Russ White said:
That's right, I also think a good 10k~20k pot is better than another active stage, which I avoided.
DC offset adjust
Hi Carlos et al
The following link is a schematic of a simple circuit using a 2SK389 dual JFET to adjust the DC offset. The idea was used successfully for years by Welborne Labs for their LT1010CT based buffered preamp. The original idea (I believe) was published in Audio Amateur 2/90 and Electronic Design 3/89. I built the circuit with 1/2 of the AD815, and it works great. I had the DC down to about 30 uV (microvolts). I even rotated the knob of the volume pot, and their was no change. Real 2SK389s can be bought such as through BorbelyAudio and others. A company, Linear Systems in California is manufacturing a copy, the LS389 with the same or better specs. The 2SK389 is very low noise, as good or better then the AD815.
http://home.wi.rr.com/gtgelectronics/AD815_Adjust.CIR
Bruce🙂
Hi Carlos et al
The following link is a schematic of a simple circuit using a 2SK389 dual JFET to adjust the DC offset. The idea was used successfully for years by Welborne Labs for their LT1010CT based buffered preamp. The original idea (I believe) was published in Audio Amateur 2/90 and Electronic Design 3/89. I built the circuit with 1/2 of the AD815, and it works great. I had the DC down to about 30 uV (microvolts). I even rotated the knob of the volume pot, and their was no change. Real 2SK389s can be bought such as through BorbelyAudio and others. A company, Linear Systems in California is manufacturing a copy, the LS389 with the same or better specs. The 2SK389 is very low noise, as good or better then the AD815.
http://home.wi.rr.com/gtgelectronics/AD815_Adjust.CIR
Bruce🙂
The http!!!!!
I am so sorry everyone, but if you click on that link, it will not come up. I do not know why. If you type it in by hand on your address line it will.
I'm very sorry.
Bruce
I am so sorry everyone, but if you click on that link, it will not come up. I do not know why. If you type it in by hand on your address line it will.
I'm very sorry.
Bruce
I have some 2sk389 dual JFETs. I've made buffers with them, very good.
Your link doesn't work, even with copy-paste of the text.
Or is it a netlist you want to show? 😕
Your link doesn't work, even with copy-paste of the text.
Or is it a netlist you want to show? 😕
Sorry Carlos for the frustration. I'm very computer stupid, YOU are not!🙂 Do not cut and paste. Actually hand type in the http by hand into the address bar. I will try to post the address again differently. Please be patient.
Thanks...Bruce
By the way, I do not know what "netlist" means......sorry.
Thanks...Bruce
By the way, I do not know what "netlist" means......sorry.
Russ White said:
Now Russ why would somebody like Jeff Rowland use this volume control chip if it wasn't good. and I also mentioned that you could use the BB as a direct replacement. I have tried both and the BB 2311UA has a even better spec than the 2310 that you are using and frankly I can't tell the difference. between the CS chip and the BB one
I also did a direct comparison with a Noble pot and the CS version is just alot cleaner
I have been listening to your freebird for the last month and when I changed over to the AD815 it opened up everything , personally no contest. some systems reveal changes much more than others.
Sorry Russ. just noticed that you did yours with the 2311. for some reason i thought you went with the higher voltage version
we all get caught up in the numbers game to quickly and we very soon we loose focus of the what is important and that is how does it reproduce music. for instance. AD797 - ultra low noise preamp opamp. excellent figures but it sounds dead. you could not use this in place of the OPA627 for your freebird, you will hate it.
then if you look at a top notch valve amp. it might measure like a dog. but it still sounds good.
we all get caught up in the numbers game to quickly and we very soon we loose focus of the what is important and that is how does it reproduce music. for instance. AD797 - ultra low noise preamp opamp. excellent figures but it sounds dead. you could not use this in place of the OPA627 for your freebird, you will hate it.
then if you look at a top notch valve amp. it might measure like a dog. but it still sounds good.
BC,
Please can youy repost the link for
http://home.wi.rr.com/gtgelectronics/AD815_Adjust.CIR
It only shows a netlist
Russ White, have you found something that sounds better than the AD815?
Please can youy repost the link for
http://home.wi.rr.com/gtgelectronics/AD815_Adjust.CIR
It only shows a netlist
Russ White, have you found something that sounds better than the AD815?
HI Dr H.,
I have several preamps in my collection now which I would say match well the AD815 circuit I built. I Just got some digital balanced attenuators (no opamp in loop like CSxxxx or PGAxxx) which I am using with a rough prototype of a "super symetric constant current source cascoded bride of son of zen" which I would put up against anything. I am not going to get into the "better" game. Thats gets us nowhere. There is no accounting for taste, so who is to say what is really best, but I love the Pass preamp 🙂
Rudi,
This forum is for DIYers of differing skills. The Freebird is a beginners project, no intended to be an "end all" preamp, but really a learning experience for those who want it.
Now that said, if you DC couple the input and bias the opamp class A (for certian opamps) and drive a reasonably high impedance load the Freebird can perform very well indeed, you have to know enough to tweak it to get the best out of it. You must ajdust the feeback resistors and load resistors to match the opamp and the source/load this is where the fun is.
I am very glad you found something you like.
The reason the CSxxxx is drastically inferior to the PGAxxxx is the opamp inside it, the CS opamp is just simply not anything like the BB piece, so performance of the opamp in either the PGA or the CS will dominate the sound coming out of the preamp. So in essence adding an AD815 to end of a CS is really just like adding a highbandwidth buffer. If you are using a high impedance power amp (like your "x-caliber") you could simply omit the AD815 and get identical performance, probably better as you would remove source of distortion. 🙂 So if you use the AD815 if would be best to use some other type of attenuator like a pot or a digital pot/attenuator without opamp.
Have fun.
Russ
I have several preamps in my collection now which I would say match well the AD815 circuit I built. I Just got some digital balanced attenuators (no opamp in loop like CSxxxx or PGAxxx) which I am using with a rough prototype of a "super symetric constant current source cascoded bride of son of zen" which I would put up against anything. I am not going to get into the "better" game. Thats gets us nowhere. There is no accounting for taste, so who is to say what is really best, but I love the Pass preamp 🙂
Rudi,
This forum is for DIYers of differing skills. The Freebird is a beginners project, no intended to be an "end all" preamp, but really a learning experience for those who want it.
Now that said, if you DC couple the input and bias the opamp class A (for certian opamps) and drive a reasonably high impedance load the Freebird can perform very well indeed, you have to know enough to tweak it to get the best out of it. You must ajdust the feeback resistors and load resistors to match the opamp and the source/load this is where the fun is.
I am very glad you found something you like.
The reason the CSxxxx is drastically inferior to the PGAxxxx is the opamp inside it, the CS opamp is just simply not anything like the BB piece, so performance of the opamp in either the PGA or the CS will dominate the sound coming out of the preamp. So in essence adding an AD815 to end of a CS is really just like adding a highbandwidth buffer. If you are using a high impedance power amp (like your "x-caliber") you could simply omit the AD815 and get identical performance, probably better as you would remove source of distortion. 🙂 So if you use the AD815 if would be best to use some other type of attenuator like a pot or a digital pot/attenuator without opamp.
Have fun.
Russ
HI Russ
I will have the PGA2311ua back into the mix after the weekend and I will report the difference combined with the AD815.
btw. on its own the CS3310 is sterile and with the AD815 it is a different animal. but that said. i will let you know
I will have the PGA2311ua back into the mix after the weekend and I will report the difference combined with the AD815.
btw. on its own the CS3310 is sterile and with the AD815 it is a different animal. but that said. i will let you know
Hello Russ,
I'd be very interested to see the schematics for the "super symetric (sic) constant current source cascoded bride of son of zen". I imagine it is a discrete design?
There-in lies the major benefit of the AD815-add less than a handful of parts and you're achieving stratospheric performance, at least according to my ears and a couple of buyers of Jeff Rowlands pre-amps.
For the neophytes, part-time and less-than-part-time diyers amongst us, the AD815 is an ideal realisation of the goals of
maximum performance per dollar and time invested
minimum circuit intricacy
For the hardcore diyers, nothing quite as interesting as pushing the envelope with novel topologies. Lets see that ssccsc-BOSOZ!
Regards
Ryan
I'd be very interested to see the schematics for the "super symetric (sic) constant current source cascoded bride of son of zen". I imagine it is a discrete design?
There-in lies the major benefit of the AD815-add less than a handful of parts and you're achieving stratospheric performance, at least according to my ears and a couple of buyers of Jeff Rowlands pre-amps.
For the neophytes, part-time and less-than-part-time diyers amongst us, the AD815 is an ideal realisation of the goals of
maximum performance per dollar and time invested
minimum circuit intricacy
For the hardcore diyers, nothing quite as interesting as pushing the envelope with novel topologies. Lets see that ssccsc-BOSOZ!
Regards
Ryan
Dr. H,
I have an AD815 preamp, so I am well aware of its capability. It is indeed most excellent, right up there with the best, but certainly not the only preamp in that category. Carlos did a wonderful job with his implementation, it is quite solid. Top notch. I am just not ready to say it relegates other designs to the dustbin, as I know that also is not the case.
Browse the Pass Labs forum and you will find the XBOSOZ.
Since you asked...
http://www.diyaudio.com/forums/showthread.php?postid=761059#post761059
The parts count is actually not very high for what it is, it is actually a very simple project even for the beginer.
Note, while I did a substantial bit of work on it, the core credit goes to Mr Pass, and Terry Aben (metalman).
Cheers!
Russ
I have an AD815 preamp, so I am well aware of its capability. It is indeed most excellent, right up there with the best, but certainly not the only preamp in that category. Carlos did a wonderful job with his implementation, it is quite solid. Top notch. I am just not ready to say it relegates other designs to the dustbin, as I know that also is not the case.
Browse the Pass Labs forum and you will find the XBOSOZ.
Since you asked...
http://www.diyaudio.com/forums/showthread.php?postid=761059#post761059
The parts count is actually not very high for what it is, it is actually a very simple project even for the beginer.
Note, while I did a substantial bit of work on it, the core credit goes to Mr Pass, and Terry Aben (metalman).
Cheers!
Russ
Hello again Russ
Interesting! Have you compared this with your AD815 pre? I agree that it seems reasonably straight forward and of course appeals to the "discrete is better" school of thought.
Is it better/same/worse than AD815-just need to determine whether I should go out and build it or wait for more envelope pushing!
Ciao
Ryan
Interesting! Have you compared this with your AD815 pre? I agree that it seems reasonably straight forward and of course appeals to the "discrete is better" school of thought.
Is it better/same/worse than AD815-just need to determine whether I should go out and build it or wait for more envelope pushing!
Ciao
Ryan
Greetings Dr. H,
No direct comparison has been done, and is not likely to be done. My AD815 is on loan to my brother in law who is a musician here in Nashville, and I may not ask for it back as I have plenty to replace it with, and I am tending to favor balanced sources and amps these days. Thus my work on a super symmetric LM3886 amp with Terry Aben.
Cheers!
Russ
No direct comparison has been done, and is not likely to be done. My AD815 is on loan to my brother in law who is a musician here in Nashville, and I may not ask for it back as I have plenty to replace it with, and I am tending to favor balanced sources and amps these days. Thus my work on a super symmetric LM3886 amp with Terry Aben.
Cheers!
Russ
Hello Russ,
I agree with your preference for balanced audio, but only when implemented properly-there are a couple of well known brands that tend to do a half job (literally) on balanced signals.
I use a Theta GEN Va as a DAC which is balanced in the real sense of the word, i.e. all circuitry is doubled up, so as to handle the + and - phases seperately and correctly.
In my pre I use a THAT1200 device that the inventors claim provides the same benefit as that of a very well designed audio transformer (eg Jensen, etc). Performance is fantastic!
On the 815, pity the comparison was not run, but frankly, I am pretty happy with the AD815 for now. It's performance, to use your words, is up there with the best!
Ciao
Ryan
I agree with your preference for balanced audio, but only when implemented properly-there are a couple of well known brands that tend to do a half job (literally) on balanced signals.
I use a Theta GEN Va as a DAC which is balanced in the real sense of the word, i.e. all circuitry is doubled up, so as to handle the + and - phases seperately and correctly.
In my pre I use a THAT1200 device that the inventors claim provides the same benefit as that of a very well designed audio transformer (eg Jensen, etc). Performance is fantastic!
On the 815, pity the comparison was not run, but frankly, I am pretty happy with the AD815 for now. It's performance, to use your words, is up there with the best!
Ciao
Ryan
Russ White said:
I may be suffering from too much solder fumes, but an inverting opamp (LM318) with a 3.3k input resistor doesn't seem like high impedance at all.
Carlos look closer at the circuit. The impedance is 100K(R13) set by the resistor to GND. 🙂 Not 3.3K. This is covered in the docs Mauro provided, but is actually easy to see in the schematic.
Russ White said:
I saw that 100k resistor.
The amp doesn't have 100k input impedance.
The inverting input on the opamp is a virtual ground.
With a 3.3k input resistor, it is not easy to drive.
An easy job for the AD815, then. 😀
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