BC said:😕
Bruce![url]](/community/proxy.php?image=http%3A%2F%2F%5Burl%5Dhttp%3A%2F%2Fhome.wi.rr.com%2Fgtgelectronics%2FAD815_Adjust.CIR%5B%2Furl%5D&hash=bfea76f98110efb1e1dba9d77bce021a)
If someone is kind enough, please try this. It works for me.😕
As I told you yesterday, it shows a netlist. 😀
Carlos et al
This link WILL work! A dear friend helped. Using the dual JFET with a trimming pot, and 2 resistors is much better than adding more active circuitry. As I posted earlier, the DC offset can be nulled.
http://home.wi.rr.com/gtgelectronics/AD815_Adjust.bmp
Bruce
You can use a 2K pot instead. With the 5K, set it to about 1.2K.🙂
This link WILL work! A dear friend helped. Using the dual JFET with a trimming pot, and 2 resistors is much better than adding more active circuitry. As I posted earlier, the DC offset can be nulled.
http://home.wi.rr.com/gtgelectronics/AD815_Adjust.bmp
Bruce
You can use a 2K pot instead. With the 5K, set it to about 1.2K.🙂
BC, the 2SK389 is being used as an input buffer
You can null the DC-offset that way, but you are inserting an input buffer on the circuit.
That's an additional active stage. 😀
Warning: ~1.5Mb schematic.
You can null the DC-offset that way, but you are inserting an input buffer on the circuit.
That's an additional active stage. 😀
Warning: ~1.5Mb schematic.
You are correct Carlos, I chose my words poorly. I'm so glad you at least saw the schematic. Sorry about the 1.5MB. At this time, it works. I hope you try it, "buffer" as it is.
Bruce🙂
Bruce🙂
BC said:
I have made a similar buffer, with 2SK389 JFETs, but with much smaller value resistors.
Anyway, my goal on the AD815 pre was to avoid using any kind of additional active stage.
I'm injection PSU voltage, I know, but it's fairly well filtered and it seems to have no impact on sound, while other 'solutions' have.
I understand what you are doing, and the suggestions of others, but forgive me, the DC will not be nullified, as you have already seen. I realize this is "active". However IMO the simplicity and very low noise will add very little to the sound. The big PLUS is that IT WORKS. You have added other active circuitry, but not this one. I have seen and used other buffers. This is not exactly the same. For those worried about the trimming pot, use a Vishay foil trimming pot. Also, the "passive" volume pot can do more noise damage than this "buffer", let alone create havoc with the offset using the other method you have used. 🙂
Bruce
Bruce
Carlos,
Eu desculpo-me se eu escrever rudely. Eu não signifiquei a. I, como você, são passionate sobre o áudio.
I thank you for your input to the forum. I also thank you for exploring new or different ICs for audio use.
Bruce
Eu desculpo-me se eu escrever rudely. Eu não signifiquei a. I, como você, são passionate sobre o áudio.
I thank you for your input to the forum. I also thank you for exploring new or different ICs for audio use.
Bruce
BC said:
Thanks, but no need to write 'portuglish'. 😕
BC said:I thank you for your input to the forum. I also thank you for exploring new or different ICs for audio use.
Bruce
I have something unfinished for months, due to lack of time and some other things got in the way.
It's current feedback (again), and doesn't need a volume pot to control volume.
It's in the secret of the gods, as I only share working schematics, and those that are worthwhile (if it sounds good, I mean).
It's actually working, but it's somewhere around here on a shef wainting to be optimized and then tested on my main system.
News soon (maybe?), if it sounds as I expect.
Some things to finish first...
carlosfm said:Let is
It will be hard to shut it down, when you start listening.
Carlos when you're right, you're right.
I changed the 100k pot for a 10k,the sound is much better.
I have to do little tweaking on the resistors in the offset circuit but the thing sound great as is.😀
And the thing is quiet,I mean my ear is so close to the woofers that I inhale and touch it. I cant get that close to the tweeter for fear of smashing the dome.
100K POT OR 100k resistor?
Did you try a 100K pot on the front end, and lower the value, or did you lower the value of the 100K loading resistor?
I am concerned about lowering the 100K resistor to keep from messing with the dc nulling circuit. But if it sounds better, I will go for it.
George
jaudio said:
Did you try a 100K pot on the front end, and lower the value, or did you lower the value of the 100K loading resistor?
I am concerned about lowering the 100K resistor to keep from messing with the dc nulling circuit. But if it sounds better, I will go for it.
George
jaudio said:
Hey, who told you to use a 100k pot?
Respect my schematic, please! 😀
10k to 20k is what works best.
BC said:
No, it's not via the feedback. It's DC voltage.
I don't know if it's worth it, and I have been very happy with the AD815, so the interest in trying other solutions is not so great.
When I try it on my main system, if it's anything to shout about, I will shout, don't worry. 😎
carlosfm said:
Well it was either that or wait weeks for the right pots. I could not wait and I have absolutely no regrets
George I just changed the pot
DC servo
I Have had some problems with using the nulling circuit with the digital volume control. a very good friend of mine helped me design a DC servo using opamps. I have been running this for a day and the results so far have been very good. no adjustment required and you have a 25-30uV offset
the downside is that the regulators have more load to deal with and they require additional heatsinking.
I am also working on optimizing the circuit for the SOIC package so it doesn't run so hot but without affecting performance.
I will post some more info as soon as I am happy that it is stable.
I Have had some problems with using the nulling circuit with the digital volume control. a very good friend of mine helped me design a DC servo using opamps. I have been running this for a day and the results so far have been very good. no adjustment required and you have a 25-30uV offset
the downside is that the regulators have more load to deal with and they require additional heatsinking.
I am also working on optimizing the circuit for the SOIC package so it doesn't run so hot but without affecting performance.
I will post some more info as soon as I am happy that it is stable.
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