scott wurcer said:
Absolutely agreed for MC preamps, as I mentioned a few times along, distortions of any type are the last important thing in a MC preamp.
I was only trying to show that the stupid process of hand maching and pairing JFETs can be replaced with a little feedback
Not that matching would hurt, but I'm in particular not a big fan of trimpots, in particular in low noise designs. It's funny how a input reed relay contact is assumed bad for the noise, while a wirewound trimpot contact is considered benign syn08 said:
Have a little patience and no, don't flatter yourself, I'm not asking for your opinion. I promised more hard data after this weekend. Of course, nobody knows what you are looking for, and I'm pretty sure that as soon as you'll see the data, you will call for the GEB support :rotfl:
Meantime, perhaps you can share some of your own achievements? I don't recall anything posted here, but as you seem to be intimate with John, I'm sure we can all learn something from your experience
I guess if you can't answer the question, it's always better to try to discredit the questioner. Or be condescending.
When you asked for all of us to believe that this design is just what you claim it is without evidence, you are indeed asking for not only my opinion but everybody else's, too. That is not necessarily flattering in any way. The fact is that you claimed success without having completed the job and are not able to offer evidence. That has not been acceptable in the past here. As I said, this preamp may be the best device ever created, but that hasn't been proven by the standards that everyone else have been held to.
For the record, I have never met nor even spoken with John Curl. Without speaking for him, I think he will probably verify that if it's important to you. Why do you think that if I don't instantly accept your claims without evidence that I am intimate with him? Is this some kind of zero-sum contest?
Why are my credentials relevant? The question at hand is related to this specific preamplifier's performance. My credentials have nothing at all to do with your preamp or its (yet) unmeasured performance. Nor are your credentials relevant here, either. Other people's past or recent credentials haven't been relevant in other discussions.
I apologize to everyone who has read through this - this is pointless.
scott wurcer said:
I'm not sure quite how to do what you ask. I believe you mean a 1/3 Octave band centered around 3 KHz and look for the harmonics. I don't know of such a test record, but I'm working on a test record project and can add that to the list of content if its relevant. I was going to include some spectral contamination tracks which would do essentially the same thing. And some content to determine the actual frequency response to validate the .1 dB RIAA accuracy or allow a way to correct for the cartridge if the adjustments are provided.
CG said:
Mr. CH,
If you would have the patience to read my post you would find out that this version was already implemented and measured (preliminary):
http://www.diyaudio.com/forums/showthread.php?postid=1726323#post1726323
syn08 said:
The numbers above are measurements not simulations. If you would have the decency to keep your mouth shut and wait a few days, or even better, you would indicate a few measurements that you would consider adequate, we could have a decent and useful dialogue. Instead, you chosed to argue against something you don't even bothered to read about.
I usually don't let things in the prototype stage, but continue until the construction is completed. That's the whole point of rebuilding the PCB layout, I simply hate patched and strapped PCBs. But I doubt there's anything further that you would be interested in.
As of knowing JC, what can I say other than
? I'm on this forum for quite some time, and my memory is still good, here's a random quote from 2007:john curl said:
syn08 said:
Mr. CH,
If you would have the patience to read my post you would find out that this version was already implemented and measured (preliminary):
http://www.diyaudio.com/forums/showthread.php?postid=1726323#post1726323
The numbers above are measurements not simulations. If you would have the decency to keep your mouth shut and wait a few days, or even better, you would indicate a few measurements that you would consider adequate, we could have a decent and useful dialogue. Instead, you chosed to argue against something you don't even bothered to read about.
I usually don't let things in the prototype stage, but continue until the construction is completed. That's the whole point of rebuilding the PCB layout, I simply hate patched and strapped PCBs. But I doubt there's anything further that you would be interested in.
As of knowing JC, what can I say other than
This is just plain stupid.
First, I am not Charles Hansen. The moderators can verify that. Nor have I ever met him or spoken to him, either. I don't think the moderators can verify that part, but he certainly can. Your memory may be great, but your fact finding skills apparently aren't. Just where did you get that idea anyway?
Second, the ONLY point I have been trying to make, you have just verified. That is, you haven't completed your measurements on this preamp yet. You plan to this weekend.
What I am calling you on is that you have on a number of occasions blasted people for making claims that you don't find the evidence supportive of. Bybee's devices, whatever it is that they do or don't do, being one example that you have brought up in the past 24 hours in a snide way, as part of an ad hominem attack on me. Now you are doing the very same thing yourself that you've accused him of.
You might find me impolite in pointing that out, so, just for you, I'll stop posting that the emperor has no clothes. Again, I apologize for wasting the forum's time. No more from me.
After 5 years, I eventually finished my JC-2 clone. The sonic quality of my JC-2 is amazing. About 10 of my friends have listened to the pre-amp and they all give very positive comments to it.
I want to say thank you to you guys who gave suggestions and advices here.
I only built the line stage, I am going to build the phono amp then.
Top view of the pre-amp:
I want to say thank you to you guys who gave suggestions and advices here.
I only built the line stage, I am going to build the phono amp then.
Top view of the pre-amp:
Attachments
.
HKC --
Thanks for the pictures. I was just looking at that 1998 article today and saw your pictures on the Vendetta thread (I think.....).
One improvement you can make to the 317/337 regulators in that Positive Feedback article is to bootstrap the internal reference voltage of the 317 and 337 regulators with an LM329 "zener" as described in National Semi's application notes. It makes an audible difference, even when using the 317s or 337s as pre-regulators.
Phil
Thanks for the pictures. I was just looking at that 1998 article today and saw your pictures on the Vendetta thread (I think.....).
One improvement you can make to the 317/337 regulators in that Positive Feedback article is to bootstrap the internal reference voltage of the 317 and 337 regulators with an LM329 "zener" as described in National Semi's application notes. It makes an audible difference, even when using the 317s or 337s as pre-regulators.
Phil
CG, it is best not to get too tied up with disruptive people. They will accuse us of almost anything, in order to put themselves in a better light.
Also, I do not believe Syn08's specs. Nothing, so far, including mathematical calculation shows me that he as achieved his noise level in a real circuit. Close, but not what he states.
The devices would have to be PERFECT with NO 1/f noise, no contribution from any other source but the input, etc.
Anyone can check this out. Just find the inverse of the total transconductance at current Multiply that number by 2/pi to get a result and add 1/2 ohm to get the best case noise.
Also, I do not believe Syn08's specs. Nothing, so far, including mathematical calculation shows me that he as achieved his noise level in a real circuit. Close, but not what he states.
The devices would have to be PERFECT with NO 1/f noise, no contribution from any other source but the input, etc.
Anyone can check this out. Just find the inverse of the total transconductance at current Multiply that number by 2/pi to get a result and add 1/2 ohm to get the best case noise.
1audio said:
Sorry I didn't remember the exact standard center frequency, but I have several test records that contain the complete set. I just remember by 3k the effect was pretty bad. Noise in 1/3 octave bands are pretty standard, they also come on most test CD's. The Telarc Omni Disk (LP) has a warning about the funny crackling noises you hear being "normal". They essentially say, to me at least, the LP medium is not capable of reproducing them. By 10-12kHz you hear nothing but the low order IMD.
john curl said:
John,
I'm confused, you said a few pages before:
john curl said:
If your SCP-2 is specified at 0.4nV/rtHz (as you mentioned), why would you think my results are wrong? And BTW, my preamp has 0.5ohm in series, not 1ohm. And if you don't know, most of the SK170/SJ74 noise is determined by the intrinsic source resistance (technologically much like rbb'), hence the sorting for noise is effective.
scott wurcer said:
I remember a Soundcraftsmen LP that was meant to be used with a sound level meter to adjust their equalizer. I'm sure those are exceedingly rare. I will put in some clean tones for looking at distortion products. I suspect the straight line tracking issue won't fare too well either.
With some effort, cooperation from the right parties and luck I should be able to put together a test record (and tape) that will allow users to align and optimize an analog playback system with a PC sound card. A truly anacronistic effort. I am soliciting ideas for the project. I have a suspicion that many differences between transducers can be reduced to response issues.
This is fun! I calculated the transconductance of my design, and the transconductance of your design. Show me where I am wrong:
The transconductance of the SCP-2 design is 270,000 umhos (somewhat more current)
The transconductance of your design is 250,000 umhos
My series resistance is 2.5 ohms, which is composed of two 5 ohm resistors in parallel.
Your series resistance is 0.5 ohms, which is composed of two 1 ohm resistors in parallel.
The normal measured noise is 9 ohms in the SCP-2, normally.
Your normal measured noise should be 2 ohms less, ideally, or 7 ohms, BUT I will give you the benefit of the doubt that you have reduced it to 5 ohms. Any less is next to impossible without lowering the temperature, increasing the idle current, or paralleling more devices.
Please show why meshed-gate fet devices should operate on any noise formula not specifically stated by Yishay Netzer in his IEEE paper, on the same page as he puts the Toshiba devices.
The transconductance of the SCP-2 design is 270,000 umhos (somewhat more current)
The transconductance of your design is 250,000 umhos
My series resistance is 2.5 ohms, which is composed of two 5 ohm resistors in parallel.
Your series resistance is 0.5 ohms, which is composed of two 1 ohm resistors in parallel.
The normal measured noise is 9 ohms in the SCP-2, normally.
Your normal measured noise should be 2 ohms less, ideally, or 7 ohms, BUT I will give you the benefit of the doubt that you have reduced it to 5 ohms. Any less is next to impossible without lowering the temperature, increasing the idle current, or paralleling more devices.
Please show why meshed-gate fet devices should operate on any noise formula not specifically stated by Yishay Netzer in his IEEE paper, on the same page as he puts the Toshiba devices.
You can get a bulk metal foil pot with 5 Ohms resistance. Multiturn and perfect for MC-amplifiers.
I only use the bulk metal foil pots from Texas components and they are as good as it gets. Price is OK, too. Not cheap but not expensive either.
If TCR is not vital, you can get the cheaper larrger pots.
Sigurd
I only use the bulk metal foil pots from Texas components and they are as good as it gets. Price is OK, too. Not cheap but not expensive either.
If TCR is not vital, you can get the cheaper larrger pots.
Sigurd
syn08 said:
I was only trying to show that the stupid process of hand maching and pairing JFETs can be replaced with a little feedback
Have a look here: http://www.adjustplus.de/index.php?lang=english Not sure if this is exaclty what you intend to do but it might give you some ideas.
Just to make clear that when I say bulk metal foil resistors, I do mean the "nude" TX2352:s.
I am now testing the new TX2575 bulk metal foil resistors which is a "nude" version of the Z201, and it has another foil pattern.
One can also get power resistors in bulk metal foil, which I plan to test as emitter/source resitors in a class A power amp late this year.
/S
I am now testing the new TX2575 bulk metal foil resistors which is a "nude" version of the Z201, and it has another foil pattern.
One can also get power resistors in bulk metal foil, which I plan to test as emitter/source resitors in a class A power amp late this year.
/S
Sigurd Ruschkow said:
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