Volume difference on Quad Preamp?

[joe web]

hi folks,

i bought a quad pre few weeks ago. really a cool preamp with a lot of different sounds, i like it.
but is it normal, that channel 1 is louder as channel 2? nevermind if i choose lead or rhythm.
and is it normal, that you get a volume drop by switching in the graph eq?

with my studio pre i get a minimal volume rise with the graph in, but with the quad the volume goes down.

would be nice if some quad users could write their experience.

 

[MetalMatt]

Not sure what is normal, but my Quad is the same way. R1 and L1 are louder than R2 and L2 with the same volume settings. I can have each channel and mode have unity volume as long as Channel 1's volume is turned down. This must be of the different volume tapers in the channels (the manual explains this). As for the EQ it depends on how I have it set. My volume could rise or drop when activating it. The only time I get a drop in volume is when I drop all sliders, but that is to be expected.

 

[ak47]

Try the settings in the following thread.... it is all a question of balance so you should be fine once you mess around some more.

http://forum.grailtone.com/viewtopic.php?f=5&t=27607

Remember that gig settings are a lot different to the settings you would normally use in your bedroom!

 

[boyfrenzy]

It could be the optocouplers . It's the weakness of Quad preamp ...

 

[dmt]

can you explain the function of optocouplers and what it has to do with the quad specifically? I just want to know what the symptoms are of this so that if it happens i qill know what too look for and what to do and or avoid doing. thnx in advance.

 

[boyfrenzy]

The optocouplers are the switching machine of the Quad preamp. As you can see on the picture it's led+resistor. So it's not really a switch! When it's OFF the resistance increases to 50 Mohm => the signal is blocked. When it's ON the resistance decrease to 630 ohm => the signal is NOT blocked.

The problem is that optocouplers gets damaged with time. So the resistance When it's ON increase and signal is affected : volume decrease inversely proportional with the resistance value.

Another problem : opto are expensive 5€ and there is 19 optocoupler in a Quad, You do the math!

 

[joe web]

The optocouplers are the switching machine of the Quad preamp. As you can see on the picture it's led+resistor. So it's not really a switch! When it's OFF the resistance increases to 50 Mohm => the signal is blocked. When it's ON the resistance decrease to 630 ohm => the signal is NOT blocked.

The problem is that optocouplers gets damaged with time. So the resistance When it's ON increase and signal is affected.

Another problem : opto are expensive 5€ and there is 19 optocoupler in a Quad, You do the math!

that´s interessting!
but how do i know that the problem really comes from the optos? it there any other way to check this as to change them all?

 

[boyfrenzy]

The only way is to sloder out the opto, apply 2 Volts on the LED and check the résistance value (with ohmmeter) when LED it's ON.

 

[Niksounds]

Here the same..
ch1 louder as ch2

I don't think on a optocouplers problem.. imho it's to affinate all the balance between the masters and lead masters.
(this only becouse i find this point, the volume difference, too much "common".. the "attitude" of our Quad is the same)