BA BA2 BA4 BAD Dual99v Build Thread

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by Joe Malone »

tazwolf wrote: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?
NO need to fit that jumper as is for no transformer out so the -out as a 0v reference. When using a output transformer -out is not used as all as the transformer connects between +out and 0v.

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 could be the cause.
Do you mean 50/100Hz (60/120Hz USA) so hum and buzz? At 500Hz is an unusually low frequency for a oscillation in a pre?

Definitely leave off the 47uF cap mentioned on a Hybrid to stop high frequency noise from the SMPS getting in.

If the hum/buzz changes when you move the mic pre around then it is being picked up by the input transformer and will be worse if no mic is plugged in.

Check the metal case around the mic pre has 0v connected to it.

If using a DC connector it is best to wire from the 0v on the DC connector to a bolt on the back of the case to make sure 0v is connected properly.

A lot of cases that are powder coated need to have the powdercoating removed under the screw heads to make sure all panels are connected to 0v.
On our rack cases we do this already and use silver screws in the bottom panel to make sure all panels are shorted together properly

Make sure gain pot wiring is tightly twisted together and short and same for impedance pot wiring. Keep impedance pot wiring, gain wiring and in and out wiring away from each other.

Otherwise feel free to send me some photos of the wiring and top and bottom of the PCB and a small sound file of the noise you mention to see if I can spot anything.
Joe :-)
JLM Audio
Capturing Audio without Injury

tazwolf
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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by tazwolf »

Hi Joe
Thanks for the all your help and information.
Removing the capacitor on the Hybrid discrete opamp that is opposite the LED solved
the noise problems.
I also had problems with the enclosure being painted so I scratched around the screw holes and
checking for continutiy showed that all was good.
I am using a Beyer 1:10 input tranformer, its one of the stud mounted metal can ones
TR/BV 351 110 005
In an old Baby Animal thread (form prodigy pro I think) someone asked the question about what the
correct RL resistor was and someone replied 150k, which I tried but got a treble boost.
I found the following beyer catalogue
http://www.technicalaudio.com/pdf/Beyer ... ct_cat.pdf

and on page 7 it shows that for a 200 ohm input impedance Rl should be 50k, i tried a 47k and the response was much flatter.
Is this correct, am i interpreting the catalogue right for its application in a BA?

Regards
/taz

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by Joe Malone »

tazwolf wrote:Hi Joe
Thanks for the all your help and information.
Removing the capacitor on the Hybrid discrete opamp that is opposite the LED solved
the noise problems.
I also had problems with the enclosure being painted so I scratched around the screw holes and
checking for continutiy showed that all was good.
I am using a Beyer 1:10 input tranformer, its one of the stud mounted metal can ones
TR/BV 351 110 005
In an old Baby Animal thread (form prodigy pro I think) someone asked the question about what the
correct RL resistor was and someone replied 150k, which I tried but got a treble boost.
I found the following beyer catalogue
http://www.technicalaudio.com/pdf/Beyer ... ct_cat.pdf

and on page 7 it shows that for a 200 ohm input impedance Rl should be 50k, i tried a 47k and the response was much flatter.
Is this correct, am i interpreting the catalogue right for its application in a BA?

Regards
/taz
Yes best flat frequency response from data sheet is with RLoad = 50k and CLoad = 100pF. With NO RZobel and NO CZobel fitted.
Joe :-)
JLM Audio
Capturing Audio without Injury

tazwolf
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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by tazwolf »

Great, thanks for your help!

/Taz

mybishi
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BA 2 Dingo Incorporation Power Query

Post by mybishi »

Hey Joe and everyone,

I just finished my first BA2 and a pair of dingos with a passive eq on each. I was hoping to incorporate these dingos into the BA2 chassis. I've got the switching and layout all set but I'm stumped on the power. Is it possible to run both the single rail +48v BANs with the +/-24v dingos? My attempt to daisy chain the two units lead to Zener shorts on the dingos. I removed the DC connector from the chassis panel so that it would not be grounded to it (I'll get a plastic connector if this ends up working). I ran +48v and 0v to the appropriate spots on the BANs and then ran +48v and 0v from the BAN to +/-V on the dingos and grounded the dingos 0v to the chassis. Unless I made a mistake, this wild guess at a solution blew my zenners and the power supply went into hiccup mode. Any thoughts?

I said this before, but again, thank you Joe and all of the users here for giving me the resources to learn a whole new discipline in the music engineering field. I'm now hopelessly addicted!

Nick

mybishi
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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by mybishi »

Hey Joe and everyone,

I just finished my first BA2 and a pair of dingos with a passive eq on each. I was hoping to incorporate these dingos into the BA2 chassis. I've got the switching and layout all set but I'm stumped on the power. Is it possible to run both the single rail +48v BANs with the +/-24v dingos? My attempt to daisy chain the two units lead to Zener shorts on the dingos. I removed the DC connector from the chassis panel so that it would not be grounded to it (I'll get a plastic connector if this ends up working). I ran +48v and 0v to the appropriate spots on the BANs and then ran +48v and 0v from the BAN to +/-V on the dingos and grounded the dingos 0v to the chassis. Unless I made a mistake, this wild guess at a solution blew my zenners and the power supply went into hiccup mode. Any thoughts?

I said this before, but again, thank you Joe and all of the users here for giving me the resources to learn a whole new discipline in the audio engineering world.

Nick
mybishi

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by Joe Malone »

mybishi wrote:Hey Joe and everyone,

I just finished my first BA2 and a pair of dingos with a passive eq on each. I was hoping to incorporate these dingos into the BA2 chassis. I've got the switching and layout all set but I'm stumped on the power. Is it possible to run both the single rail +48v BANs with the +/-24v dingos? My attempt to daisy chain the two units lead to Zener shorts on the dingos. I removed the DC connector from the chassis panel so that it would not be grounded to it (I'll get a plastic connector if this ends up working). I ran +48v and 0v to the appropriate spots on the BANs and then ran +48v and 0v from the BAN to +/-V on the dingos and grounded the dingos 0v to the chassis. Unless I made a mistake, this wild guess at a solution blew my zenners and the power supply went into hiccup mode. Any thoughts?

I said this before, but again, thank you Joe and all of the users here for giving me the resources to learn a whole new discipline in the audio engineering world.

Top
BA BAD BAN use 48v SMPS as 0v ground, +24vdc +48vdc. Can use a metal non isolated dc connector bolted to chassis.

Where as dingo uses 48v SMPS as +24v, 0v ground, -24v which is why it must use a fully plastic isolated DC connector. No terminal of the DC connector can connect to the chassis.

So the 2 cannot share a power supply between them otherwise half the 48v SMPS will be shorted out and make some zeners on the dingo go short circuit.
Joe :-)
JLM Audio
Capturing Audio without Injury

htm
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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by htm »

I just finished my first BA, and it works! Output is very low though even with the gain cranked.

I'm using an old 1:8 input transformer with JLM25HV opamp. No output tx.
I'm kinda confused with some component values. Voltages are 0,4 V lower than in they should, but I'm guessing that's ok?

I used the API312 style BA guidelines because of the JLM25HV so:
- no CL (no wire link there either?)
- CZ is 220pf
- no RL (no wire link either?)
- RZ 4K7 (had no 5K1 at hand)
- no zeners or BD681's
- no *10K
- no #10K

Should I link something or change something. Or what could be the cause of the low output?

Thanks,
Hannu

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by Joe Malone »

htm wrote:I just finished my first BA, and it works! Output is very low though even with the gain cranked.

I'm using an old 1:8 input transformer with JLM25HV opamp. No output tx.
I'm kinda confused with some component values. Voltages are 0,4 V lower than in they should, but I'm guessing that's ok?

I used the API312 style BA guidelines because of the JLM25HV so:
- no CL (no wire link there either?)
- CZ is 220pf
- no RL (no wire link either?)
- RZ 4K7 (had no 5K1 at hand)
- no zeners or BD681's
- no *10K
- no #10K

Should I link something or change something. Or what could be the cause of the low output?

Thanks,
Hannu
OK you can usually always tell is the main amp section is working as when you turn up the gain the hiss should go up with it. Can you hear the hiss turn up with the gain control and no audio input?

If no real audio is coming out it is usually a hole in the input audio either in the wiring or if dual primary ratio jumper missing.

Other main problem we see is grounding the centre of the secondary on a transformer that is dual secondary which should be done.

Otherwise as always if not sure send to my email a large clear in focus well lit photo of the top and bottom of the PCB with opamp removed so we can check it over for you.
Joe :-)
JLM Audio
Capturing Audio without Injury

htm
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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by htm »

Audio is going through. I tested with a mic, and recorded a test bit. The problem is, the output level with gain maxxed equals my soundcards micpre with a gain at 25%.
The input tx is a bit tricky. It has only six taps. I wired it the same way it was in an old Tapco mixer. I'll play with the taps and see if it helps.
I'll send you photos of the circuit

Hannu

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by Joe Malone »

htm wrote:Audio is going through. I tested with a mic, and recorded a test bit. The problem is, the output level with gain maxxed equals my soundcards micpre with a gain at 25%.
The input tx is a bit tricky. It has only six taps. I wired it the same way it was in an old Tapco mixer. I'll play with the taps and see if it helps.
I'll send you photos of the circuit

Hannu
Ok but when you have a hole in the input wiring there is usually enough capacitive leaking to still get audio at the output but it will be low level even at full gain.
Joe :-)
JLM Audio
Capturing Audio without Injury

htm
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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by htm »

Ok, thanks for the answer. There seems to have been a bad connection in the input wiring, and I have two BA:s working now.

One thing puzzles me though. I'd be glad to get somebodys opinion on this. My vintage input transformers seem to have their primaries connected. So when I test with a beeper the IN + and IN - are connected. This makes the input unbalanced, right? What are the disadvantages, if any? Should I get another set of t-x?

thanks,
Hannu

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by Joe Malone »

htm wrote:Ok, thanks for the answer. There seems to have been a bad connection in the input wiring, and I have two BA:s working now.

One thing puzzles me though. I'd be glad to get somebodys opinion on this. My vintage input transformers seem to have their primaries connected. So when I test with a beeper the IN + and IN - are connected. This makes the input unbalanced, right? What are the disadvantages, if any? Should I get another set of t-x?

thanks,
Hannu
This doesn't make it unbalanced at all. The primary is a coil of wire so of course the +in and -in will buzz as they are low ohms. The primary will be fully floating so is balanced in if driven by a balanced or floating output of a microphone etc.
Joe :-)
JLM Audio
Capturing Audio without Injury

FrankD
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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by FrankD »

Hey Joe, just have a question about my BA's...I'm using the 48v 40w SMPS with four BA's in the same rackmount case, and am getting a strange noise problem. The SMPS is located outside the unit. I have no noise floor problems when no sound is being played into a microphone and to my ears all the pre's sound great. Here's my config:
1 x JLM99v with 1:4JLM input trans
3 x GAR2520 with EA2622 input trans, EA2503 output trans
Whenever I play a sound into a microphone (ie start strumming a guitar continuously), a strange 'pop' noise occurs...it then happens sporadically after, but does not happen if I do not play any sound into the microphone. The noise is about 60ms long and can't be removed using a click removal plugin (ie Waves X-click or something similar).
The same phenomenon happens on all 4 BA's.
I am beginning to think it's the power supply, since I've tried the same power supply with every BA individually (while not linking the power supply to the other three BA's) and the same thing happens. Unless I've made the same build mistake on every BA...
Have you got any suggestions on where I should troubleshoot?
I can post audio if you would like to hear the sound :mrgreen:
Thanks 8)

EDIT: I've since located the source of the problem...the DA converter was not properly sync'd to the external clock! Preamps are perfect. Everything's sweet now :mrgreen:

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by Joe Malone »

FrankD wrote:Hey Joe, just have a question about my BA's...I'm using the 48v 40w SMPS with four BA's in the same rackmount case, and am getting a strange noise problem. The SMPS is located outside the unit. I have no noise floor problems when no sound is being played into a microphone and to my ears all the pre's sound great. Here's my config:
1 x JLM99v with 1:4JLM input trans
3 x GAR2520 with EA2622 input trans, EA2503 output trans
Whenever I play a sound into a microphone (ie start strumming a guitar continuously), a strange 'pop' noise occurs...it then happens sporadically after, but does not happen if I do not play any sound into the microphone. The noise is about 60ms long and can't be removed using a click removal plugin (ie Waves X-click or something similar).
The same phenomenon happens on all 4 BA's.
I am beginning to think it's the power supply, since I've tried the same power supply with every BA individually (while not linking the power supply to the other three BA's) and the same thing happens. Unless I've made the same build mistake on every BA...
Have you got any suggestions on where I should troubleshoot?
I can post audio if you would like to hear the sound :mrgreen:
Thanks 8)

EDIT: I've since located the source of the problem...the DA converter was not properly sync'd to the external clock! Preamps are perfect. Everything's sweet now :mrgreen:
:D 8)
Joe :-)
JLM Audio
Capturing Audio without Injury

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