Quad 606 modifications

[aarsoe]

Hi

Does anyone have experience in modding the Quad 606 power amp? I am especially looking for one thing to achieve.
Namely - lower input sensitivity. As it is original, a 0.5V signal will give full power, and I really would like to increase this to at least 2.0V

Should you have other ideas, then please feel free to add..

PS: Schematics can be found here: http://iquebec.ifrance.com/quadfranc...s/schemas.html

[Graham Maynard]

Hi Aarsoe,

I would not change anything within this amplifier as Quad have gone to a lot of trouble to optimise it.

Why not make up an external fixed potentiometer using resistors ?

Cheers ........ Graham.

[pinkmouse]

I agree with Graham, a simple two resistor voltage divider in the input lead seems the way to go to me.

[aarsoe]

Thanks - I was also under the impression that the easiest way was to use resistors - that is until I saw someone reducing the gain on a 405 by chanching the input module. so why not do the same on the 606 - anyway any other people have ideas?

[analog_sa]

Ehm, what exactly do you call an input module? It's very simple - you can either reduce the gain before the amp or you can change the feedback to suit you. The fb route seems extremely inappropriate with the Quads but may well work.

[Zombie]

The 405 and 306/606 have different input stages....

[aarsoe]

Well - what can I say but bummer...
I really love my 606, but using it with my Krell KRC-3 that can gives an output of max 9V makes it somewhat difficult. Guess I will have to try the resister solution... Thanks..

[Phasenoise]

Well here is my first post.

The 606 is a fine amp, I wouldn't mess about with the input stage or the feedback as the current dumping is from what I remember part of the feedback loop. (Probably wrong, it's been a long time.)

I would use external resistors.

All that needs changing really is some nice cable from the phono plugs to the boards as they used nasty generic cable and not of equal length, and some nice speaker cable from the boards to the outputs.

When I had the 606 MK1 I used Van Den Hul Thunder line to the amp modules and Van Den Hul The Wind for the outputs. I also changed the binding posts as the counter sunk ones tend to melt when trying to solder anything but the nasty string cable they used.

The 606 as I said is a fine amp and doesn't relly need any more re working, Good solid clean design and well implemented.

Hope this helps

Phasenoise

[aarsoe]

Phasenoise

The speaker post are already changed. They are typical of the time when the amp was built, pretty cheap stuff (even though you can still see something like that being used today). Was pretty easy. All it took was a nice sharp drill to enlarge the holes to the new speaker post's.
Have also changed the rca plugs, as they are also pretty bad. On the cable side, I am waiting for some cable I have ordered to do so.
Have also done some changes to the cabinet, as it have a tendency to ring if you knock on it. So some dampening have been applied.
Finnally I have exchanged a few capacitors to black gate types, but as the amp is still running in, it is to early to judge the end results. Have alwayes found that black gates, and in fact most caps, sound awfull for the first 100 hours before they start to open up.
So the input sensitivity was really just the final icing on the cake I was looking for when I was due to change the cables anyway..

[Zombie]

Or why not go the other way around...damp the Krell...I know that Quad does this on the 34, just change som resistors at the output...