Hi!
Well, I have a time ago finished my Leach amp. At the input i placed a 10k Alps pot from RS-components.
At the first listening test, I immidiately realised that the left channel was playing verymuch less than the Right. I tracked this down to the Pot, Having a 11,4K ohms on the one side and 9,2k ohms on the other. So obviously this was too much spread between the channels, makeing the right channel play alot louder than the left.
So, I bought a Bourns Conductive plastic pot, also 10k, only to face the same problem. But this pot had some other quircks as well. After a few days, The problem suddenly dissapeared! The channels played equally loud. Only given that I had the pot over a certian point, witch under that point there was no sound at all in the left channel (at all!). (Ill never use conuctive plastic again!!)
So, I used this pot awhile, only to realise that an input impedance of 10k // R1 (20K) = ~6,6K was far to small for my cd player and phono preamp...
Therefore I bought a 50k Alps again and unsoldered R1, making the Input Z 50k. And now I was back at the Channel phase problem again. (and some scratching noise in the right channel). I have tested only the left channel, and it works, if I unplyg the right one, I can play as loud as I want. A little thin in the bass area, but this goes for both channels...
Is it the Pots that do this? I am beginning to suspect that maybe my left channel have some wierd error, not as much gain as the right channel or whatever... Have not done any comprehensive measurments, but the channels draw the same bias current of course, 150mA.
PLease helpe me!
Stig
Well, I have a time ago finished my Leach amp. At the input i placed a 10k Alps pot from RS-components.
At the first listening test, I immidiately realised that the left channel was playing verymuch less than the Right. I tracked this down to the Pot, Having a 11,4K ohms on the one side and 9,2k ohms on the other. So obviously this was too much spread between the channels, makeing the right channel play alot louder than the left.
So, I bought a Bourns Conductive plastic pot, also 10k, only to face the same problem. But this pot had some other quircks as well. After a few days, The problem suddenly dissapeared! The channels played equally loud. Only given that I had the pot over a certian point, witch under that point there was no sound at all in the left channel (at all!). (Ill never use conuctive plastic again!!)
So, I used this pot awhile, only to realise that an input impedance of 10k // R1 (20K) = ~6,6K was far to small for my cd player and phono preamp...
Therefore I bought a 50k Alps again and unsoldered R1, making the Input Z 50k. And now I was back at the Channel phase problem again. (and some scratching noise in the right channel). I have tested only the left channel, and it works, if I unplyg the right one, I can play as loud as I want. A little thin in the bass area, but this goes for both channels...
Is it the Pots that do this? I am beginning to suspect that maybe my left channel have some wierd error, not as much gain as the right channel or whatever... Have not done any comprehensive measurments, but the channels draw the same bias current of course, 150mA.
PLease helpe me!
Stig
In order to understand your problem, can you make a schematic over your pot connection?
If you have a rather low input impedance together with a logarithmic(?) potentiometer you can easily get unequal volume. Also your scratching sounds, do you run any DC (from the input transistors) through the pot? If yes, one solution may be to add a resistor between the wiper of the pot and ground. This creates a safe and stable DC-path. Resistor value 100k - 1Mohms. Better with lower value but may influence the pot function.
There's nothing wrong with conductive plastic if the pot is in the right place.
If you have a rather low input impedance together with a logarithmic(?) potentiometer you can easily get unequal volume. Also your scratching sounds, do you run any DC (from the input transistors) through the pot? If yes, one solution may be to add a resistor between the wiper of the pot and ground. This creates a safe and stable DC-path. Resistor value 100k - 1Mohms. Better with lower value but may influence the pot function.
There's nothing wrong with conductive plastic if the pot is in the right place.
stigla said:
I think < 1kohms is considered to be low for some gear especially battery powered but for normal gear, 600 ohms and max 1V out, is not so heavy.
Grrr... I can't get my Image Attached!!
But, Here's a link to the schematic...
http://users.ece.gatech.edu/~mleach/lowtim/
I've connected the pot in the usual manner, the viper goes to R2 with one end of the track to gnd and the other to my input relays.
There is no coupling cap at the input, so I don't think there's any DC current running around.
The reason for using higher Input Z is because my Sony 930' CD player needs at least 50k, it says in the manual.
My amp is nearly a year old. Now in the reasent time I've started to notice some noise too, in the left channel. This noise is like normal noise, but very unstable! Sometimes I can hear it from my listening position! Maybe some transistors are on their way out?
But, Here's a link to the schematic...
http://users.ece.gatech.edu/~mleach/lowtim/
I've connected the pot in the usual manner, the viper goes to R2 with one end of the track to gnd and the other to my input relays.
There is no coupling cap at the input, so I don't think there's any DC current running around.
The reason for using higher Input Z is because my Sony 930' CD player needs at least 50k, it says in the manual.
My amp is nearly a year old. Now in the reasent time I've started to notice some noise too, in the left channel. This noise is like normal noise, but very unstable! Sometimes I can hear it from my listening position! Maybe some transistors are on their way out?
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