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Expensive signal caps extinguish bass?
Expensive signal caps extinguish bass?
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Old 13th March 2009, 10:32 PM   #1
FlexQ is offline FlexQ  Denmark
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Default Expensive signal caps extinguish bass?

Hi Guys

Im just here for a fast question.

I have build the first part of a pa150W gainclone.

Noninverted with 20x amplification, 10k input resistance, and this little bugger.

http://img23.imageshack.us/img23/5669/dsc01243r.jpg

However, when it is mounted, the bass sems to be gone - and not out in the loudspeaker, unfortunetly.

So my question is, how can that be?

I tried just as a test to use a 1uF wima cap, it doesent sound good, but it has all the bass that the Jensen cap seems to have lost.

Hope someone can give an explanation.

FlexQ
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Old 13th March 2009, 10:50 PM   #2
Nuuk is offline Nuuk  United Kingdom
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0.7uF is too small a value. It is obviously forming a high-pass filter with the input resistor. Try using at least 2.2uF.
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Old 14th March 2009, 12:15 AM   #3
Dr_EM is offline Dr_EM  United Kingdom
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Yes, just parrallel it with your 1uF WIMA cap, should do fine
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Old 14th March 2009, 10:14 AM   #4
FlexQ is offline FlexQ  Denmark
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Quote:
Originally posted by Nuuk
0.7uF is too small a value. It is obviously forming a high-pass filter with the input resistor. Try using at least 2.2uF.
With 10k input resistance it should form a highpass filter at 22Hz.


Quote:
Originally posted by Dr.EM
Yes, just parrallel it with your 1uF WIMA cap, should do fine
I will tryk that, will return when tested .

Btw, the cap is made for tact audio, has been sitting in the input of a pre amp at the cost of around 20.000$ :P.
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Old 14th March 2009, 10:20 AM   #5
Nuuk is offline Nuuk  United Kingdom
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Quote:
Btw, the cap is made for tact audio, has been sitting in the input of a pre amp at the cost of around 20.000$ :P.
Sadly, that means diddly-squat!
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Old 14th March 2009, 10:21 AM   #6
FlexQ is offline FlexQ  Denmark
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Quote:
Originally posted by Nuuk


Sadly, that means diddly-squat!
Well, it almost does :P.

When it has been working, i can make it working .

But testing is ongoing ,).
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Old 14th March 2009, 12:18 PM   #7
pacificblue is offline pacificblue  Germany
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Quote:
Originally posted by FlexQ
With 10k input resistance it should form a highpass filter at 22Hz.
Right. -3 dB at 22 Hz and attenuating up to 110 Hz. Do you use Ci? Tuned to what frequency? How do those two filters add up?

Quote:
Originally posted by FlexQ
When it has been working, i can make it working .
Maybe. What was the input resistance of that Tact Audio preamp?
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Old 14th March 2009, 03:18 PM   #8
FlexQ is offline FlexQ  Denmark
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Quote:
Originally posted by pacificblue

Right. -3 dB at 22 Hz and attenuating up to 110 Hz. Do you use Ci? Tuned to what frequency? How do those two filters add up?


Maybe. What was the input resistance of that Tact Audio preamp?

There was 2 flaws in my theory ;P

the first one was me thinking i knew all about that circuit, and the second that this cap is used in another type of circuit.

So right now i am using another cap

It sounds good, all three amps playing right now.

I am currently playing it up against NAD 214, and it suck quite a bit in relation to detail - but it has a tighter bass. But that could be because of that input-cap.

any suggestions to which i could use instead of?

FlexQ

EDIT: Here is what happens when one doesent have a place to work ..... dinnertable-invasion .

http://img223.imageshack.us/img223/3269/image063.jpg

And of the pride:P

http://img10.imageshack.us/img10/5996/image064r.jpg
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Old 14th March 2009, 03:32 PM   #9
analog_sa is offline analog_sa  Europe
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Expensive signal caps extinguish bass?
FlexQ

The fact that a capacitor is expensive or used in expensive equipment means very little. Is it properly broken in? Still, is it very difficult to raise the input impedance to 100k? Assuming it's a non-inverting amp.
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Old 14th March 2009, 03:50 PM   #10
AndrewT is offline AndrewT  Scotland
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if your input impedance (Zin) is 10k then I would suggest you try >=9uF as the DC blocking cap to hear what it sounds like.
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