Here it is in all it's glory
With this circuit I have absolutely no DC-offset on the input.
No input caps needed.
I have two outputs on the board.
The direct output, depending on the position of the (20k log Alps Blue) pot varies between -30mv to 100mv DC-offset at max. volume.
I'm using the other output (with the caps).
The sound is fantastic, enjoy.
With this circuit I have absolutely no DC-offset on the input.
No input caps needed.
I have two outputs on the board.
The direct output, depending on the position of the (20k log Alps Blue) pot varies between -30mv to 100mv DC-offset at max. volume.
I'm using the other output (with the caps).
The sound is fantastic, enjoy.
Attachments
If I may answer your Q.
It's to null the DC on the output of the AD815 (before the cap) at the direct output.
It will be connected on the + input of the AD815(* at the connection of R2 & R3) and trimed by the pot R3 & R6.
Audiofanatic
Nuuk said:Carlos - I'm confused! What is the bit of the circuit using the 78L09 regulator doing?
It's to null the DC on the output of the AD815 (before the cap) at the direct output.
It will be connected on the + input of the AD815(* at the connection of R2 & R3) and trimed by the pot R3 & R6.
Audiofanatic
Re: do you use both halves?
Yes.
Double the regulation?
No.
The LM317/337s are on-board, the PSU is unregulated with schottky diodes and 4700uf caps.
Regulation before the LM317/337s sounds worse to me.
The 78L09 is to null dc-offset.
This is a current-feedback op-amp and, as normal, it has DC on the inputs and outputs.
This way DC is low on the output and none at the input.
DC was a little high because I'm not matching impedances.
Otherwise the input signal would be very attenuated.
Remember, here we can't use the feedback resistor we want as in voltage-feedback op-amps.
As I said, the schematic was halfway done.
I finished it yesterday night.
I had the two channels on the schematis (it's redundant anyway) but I had to remove the other one because I reached the limit of 50 parts on CircuitMaker 6 Student.
This software makes very "clean" schematics, I like it.
But 50 parts is a very low limit.
EDIT: Oh, if you are worried, let me tell you that soundstage is very good and channel separation too.
earsandeyes said:
Yes.
earsandeyes said:
Double the regulation?
No.
The LM317/337s are on-board, the PSU is unregulated with schottky diodes and 4700uf caps.
Regulation before the LM317/337s sounds worse to me.
The 78L09 is to null dc-offset.
This is a current-feedback op-amp and, as normal, it has DC on the inputs and outputs.
This way DC is low on the output and none at the input.
DC was a little high because I'm not matching impedances.
Otherwise the input signal would be very attenuated.
Remember, here we can't use the feedback resistor we want as in voltage-feedback op-amps.
As I said, the schematic was halfway done.
I finished it yesterday night.
I had the two channels on the schematis (it's redundant anyway) but I had to remove the other one because I reached the limit of 50 parts on CircuitMaker 6 Student.
This software makes very "clean" schematics, I like it.
But 50 parts is a very low limit.
EDIT: Oh, if you are worried, let me tell you that soundstage is very good and channel separation too.
analog_sa said:
Yes, there are better solutions, but this simple thing works quite well.
The 78L09 is pre-regulated, anyway.
Someday, who knows, I make another board and think of something different.
For now, this works like a charm.
Gotta go, there's Morphine playin' and that unique bass kills me.
This is for Carlos !
Hi Carlos,
You might be from another planet . 72 hour day ! It doesn't matter .
Great to see your experiments. Have you ever tried PIO caps at the input ? I know they are expensive and you might not care for them.
There is Bees Wax too !
I agree with you that direct generally sounds better than with cap unless the cap is REALLY good. I found Jensen Al foil pretty good , better than most foil caps. Not as good as a DC connection . Cu foil was better in some ways .
I hate anything expensive because I can't afford to spend too much.
I like the way a cathode follower sounds but it needs the **** capacitor ! I'm thinking of using an opamp ( 637?) . I dislike that compared to a tubed input ! I tried all kinds of ( cheap ) film caps and finally gave up. Damn DC.
Cheers.
It is a Saturday night here ( already ) and I'm on my second
Can't imagine what I'd do without good music. Yeah I'm listening to my first tubed IGC with Jensen Al PIO's.
Hi Carlos,
You might be from another planet . 72 hour day ! It doesn't matter .
Great to see your experiments. Have you ever tried PIO caps at the input ? I know they are expensive and you might not care for them.
There is Bees Wax too !
I agree with you that direct generally sounds better than with cap unless the cap is REALLY good. I found Jensen Al foil pretty good , better than most foil caps. Not as good as a DC connection . Cu foil was better in some ways .
I hate anything expensive because I can't afford to spend too much.
I like the way a cathode follower sounds but it needs the **** capacitor ! I'm thinking of using an opamp ( 637?) . I dislike that compared to a tubed input ! I tried all kinds of ( cheap ) film caps and finally gave up. Damn DC.
Cheers.
It is a Saturday night here ( already ) and I'm on my second
Can't imagine what I'd do without good music. Yeah I'm listening to my first tubed IGC with Jensen Al PIO's.
Here's the ML38 output buffer schematic with servo. You might try that servo and see how good it works. I still didn't have time to substitute it with a cap and compare, PS is +/-15V
Dual transistors are SSM2210/SSM2220, later upgraded to MAT03/MAT02
The input stage is based on OPA627 followed by OPA2604. DAC8222 takes care of volume control (in analog domain), AD823 is used for I/V conversion.
Dual transistors are SSM2210/SSM2220, later upgraded to MAT03/MAT02
The input stage is based on OPA627 followed by OPA2604. DAC8222 takes care of volume control (in analog domain), AD823 is used for I/V conversion.
Attachments
Carlosfm,
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EAGLE Light Edition
Try EAGLE Layout Editor'? The EAGLE Light Edition can be used for free!
The following limitations apply to the EAGLE Light Edition in general:
-The useable board area is limited to 100 x 80 mm (4 x 3.2 inches).
-Only two signal layers can be used (Top and Bottom).
-The schematic editor can only create one sheet.
-No part limited
EAGLE Light Edition
Hi Peter
How certain are you about the accuracy of the schematic? I might need to redraw it but so far fail to make much sense. By the part types i would expect a dual differential amp with each phase buffered by a EL2020. The discrete transistors look like current sources. Could it be the El2020s need to point the other way round? Or am i just being more stupid than usual?
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