Are you going to try it with a dummy load ?colin.hepburn wrote:No The amp is on the table no connections in or out the MM is connected to it monitoring the currentMike H wrote:So the inputs are not AC grounded in any way then? Or are you actually playing music through it from something else?
Sick pioneer SA6200
- pre65
- Amstrad Tower of Power
- Posts: 21400
- Joined: Wed Aug 22, 2007 11:13 pm
- Location: North Essex/Suffolk border.
#121
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
- colin.hepburn
- Shed dweller
- Posts: 2294
- Joined: Sat Jun 02, 2007 1:24 am
- Location: Scotland Aberdeenshire
#122
Well after running the sick pioneer SA-6200s /power amp with nad preamp and running the other pioneer SA-6200 it seems to sound different too sick pioneer SA-6200 After opening it up and checking I see the left channel has two different small single transistors and all drive and output transistors have been replaced but the numbers have faded will have to look again in day light but this amp does't sound as good
- colin.hepburn
- Shed dweller
- Posts: 2294
- Joined: Sat Jun 02, 2007 1:24 am
- Location: Scotland Aberdeenshire
#123
HO Dear I seem to have a problem with the Sick pioneer SA6200 I was running my headphone amp as a pre with some Sade sounding great then suddenly the amps sound brake up with a distorted cracking bass sound but oddly when switching off the SA6200 the sound come back OK for a few seconds with the capacitors discharging any ideas the amp is cap coupled to the speakers could it be a capacitor
- colin.hepburn
- Shed dweller
- Posts: 2294
- Joined: Sat Jun 02, 2007 1:24 am
- Location: Scotland Aberdeenshire
#124
AH Breathing againcolin.hepburn wrote:HO Dear I seem to have a problem with the Sick pioneer SA6200 I was running my headphone amp as a pre with some Sade sounding great then suddenly the amps sound brake up with a distorted cracking bass sound but oddly when switching off the SA6200 the sound come back OK for a few seconds with the capacitors discharging any ideas the amp is cap coupled to the speakers could it be a capacitor
I over looked the fact there are two fuses in the speaker line strange thou any ideas what happened
- Mike H
- Amstrad Tower of Power
- Posts: 20189
- Joined: Sat Oct 04, 2008 5:38 pm
- Location: The Fens
- Contact:
#125
Without watching it do it with a 'scope or something can't really say.
Maybe a large slow DC offset on the input? Is the headphones amp loaded like it would be with headphones connected?
Maybe a large slow DC offset on the input? Is the headphones amp loaded like it would be with headphones connected?
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
- colin.hepburn
- Shed dweller
- Posts: 2294
- Joined: Sat Jun 02, 2007 1:24 am
- Location: Scotland Aberdeenshire
#126
The Headphones were unplugged at the time Shunt pot is over sensitive there was a mains power Dip which may have contributed perhaps the pre out is 1uf polypropylene Caps and 1M resistorsMike H wrote:Without watching it do it with a 'scope or something can't really say.
Maybe a large slow DC offset on the input? Is the headphones amp loaded like it would be with headphones connected?
- Mike H
- Amstrad Tower of Power
- Posts: 20189
- Joined: Sat Oct 04, 2008 5:38 pm
- Location: The Fens
- Contact:
#127
Looking at the diagram again, the power amp input impedance is about 50 kilohms, so 1uF should be about right for that. However is the headphones amp a valve circuit?
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
- colin.hepburn
- Shed dweller
- Posts: 2294
- Joined: Sat Jun 02, 2007 1:24 am
- Location: Scotland Aberdeenshire
#128
Yep its my 5757/12B4AMike H wrote:Looking at the diagram again, the power amp input impedance is about 50 kilohms, so 1uF should be about right for that. However is the headphones amp a valve circuit?
- Mike H
- Amstrad Tower of Power
- Posts: 20189
- Joined: Sat Oct 04, 2008 5:38 pm
- Location: The Fens
- Contact:
#129
Ah right so I'm guessing mains had a dip, BIG Voltage shift into the Pioneer. Probably drove it up to one supply rail or the other so no wonder it was clipping.
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
- colin.hepburn
- Shed dweller
- Posts: 2294
- Joined: Sat Jun 02, 2007 1:24 am
- Location: Scotland Aberdeenshire
#130
\Ah OK thanks mike that hadn't occurred to me thatMike H wrote:Ah right so I'm guessing mains had a dip, BIG Voltage shift into the Pioneer. Probably drove it up to one supply rail or the other so no wonder it was clipping.
Next up is the over sensitive Shunt Alps pot 100k could do with a bit less gain
Pre out connected to 12B4A
See Page four
http://hollowstate.netfirms.com/mapletreebranches1.pdf
- Mike H
- Amstrad Tower of Power
- Posts: 20189
- Joined: Sat Oct 04, 2008 5:38 pm
- Location: The Fens
- Contact:
#131
Yes I see, though I think it probably wants a regulated HT supply.
That's the trouble with feeding valves outputs into tranny circuits, large Voltage shifts whenever the supply changes.
Can also be demonstrated on an oscilloscope, turn it up and the trace can disappear off the screen for a second or so next time the boiler thermostat goes on or off Viz, causes the mains to change a bit.
That's the trouble with feeding valves outputs into tranny circuits, large Voltage shifts whenever the supply changes.
Can also be demonstrated on an oscilloscope, turn it up and the trace can disappear off the screen for a second or so next time the boiler thermostat goes on or off Viz, causes the mains to change a bit.
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."