watt Power Amp build thread.

Post by chrisp »

I'm about to embark on a rebuild of my [insert low end name here] 30W guitar amp combo, and have tagged a 60W 10" Celestion as the driver so I can use the JLM kit.

Big question to those who have gone this route before me: did you bother applying a low pass filter to the signal? Guitar drivers generally don't cope well with much over about 5kHz, so I was planning to add in a simple RC network (300 ohms, 100n) prior to the volume control, or possibly at the signal input. Any thoughts?
Chris P
---------------------------------------------------------
I do lots of things. I believe eclectic skills are best.

User avatar
Mick@ITC
Posts: 32
Joined: Fri Aug 24, 2007 1:20 pm
Location: Melbourne
Contact:

Re: 120 Watt Power Amp build thread.

Post by Mick@ITC »

chrisp wrote:I'm about to embark on a rebuild of my [insert low end name here] 30W guitar amp combo, and have tagged a 60W 10" Celestion as the driver so I can use the JLM kit.

Big question to those who have gone this route before me: did you bother applying a low pass filter to the signal? Guitar drivers generally don't cope well with much over about 5kHz, so I was planning to add in a simple RC network (300 ohms, 100n) prior to the volume control, or possibly at the signal input. Any thoughts?
Hi Chris.

No I didn't put in any "tone" control. I'm not sure I would bother with it for the guitar amp. Guitar amplification seems to be a bit of a strange "art" and I know I have got it wrong a few times trying to play with the amp/speaker combo. My suggestion would be to go clean (at the start) see what the combination of the amp and speaker sounds like then tinker after you get a feel for it.

Ironically I am in the middle of putting a rack together with a few different pres (an old tube bass pre, a clean quality pre (probably a BA), and a Marshall SS rack pre. I'll then run these through the 120 Watt into a Lorenz 2x12 Cab I have. Could sound great, could sound ....well you know the word... :wink:

Interested to hear others comments on this...


Oh and if you have a suggestion for a JLM kit to use with a Strat...let me know.


Mick

Post Reply