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Setting up a ESP active crossover with gainclone
Setting up a ESP active crossover with gainclone
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Old 17th August 2007, 04:33 PM   #41
Dan_Steele is offline Dan_Steele  United Kingdom
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thanks pinkmouse,

Bit more of an update, got home today and decided to try the 220pf's at the xover end aswel.

Well alot more of the hum went so i tried .1 uf's and wow, one channel is about as silent as i think im going to get it (ear against speaker at full volume input shorted faint hiss) and the other has a little bit of hum left.

Am i likely to come into any problems with this extra capacitance?
(still sounds awesome)

If not, i think thats it, job done!
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Old 17th August 2007, 05:15 PM   #42
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by Dan_Steele
thanks pinkmouse,

Bit more of an update, got home today and decided to try the 220pf's at the xover end aswel.

Well alot more of the hum went so i tried .1 uf's and wow, one channel is about as silent as i think im going to get it (ear against speaker at full volume input shorted faint hiss) and the other has a little bit of hum left.

Am i likely to come into any problems with this extra capacitance?
(still sounds awesome)

If not, i think thats it, job done!
where have you fitted 0.1uF (=100nF)?
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Old 17th August 2007, 05:42 PM   #43
Dan_Steele is offline Dan_Steele  United Kingdom
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On the RCA output of thre x-over (right high / low & left high/low)
Between signal and ground.

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Dan
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Old 17th August 2007, 07:09 PM   #44
AndrewT is offline AndrewT  Scotland
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That sounds like the opamps are driving a 100nF load.
If that is the case the opamps are being very heavily stressed.
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Old 17th August 2007, 07:17 PM   #45
pinkmouse is offline pinkmouse  Europe
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Setting up a ESP active crossover with gainclone
You have put a sort of Zobel on the crossver outputs. The fact that this has helped suggests possible oscillation. Remove your 0.1uF, and try tacking some of the 220pF caps across the power pins of the opamps .
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Old 17th August 2007, 07:39 PM   #46
Dan_Steele is offline Dan_Steele  United Kingdom
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Ok guys thanks for that,

Likely to be the ouput buffers or all 7 opamps? I've run out of time tonight but I'll spend all day tommoro on it, therefore best to start at buffer end or input end?

Also, only have 4 220pf's until the rest turn up later this week,

Regards

Dan
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Old 17th August 2007, 07:48 PM   #47
pinkmouse is offline pinkmouse  Europe
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Setting up a ESP active crossover with gainclone
Quote:
Originally posted by Dan_Steele
I've run out of time tonight but I'll spend all day tommoro on it, therefore best to start at buffer end or input end?
Hard to say without the circuit in front of me. I'd start on just one channel, so if possible, bypass all the opamps doing, say, left highs and see where that gets you.
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Old 19th August 2007, 07:09 PM   #48
Dan_Steele is offline Dan_Steele  United Kingdom
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Right well the output buffers have 220pf's on them now and so does the input opamp.

Im waiting to do the other four when the new caps arrive as I cant get my sodlering iron in to solder them from the top.

This seemed to marginally improve things, I had another look at the datasheet and I see in some of the application circuits there is 5nF on the output, ive taken the 100nF's out and for the time being 50nF's are installed (I will order some (0.047uF) this week).

Now, the noise left is only on one channel & seems to alternate in magnitude depending on the time of day (EMF then?)

Also this channel is silent until both inputs are connected to the two monoblocks (I hope that makes sense)
i.e tweet amp connected then bring the mid phono to the socket and (hummmmmm)
Or mid silent and then bring tweet phono to socket and hummmmm (from the mid of course)

So on the input of the noisy (circa 50Hz) low freq amp, I first installed a 3.3uf Mundorf (in series with input) i had left from my playstation mods, all noise virutally disspeared but then I did a calculation and I think (please correctly me if im wrong) with the aid of the 680ohm input resistor what ended up making was a filter circa 220Hz (effectivley getting rid of the hum but the wrong method)

Therefore I brought this up to around 30uF (using lesser quality caps) bringing the F down to around 20Hz and there was barely any difference in level of hum.

Before I did notice this amp getting considerably hotter than the other channel. ~ pointing to oscilation (or just the result of the low amplitude 50Hz hum?)

all earths including safety were removed from this channel for test purposes only

I appreciate how difficult it is to make judgement calls with long distance fault finding!

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Old 19th August 2007, 07:34 PM   #49
AndrewT is offline AndrewT  Scotland
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680r is the wrong figure to use for that calculation.
Zin is the resistor value that makes up the CR high pass filter.
The 680r in series with the input is part of the RC low pass filter.
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Old 19th August 2007, 08:38 PM   #50
Dan_Steele is offline Dan_Steele  United Kingdom
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Hi Andrew thanks,

The 680 looking at it now is on the feedback loop (or this is how i see it) and therefore its the 220ohm resistor that forms part of the low pass?

Process of elimination (and looking at the diagram ) brings up the 22k caddock being the value im after, which co-incidently is the same as I used on the output of the playstation, bringing f to 2.2Hz lovelly jubley!

But im sure its not as simple as that!
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