Nuuk, what is the current demand for that class a transistor buffer of yours... I would love to use it with a preregulator so I could use the amp's 70V supply, but it can only supply about 100ma per rail withthe transistors I have now for the prereg.
I kinda designed PCBs and all without checking if the supply could match the load.
I kinda designed PCBs and all without checking if the supply could match the load.
Nordic said:
Do you mean this one on Nuuk's site?
An externally hosted image should be here but it was not working when we last tested it.
If so, it's pretty easy to determine a rough estimate of the current draw. It's just a simple buffer with constant current source. 0.7V/120ohm is about 6mA and (30V-1.4V)/27kohm is about 1mA. You should be able to run that off of your supply rails provided you change R1 to a value that will keep the current roughly the same.
Most line receiver chips like the INA134 or the SSM2141 run on 15V+- or 18V+- max. How does one incorporate a little preamp/buffer like that into an LM3875 chipamp kit which runs at like 25V+-? Is it possible to share the same power supply and just use resistors to step down the voltage for just the preamp/buffer section? The LM3875 kit is powered through an unregulated bridge diode setup since I guess the LM3875 is OK with it. Would it be better to run everything off a lower voltage power supply?
LM337 and LM317 regulators should be able to step that down for you very nicely... look up the datasheets...
for higher voltage supplies yuo can use this prereg
http://sound.westhost.com/project102.htm
for higher voltage supplies yuo can use this prereg
http://sound.westhost.com/project102.htm
An externally hosted image should be here but it was not working when we last tested it.
after which the regulators from the opening paragraphs would come..
CarlosT said:
The Power supply I use has a Regulated +/-15v and unregulated +/-24v useing the LM317/337 regulator chips.....
The supply was originally designed for Mic preamps but I changed the design so I could Run a LM3886 Chip amp and a Opamp Based +/-15v preamp from it, I just removed the Phantom power circuit and I modified it so I could have More PSU filter caps and just took the Power off the PSU before the regulators but after the Filter caps for the Unregulated 24v rails.....
I have a PCB and stuffing guide for this PSU if you want it?? Let me know and I"ll post it for you.....
Cheers
PS: I also designed a simple Preamp to use with the Chip amp that uses 2 Opamps (One dual and one single) all useing Inverted Topologies...It has Tone controlls (Bass,Treble,Mid) and Volume controlls and has a very High Gain.... I use if for Guitar and Bass but it could just as easilly be used for anything else....
Well tone controlls work pretty much the same in Opamps as they do in any circuit....
All I did with this design was used a simple Tone Stack circuit and put it in between a couple Opamp gain stages with an Input buffer.....
For low impedance sources (Under say 100K) I would use a NE5532 on the input or some other Non fet input opamp but for High impedance sources a fet opamp is best....
Cheers
All I did with this design was used a simple Tone Stack circuit and put it in between a couple Opamp gain stages with an Input buffer.....
For low impedance sources (Under say 100K) I would use a NE5532 on the input or some other Non fet input opamp but for High impedance sources a fet opamp is best....
Cheers
Attachments
Yes, a tone controll is a potentiometer,...
The Preamp I posted has a Treble, Bass and Mid controll...
If you want to have just a single knob for tone controll then you could drop the Mid range controll and use a Dual Ganged 250k Linear Pot and Connect the treble normally to one of the Gangs and connect the Bass to the other but in reverse then when you turned the Knob one way the Treble would increase at the same time the Bass decreases and the other way the treble decreases while the Bass increases.....
You would get better controll with the 3 Pots, or you could use Three Slider pots and have it set up like a 3 band EQ.....
Cheers
The Preamp I posted has a Treble, Bass and Mid controll...
If you want to have just a single knob for tone controll then you could drop the Mid range controll and use a Dual Ganged 250k Linear Pot and Connect the treble normally to one of the Gangs and connect the Bass to the other but in reverse then when you turned the Knob one way the Treble would increase at the same time the Bass decreases and the other way the treble decreases while the Bass increases.....
You would get better controll with the 3 Pots, or you could use Three Slider pots and have it set up like a 3 band EQ.....
Cheers
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