hi,
I am ready to put the electronics in my amplifier project. I have pretty much finished the cabinet, or at least as much as I can without the circuitry in place.
I am sorted in terms of pre amp and power amp, but I am not sure what to do with a power supply. My power amp will use the lm3886 chip which requires about 24V, if I remember correctly. The preamp circuit requires +-15v and can be seen here; 100W Guitar Amplifier (Mk II)
There is a power supply featured on this page, would something like this do the trick?
I would also like to run some LED strip lights off it, which use roughly 12v, as well if possible to backlight parts of the cabinet.
Any schematics or a point in the direction of some would be great, any advice much appreciated. Thanks.
Callum
I am ready to put the electronics in my amplifier project. I have pretty much finished the cabinet, or at least as much as I can without the circuitry in place.
I am sorted in terms of pre amp and power amp, but I am not sure what to do with a power supply. My power amp will use the lm3886 chip which requires about 24V, if I remember correctly. The preamp circuit requires +-15v and can be seen here; 100W Guitar Amplifier (Mk II)
There is a power supply featured on this page, would something like this do the trick?
I would also like to run some LED strip lights off it, which use roughly 12v, as well if possible to backlight parts of the cabinet.
Any schematics or a point in the direction of some would be great, any advice much appreciated. Thanks.
Callum
The chipamp needs dual polarity supply.
Not a single polarity 24Vdc.
Unless you modify the chipamp schematic to work with a single polarity supply.
Not a single polarity 24Vdc.
Unless you modify the chipamp schematic to work with a single polarity supply.
The LM3886 also won't deliver 100 Watts...
it is rated at 86W into 4 Ohm loads.
using a 8 ohm speaker gives you about 40.
this requires a dual 28V supply, I would get a 2x20 V 80VA toroidal transformer, 6A Bridge rectifier, Filter caps (2x4700µ/40V should do).
the supply on the page is ok so far, but do not use the suggested 2x25V transformer, this will result in overvoltage for the LM3886!
If the +- 15V for the preamp are not reached because of the lower voltage, you can change R18/19 to 560R.
Do not forget adeqate cooling for the LM!
it is rated at 86W into 4 Ohm loads.
using a 8 ohm speaker gives you about 40.
this requires a dual 28V supply, I would get a 2x20 V 80VA toroidal transformer, 6A Bridge rectifier, Filter caps (2x4700µ/40V should do).
the supply on the page is ok so far, but do not use the suggested 2x25V transformer, this will result in overvoltage for the LM3886!
If the +- 15V for the preamp are not reached because of the lower voltage, you can change R18/19 to 560R.
Do not forget adeqate cooling for the LM!
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HI,
Thanks, I am not worried about it producing 100Watts, that was just the page that happened top have the preamp on it. So it is possible to get this working then?
Good..
Callum
Thanks, I am not worried about it producing 100Watts, that was just the page that happened top have the preamp on it. So it is possible to get this working then?
Good..
Callum
Just saw that the 3886 can handle more than +/- 28 Volts, sorry - so go ahead, the 2 x 25V transformer should work. But I would recommend not to use a speaker below 8 Ohms then.
you are going to use a standard circuit round the 3886 then?
should be no big deal as far as i see.
If you are not familiar with power supplies and line voltage take care! have more than a second look every time. again, do not forget cooling! Attaching tle 3886 to the chassis may not be sufficient. (Heat transfer paste + isolation material anyway!!!)
you are going to use a standard circuit round the 3886 then?
should be no big deal as far as i see.
If you are not familiar with power supplies and line voltage take care! have more than a second look every time. again, do not forget cooling! Attaching tle 3886 to the chassis may not be sufficient. (Heat transfer paste + isolation material anyway!!!)
sorry for the delay,
ok, I have a celestion speaker that is rated at 50 watt and i belive is 4 ohm, how could i alter the supply to make this sufficient? Or would it just be easier to use a less powerful chip?
Yes, I was planning on just doing a standard circuit as this is a school project and needs to be kept to a deadline.
Callum
ok, I have a celestion speaker that is rated at 50 watt and i belive is 4 ohm, how could i alter the supply to make this sufficient? Or would it just be easier to use a less powerful chip?
Yes, I was planning on just doing a standard circuit as this is a school project and needs to be kept to a deadline.
Callum
In this case, just choose the operating voltage. Mathematically, 50 Watts @ 4 Ohms means ca 14V RMS. (U=sqrt(PxR)) Your power supply has to deliver slightly above 2 x 20 Volts then. No transformer reaches exact values at changing loads, so 2 x 15...18VAC transformer voltage will work. After rectifying and filtering this results in the required 20...24 Volts DC.
Why do you think the celestion has 4 Ohms? Is there a sticker on it or have you tried to measure with a multimeter? If you read about 6 Ohms then you have an 8 Ohm speaker.
Why do you think the celestion has 4 Ohms? Is there a sticker on it or have you tried to measure with a multimeter? If you read about 6 Ohms then you have an 8 Ohm speaker.
oh ok, thats not too bad then 🙂 Will that still be ok for the Preamp supply?
I'm pretty sure it is a 4 ohm as I remember there being a sticker on it, however It is currently at school so I am relying on my memory which is not always that trustworthy...
I'm pretty sure it is a 4 ohm as I remember there being a sticker on it, however It is currently at school so I am relying on my memory which is not always that trustworthy...
If your power amp runs off of say +/- 24v DC you can use a couple regulators to get the +/-15v DC for the preamp ......
When building solid state guitar amps I usually tend to design the preamp to run of off a single supply so I can run it off of the positive DC power amp supply , it saves from having to build a separate regulated supply for the preamp ......
CHEERS
The preamp has its own Z-Diode regulation if it's the same as in the schematics. If the +/-15V cannot be reached make the two resistors smaller as I described before.
I don't really understand the desperation of most the experts here to force the LM3886 to be a dual supply direct coupled amp. The National datasheet for the LM3886 has a clear application diagram of a single supply amp with an output capacitor between it and the speaker. Having watched my capacitor coupled amp go up in flames a couple of times until I upgraded the heat rejection, without hurting the speakers, and seeing all the PA and guitar speakers with new cheap drivers at the music resale shop, I'm rather fixed on using the $5 electrolytic capacitor as a fairly foolproof speaker protection device. Especially when my speakers cost 4-8 times what the amp costs. Hint- an electrolytic cap biased to 20 or 40 volts doesn't go through slow (audible) chemical events crossing zero volts.
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any op-amp can be made to run on a single rail if one wants to, never mind what some experts say....specially those with nothing to show for in terms of completed projects....
@Tony: Of course it can but why? The TO has a complete schematic (or even a complete board) for dual supply, a schematic for a power supply, so what would be the use to rework all this in favour for a single supply?
Ok, the capacitor as a protective device is an argument - for the power amp. But in how many industrial guitar amps do you see such a configuration? How confusing should it become for a beginner?
Ok, the capacitor as a protective device is an argument - for the power amp. But in how many industrial guitar amps do you see such a configuration? How confusing should it become for a beginner?
oh no, it's not about you.....😀
i was just reacting to another poster re: operating on a single rail to which i agree can be done if one wants to....
i was just reacting to another poster re: operating on a single rail to which i agree can be done if one wants to....
ok, peace then... 😎 🙂
One more word about output power: limiting power to eg undistorted 50 Watts does not mean you cannot destroy a 50W speaker when driving the amp heavily into clipping. Choose the power amp's gain wisely so to get a sensible range on the master volume.
One more word about output power: limiting power to eg undistorted 50 Watts does not mean you cannot destroy a 50W speaker when driving the amp heavily into clipping. Choose the power amp's gain wisely so to get a sensible range on the master volume.
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