Andre Visser said:
Two PSU's indeed - two totally independant channels...
I did try a single channel but unfortunately hum still features.
Also connected the transistor B-E as zener but no noticable difference...
D
Can "over voltage" be the cause of this hum?
I measure 17.98 vDC at the supply points at the amplifiers after the cap multiplier.
D
I measure 17.98 vDC at the supply points at the amplifiers after the cap multiplier.
D
You said a while ago that you measure 14.5V from the PSU?
Try to add a 12V zener from the base of the cap multiplier transistor to 0V. (Cathode on base, anode on 0V star earth)
Try to add a 12V zener from the base of the cap multiplier transistor to 0V. (Cathode on base, anode on 0V star earth)
Hi GD,
When you dangled the B-E junction over the 100mfd cap in the multiplier did you re - read the voltage at the amps themselves. It should have dropped to around 7 or 8 volts. This would "prove" it was working OK as a zener. It would prove a lot as to whether it really is a PSU ripple issue ! You ask about overvoltage. That in itself will not affect the hum. I am a little suprised it made no change at all, I think we could do with making sure the multiplier is working correctly. If you disconnect the 4.7 K resistor the voltage to the amps should drop to zero. Could you try that as well. Something does not sound quite right here.
The quality thing is interesting. Quite a few years ago now I had a Pioneer A80. If specs meant anything at all this was the ultimate. Sadly, although I tried to convince myself there must be other shortcomings in the rest of the system it wasn't so. The amp was unmusical, cold sounding. That's how I ended up with my present design, it's not perfect technically, but it sounds fantastic, now 95% of my music collection sound fabulous, the music shines through whatever the shortcomings of the recording.
When you dangled the B-E junction over the 100mfd cap in the multiplier did you re - read the voltage at the amps themselves. It should have dropped to around 7 or 8 volts. This would "prove" it was working OK as a zener. It would prove a lot as to whether it really is a PSU ripple issue ! You ask about overvoltage. That in itself will not affect the hum. I am a little suprised it made no change at all, I think we could do with making sure the multiplier is working correctly. If you disconnect the 4.7 K resistor the voltage to the amps should drop to zero. Could you try that as well. Something does not sound quite right here.
The quality thing is interesting. Quite a few years ago now I had a Pioneer A80. If specs meant anything at all this was the ultimate. Sadly, although I tried to convince myself there must be other shortcomings in the rest of the system it wasn't so. The amp was unmusical, cold sounding. That's how I ended up with my present design, it's not perfect technically, but it sounds fantastic, now 95% of my music collection sound fabulous, the music shines through whatever the shortcomings of the recording.
Goodie good!
I received all the ordered parts late today and tomorrow can start experimenting with the regulators etc...
D
I received all the ordered parts late today and tomorrow can start experimenting with the regulators etc...
D
Whoa-hey!! What did I tell you??
All the amplifiers needed were a simple regulator.
The sound, using the mains transformer, is now breathtakingly brilliant. Dead quiet background - ZERO hum or buzz.
I am using a 1A, 7812CT regulator with a 400mfd cap on output. Works like a charm!
D
All the amplifiers needed were a simple regulator.
The sound, using the mains transformer, is now breathtakingly brilliant. Dead quiet background - ZERO hum or buzz.
I am using a 1A, 7812CT regulator with a 400mfd cap on output. Works like a charm!
D
Attachments
Hmm. I appear to have missed something!
Is the end result different enough to post a schematic? I must have a schematic of everything that sounds good...
- keantoken
Is the end result different enough to post a schematic? I must have a schematic of everything that sounds good...
- keantoken
keantoken said:
Hi Kean
I'll draw up a detailled schematic of the stereo amp including the regulator circuit and mail it to you.
Drop me a mail at: dewald (AT) greenlizard (dot) co.za
I would also then be honoured if you can build the amp and tell me what you think of the sound.
Dewald
Good news Dewald.
Try to put your regulator as close as possible to the amplifiers. I would even suggest using one for each channel with separate wiring between GND pin and star earth. Also try 100nF caps just before and after the regulator.
André
Try to put your regulator as close as possible to the amplifiers. I would even suggest using one for each channel with separate wiring between GND pin and star earth. Also try 100nF caps just before and after the regulator.
André
Mooly said:
Well Mooly
I also built one of these today: http://www.diyaudio.com/forums/showthread.php?s=&postid=1547659
See last post.
I would like to expand on that subject as well.
D
Hi,
Now something like that does need clean supplies 😀
Are you after building a few different RIAA amps to compare.
Now something like that does need clean supplies 😀
Are you after building a few different RIAA amps to compare.
Mooly said:
No... just one very good one that I can use every day. The EAR 834P that I am cuurently using is on loan from a friend. (think I might clone it... he-he!)
D
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