Pre Amp

[kbyrne]

I just bought a Pre_Amp kit and have a question. I want to add a balance pot
of 100k blue velvet type to match 100k volume pot. How will this affect the circuit of pdf. Am I right to assume that the volume will be lowered other than that it will not adversly affect the circuit.

 

[JMFahey]

Please post what actual balance circuit you will use.
You show active side of preamp only but not the passive one, where your doubt lies.

 

[kbyrne]

I was only thinking about a board with volume alps and the second alps wired backwards then wired to kit board.

 

[kbyrne]

I am not shure what you ment by your post reply. This is a buffered pre amp with a tone control board after it. What type? transistor or op_Amp. That is another question so I can figure out this box idea I have.

 

[PRR]

There are several connections for balance pots. Which plan will you use?

 

[DF96]

Perhaps he is asking us to tell him how to do it?

 

[kbyrne]

I just uploaded a sch that I have in Eagle. Question is how will this brd before my kit affect the outcome of buffered Pre Amp? What can I expect and is there a better way to get Volume and Balance into the front end of my kit project?

 

[PRR]

I just uploaded a sch....

If P2 is a dual Linear, you get 6dB lower signal (often not a problem) and very insignificant change of your Loudness compensation.

 

[kbyrne]

Thank you for reply. Both pots are blue velvet Alps types bought in China and are B100k
linear types. I heard on a few web sites Alps are the type to buy but am new to this type of thinking. At 6db loss is NE5532 Treble, Midrange & Bass better or would a transistor
tone control be better?

 

[PRR]

... NE5532 Treble, Midrange & Bass better or would a transistor tone control be better?

Now there is a tone control involved?

Might be best to find plans for a "complete" control preamp, not a basic preamp with things attached.

 

[kbyrne]

Sorry I wasn't clear of the whole picture but with a additional pot I knew the volume would be less due to additional resistance. I found a site about db definition and am going to look
at that aspect trying to figure it all out without training. I have successful Pre Amps, and tone controls in boxes and wanted one good one in the same box. I will look into what you stated. Best Kevin

 

[AndrewT]

using a vol pot as a balance control adds resistance/impedance to your input circuit.
That is not a nice way to do balance adjustment.
They make balance pots. They have zero ohms resistance on one half of the track and all the balance resistance is built into the other 50% of the track. For a two channel balance control the two halves of zero ohms are on opposite sides to the centre detent rotation.
This gives a zero ohms straight through with a paralleled load to signal ground when centred. As one turns towards one side the ohms of resistance is inserted to reduce the level on that side, while the other side is still on the zero ohms straight through section of track.
You will have to search to find any retailers of these balance pots.

 

[kbyrne]

Andrew is a blend pot for guitars, amps the same type of pot you talk about? They have 250k and 500k mentioned in first google search.

 

[kbyrne]

I have found a 0 detent Alps blue velvet but have one question. Rod Eliot has a better volume control pdf. He states a formula that needs a 250k ballance pot for use with a 100k volume pot. Is anyone experienced with his work? I tried to upload a pdf but its size is too big. I could try a link if need be for all to view.