Hi all. I have just rebuilt a pair of Quad 50e amplifiers and they sound good no noise at all. I boxed them up and sent them to a friend, when he received the amplifiers and set them up they both have a buzz. I asked him to check to see if anything as come loose in transportation, he as also checked for earth loops. The amplifiers buzz with out a load. I cannot get to see them because my friend lives to far from me I would be grateful for any help that anyone can give me.
Regards Western 91.
Regards Western 91.
Perhaps possible to isolate amps from rest of the stereo set? i.e. different socket/ power strip. Had some hum with my combo Quad 303 and Perreaux preamp and had to detach one of the grounds to avoid loop. Btw my speakers' sensitivity is high and I still hear a slight hum.
You could ask DADA Electronics as they are very knowledgable and have a forum too.
You could ask DADA Electronics as they are very knowledgable and have a forum too.
I have a set of quad 50e amplifiers and I too get a slight hum / hiss from both channels with or with out the preamp on or off or connected physically. this includes one unit that was recently serviced. but the sound is the same both sides. the preamp is a 33.
my speakers are a pair of lowthers with single drive new Dx3 units which are known for being quite sensitive . one thing I noticed recently was that I had the lowthers connected down stairs to my quad 2 /22 set up and indeed there is a slight bit of noise hum hiss when they are sitting there switched on, but nothing going through them (zero volume).
when I recently swapped them out for a set of ESL57s onto the same quad 2/22 system the hum and noise is completely gone. the amount of volume required on the quad 2/22 ESL57 is far greater than with the lowthers generally.
I have tried a number of unplugging and extensions etc even just one Q50 plugged on its own with no preamp and still the same hum and slight hiss
the hum and hiss is no better or worse even when the preamp is turned up with no signal. so I dont think its the 33 at all as the same is heard when the 33 is not even on or connected.
the hum and hiss is only really noticeable at close up distance and is barely noticeable at 6 feet listening. once there is sound is up you can not notice it over music although it is obviously I know there now in reality.
I suspect it is the sensitivity of the speakers as I think originally the ESL 57s just weren't sensitive enough to pick up the background and noise.
to triple check the obvious some may be picking up was I connected the lowthers to a modern (post 60s set up ) a Sony receiver amplifier to see if its the lowthers . not a peep out of them silent so its the not the speakers other than their sensitivity picking up something from my Stone Age quad amps.
the sound coming out of the 33/ 50e / lowther set up is actually very good and I have no complaints there.
I do understand that the quad 50e have out put transformers rather than capacitors in the later transistor amps and that is the reason the distortion in the 50s is great than the 303s although at my age I can't hear much above 10Khz any way . could this also be the reason we are getting hum and hiss in very sensitive speakers. I suppose I could lug the ESLs ( or maybe just one) upstairs to see if there is any discernible hum or hiss at zero volume with them. perhaps when Mr Walker was testing the set ups there was never anything to hear so it was never seen as an issue. Perhaps this is a niche issue and it may be that this is just a fact for any one using modern sensitive speaker units with old quad stuff and may be it is the case that output transformers of that age have a certain amount of noise when driving speakers with such sensitivity . any ideas?
my speakers are a pair of lowthers with single drive new Dx3 units which are known for being quite sensitive . one thing I noticed recently was that I had the lowthers connected down stairs to my quad 2 /22 set up and indeed there is a slight bit of noise hum hiss when they are sitting there switched on, but nothing going through them (zero volume).
when I recently swapped them out for a set of ESL57s onto the same quad 2/22 system the hum and noise is completely gone. the amount of volume required on the quad 2/22 ESL57 is far greater than with the lowthers generally.
I have tried a number of unplugging and extensions etc even just one Q50 plugged on its own with no preamp and still the same hum and slight hiss
the hum and hiss is no better or worse even when the preamp is turned up with no signal. so I dont think its the 33 at all as the same is heard when the 33 is not even on or connected.
the hum and hiss is only really noticeable at close up distance and is barely noticeable at 6 feet listening. once there is sound is up you can not notice it over music although it is obviously I know there now in reality.
I suspect it is the sensitivity of the speakers as I think originally the ESL 57s just weren't sensitive enough to pick up the background and noise.
to triple check the obvious some may be picking up was I connected the lowthers to a modern (post 60s set up ) a Sony receiver amplifier to see if its the lowthers . not a peep out of them silent so its the not the speakers other than their sensitivity picking up something from my Stone Age quad amps.
the sound coming out of the 33/ 50e / lowther set up is actually very good and I have no complaints there.
I do understand that the quad 50e have out put transformers rather than capacitors in the later transistor amps and that is the reason the distortion in the 50s is great than the 303s although at my age I can't hear much above 10Khz any way . could this also be the reason we are getting hum and hiss in very sensitive speakers. I suppose I could lug the ESLs ( or maybe just one) upstairs to see if there is any discernible hum or hiss at zero volume with them. perhaps when Mr Walker was testing the set ups there was never anything to hear so it was never seen as an issue. Perhaps this is a niche issue and it may be that this is just a fact for any one using modern sensitive speaker units with old quad stuff and may be it is the case that output transformers of that age have a certain amount of noise when driving speakers with such sensitivity . any ideas?
I serviced total of 9 QUAD 50E lately. The works I did including checking the capacitor's ESR and capacitance (replaced those one with high ESR), replacing all 3 trim pots (1x 2.2K, and 2x 100-ohm), replacing the 180 ohm 10W resistor with aluminum chassis mount resistor.
The large 5000uF 50V capacitors were fine in all the units.
I set the bias current to approximately 200~260mA for the lowest THD (below 0.1%) below 2 watts. The THD rams up from 2W to 0.2% and THD remains same upto 50 watts rms.
I am so amazing with the sound of the Quad 50E because I am a tube amp guy.
The large 5000uF 50V capacitors were fine in all the units.
I set the bias current to approximately 200~260mA for the lowest THD (below 0.1%) below 2 watts. The THD rams up from 2W to 0.2% and THD remains same upto 50 watts rms.
I am so amazing with the sound of the Quad 50E because I am a tube amp guy.
The factory specification is 30-40mA each side when cold. It's surprising that you didn't get thermal runaway.