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/quadfranco/schemas/schemas.html
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/quadfranco/schemas/schemas.html
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
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
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..
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
That would be blasfemie.. I love my Krell - and also love my 606. Fact is, I REALLY love the two together. They have a synergy effect that is just perfect! (Well not keep my hand off perfect - nothing is...) but would like to get a lowered noisefloor and more real usage on the dial from the krell. Currently 9 o'clock is pretty high using an unbalanced input - but to high using the balanced input...
That would be blasfemie.. I love my Krell - and also love my 606. Fact is, I REALLY love the two together. They have a synergy effect that is just perfect! (Well not keep my hand off perfect - nothing is...) but would like to get a lowered noisefloor and more real usage on the dial from the krell. Currently 9 o'clock is pretty high using an unbalanced input - but to high using the balanced input...
dunno about blasphemy, an amp is a just dead object...
there's four places to put the resistors: in each end of a cable, at the preamp output och at the power amp input
or if the Krell preamp has adjustable inputs, then lower their sensivity accordingly
or maybe check how it's done on the Quad 520, it has adjustable inputs
there's four places to put the resistors: in each end of a cable, at the preamp output och at the power amp input
or if the Krell preamp has adjustable inputs, then lower their sensivity accordingly
or maybe check how it's done on the Quad 520, it has adjustable inputs
on 520 there's a 100k pot to ground, the input circuit exactly the same as for 306/606
suggest you get a 100k pot, connect it to the amp temporarily, set the level and then measure the R between the input to the pot and the output (middle pin) and then from the middle pin to ground...there's your two restistors that you can solder whereever you like
suggest you get a 100k pot, connect it to the amp temporarily, set the level and then measure the R between the input to the pot and the output (middle pin) and then from the middle pin to ground...there's your two restistors that you can solder whereever you like
imagine you split the pot into two resistors...let's assume that the right level is when the resistance from the input pin of the pot to the middle pin of the pot is 50k, you put a 50k from the preamp output signal to the 606 input and a 50k to ground from where the signal goes into the 606...
o-50k--o-----o
..........I
.........50k
..........I
o------o------o
(the dots are to get the horisontal formatting right)
520F schematic
o-50k--o-----o
..........I
.........50k
..........I
o------o------o
(the dots are to get the horisontal formatting right)
520F schematic
Until now I had modified my OLD 606 (> 15 years?) for three times.
For the first time, I replaced each 6800uF power filter capacitor with new 4700uF x 2.
I then rewired the connections among PCB, PSU, and the sockets.
The grounds are wired by using the single-core 2.6mm OFC cables.
The binding posts have also been replaced.
After playing I immediately noticed that the base is getting tighter and deeper (just a little).
For the second time, I replaced all the small capacitor to silver mica cap and PP cap.
The bridge rectifier was changed to Motorola 25A. In this time, the SPEED of the sound is dramatically improved!
Finally, I change the 47uF electrolytic cap (C7) to 47uF PP cap.
Wow, the sound is so clear. A lot of details¡K
Now I have been thinking about separating PSU for the two channels,
or, add regulated PSU for the driver-units / OP-amp.
I also thinking about replace the power transistors from GE17556 to MJ15003, and, replace the old 0.1R emit resistors.
Don¡¦t know whether these help...
For the first time, I replaced each 6800uF power filter capacitor with new 4700uF x 2.
I then rewired the connections among PCB, PSU, and the sockets.
The grounds are wired by using the single-core 2.6mm OFC cables.
The binding posts have also been replaced.
After playing I immediately noticed that the base is getting tighter and deeper (just a little).
For the second time, I replaced all the small capacitor to silver mica cap and PP cap.
The bridge rectifier was changed to Motorola 25A. In this time, the SPEED of the sound is dramatically improved!
Finally, I change the 47uF electrolytic cap (C7) to 47uF PP cap.
Wow, the sound is so clear. A lot of details¡K
Now I have been thinking about separating PSU for the two channels,
or, add regulated PSU for the driver-units / OP-amp.
I also thinking about replace the power transistors from GE17556 to MJ15003, and, replace the old 0.1R emit resistors.
Don¡¦t know whether these help...
Ibchen
I agree on the 47uF cap. Funny how big an influence that single component have on the sound. I have however, been changing it a couple of times - but so far I have not found the perfect match. So I am currently thinking of lowering the value to 22uF - but not sure if I can do this without other changes... Maybee someone with better skills can help in answering?
On the power caps - You have a mrk 1 version. Mine is a mrk II where the change was in the power supply. So mine have 2x15000 uF pr channel. Compared to a mrk 1 version, it is a lot better.
I agree on the 47uF cap. Funny how big an influence that single component have on the sound. I have however, been changing it a couple of times - but so far I have not found the perfect match. So I am currently thinking of lowering the value to 22uF - but not sure if I can do this without other changes... Maybee someone with better skills can help in answering?
On the power caps - You have a mrk 1 version. Mine is a mrk II where the change was in the power supply. So mine have 2x15000 uF pr channel. Compared to a mrk 1 version, it is a lot better.
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