hi. when i connect my pa-amp to the subwoofer-preout on my main amp, i have to turn the pre-amp output and the input gain on the pa-amp to the max to get enough volume on the subwoofer. so i need a curcuit which increases the signal strength so it matches the pa-amp! (775mV i think)
whats a such curcuit called? can i find something like that on esp's pages? (going to order some stuff from there soon)
Øyvind
whats a such curcuit called? can i find something like that on esp's pages? (going to order some stuff from there soon)
Øyvind
PA-amps often need higher level than line level (preamp output). The old school mix boards do this and act as the preamp. Depends on how much you want to spend or how much time to invest. The easy and expensive way is to buy a preamp. The longer, more fun and may be cheaper way is to build a little opamp circuit to act as your preamp. I guess the fast and cheap way might be to get a used mix board, a simple one from DJ or PA systems. It will do the preamp for you.
-SL
-SL
i will be using a H\K avr245 as main amp. and TA2400 PA-amp for the subwoofer. im going to build a preamp for it, including 8-band eq, individual phase controll, adjustable lowpassfilter, a rumble filter, and now hopefully a gainstage.
Is a such gainstage complex to build? anyone have design for me?
the power amp for my mains are not seperate by btw.
Is a such gainstage complex to build? anyone have design for me?
the power amp for my mains are not seperate by btw.
Most PA amps and most commercial amps only require a signal of .775 to achieve full power. The home line of products however require usually 1.00-1.50v to achieve full power.
Like Andrew mentioned in his post an input buffer of +6- +12 db
of gain would probably do the job. It is probably a far smarter thing to do than to raise the gain of the amplifier.
Brett said:
hmm, so your saying that i could modify one of the stages on the preamp so that it makes the gain i need? for example if i change some of the resistors in for example the rumble filter or phase control?
or have i misunderstund?
for example in this design: http://sound.westhost.com/project99.htm . can i change for example R7 the get some gain?
thanks for the help people
i have just connected my pa-amp, using the pre-amp stage on my plate-amp. and it drives my TC2 driver with an iron fist
Hi,
Your amp has 0.775V input sensitivity for full power and balanced inputs I guess. Feeding that amp from an unbalanced source into the 1/4" jack or XLR you normally ground the inverting "cold pin" (automatically done with 1/4" mono plug). If so you will loose half of the sensitivity which now will be 1.55V.
On simple way to reach the original 0.775V sensitivity (or lower) is to make a buffer that also feeds the "cold input" so the amp will get balanced signal, i.e. an unbalanced to balanced converter. If this circuit is placed close to the preamp you also will have the benefit of providing balanced signal to the amp. This circuit could be based on one dual op-amp.
As previously mentioned one could also alter the feedback in the front balanced to unbalanced op-amp. But isn't it nicer to leave the amp in its original state?
Your amp has 0.775V input sensitivity for full power and balanced inputs I guess. Feeding that amp from an unbalanced source into the 1/4" jack or XLR you normally ground the inverting "cold pin" (automatically done with 1/4" mono plug). If so you will loose half of the sensitivity which now will be 1.55V.
On simple way to reach the original 0.775V sensitivity (or lower) is to make a buffer that also feeds the "cold input" so the amp will get balanced signal, i.e. an unbalanced to balanced converter. If this circuit is placed close to the preamp you also will have the benefit of providing balanced signal to the amp. This circuit could be based on one dual op-amp.
As previously mentioned one could also alter the feedback in the front balanced to unbalanced op-amp. But isn't it nicer to leave the amp in its original state?
i've worked on some commercial PA amps that require almost 2vrms for full output. the above "8 minutes and 2 resistors" solution requires either a schematic or one who knows their way around the innards of an amp well enough to find the feedback resistors. doubling the value of the output side feedback resistor will double the amp sensitivity (aka gain). be very careful here, since there are integrating capacitors across this particular resistor, to "slow down" the amp to keep it from oscillating. if this is the case, you need to also change the capacitor to maintain the correct time constant. if you don't feel confident "working without a net", build a gain stage with a gain of 2 or 3.
Yes to the first part.skogs said:
hmm, so your saying that i could modify one of the stages on the preamp so that it makes the gain i need? for example if i change some of the resistors in for example the rumble filter or phase control?
or have i misunderstund?
for example in this design: http://sound.westhost.com/project99.htm . can i change for example R7 the get some gain?
thanks for the help people
The ESP project you selected isn't what you said you wanted earlier, and changing R7 wouldn't help anyway.
I was thinking of somethin more like http://sound.westhost.com/project84.htm as an example, even though it doesn't Meet all your needs. Simplest would be to add two resistors around U1A to give it some gain.
You'll need this one too to get phase control.
http://sound.westhost.com/project103.htm
Hi,
increasing the gain of the amplifier, will decrease the difference between open loop and closed loop gain.
This will effect an increase in gain margin, making the amplifier more stable, or at worst no decrease in phase margin.
This possibility of a gain increase can easily be assessed if we have a schematic.
Does this amp have a balanced input?
If it has, then the source should have at least balanced impedances to feed it or better if a true balanced output were provided.
increasing the gain of the amplifier, will decrease the difference between open loop and closed loop gain.
This will effect an increase in gain margin, making the amplifier more stable, or at worst no decrease in phase margin.
This possibility of a gain increase can easily be assessed if we have a schematic.
Does this amp have a balanced input?
If it has, then the source should have at least balanced impedances to feed it or better if a true balanced output were provided.
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