8PAKAMP & 12PAKAMP KIT BUILD THREAD

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cowneko
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Re: 8PAKAMP KIT BUILD THREAD

Postby cowneko » Tue May 29, 2018 8:59 pm

Thanks a lot Joe ;)

Well, to test if the amp clips, may I use a repeated 1000hz sine signal track on the dap or better on my cd player, and look at the output (with a 50w 8R res load) with a scope to see if the sine begins to turn to square at highest volume?

Also, no stability issues when bridged on 4ohm loads (woofers)?

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Re: 8PAKAMP KIT BUILD THREAD

Postby Joe Malone » Wed May 30, 2018 3:01 pm

cowneko wrote:Thanks a lot Joe ;)

Well, to test if the amp clips, may I use a repeated 1000hz sine signal track on the dap or better on my cd player, and look at the output (with a 50w 8R res load) with a scope to see if the sine begins to turn to square at highest volume?


1000Khz tone out of DAP and check output of amp swings at least +/-30P-P with scope (no load needed)

Also good time to check max output volts Peak to Peak from DAP without clipping volts P-P=?

Also, no stability issues when bridged on 4ohm loads (woofers)?

No but always check you have 0v measured between the +amp out and -amp out first.
Joe :-)
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nm4711
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Re: 8PAKAMP KIT BUILD THREAD

Postby nm4711 » Wed Sep 19, 2018 2:22 am

Hey there,

I just recieved my 12PAKAMP Kit (blue) and I am going to use it to power a pair of LXmini + Subs. The PCB looks pretty good. For the Sub (8Ohm) and the Bass (8Ohm) units I want to use 2 channels bridged for each driver and for the tweeters (4Ohm) one channel per driver. But I have some questions before I solder it all together:

1: Does the pots reduce the gain with every turn by a fixed value or not? If it is fixed: How many decibels are it? I am asking because I need the same gain for the seperate and the bridged units. So it would be nice to reduce the gain by 6dB on the bridged channels using the pots on the bridged ones.

2: What is the gain for a single channel used asymmetric. I am asking because I dont find some resistors mentioned in this thread earlier for the 8PAKAMP. So I am wondering if it is the same.

3: Two channels will be unused in my setup. Is this amp stable without load? Or is it better to use a 16Ohm? high power resistor as load while they are unused? Or is the amp stable when muted?
Edit: You already answered this in the post above me.

4: I want to mute the complete amp with a switch or something like this. Wich resistor is between the mute pin and the negative supply rail? I want to replace it with wires going to a seperate PCB.

5: How are the pins used on the 40pin header? I followed the lines on the PCB and got the answer by myself but it would be nice to be sure about it. ;)

Lots of questions, I know. :D Thank you and have a nice day!

Niklas

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Re: 8PAKAMP KIT BUILD THREAD

Postby Joe Malone » Wed Sep 19, 2018 8:15 am

nm4711 wrote:Hey there,

I just recieved my 12PAKAMP Kit (blue) and I am going to use it to power a pair of LXmini + Subs. The PCB looks pretty good. For the Sub (8Ohm) and the Bass (8Ohm) units I want to use 2 channels bridged for each driver and for the tweeters (4Ohm) one channel per driver. But I have some questions before I solder it all together:

1: Does the pots reduce the gain with every turn by a fixed value or not? If it is fixed: How many decibels are it? I am asking because I need the same gain for the seperate and the bridged units. So it would be nice to reduce the gain by 6dB on the bridged channels using the pots on the bridged ones.

2: What is the gain for a single channel used asymmetric. I am asking because I dont find some resistors mentioned in this thread earlier for the 8PAKAMP. So I am wondering if it is the same.

3: Two channels will be unused in my setup. Is this amp stable without load? Or is it better to use a 16Ohm? high power resistor as load while they are unused? Or is the amp stable when muted?
Edit: You already answered this in the post above me.

4: I want to mute the complete amp with a switch or something like this. Wich resistor is between the mute pin and the negative supply rail? I want to replace it with wires going to a seperate PCB.

5: How are the pins used on the 40pin header? I followed the lines on the PCB and got the answer by myself but it would be nice to be sure about it. ;)

Lots of questions, I know. :D Thank you and have a nice day!

Niklas


HI Niklas I will draw you up a custom overlay to match your setup above and post it here when I have it done. Best to not fit any parts as to do the remote mute switch the 1N4007 diodes will be left off the pcb and 10k end moved across which I will show on the custom overlay.
Joe :-)

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Re: 8PAKAMP KIT BUILD THREAD

Postby Joe Malone » Wed Sep 19, 2018 3:50 pm

nm4711 wrote:Hey there,

I just recieved my 12PAKAMP Kit (blue) and I am going to use it to power a pair of LXmini + Subs. The PCB looks pretty good. For the Sub (8Ohm) and the Bass (8Ohm) units I want to use 2 channels bridged for each driver and for the tweeters (4Ohm) one channel per driver. But I have some questions before I solder it all together:

1: Does the pots reduce the gain with every turn by a fixed value or not? If it is fixed: How many decibels are it? I am asking because I need the same gain for the seperate and the bridged units. So it would be nice to reduce the gain by 6dB on the bridged channels using the pots on the bridged ones.

2: What is the gain for a single channel used asymmetric. I am asking because I dont find some resistors mentioned in this thread earlier for the 8PAKAMP. So I am wondering if it is the same.

3: Two channels will be unused in my setup. Is this amp stable without load? Or is it better to use a 16Ohm? high power resistor as load while they are unused? Or is the amp stable when muted?
Edit: You already answered this in the post above me.

4: I want to mute the complete amp with a switch or something like this. Wich resistor is between the mute pin and the negative supply rail? I want to replace it with wires going to a seperate PCB.

5: How are the pins used on the 40pin header? I followed the lines on the PCB and got the answer by myself but it would be nice to be sure about it. ;)

Lots of questions, I know. :D Thank you and have a nice day!

Niklas


HI Niklas
See attachments. For level adjustment fit trimpots and leave them set to the middle (which is how they come new) until you have the amp running. When you have it running then turn up the tweeter trimpots only to get a rough balance between tweeter and woofer. Then if you can let me know at your loudest listening level were your volume pot is set to 50% etc. I can then calc the values to set the trimpots too so you will have best volume control use and do accurate 6dB boost to tweeters. You will then be able to set all trimpots with a ohmmeter and the amp turned off.

For this configuration best to use a 2 x 18vac transformer to make +/-25vdc rails for the amp to run on.

Let me know if you have any more questions as you build.

12PAKAMP BLUE MUTE REMOTE SWITCH MOD.png
12PAKAMP BLUE LXMINI.png
12PAKAMP BLUE INPUT.jpg
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Joe :-)

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nm4711
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Re: 8PAKAMP & 12PAKAMP KIT BUILD THREAD

Postby nm4711 » Wed Sep 19, 2018 10:14 pm

Hi Joe,

thanks a lot for the quick and detailed answer! In Germany we say something like: A picture tells more than a thousand words. :)
The muting is much easier than I thought. Cool!
I have already bought a 2x18V Trafo and the bridge rectifier, because it was mentioned earlier in this thread.

I will ask again if the speakers and amps are built for gain settings.
Good idea to use the ohmmeter for the trimpots. So I dont have to count the clicks. :D

Thanks a lot

Niklas

nm4711
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Re: 8PAKAMP & 12PAKAMP KIT BUILD THREAD

Postby nm4711 » Thu Sep 20, 2018 3:48 am

Hi,

just because I am curious: What is the use of the diodes and the two fan parts when fitted as intended?

Greetings

Niklas

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Re: 8PAKAMP & 12PAKAMP KIT BUILD THREAD

Postby Joe Malone » Thu Sep 20, 2018 10:09 am

nm4711 wrote:Hi,

just because I am curious: What is the use of the diodes and the two fan parts when fitted as intended?

Greetings

Niklas


HI Niklas
The diode fan option allows a fan to run slowly to help cooling and when the amps are working hard swinging lots of ac volts level it turns the fan up to full speed but drops back instantly when audio level drops so you never hear fan noise in quiet environments. In a normal home system with good heatsink the fan is not needed at all.
Joe :-)

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nm4711
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Re: 8PAKAMP & 12PAKAMP KIT BUILD THREAD

Postby nm4711 » Thu Sep 20, 2018 3:36 pm

Hi Joe,

wow, thats a cool feature. But I also dont think I need it. Even if I need to use some fans, I would probably let them run at low speed the whole time and it would make a bog difference.

Thanks for the great support

Niklas

nm4711
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Re: 8PAKAMP & 12PAKAMP KIT BUILD THREAD

Postby nm4711 » Thu Oct 11, 2018 1:36 am

Hi Joe,

the Amp is running. :D After having some stability issues with the tweeten channels the amp is running fine now. The problem occured when no Input was connected in my non balanced setup. But I found a solution in this thread. The problem was, that I’ve connected In- and GND to the RCA Gnd. I fixed it by only connecting In- to the RCA Gnd as suggested on page 4? of this thread.

After listening to some songs with the tweeter gain raised by around 6dB, I found that in most cases I put the volume to around -9dB on my miniDSP to listen at an enjoyable level. There is noise coming from the speakers, but the transformer is louder. I would like to have some headroom for quiet recordings.

So yeah, it would be nice if you could calculate the best settings for the pots as you proposed. :D

Thank you and have a nice day :)

Niklas

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Re: 8PAKAMP & 12PAKAMP KIT BUILD THREAD

Postby Joe Malone » Sun Oct 14, 2018 6:04 pm

nm4711 wrote:Hi Joe,

the Amp is running. :D After having some stability issues with the tweeten channels the amp is running fine now. The problem occured when no Input was connected in my non balanced setup. But I found a solution in this thread. The problem was, that I’ve connected In- and GND to the RCA Gnd. I fixed it by only connecting In- to the RCA Gnd as suggested on page 4? of this thread.

After listening to some songs with the tweeter gain raised by around 6dB, I found that in most cases I put the volume to around -9dB on my miniDSP to listen at an enjoyable level. There is noise coming from the speakers, but the transformer is louder. I would like to have some headroom for quiet recordings.

So yeah, it would be nice if you could calculate the best settings for the pots as you proposed. :D

Thank you and have a nice day :)

Niklas


HI Niklas

I will be back from AES New York around the 23rd October so I can work this out for you then. IN the mean time with the amp off measure the trimpot ohms between the outside legs of each pot and post here so I can work out the ideal setup.
Joe :-)

JLM Audio

Capturing Audio without Injury

nm4711
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Re: 8PAKAMP & 12PAKAMP KIT BUILD THREAD

Postby nm4711 » Mon Oct 22, 2018 4:27 am

Joe Malone wrote:
HI Niklas

I will be back from AES New York around the 23rd October so I can work this out for you then. IN the mean time with the amp off measure the trimpot ohms between the outside legs of each pot and post here so I can work out the ideal setup.


Hi Joe,

that would be nice, thank you! Yeah, I've seen on your website that you visit AES.

I measured the resistance of the different pots: Around 2.8 kOhms for the bridged amps and 1.5 kOhms for the non bridged ones.

Greetings
Niklas

DannyMayes
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Re: 8PAKAMP & 12PAKAMP KIT BUILD THREAD

Postby DannyMayes » Mon Mar 25, 2019 2:51 pm

Hi Joe,

I am driving an 8Pak with an Amp Head.

Below is a block digram of how I will configure it.

IMG_0952.jpg


(missed putting on the digram, the output from the amp head are both unbalanced)

Was hoping you might cast an eye over it and offer any feedback regarding how I have arranged the 10k pots as volume controls and do I need any other resistors in there to stop them interacting with each other?

Also, I currently only have 2 opamps in my Amp Head, is that enough to drive all this or will I need the other 2?

Any help much appreciated.

Kind regards,

Danny
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Re: 8PAKAMP & 12PAKAMP KIT BUILD THREAD

Postby Joe Malone » Mon Apr 01, 2019 2:27 pm

DannyMayes wrote:Hi Joe,

I am driving an 8Pak with an Amp Head.

Below is a block digram of how I will configure it.

IMG_0952.jpg

(missed putting on the digram, the output from the amp head are both unbalanced)

Was hoping you might cast an eye over it and offer any feedback regarding how I have arranged the 10k pots as volume controls and do I need any other resistors in there to stop them interacting with each other?

Also, I currently only have 2 opamps in my Amp Head, is that enough to drive all this or will I need the other 2?

Any help much appreciated.

Kind regards,

Danny


Yes 2 opamps is enough to drive all of this but are the volume pots wired as normal volume pots to 0v?
As the diagram doesn't make much sense to me the way it is drawn.
Joe :-)

JLM Audio

Capturing Audio without Injury

nm4711
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Re: 8PAKAMP & 12PAKAMP KIT BUILD THREAD

Postby nm4711 » Fri Apr 05, 2019 7:39 pm

Hey there,

I am really happy with my 12PAKAMP, powering a pair of LXmini+. The woofers and subs are powered by a pair of bridged amp channels each and the tweeters by a single channel each. It is powered by an 18 V transformer.
The amp is running quite a while now, but I finally put it into a nice case, so I can share some pictures. ;)

1.jpg


2.jpg


3.jpg


Greetings

Niklas
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