great info Greg
wow, and I already find the design I was workingon with very very competitive, exluding the humm factor that is.
I am ordering some more parts tomorrow including 6 LM385
some of the R's you used are not in my stack-on cabinet.....
I found another design (from decdun) today.
If the ultimate schematic causes me anymore trouble the following days I think i will try the decdun design. seems pretty simple as well.
Jean-Pierre
wow, and I already find the design I was workingon with very very competitive, exluding the humm factor that is.
I am ordering some more parts tomorrow including 6 LM385
some of the R's you used are not in my stack-on cabinet.....
I found another design (from decdun) today.
If the ultimate schematic causes me anymore trouble the following days I think i will try the decdun design. seems pretty simple as well.
Jean-Pierre
Re: I am first
J-P,
Try this one, please. It's very close to the "Ultimate" but with beter DC offset. The pot can be 50k if you want. R* can be anything between 330 Ohm and 1K (keeps DC offset from changing too much at lowest volume levels). R5 I changed to 1K to get the gain down to 22. As per my observations it sounded beter to me. It's your call at the end.
uvodee said:
J-P,
Try this one, please. It's very close to the "Ultimate" but with beter DC offset. The pot can be 50k if you want. R* can be anything between 330 Ohm and 1K (keeps DC offset from changing too much at lowest volume levels). R5 I changed to 1K to get the gain down to 22. As per my observations it sounded beter to me. It's your call at the end.
Attachments
measuring LS
i made the schematic you have on top of here
I did not have a 100 k pot
so i used a new 25 k
same thing crackling followed by hum
this time i could almost swear i could hear radio conversations while the hum was present
i added for fun a 2000 uf 35 volts cap paralel to the 1000 uf from the V+ (c1)
result is a little les volume but crakling much less and there is no more hum??????? not sny other interference
i measured the dc offset ( i used a 9 ohm R}
offset was 35 mv without load and between 0 (or -0) and 28 mv fluctuatung, with music
Greg what do you suggest?
J-P
i made the schematic you have on top of here
I did not have a 100 k pot
so i used a new 25 k
same thing crackling followed by hum
this time i could almost swear i could hear radio conversations while the hum was present
i added for fun a 2000 uf 35 volts cap paralel to the 1000 uf from the V+ (c1)
result is a little les volume but crakling much less and there is no more hum??????? not sny other interference
i measured the dc offset ( i used a 9 ohm R}
offset was 35 mv without load and between 0 (or -0) and 28 mv fluctuatung, with music
Greg what do you suggest?
J-P
It looks like powersupply (PS) related.
First, add a 100pF cap between +in and -in of the amp (pin 7 and 8) and see if you'll stop hearing the radio. Do that first please.
Second (if the above doesn't help) I looks like the 1000uF cap didn't work very well (maybe a bad cap). What hapenes if you replace that cap with another 1000uF cap? remove the old one and put a new one in place. Also the volume shoudn't depend on that cap at all.
What kind of transformer do you use? Is it possible to be too small for the porpose and not be able give you enough power.
What type of PS caps do you use? One or two transformers per chanel. one or two bridges per chanel.
Important!!!
I reread your previous messages and couldn't find any PS details. You said 60V after the bridge. Can you tell me what voltage do you have between pin1 and GND and between pin4 and GND.
I realy need those voltages.
Thanks!
First, add a 100pF cap between +in and -in of the amp (pin 7 and 8) and see if you'll stop hearing the radio. Do that first please.
Second (if the above doesn't help) I looks like the 1000uF cap didn't work very well (maybe a bad cap). What hapenes if you replace that cap with another 1000uF cap? remove the old one and put a new one in place. Also the volume shoudn't depend on that cap at all.
What kind of transformer do you use? Is it possible to be too small for the porpose and not be able give you enough power.
What type of PS caps do you use? One or two transformers per chanel. one or two bridges per chanel.
Important!!!
I reread your previous messages and couldn't find any PS details. You said 60V after the bridge. Can you tell me what voltage do you have between pin1 and GND and between pin4 and GND.
I realy need those voltages.
Thanks!
Greg, Greg, Greg.....
the more I thought about going another schematic, the more I started doubting my components....
and guess what, the IEC receptacle (with some kind of filter in, did not let ground go through, I have a few (recycled from old pc's and I guess that a)it had a default when it came here or I used too much heat when desoldering the original wiring - for that I use a 100Watt gun....
I used another (recycled) receptacle (after testing the ground and..........................
everything is PURRRRRRFECT now!!
It sounds perfect, no crackling, no humm....
and i use the setup of the original Ultimate Schematic of the Gainclone
exactly like the first duo I made...
Thanks for standing by me!!!!!
J-P
the more I thought about going another schematic, the more I started doubting my components....
and guess what, the IEC receptacle (with some kind of filter in, did not let ground go through, I have a few (recycled from old pc's and I guess that a)it had a default when it came here or I used too much heat when desoldering the original wiring - for that I use a 100Watt gun....
I used another (recycled) receptacle (after testing the ground and..........................
everything is PURRRRRRFECT now!!
It sounds perfect, no crackling, no humm....
and i use the setup of the original Ultimate Schematic of the Gainclone
exactly like the first duo I made...
Thanks for standing by me!!!!!
J-P
Glad to be of help and to hear everithing is fine now.
I 'd still recomend the sch from my post above (with the red corrections) and if not just add a 470ohm to 1k res. in ser. of +in (the DC offset will be under control at near 0 volume level). Tell me if you don't know what I mean exactly.
Happy listening!
Greg
I 'd still recomend the sch from my post above (with the red corrections) and if not just add a 470ohm to 1k res. in ser. of +in (the DC offset will be under control at near 0 volume level). Tell me if you don't know what I mean exactly.
Happy listening!
Greg
funny that you mention it
I orderd some extra parts (like the 100K pot and some R's with other values=1K)
and a whole bunch of values from a guy from ebay as well.
now it's time to go and look for some more expensive caps to switch and see what happens...
what do you think of nichicon computer grade?
Jean-Pierre
I orderd some extra parts (like the 100K pot and some R's with other values=1K)
and a whole bunch of values from a guy from ebay as well.
now it's time to go and look for some more expensive caps to switch and see what happens...
what do you think of nichicon computer grade?
Jean-Pierre
Re: no
It could be the missing ser. res. that I suggest you use. Some of the IC's are not as balanced as others. That why I suggested it. My amp for example, one channel is between -5mV@0 vol. and +8mV@max vol. The other one 0-15 mV (with the 1k res ser to +in). Also when you measure the DC offset don't connect any source to the input of the amp, so that the output AC signal doesn't affect the DC offset reading.
uvodee said:it lingers between 0 and 5 mv
when there is no sound it goes to 0
mind you, it seems to differ when using different LM's
I had one (my first work) that went to about 600 mv...
may have been because of my abilities or inablities i should say
J-P.
It could be the missing ser. res. that I suggest you use. Some of the IC's are not as balanced as others. That why I suggested it. My amp for example, one channel is between -5mV@0 vol. and +8mV@max vol. The other one 0-15 mV (with the 1k res ser to +in). Also when you measure the DC offset don't connect any source to the input of the amp, so that the output AC signal doesn't affect the DC offset reading.
I am ready to start a new
set of LM 3875's and as you could expect, I have a new question!
Beside the Basler transformers I have (quite a few I may say), I also have a toroid that has:
- input 120 vac
- output 88 vct (44vas/0/44vac dual secondary)
- Av= 400
- I = 5.2 A
- weighs about 5 lbs, diameter is 5"
The wiring =
A) 2wires (1 is purple and 1 is transparent) they serve as input wires
B) 1 grey wire and 1 blue wire (when measuring both = 88volts
C) 2 naked copper wires,twisted around each other and protected with a loose black sleeve. When measuring the grey or blue wire with the copper wire(s) I get 44 vac
Can I use this one toroid for 2 LM3875's ??????? And if so, how do I use this toroid?
Jean-Pierre
set of LM 3875's and as you could expect, I have a new question!
Beside the Basler transformers I have (quite a few I may say), I also have a toroid that has:
- input 120 vac
- output 88 vct (44vas/0/44vac dual secondary)
- Av= 400
- I = 5.2 A
- weighs about 5 lbs, diameter is 5"
The wiring =
A) 2wires (1 is purple and 1 is transparent) they serve as input wires
B) 1 grey wire and 1 blue wire (when measuring both = 88volts
C) 2 naked copper wires,twisted around each other and protected with a loose black sleeve. When measuring the grey or blue wire with the copper wire(s) I get 44 vac
Can I use this one toroid for 2 LM3875's ??????? And if so, how do I use this toroid?
Jean-Pierre
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