I've started this thread to post some measurements of my Gainclone. This is an LM3886 inverting GC with buffer and 3300 uF per rail, 500 VA transformer.
We see a lot of gainclones here but very little in the way of performance data. If you have some data, add your own.
Here is a shot of the onset of clipping with a 40 Hz input signal into a 5 ohm load, about 45 watts. 5 v/div on channel 1.
We see a lot of gainclones here but very little in the way of performance data. If you have some data, add your own.
Here is a shot of the onset of clipping with a 40 Hz input signal into a 5 ohm load, about 45 watts. 5 v/div on channel 1.
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Power supply - operate
Power supply ripple when the chip is operated and not clipping.
channel 1, .5v/div
It would be interesting to compare this to an implementation using 1000 uF per rail. I had one of these but added more caps due to the large amount of ripple. Now the ripple is not so bad, but still not great.
Power supply ripple when the chip is operated and not clipping.
channel 1, .5v/div
It would be interesting to compare this to an implementation using 1000 uF per rail. I had one of these but added more caps due to the large amount of ripple. Now the ripple is not so bad, but still not great.
Attachments
Power supply at clipping
Here is the positive power supply when the amp is clipping, and flattening the top peaks. This is a DC measurement at 5 v/div, and ground is the bottom line on the graticule. Thus you are seeing ripple at about 30-35 volts, much higher than the clipping point of about 12 volts in the first 2 posts.
Here is the positive power supply when the amp is clipping, and flattening the top peaks. This is a DC measurement at 5 v/div, and ground is the bottom line on the graticule. Thus you are seeing ripple at about 30-35 volts, much higher than the clipping point of about 12 volts in the first 2 posts.
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clipping
Yeah, the clipping is not symetrical, but DC offset is never more than 25 mv. I'll look at it again into different loads (maybe different results) but I would have no idea what's causing it, since it seems to be working fine. That's why I posted my data, wondering what everyone else's looks like on clipping?
Scope is a Tektronix 265M.
Yeah, the clipping is not symetrical, but DC offset is never more than 25 mv. I'll look at it again into different loads (maybe different results) but I would have no idea what's causing it, since it seems to be working fine. That's why I posted my data, wondering what everyone else's looks like on clipping?
Scope is a Tektronix 265M.
Low Noise Regulated Supply - Mute
this is the Low Noise power supply, shown here. This has the input buffer (differential receiver) on it.
In these shots I am looking for noise on the power supply. Scope is set at .5 msec/div (and its highest sensitivity which is 5 mv/div). This rail is +9.5 volts.
This is the positive rail with the amp operating but muted.
It also shows the entire scope for those of you interested in seeing my TEK 465M.
this is the Low Noise power supply, shown here. This has the input buffer (differential receiver) on it.
In these shots I am looking for noise on the power supply. Scope is set at .5 msec/div (and its highest sensitivity which is 5 mv/div). This rail is +9.5 volts.
This is the positive rail with the amp operating but muted.
It also shows the entire scope for those of you interested in seeing my TEK 465M.
Attachments
LN PS positive rail with 4KHz input
Here is the +9.5 volt rail of the low noise power supply input buffer with a 4KHz input signal applied. You see that I am getting a 4KHz input signal component on the rail. Dont know if this is a measurement artifact (picked up by the probes and wires) or if its actually there. Interesting though.
The scope is still at its highest sensitivity, 5 mv/div (top trace) where the bottom trace is just showing the input at a lesser setting.
This pic also shows the entire scope.
Here is the +9.5 volt rail of the low noise power supply input buffer with a 4KHz input signal applied. You see that I am getting a 4KHz input signal component on the rail. Dont know if this is a measurement artifact (picked up by the probes and wires) or if its actually there. Interesting though.
The scope is still at its highest sensitivity, 5 mv/div (top trace) where the bottom trace is just showing the input at a lesser setting.
This pic also shows the entire scope.
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Re: clipping
If you think so....
...Your scope looks nice, but some readings not...
(If you want to somebody help you, set your scope channels to DC, move second channel var input pot fully clockwise, set divs to 10V, traces position in midle, set sine signal 1kHz on input, increase level just to clipping and show as result; first channel to output, second on +rail...only one picture please...)
Regards
Milan
lgreen said:
If you think so....
...Your scope looks nice, but some readings not...
(If you want to somebody help you, set your scope channels to DC, move second channel var input pot fully clockwise, set divs to 10V, traces position in midle, set sine signal 1kHz on input, increase level just to clipping and show as result; first channel to output, second on +rail...only one picture please...)
Regards
Milan
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