Line out

[arnenym]

Maybe i should publish this in another forum. The last post here is from 2016!!

What's the best way to do a line out?
I've made it with 2 resistors. I have one 47k from speaker output to line out. Plus one 4.7k to ground bypassed with a .0047 cap.
This make a quite good line out but it cut some bass.

[eschertron]

Your cap's knee freq is above 7kHz. Try a bigger cap to roll off more highs, giving the effect of more bass.

[arnenym]

Your cap's knee freq is above 7kHz. Try a bigger cap to roll off more highs, giving the effect of more bass.

I tried some different low pass calculators and i got 720 hz. The 47K resistor is the resistor before the cap to ground.
C=4.7nF R=47kΩ =720.48Hz

Should i calculate with the bypassed resistors value?
C=4.7nF R=4.7kΩ =7.2kHz

It is this type of line out, but with other resistor values https://robrobinette.com/images/Guit..._Schematic.bmp

[J M Fahey]

Long story, but the net resistance you need to put in the equation is 47k in parallel with 4k7 so about some 4200 ohms.
In any case you are complaining about lack of Bass.
Point is, that circuit does not cut Bass at all, so I guess your Harp amplifier does not have much Bass to begin with (to say it politely).

But there is also an important question: what are you feeding that signal into?

[arnenym]

I recorded it in to a zoom H4 recorder .
I Will post som pictures screen dumps from my sound editing program.

[J M Fahey]

Ok, which Zoom inputs did you plug into?

* XLR main inputs?
* 1/4" main inputs?
* "External Mic" Mini stereo phone jack?

all completely different from each other.

[arnenym]

I Use 1/4 to 1/4 cable..
This is how it looks.
a link to the picture

[pdf64]

A 1/4" jack is likely to be medium or high impedance, so shouldn't load the line out filter.
However, as the line out filter frequency is so high, it's likely to sound weird if no other cab simulation is being applied.
Suggest you try ~33nF - 47nF across the 4k7 to try and cut some of the harsh top end, which would also tend to make the bass more prominent in comparison.
What's the picture?
Can you see it if you log out of photobucket?

[arnenym]

I tried another way to upload the picture.

I gonna try 2 different solutions.
Before i change cap to a bigger I try a DI box and use XLR input.
After that i try with a bigger cap -.033

Alt3) Rebuild the line out with 2 smaller resistors. 4k7 and 470 ohm and a 0068 cap. It would save space..

[pdf64]

...Alt3) Rebuild the line out with 2 smaller resistors. 4k7 and 470 ohm and a 0068 cap. It would save space..

To retain the same corner freq, the cap would need to be 10x bigger than before, eg 330nF = 0.33uF.
To make the cap smaller, higher value resistors would be needed, and then you may run into impedance issues, ie what you connect to it may shift the corner frequency.

[arnenym]

OK.
As you explain it i understand i do best if i use a DI box and cut the cap. Or if i put in smaller resistors and not use a cap. Because the treble roll off would differ from one sound mixer to another or if i connect it directly to a recorder.

[pdf64]

Your original plan was fine but best to use a bigger cap, eg 33nF.

[arnenym]

I have no .033 at home. I tried a .047 and get a slightly lower output but there is no annoying "sewing machine distorsion" anymore.
I have better bass response. The bass move from -10 to -4 on the scale on my sound editor.
Great tip and i thanks a lot.
I will buy some lower volt .033 and .047 for this purpose.

[eschertron]

So from a 47n, moving to 33n or 68n will give you 'shades' of tone control. A good place to start. Glad you got the results you wanted

[Chuck H]

My design uses a 2.2k series resistor off the 4 ohm tap and a 47n cap across a 500k pot. That's a roll off at 10k of about 4.5dB. Which is actually a little conservative considering the nature of guitar speakers. And (this is embarrassing considering this is an amp I sell to customers) I've actually never even ear tested it. But I've had no complaints.