BAN Build Thread

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Joe Malone
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Re: BAN Build Thread

Post by Joe Malone »

BAN Schematic now in the first post of this thread

Photo showing how the BC550C should be mounted face to face with superglue and then fitted to the BAN PCB
Image
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hitchhiker
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Re: BAN Build Thread

Post by hitchhiker »

I bread boarded the BAN pre and liked it very much and so ordered some boards. My ribbon mic has never sounded this good. I'm using two opa2604 and bc550 transistors.

But now my first build on the JLM pcb has a current draw of 375mA using the same parts from the bread board. I've checked for errors many times. Touched up all the solder joints and cleaned around every pad. Still the same current draw.

Any thoughts where a problem would tripple the current draw? Have I over heated a joint that caused a short? All voltages are good and the trim procedures were easy. I have to wait a couple of days for more parts to arrive before I can try another build.

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Re: BAN Build Thread

Post by Joe Malone »

hitchhiker wrote:I bread boarded the BAN pre and liked it very much and so ordered some boards. My ribbon mic has never sounded this good. I'm using two opa2604 and bc550 transistors.

But now my first build on the JLM pcb has a current draw of 375mA using the same parts from the bread board. I've checked for errors many times. Touched up all the solder joints and cleaned around every pad. Still the same current draw.

Any thoughts where a problem would tripple the current draw? Have I over heated a joint that caused a short? All voltages are good and the trim procedures were easy. I have to wait a couple of days for more parts to arrive before I can try another build.
Certainly sounds like a solder short or opamp plugged in backwards. Is the 10R burning?

As always with any of our kits it is best to email me large well lit in focus macro on photos of the top and bottom of the built PCB so I can check it for any errors.
Joe :-)
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hitchhiker
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Re: BAN Build Thread

Post by hitchhiker »

Thanks Joe,

It turns out this may be a meter reading error by me. I've been using an old analog meter here because my usual meter is on another job. I pulled out another back up meter and the preamp reads to draw about 35mA draw. Is that what the BAN should be drawing?

thanks,
Lance

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Re: BAN Build Thread

Post by Joe Malone »

hitchhiker wrote:Thanks Joe,

It turns out this may be a meter reading error by me. I've been using an old analog meter here because my usual meter is on another job. I pulled out another back up meter and the preamp reads to draw about 35mA draw. Is that what the BAN should be drawing?

thanks,
Lance
Yep 35mA if perfect.
Joe :-)
JLM Audio
Capturing Audio without Injury

hitchhiker
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Re: BAN Build Thread

Post by hitchhiker »

Thanks Joe.

Do you think you'll ever do a bi-polar supply version of the BAN ?

Lance

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Re: BAN Build Thread

Post by Joe Malone »

hitchhiker wrote:Thanks Joe.

Do you think you'll ever do a bi-polar supply version of the BAN ?

Lance
No as the whole concept for the BA series is that they run on one 48v power rail to make powering a heap of mic pres easier, cheaper and safer as no mains wiring or power supply needs to be built as they runs on a prebuilt external 48v SMPS that can run on any mains voltage in the world without switching anything.
Joe :-)
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sleeper
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Re: BAN Build Thread

Post by sleeper »

Hi all,
I wanted to confirm something regarding note 1 on the schematic.
I'll be using 2520 op amps in my BAN
normally those need +-16v
so I will need to use the first BD681 and a 32V Zener
I don't see anything else.
It's really this simple?

Thanks
Sleeper

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Re: BAN Build Thread

Post by Joe Malone »

sleeper wrote:Hi all,
I wanted to confirm something regarding note 1 on the schematic.
I'll be using 2520 op amps in my BAN
normally those need +-16v
so I will need to use the first BD681 and a 32V Zener
I don't see anything else.
It's really this simple?

Thanks
Sleeper
Yes fit #BD681 #10k and #33v zener which will give you about 32v(+/-16v). Most 2520 types can run +/-18v so you can use a 36v zener to give 35v (+/-17.5v). Check the voltage at +V on the opamp sockets and that there is no short to 0v on -in and out opamp sockets before fitting the 2520. With the lower 32v to 35v voltage you can use a NE5532AP as the first opamp or a OPA2604AP.
Joe :-)
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sleeper
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Re: BAN Build Thread

Post by sleeper »

Two more questions and I think I have these up and running:

ferrite/inductor
I had some ferrite beads, fair-rite 2743002112L
These measure out at around 15uH and they worked swell on some green-pre's that I made a while back... should be OK?

And lastly
I'm confused...
so if I use a 2520 (or a 990) must I run unbalanced into an output transformer?
it seems if I went ahead and placed the output IC ( IC1) in place then we would be paralleling the IC1A and that's just something I've never tried and seems likely to do weird things. OR if I were to clip a few pins on IC1A so it's out of circuit, I would be inverting the 2520 signal with a 2604 or a 5532. That could work but it seems pretty unorthodox...

Clearly the simple choice would be a pair of 2604's and save my 2520's for something else, but then again.
I'd like to hear what you think.
Thanks Joe

Kelly

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Re: BAN Build Thread

Post by Joe Malone »

sleeper wrote:Two more questions and I think I have these up and running:

ferrite/inductor
I had some ferrite beads, fair-rite 2743002112L
These measure out at around 15uH and they worked swell on some green-pre's that I made a while back... should be OK?
You only want to use single or dual ferrite beads on a solid wire as you do not want to add any series resistance except at RF.
And lastly
I'm confused...
so if I use a 2520 (or a 990) must I run unbalanced into an output transformer?
Yes +out to 0v so there is only one 51R resistor in series with the primary of the output transformer.
it seems if I went ahead and placed the output IC ( IC1) in place then we would be paralleling the IC1A and that's just something I've never tried and seems likely to do weird things. OR if I were to clip a few pins on IC1A so it's out of circuit, I would be inverting the 2520 signal with a 2604 or a 5532. That could work but it seems pretty unorthodox...
You cannot parellel IC1A as different DC offsets would overheat the opamps. If you clip of the 3 IC1A legs the rest of the opamp would do the inverted out but +out and -out would have different drive capabilities so not a good idea for electronic balanced out and no good for driving transformer
Joe :-)
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sleeper
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Re: BAN Build Thread

Post by sleeper »

sleeper wrote:You cannot parellel IC1A as different DC offsets would overheat the opamps. If you clip of the 3 IC1A legs the rest of the opamp would do the inverted out but +out and -out would have different drive capabilities so not a good idea for electronic balanced out and no good for driving transformer
I thought this, but didn't know for sure. Thanks for the confirmation.

greenmanhumming
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Re: BAN Build Thread

Post by greenmanhumming »

is BC547C an ok substitute for BC550C?

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Re: BAN Build Thread

Post by Joe Malone »

greenmanhumming wrote:is BC547C an ok substitute for BC550C?
It would work but is not the best noise wise. You can use BC109C, BC549C which are low noise types.
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greenmanhumming
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Re: BAN Build Thread

Post by greenmanhumming »

BC109C is much more expensive, is there an advantage?

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