BA BA2 BA4 BAD Dual99v Build Thread
Moderator: Joe Malone
Re: BA BA2 BA4 BAD Dual99v Build Thread
Hi!
One more question about the BA. I got all of my four API-type BA:s finished and racked. They sound really good, especially on vocals (a little surprise there). I'm wondering about the gain range though. When using a tube condenser mic, that is plenty loud on other pres, I have to crank the gain all the way up to get a usable level. On drums with dynamic mics I have to go about half the way up. With a ribbon mic I thought I'd had something broken.
Is it just that one gain stage pres are like this, or could there be some kind of impedance issue with the non standard input tx I'm using?
Or should I just get the output transformars...
Thanks, Hannu
One more question about the BA. I got all of my four API-type BA:s finished and racked. They sound really good, especially on vocals (a little surprise there). I'm wondering about the gain range though. When using a tube condenser mic, that is plenty loud on other pres, I have to crank the gain all the way up to get a usable level. On drums with dynamic mics I have to go about half the way up. With a ribbon mic I thought I'd had something broken.
Is it just that one gain stage pres are like this, or could there be some kind of impedance issue with the non standard input tx I'm using?
Or should I just get the output transformars...
Thanks, Hannu
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Re: BA BA2 BA4 BAD Dual99v Build Thread
The output transformer will give you 6dB extra gain. But remind me which input transformers and opamp you are using?htm wrote:Hi!
One more question about the BA. I got all of my four API-type BA:s finished and racked. They sound really good, especially on vocals (a little surprise there). I'm wondering about the gain range though. When using a tube condenser mic, that is plenty loud on other pres, I have to crank the gain all the way up to get a usable level. On drums with dynamic mics I have to go about half the way up. With a ribbon mic I thought I'd had something broken.
Is it just that one gain stage pres are like this, or could there be some kind of impedance issue with the non standard input tx I'm using?
Or should I just get the output transformars...
Thanks, Hannu
Because depending on the opamp type RGain could be made smaller than 68R to give you more gain.
Joe
JLM Audio
Capturing Audio without Injury
JLM Audio
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Re: BA BA2 BA4 BAD Dual99v Build Thread
Hi
I'm using 1:8 input transformer with JLM25HV. How much smaller could I go from 68R?
- Hannu
I'm using 1:8 input transformer with JLM25HV. How much smaller could I go from 68R?
- Hannu
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Re: BA BA2 BA4 BAD Dual99v Build Thread
If the transformer is wired as 1:8 properly and loaded correctly you should have almost 60dB of gain already without adding the output transformer.htm wrote:Hi
I'm using 1:8 input transformer with JLM25HV. How much smaller could I go from 68R?
- Hannu
What info do you have on the input transformer? If none measure all the winding for dc resistance and let me know the measurements and which winding's are connected to each other etc.
Joe
JLM Audio
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JLM Audio
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Re: BA BA2 BA4 BAD Dual99v Build Thread
The tx's are from an old AKG Tapco 6100 series mixer. No markings on them, and the manual doesn't say much.
"Custom built high nickel alloy"
"Microphone impedance matching 30 to 600 ohms"
"Common mode rejection 105 db"
I wired them the same way they were in the mixer. Three taps on each side.
Primary side: 1 + 3 for signal, 2 N.C.
Secondary : 1 ground, 2 + 3 for signal
I tested them the other way around and tried also the middle tap on the primary. The way mentioned above was the one that worked.
I'll get the multimeter out, when I get home from work and post the measurements.
"Custom built high nickel alloy"
"Microphone impedance matching 30 to 600 ohms"
"Common mode rejection 105 db"
I wired them the same way they were in the mixer. Three taps on each side.
Primary side: 1 + 3 for signal, 2 N.C.
Secondary : 1 ground, 2 + 3 for signal
I tested them the other way around and tried also the middle tap on the primary. The way mentioned above was the one that worked.
I'll get the multimeter out, when I get home from work and post the measurements.
Re: BA BA2 BA4 BAD Dual99v Build Thread
Ok. Here we go. I hade a spare one to test.
Primaries
1+2 is 12,2 ohm
2+3 is 12,2 ohm
1+3 is 19,2 ohm
Secondaries
1+2 is 83,5 ohm
2+3 is 83,5 ohm
1+3 is 3,3 ohm
Primaries
1+2 is 12,2 ohm
2+3 is 12,2 ohm
1+3 is 19,2 ohm
Secondaries
1+2 is 83,5 ohm
2+3 is 83,5 ohm
1+3 is 3,3 ohm
- Joe Malone
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Re: BA BA2 BA4 BAD Dual99v Build Thread
Something strange about the secondary 1+ 3 = 3.3ohms ? Should be 169ohms?? Can you check that is correct or not?htm wrote:Ok. Here we go. I hade a spare one to test.
Primaries
1+2 is 12,2 ohm
2+3 is 12,2 ohm
1+3 is 19,2 ohm
Secondaries
1+2 is 83,5 ohm
2+3 is 83,5 ohm
1+3 is 3,3 ohm
Joe
JLM Audio
Capturing Audio without Injury
JLM Audio
Capturing Audio without Injury
Re: BA BA2 BA4 BAD Dual99v Build Thread
It thought it was weird too, but I checked, and its 3,3
I took another one I had lying around an it reads:
8,5 + 8,5 /15,5 primary
80,5 + 80,5/2,3 secondary
i changed the multimeter battery and the readings are the same +/- 2 ohm
the earlier reads about the same with the new battery
If you want to look at the 6100 mixer schematic, its here:
https://www.google.co.uk/url?sa=t&rct=j ... 2846,d.ZWU
The input schematic is on page 13
Should I just get AE2622's from classicapi or can I get more gain out of these? I kinda wanted tu use them.
- Hannu
I took another one I had lying around an it reads:
8,5 + 8,5 /15,5 primary
80,5 + 80,5/2,3 secondary
i changed the multimeter battery and the readings are the same +/- 2 ohm
the earlier reads about the same with the new battery
If you want to look at the 6100 mixer schematic, its here:
https://www.google.co.uk/url?sa=t&rct=j ... 2846,d.ZWU
The input schematic is on page 13
Should I just get AE2622's from classicapi or can I get more gain out of these? I kinda wanted tu use them.
- Hannu
- Joe Malone
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Re: BA BA2 BA4 BAD Dual99v Build Thread
Yes the transformer only gives 6db so is only 1:2 ratio which why you have low gainhtm wrote:It thought it was weird too, but I checked, and its 3,3
I took another one I had lying around an it reads:
8,5 + 8,5 /15,5 primary
80,5 + 80,5/2,3 secondary
i changed the multimeter battery and the readings are the same +/- 2 ohm
the earlier reads about the same with the new battery
If you want to look at the 6100 mixer schematic, its here:
https://www.google.co.uk/url?sa=t&rct=j ... 2846,d.ZWU
The input schematic is on page 13
Should I just get AE2622's from classicapi or can I get more gain out of these? I kinda wanted tu use them.
- Hannu
Joe
JLM Audio
Capturing Audio without Injury
JLM Audio
Capturing Audio without Injury
- Joe Malone
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Re: BA BA2 BA4 BAD Dual99v Build Thread
manual says the transformer only gives 6db so is only 1:2 ratio which why you have low gainhtm wrote:It thought it was weird too, but I checked, and its 3,3
I took another one I had lying around an it reads:
8,5 + 8,5 /15,5 primary
80,5 + 80,5/2,3 secondary
i changed the multimeter battery and the readings are the same +/- 2 ohm
the earlier reads about the same with the new battery
If you want to look at the 6100 mixer schematic, its here:
https://www.google.co.uk/url?sa=t&rct=j ... 2846,d.ZWU
The input schematic is on page 13
Should I just get AE2622's from classicapi or can I get more gain out of these? I kinda wanted tu use them.
- Hannu
Joe
JLM Audio
Capturing Audio without Injury
JLM Audio
Capturing Audio without Injury
Re: BA BA2 BA4 BAD Dual99v Build Thread
Darn. I must have missed that. Seems that I have to get new ones.
Thank you so much for the quick answers.
- Hannu
Thank you so much for the quick answers.
- Hannu
- Joe Malone
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Re: BA BA2 BA4 BAD Dual99v Build Thread
Since the input transformer is so low you should be able to make RGain maybe as small as 10R which would give you about 15dB extra gain. Just need to try it and see if you any oscillation or not.htm wrote:Darn. I must have missed that. Seems that I have to get new ones.
Thank you so much for the quick answers.
- Hannu
Also this transformer would need Rload 10k or variable impedance 2k2 in seres with 50k log pot. If you have variable impedance the oscillation is most likely to happen at high impedance.
Also Cload of 220pF to 440pF maybe needed if you get oscillation to stop it.
Joe
JLM Audio
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JLM Audio
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Re: BA BA2 BA4 BAD Dual99v Build Thread
Hi Joe
Would it be possible to use an LL1528 instead of the LL1538 for the BA? Just because I have a couple of LL1528s lying around.
Many thanks
Dave
Would it be possible to use an LL1528 instead of the LL1538 for the BA? Just because I have a couple of LL1528s lying around.
Many thanks
Dave
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Re: BA BA2 BA4 BAD Dual99v Build Thread
You can use the LL1528 but its pinout doesn't line up on the PCB so would have to be wired to the PCB. The four input pins do line up but the rest do not.Dais3 wrote:Hi Joe
Would it be possible to use an LL1528 instead of the LL1538 for the BA? Just because I have a couple of LL1528s lying around.
Many thanks
Dave
Joe
JLM Audio
Capturing Audio without Injury
JLM Audio
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Re: BA BA2 BA4 BAD Dual99v Build Thread
Hi Joe, is there any reason why i couldn,t wire a bad pcb with separate gain pots for each section, i've not got any dual rev 10ks at the moment but have some single rev 10ks. I have some dual rev 5ks pots - could i use these instead?