[Denton J]

Hello everyone, I am throwing my hat into building high pass filters.  I have one issue, there is a system (the wife’s) I want to practice on.  However, she has an amplifier with a 12 ohm impedance value.  She is using a LGK 2.1 for desk top listening. Here are my questions:

1. Does anyone know the values for the cap in order to get a 70-80htz roll off with an amp with 12ohm impedance?  (Danny’s chart doesn’t list 12 ohm) If there is a formula I would be interested in it. (at some point in school I was probably taught how to figure this out)  If I am satisfied with the filters, I will be building some for a few systems. (son, daughter and myself)

2. I have no idea what is good quality RCA and XLR connecter brands are, can someone throw a link and a brand down below I’d appreciate it. 

Thanks a ton everyone.

[nlitworld]

You'll want to look at the INPUT impedance of the amp, which should be somewhere between 10K and 100K. Place the filter before the amp and you're good.

As for rca connectors, KLE are the best ones I've found. Even their standard copper series are great but their Absolute and Perfect series are phenomenal. Pop over to Sonic Craft and snag some of the basic ones, or Parts Connection has the fancy pants ones.

[Glady86]

You mean 12Kohm? There’s a link at the GR website. Click on the HIGH PASS FILTER CALCULATOR near the end of the high pass filter information.

I got gold plated copper RCA inputs from Amazon and plastic project boxes for good price.

[nlitworld]

Also, a simple high pass filter calculator online will give you the capacitance value if it's in between what Danny has listed.

[Denton J]

You mean 12Kohm? There’s a link at the GR website. Click on the HIGH PASS FILTER CALCULATOR near the end of the high pass filter information.

I got gold plated copper RCA inputs from Amazon and plastic project boxes for good price.

I don’t know how I missed it, I found it. 

[Denton J]

You'll want to look at the INPUT impedance of the amp, which should be somewhere between 10K and 100K. Place the filter before the amp and you're good.

As for rca connectors, KLE are the best ones I've found. Even their standard copper series are great but their Absolute and Perfect series are phenomenal. Pop over to Sonic Craft and snag some of the basic ones, or Parts Connection has the fancy pants ones.

It’s 12k.  Thanks for listing the connectors!

[stubafeller]

I suppose I can piggy back onto this thread since it is a similar question.

I have a three piece system of Preamp --> Tube EQ (47k impedance) --> Power Amp (100K impedance)

I'm looking to place the filter in between the preamp and EQ.  Would I just consider the 47K impedance in the calculation or is it a sum of the EQ and amp?
Thanks for the help!

[Hobbsmeerkat]

It’s 12k.  Thanks for listing the connectors!

0.15uF will get you -3dB at ~88Hz
0.22uF will be -3dB at ~60Hz

Personally, I would go for the 0.22uF cap

As for RCA ends I really like the KLEI female ends as they are super easy to solder to.
https://partsconnexion.com/klei-classic-harmony-rca-female-jacks-1/
for male ends, I like these:
https://partsconnexion.com/ms-audio-star-male-rca-plugs/

I don't have any specific recommendations for XLR connectors.


Here's the calculator, just make sure the cap info is set to uF (microfarads)
https://www.learningaboutelectronics.com/Articles/High-pass-filter-calculator.php

I suppose I can piggy back onto this thread since it is a similar question.

I have a three piece system of Preamp --> Tube EQ (47k impedance) --> Power Amp (100K impedance)

I'm looking to place the filter in between the preamp and EQ.  Would I just consider the 47K impedance in the calculation or is it a sum of the EQ and amp?
Thanks for the help!

Personally, I would put it after the Tube EQ, so there no unexpected issues with getting the cap value correct.

for 47K you will need 0.047uF for -3dB at ~72Hz
for 100K you will need 0.022uF for -3db at ~72Hz

[Glady86]

Here’s an example I made from Amazon parts and a .15uf  Miflex. The amps are 22Kohm so the frequency will be 48hz.  Hopefully that will work out for me.

[Denton J]

Thanks again everybody.  I got everything ordered up.

[Denton J]

Here’s an example I made from Amazon parts and a .15uf  Miflex. The amps are 22Kohm so the frequency will be 48hz.  Hopefully that will work out for me.

Let us know how it worked out.

[Denton J]

This might be more of a DIY question, but are there plans floating around for a tube buffer stage that also acts as a high pass filter?

[Rikard Ekval]

I don't have any specific recommendations for XLR connectors.


Dear AS and Hobbs


Anyone, please show med a XLR inline filter with SUB out.
Seen XLR filters with dual Miflex but no sub out.
Just go on one of the legs or what?



BR// Rikard

[Hobbsmeerkat]

We've not built any XLR based filters, so we don't have pictures.
You will need 2 wires coming off each pin of the input connector. One set of wires will go directly to another XLR connector, this will be the full-range for your sub.
The remaining set of wires connecting to the capacitors (except ground) before connecting to the remaining output connector.

The much easier option would be to use a set of XLR Y-splitter cables before the filter.

[oz_audio_todd]

Just out of curiosity, is there a low pass version of this sorta concept? 

[Hobbsmeerkat]

Just out of curiosity, is there a low pass version of this sorta concept? 

It's a lot more difficult to make a "simple" low-pass filter than it is to make a "simple" high-pass filter, especially before an amplifier.
As impedance doubles, the value of the coil you need also doubles. So for a 4 ohm driver you need 1.5mH to get the same roll off as a 3mH coil on an 8 ohm drivers.
and when most amps have an input impedance somewhere between 10,000-100,000 ohms, the value of the coil is going to be exceedingly astronomical, to the point such coils likely don't exist.

[Gearguy]

I'm thinking of taking a set of interconnects, cutting it and splicing in the appropriate capacitor for my amp. Fewer connections, no project box, etc. Besides making the cable now dedicated to this application, any sonic downsides?

[Glady86]

I'm thinking of taking a set of interconnects, cutting it and splicing in the appropriate capacitor for my amp. Fewer connections, no project box, etc. Besides making the cable now dedicated to this application, any sonic downsides?

No sonic downside, fewer connections should always better. If one could actually hear it is a different question. I doubt I could hear any difference.

[nlitworld]

 

I'm thinking of taking a set of interconnects, cutting it and splicing in the appropriate capacitor for my amp. Fewer connections, no project box, etc. Besides making the cable now dedicated to this application, any sonic downsides?

If your preamp has room inside the case, why not insert them there? I understand some won't have room, but it's super easy to unsolder the + connection wire, and pop that guy right to the output rca connector. If your preamp has 2 outputs, just run the capacitor from + output1 to + output2.