Hi!
Perhaps you have some DC on your line, and your transformer get's pre-magnetified and so humms. If you would like to investigate this, here is a goog starting point: http://www.diyaudio.com/forums/soli...oidals-summary-most-interesting-comments.html
Kind regards,
Matthias
Perhaps you have some DC on your line, and your transformer get's pre-magnetified and so humms. If you would like to investigate this, here is a goog starting point: http://www.diyaudio.com/forums/soli...oidals-summary-most-interesting-comments.html
Kind regards,
Matthias
Dear JimM
I have bypass the soft start this is not the problem.
Today i have tried another approach
I have bypass all the front end regulated psu everything is dead silent no any noise what's so ever.
I thing that the problem lies with the regulated psu transformer secondary winding.
I will try to hookup separate transformers and report back.
Dear Backbones
If i do remember correctly you have used salas regulated psu for your BA-2 front end
can you please provide your wiring diagram in order to compare.
If i do remember correctly you have used salas regulated psu for your BA-2 front end
can you please provide your wiring diagram in order to compare.
nikosgrdr,
I haven't got a wiring diagram. However, let's try and do it with words.
The 8 wires from the output of the Salas reg are joined to make two wires for the +ve, four for the ground and two for the -ve. I'm running it at -25-ground-+25.
The BA-2 board then receives these three connections.
I then also connect the ground of the BA-2 board to the star ground of the separate power supply which supplies the power boards (the design of this is identical to Nelson's circuit diagram in the BA-2 build including the CL60 thermistor connecting ground to the amplifier's chassis which is mains earthed).
If you don't connect the front end ground to the power board ground you will get a hum (from the loudspeakers not the transformers).
What is the voltage rating for your front end transformer? You may get saturation of your transformer due to poor manufacture or because it can't cope with the voltage input or both which can set up harmonic interference that can cause other transformers within the circuit to hum or buzz.
I haven't got a wiring diagram. However, let's try and do it with words.
The 8 wires from the output of the Salas reg are joined to make two wires for the +ve, four for the ground and two for the -ve. I'm running it at -25-ground-+25.
The BA-2 board then receives these three connections.
I then also connect the ground of the BA-2 board to the star ground of the separate power supply which supplies the power boards (the design of this is identical to Nelson's circuit diagram in the BA-2 build including the CL60 thermistor connecting ground to the amplifier's chassis which is mains earthed).
If you don't connect the front end ground to the power board ground you will get a hum (from the loudspeakers not the transformers).
What is the voltage rating for your front end transformer? You may get saturation of your transformer due to poor manufacture or because it can't cope with the voltage input or both which can set up harmonic interference that can cause other transformers within the circuit to hum or buzz.
Humm Problem
Dear all,
The hum problem when both front end inputs where connected with the outputs of a pre amp has been resolved by using two separate transformers (one per front end regulator also the main psu transformer for the output stage has been changed having now (4) separate secondary windings).
The amp now is silent.
One additional question.
Can someone advise were we can find very closely matched IRFP240-9240 (i cannot find any in tech diy).
Thanks
Dear all,
The hum problem when both front end inputs where connected with the outputs of a pre amp has been resolved by using two separate transformers (one per front end regulator also the main psu transformer for the output stage has been changed having now (4) separate secondary windings).
The amp now is silent.
One additional question.
Can someone advise were we can find very closely matched IRFP240-9240 (i cannot find any in tech diy).
Thanks
Attachments
Close matched IRFP240/9240
Go to search:
look for h_a
F5 power transitors
He is a European diy Audio member and sell these well matched parts.
Have had good experience.
Rgds
gku
Go to search:
look for h_a
F5 power transitors
He is a European diy Audio member and sell these well matched parts.
Have had good experience.
Rgds
gku
DC offset of Frond End
From the BA manual
"Set P201 to adjust the Drain voltage of Q203 to approximately 0 volts"
Where can we measure in order to set P201 to zero on frond end?
Thanks
From the BA manual
"Set P201 to adjust the Drain voltage of Q203 to approximately 0 volts"
Where can we measure in order to set P201 to zero on frond end?
Thanks
I guess you've read them, but just for reference, if anybody is wondering where to look for those jewels: 
FIRST WATT ARTICLES
FIRST WATT ARTICLES
yep , read those too. I was confused because I only had N boards,not N,P so Now I understand you can cascade 2 or more together or use 2 and bridge the outputs.
I had ordered BA-1,and looked at BA-2 also ,
Thanks,
Have a great day the sun is shinenin' in TEXAS
NS
I had ordered BA-1,and looked at BA-2 also ,
Thanks,
Have a great day the sun is shinenin' in TEXAS
NS
Hi NoSmoking,
one BA-1 output board works as one channel (= 1 mono), if you want stereo, build two. Of cause you can operate them as stated in the F4 article.
As the BA-1 is a single-ended amp, there's no need for complementary devices.
BA-2 is push pull, so you have n-channel and p-channel devices.
Thanks for the wishes, I would be glad if we'll get some sun and warmth here in Germany where I life, but the last days we had so much rain you could get the idea it's already november.
Have a nice day!
Matthias
one BA-1 output board works as one channel (= 1 mono), if you want stereo, build two. Of cause you can operate them as stated in the F4 article.
As the BA-1 is a single-ended amp, there's no need for complementary devices.
BA-2 is push pull, so you have n-channel and p-channel devices.
Thanks for the wishes, I would be glad if we'll get some sun and warmth here in Germany where I life, but the last days we had so much rain you could get the idea it's already november.
Have a nice day!
Matthias