Power Supply part
Left pic:
var. resistor short side on pcb --> bias B
var. resistor left on long side pcb --> bias A
the other one ... filament hum removal
Right pic:
var. resistor short side pcb --> bias C
var. resistor right on long side pcb --> bias D
the other one ... the other filament hum remover
Left pic:
var. resistor short side on pcb --> bias B
var. resistor left on long side pcb --> bias A
the other one ... filament hum removal
Right pic:
var. resistor short side pcb --> bias C
var. resistor right on long side pcb --> bias D
the other one ... the other filament hum remover
Attachments
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I am still waiting for my Music Angel to arrive from Hong Kong and am eager to start working on it - so this is my first comment on this forum. It really sounds to me that the whistling problem is being caused by instability. This may be due to any one of the following or a combination. A microphonically sensitive valve - a wiring layout problem around the valve base (causing pickup), missing or wrong components in that part of the circuit, the need for a decoupling capacitor that may not have been included in the original design. I hope this has helped a little. I will no doubt become more familiar with the problems of this amp when I recieve mine in a few days time.
Holy thread resurrection!
I have an MA kt88 awaiting attention. It's new and I bought it cheaper without tubes so I can put my own circuit in, just using the old iron in it.
The problem with most of the hopeless GNFB circuits around is that the designer somehow hopes that the NFB will somehow ignore the phase shifts and frequency extremes (areas with loss rather than gain) and not screw itself up.
My MA design will not have a GNFB loop for this reason, in fact the only feedback will be on the primary side of the transformer, and I'll be driving the transformer with a low impedance source - a sure fire way of getting the best out of an output transformer. Especially compared to a barely functional and laggy NFB loop messing things up!
So yes I like the MA kt88, but as a DIY building block
I have an MA kt88 awaiting attention. It's new and I bought it cheaper without tubes so I can put my own circuit in, just using the old iron in it.
The problem with most of the hopeless GNFB circuits around is that the designer somehow hopes that the NFB will somehow ignore the phase shifts and frequency extremes (areas with loss rather than gain) and not screw itself up.
My MA design will not have a GNFB loop for this reason, in fact the only feedback will be on the primary side of the transformer, and I'll be driving the transformer with a low impedance source - a sure fire way of getting the best out of an output transformer. Especially compared to a barely functional and laggy NFB loop messing things up!
So yes I like the MA kt88, but as a DIY building block
Hi, recently my friend from Scotland asked me thoroughly reworked its amplifier MA800. It worked perfectly! The input stage operates in SRPP / ECC83 /. Phase inverter operates in parallel with a common cathode / ECC81 / and final stage of AutoBias / EL34 /. UPS is operating in a bridge configuration / no-voltage Doubler / - transformers connected in series. The effect is excellent. Yours Dinkers
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Music Angel
Hi Gary, I adjusted all the Chinese amplifiers. Gladly will put diagrams, but I have to find them and draw. Another amp I made the 6SL7 and 6SN7 tubes. Beautifully played by me MA845 modified. This is worth doing, because they have excellent output transformers / core /. In drawing this week will put MA800. Regards Dinkers
Hi Gary, I adjusted all the Chinese amplifiers. Gladly will put diagrams, but I have to find them and draw. Another amp I made the 6SL7 and 6SN7 tubes. Beautifully played by me MA845 modified. This is worth doing, because they have excellent output transformers / core /. In drawing this week will put MA800. Regards Dinkers
Attachments
Has anyone bought the 808 KT88 model from MA, I would love to see some mods or any thoughts on this model. Thanks. It seems that these amps are being changed amp to amp as they are being built, when they learn of an issue they fix it, but do not let anyone know about the changes, no scematic doesnt help, but changing amp to amp, the scematics wouldnt be worth much use anyways.
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