Balanced line level high pass filters

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Hobbsmeerkat

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Re: Balanced line level high pass filters
« Reply #20 on: 13 Feb 2023, 04:29 pm »
Impedance is a measurement of electrical resistance. So long as you have the input impedance in ohms, then that is all you will need.

Speedskater

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Re: Balanced line level high pass filters
« Reply #21 on: 13 Feb 2023, 05:19 pm »
Do a search on:
measure input impedance

If your DMM has a sensitive AC scale (like 2 Volts) and you use a low frequency (maybe 400 Hz) tone.
That should be close enough.

whydontumarryit

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Re: Balanced line level high pass filters
« Reply #22 on: 13 Feb 2023, 07:48 pm »
The Marantz is a surround receiver? It has xover settings to hi pass the Manepan? Is that right?
Why are you bothering with an obviously defective method of filtering? Do you like to make things complicated?
Why are people here touting the benefits of this when a superior method of filtering is at hand?

Hobbsmeerkat

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Re: Balanced line level high pass filters
« Reply #23 on: 13 Feb 2023, 08:46 pm »
The Marantz is a surround receiver? It has xover settings to hi pass the Manepan? Is that right?
Why are you bothering with an obviously defective method of filtering? Do you like to make things complicated?
Why are people here touting the benefits of this when a superior method of filtering is at hand?

Please, enlighten us.

aceinc

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Re: Balanced line level high pass filters
« Reply #24 on: 13 Feb 2023, 09:15 pm »
The Marantz is a surround receiver? It has xover settings to hi pass the Manepan? Is that right?
Why are you bothering with an obviously defective method of filtering? Do you like to make things complicated?
Why are people here touting the benefits of this when a superior method of filtering is at hand?
The Marantz AV7704 is a sound processor.

I have 5 subwoofers. Two of the powered subs are paired with my Maggie 2.7s and are used in total as my "front" speakers.

The other 3 subs are controlled by the Marantz.

whydontumarryit

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Re: Balanced line level high pass filters
« Reply #25 on: 14 Feb 2023, 07:27 am »
The Marantz AV7704 is a sound processor.

I have 5 subwoofers. Two of the powered subs are paired with my Maggie 2.7s and are used in total as my "front" speakers.

The other 3 subs are controlled by the Marantz.

https://www.parts-express.com/FMOD-Crossover-Pair-70-Hz-High-Pass-266-272?quantity=1

These are 2nd order, 70hz. RCA though. Cheap enough to try out for a laugh.

Did you try .47uf instead of .047 caps yet to see how close you can get to 70hz.

rif

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Re: Balanced line level high pass filters
« Reply #26 on: 14 Feb 2023, 03:53 pm »
If it works, I'd make a hard pass on Harrison and go for partsexpress/Dayton crossovers.  they are speaker level, however, and you can purchase from individual components to fully assembled.

I used some of harrison attenuators years ago and they were ok.  But look at their website, they have more options.  Unfortunately I find their website unprofessional, which may or may not reflect on their products. For one, it looks like it was created in the 90s. hlabs.com

cjsailer

Re: Balanced line level high pass filters
« Reply #27 on: 16 Feb 2023, 02:04 am »
How does a capacitor's VDC rating influence the high pass filter?

Hobbsmeerkat

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Re: Balanced line level high pass filters
« Reply #28 on: 16 Feb 2023, 02:25 am »
It shouldn't influence it much if at all. Most RCA/XLR voltage levels are quite low, and in most cases you can easily get away with a 50V rated cap and still be in good shape in most cases, depending on the maximum output voltage of the preamp you're using.

Most polycaps used for DIY audio are typically rated for 100-250V with some also offering 400-600V values.

aceinc

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Re: Balanced line level high pass filters
« Reply #29 on: 16 Feb 2023, 01:37 pm »
Do a search on:
measure input impedance

If your DMM has a sensitive AC scale (like 2 Volts) and you use a low frequency (maybe 400 Hz) tone.
That should be close enough.
My DMM measures to 1/10 of a millivolt AC.

I searched for how to measure input impedance and found;

https://learnabout-electronics.org/ac_theory/impedance73.php

It appears from this how to, I would need a variable resistor which would have the the impedance of the amplifier in its resistance range.

I am not sure how to source this. Any ideas?

Speedskater

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Re: Balanced line level high pass filters
« Reply #30 on: 16 Feb 2023, 02:26 pm »
In Florida?
There might be brick & mortar electronic stores.
 
on-line see:
Parts Express
https://www.parts-express.com/electronic-parts/resistors-potentiometers/potentiometers

whydontumarryit

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Re: Balanced line level high pass filters
« Reply #31 on: 16 Feb 2023, 08:26 pm »
My DMM measures to 1/10 of a millivolt AC.

I searched for how to measure input impedance and found;

https://learnabout-electronics.org/ac_theory/impedance73.php

It appears from this how to, I would need a variable resistor which would have the the impedance of the amplifier in its resistance range.

Based on your REW results we all know what the input impedance of your amp is already. There is nothing to measure. .047uf and 700hz gives us 4.8kohms. Maybe you should have a good look at the caps you have to confirm they are .047 MICROFARADS and not nanofarad (47N) or something.

If you are really determined to be able to measure input resistance the ac signal level will drop to half its value when the series resistor you try is equal to the the amps input resistance.

At this rate you could pick up a used Mini DSP for $80.
« Last Edit: 17 Feb 2023, 05:27 am by whydontumarryit »

aceinc

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Re: Balanced line level high pass filters
« Reply #32 on: 16 Feb 2023, 08:57 pm »
Quote
Based on your REW results we all know what the input impedance of your amp is already. There is nothing to measure. .047uf and 700hz gives us 4.8kohms. Maybe you should have a good look at the caps you have to confirm they are .047 MICROFARADS and not nanofarad (47N) or something.

If you are really determined to be able to measure input resistance the ac signal level will drop to half its value when the load resistor you try is equal to the the amps input resistance.

At this rate you could pick up a used Mini DSP for $80.

I measured each cable after I built it, but I just remeasured one of the cables just in case. The cable itself measures 47-48.2nf on each leg. I believe this translates to .047-.0482 uf. The printing on the cap also said (the caps are in shrink tube now and I can't see the writing) .047 uf +/-3% and that was what I ordered from the dealer.

Yes a minidsp could work, but this introduces the whole A-D & D-A thing in the signal path.

whydontumarryit

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Re: Balanced line level high pass filters
« Reply #33 on: 16 Feb 2023, 10:36 pm »
So, you need .47uf for a 70hz xover point, as already mentioned.
The complex impedance of the pre+filter+amp is 4.8k if a .047uf cap results in a 700hz xover point, right?
R=1/2piFC

(previously meant .047N not 47N, sorry about that)