BA BA2 BA4 BAD Dual99v Build Thread

Support for JLM Audio Kits

Moderator: Joe Malone

ajsteel
Posts: 39
Joined: Tue May 07, 2013 11:40 am
Location: Melbourne
Contact:

Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby ajsteel » Tue Sep 24, 2013 8:30 pm

Hi Joe, underside of the PCM attached. When I say insert, I mean when I place the 2520 into the opamp slot
On the pcb the power supply goes into hiccup mode.

If I have three channels running all good. When I have all four channels running I have problems. However I have placed a
Working opamp from one of the other channels in this channel and I had sound, but when I add a newly built 2520 to this channel and have all 4 channels running there is an issue. Hope this is a little clearer. :)

Thanks so much for your help.
You do not have the required permissions to view the files attached to this post.

ajsteel
Posts: 39
Joined: Tue May 07, 2013 11:40 am
Location: Melbourne
Contact:

Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby ajsteel » Fri Sep 27, 2013 6:26 am

Hi Joe,

I'm not sure the other picture was that great for checking for shorts. This one should be better. :)

Thanks AJ
You do not have the required permissions to view the files attached to this post.

User avatar
Joe Malone
Site Admin
Posts: 1586
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby Joe Malone » Sat Sep 28, 2013 8:56 am

Looks ok to me. Could do with a bit of alcohol and old toothbrush cleaning to remove the flux residue.

Black wiring is blocking some of the solder joints. Also not sure why you think you need to have the black wire there? As both points should already be ground.

What power supply have you got to run the 4 of these BA PCBs. The 48v 40W one?

You can measure the voltage across the 10R resistor on each BA PCB to check the current each module is drawing.
Joe :-)
JLM Audio
Capturing Audio without Injury

ajsteel
Posts: 39
Joined: Tue May 07, 2013 11:40 am
Location: Melbourne
Contact:

Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby ajsteel » Sun Sep 29, 2013 11:14 am

Hi Joe,

I read somewhere on the forum that the EA2623 needed to be wired to the ground at the 0V on the PCB so the internal shields worked properly. Obviously misinterpreted the post. I will remove it. I guess the 0V just behind the secondary is the one, not 0V at the back of the PCB.

Yes I have the 48V 40W power supply.

Voltages across the 10r as follows;

Channel 1: 0.413V
Channel 2: 0.426V
Channel 3: 26mV ?????
Channel 4: 0.414V

Should I upload another picture without the black wire?

Thanks for your help. :)
AJ

User avatar
Joe Malone
Site Admin
Posts: 1586
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby Joe Malone » Tue Oct 08, 2013 8:21 pm

ajsteel wrote:Hi Joe,

I read somewhere on the forum that the EA2623 needed to be wired to the ground at the 0V on the PCB so the internal shields worked properly. Obviously misinterpreted the post. I will remove it. I guess the 0V just behind the secondary is the one, not 0V at the back of the PCB.

Yes I have the 48V 40W power supply.

Voltages across the 10r as follows;

Channel 1: 0.413V
Channel 2: 0.426V
Channel 3: 26mV ?????
Channel 4: 0.414V

Should I upload another picture without the black wire?

Thanks for your help. :)
AJ


Looks like channel 3 isn't drawing any current? Does it have the opamp plugged in? Does the 10R measure 10R? With the opamp in do you get the correct voltage at +V pin?
Joe :-)

JLM Audio

Capturing Audio without Injury

ajsteel
Posts: 39
Joined: Tue May 07, 2013 11:40 am
Location: Melbourne
Contact:

Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby ajsteel » Wed Oct 09, 2013 7:33 pm

Hi Joe,

I plugged an OPAMP in that works and got 38V at +V, I then plugged in the new OPAMP I built and the power supply went into hiccup mode even though only three had OPAMPS were in three channels. I think it may be the OPAMP and not the BA Circut. I plugged suspect OPAMP into a working channel and the power supply went into hiccup mode again. I am building another OPAMP now and will see what happens.

Thanks
AJ

ajsteel
Posts: 39
Joined: Tue May 07, 2013 11:40 am
Location: Melbourne
Contact:

Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby ajsteel » Wed Oct 09, 2013 9:57 pm

Hi Joe,

I built a new 2520 and I think it's definitely my OPAMP building. This one didn't work in a working channel. The power went in hiccup mode again when the OPAMP was in this working channel. But, when I placed a working OPAMP in Channel 3(not working I thought) I get clean signal as before. I assume is definitely my opamp. I might buy a pre built and tested OPAMP and plug that into my channel 3 and see what happens. If I'm right everything should work fine.

Will I need to make any adjustments to my BA Channel which is set up for a GAR 2520 if I use your 2520 OPAMP?

A.J. :)

User avatar
Joe Malone
Site Admin
Posts: 1586
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby Joe Malone » Thu Oct 10, 2013 7:24 am

ajsteel wrote:Hi Joe,

I built a new 2520 and I think it's definitely my OPAMP building. This one didn't work in a working channel. The power went in hiccup mode again when the OPAMP was in this working channel. But, when I placed a working OPAMP in Channel 3(not working I thought) I get clean signal as before. I assume is definitely my opamp. I might buy a pre built and tested OPAMP and plug that into my channel 3 and see what happens. If I'm right everything should work fine.

Will I need to make any adjustments to my BA Channel which is set up for a GAR 2520 if I use your 2520 OPAMP?

A.J. :)


Sounds like a dead GAR 2520 opamp then. Our JLM25HV will plug straight in and work without changes. But if you remove the zener the JLM25HV can also run on the full 48v (+/-24v)
Joe :-)

JLM Audio

Capturing Audio without Injury

ajsteel
Posts: 39
Joined: Tue May 07, 2013 11:40 am
Location: Melbourne
Contact:

Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby ajsteel » Thu Oct 10, 2013 7:55 pm

Hi Joe,

All fixed! :) You'll never guess what, I was checking my GAR2520 assembly instructions and saw that two transistors were in the wrong positions. I swapped them over and everything works. All four channels, no power issues, clean gain and quiet operation. I now have two spare 2520's. Cool. :) May have to build some more API flavour pre's!

Thanks for all your help.

A.J.

User avatar
Joe Malone
Site Admin
Posts: 1586
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby Joe Malone » Fri Oct 11, 2013 6:48 am

ajsteel wrote:Hi Joe,

All fixed! :) You'll never guess what, I was checking my GAR2520 assembly instructions and saw that two transistors were in the wrong positions. I swapped them over and everything works. All four channels, no power issues, clean gain and quiet operation. I now have two spare 2520's. Cool. :) May have to build some more API flavour pre's!

Thanks for all your help.

A.J.


That would do it. Good to hear you got all the mic pres going :D 8)
Joe :-)

JLM Audio

Capturing Audio without Injury

tazwolf
Posts: 6
Joined: Tue May 17, 2011 7:00 am

Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby tazwolf » Thu Nov 14, 2013 12:16 am

Hi
Iam building a BA using a beyer 1:10 input transformer and a Freed 32035 600:600 output tranformer, opamp is a jlm hybrid..
i wanted to add an output attenuator after the output transformer.

I found this schematic for an input attenuator
http://www.jlmaudio.com/PAD.gif

which looks cool but it is an input attenuator so i was wondering if it would work as an output attenuator as well?
I assume that as an input attenuator the resistor values are chosen for attenuation of a mic (150ohms?) to
mic pre input (1500ohms?) but when I try to confirm this using the many attenuation calculators on the web
i dont get the same values as the ones on the schematic.

So my question is

can I use the schematic for line level attenuation, 600:600?
How do I calculate the resistor values?
Does it make a difference if sometimes the mic pre will go straight into my audio interface (10k) but sometimes into an
eq or compressor (600ohm) before going into the audio interface.

Grateful for any help.

regards
/Taz

ajsteel
Posts: 39
Joined: Tue May 07, 2013 11:40 am
Location: Melbourne
Contact:

Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby ajsteel » Mon Nov 18, 2013 9:05 pm

Hi Joe,

I was wondering if you could tell me how I can test the Output voltages on the BA Mic pres so I can be sure there all on par. They all seem to be working well but I'm not convinced channel 3 is giving me the truth. When I measured between the 0V and the output on each channel with the unit on and gain full I got 0.2mv at the output to the transformer?

Thanks
A.J.

User avatar
Joe Malone
Site Admin
Posts: 1586
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby Joe Malone » Tue Nov 19, 2013 10:45 am

tazwolf wrote:Hi
Iam building a BA using a beyer 1:10 input transformer and a Freed 32035 600:600 output tranformer, opamp is a jlm hybrid..
i wanted to add an output attenuator after the output transformer.

I found this schematic for an input attenuator
http://www.jlmaudio.com/PAD.gif

which looks cool but it is an input attenuator so i was wondering if it would work as an output attenuator as well?
I assume that as an input attenuator the resistor values are chosen for attenuation of a mic (150ohms?) to
mic pre input (1500ohms?) but when I try to confirm this using the many attenuation calculators on the web
i dont get the same values as the ones on the schematic.

So my question is

can I use the schematic for line level attenuation, 600:600?
How do I calculate the resistor values?
Does it make a difference if sometimes the mic pre will go straight into my audio interface (10k) but sometimes into an
eq or compressor (600ohm) before going into the audio interface.

Grateful for any help.

regards
/Taz


Best to only allow a set amount of dB atten on the output as you are removing the headroom of the BA output so driving gain harder will just result in clipping on the BA output.
The below 2 ways are the best if you want a output atten pad on a BA or BAN.

ImageImage
Joe :-)

JLM Audio

Capturing Audio without Injury

User avatar
Joe Malone
Site Admin
Posts: 1586
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby Joe Malone » Tue Nov 19, 2013 10:48 am

ajsteel wrote:Hi Joe,

I was wondering if you could tell me how I can test the Output voltages on the BA Mic pres so I can be sure there all on par. They all seem to be working well but I'm not convinced channel 3 is giving me the truth. When I measured between the 0V and the output on each channel with the unit on and gain full I got 0.2mv at the output to the transformer?

Thanks
A.J.

No DC can get to the output transformer as there is a isolating capacitor between the opamp output and output transformer.

+in and -in and out on the opamp should all be sitting around half of the power rail at the opamp +V pin.
Joe :-)

JLM Audio

Capturing Audio without Injury

tazwolf
Posts: 6
Joined: Tue May 17, 2011 7:00 am

Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby tazwolf » Tue Feb 11, 2014 8:19 am

On the groupdiy mega thread there was this posting by Dirk666.


Do you fit a jumper across amp BA PCB pins (4-7) when using a hybrid for the baby animal with the jlm 1:1:1 output tran?


Joe said on page 25;
‘WHEN USING HYBRID WITH BA PCB, LEAVE OFF the 47uF cap which is on the opposite side of the PCB to the LED. As this can override the power supply filtering and let noise into the pre.’

I could not find the answer to these questions so I was wondering if someone here could help.

I am getting buzz/oscillation at 500hz on mine and am wondering if these coul dbe the cause.

Regards
/Taz

Return to “JLM Audio Kits”

Who is online

Users browsing this forum: No registered users and 5 guests