good that the sim pointed you in the right direction (the sim itself indicated the gate stopper rather than the 1M which is interesting (and I found a bit odd due to the low value of the gatestopper). Shown below. I guess if the 1M's were particularly noisy it would be being fed directly to the gate of the BS170. Great finding and may help someone else if they have noise problems as well!
Tony.
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Hi Wintermute,
Yes, I was also surprised by your comment that a low value resistor contributes so much to the noise (actually I replaced it). Anyway, 1M being big and close to the gate of bs170 was also a suspect.
Now the question is: put this one in a chassis or build juma's buffer suggested to me a few posts above. Probably both... (The buffer is almost fully populated). And there is also ver1 of this preamp which apparently behaves better at low gains.
Yes, I was also surprised by your comment that a low value resistor contributes so much to the noise (actually I replaced it). Anyway, 1M being big and close to the gate of bs170 was also a suspect.
Now the question is: put this one in a chassis or build juma's buffer suggested to me a few posts above. Probably both... (The buffer is almost fully populated). And there is also ver1 of this preamp which apparently behaves better at low gains.
I ordered some prototype pcb's for layout in post #116. Attached is a 3D view, which shows both Silmic2 and large film caps for the output, but it can accommodate smaller 47nF MKC caps. There are not many "vacant lots" left on the 110 x 60mm pcb. The BF862's will be on adapter boards to fit the TO92 pinout. I also ordered a new preamp enclosure to put the first one in, so that I will have a good working preamp to use when I modify the existing preamp that I am using now. I plan to do several changes to my existing one, especially to the remote control section, which might take time. I will get the prototype verified in the first preamp in a reasonable time.
Greg, I used that juma buffer design with a BF862 in a 2nd order crossover pcb that I drew. For each channel it has one buffer section for a full range output and 3 buffer sections for the 12dB/oct high pass output (total 8). The buffer sections sound great as expected, so I am sure you will not be disappointed. I might post it in a new thread soon, but I will first have to get ready for all the "what if you change this?" questions. If Nelson and juma and Zen Mod have time for that, I guess I can make time.
The BF862's will be on adapter boards to fit the TO92 pinout. I also ordered a new preamp enclosure to put the first one in, so that I will have a good working preamp to use when I modify the existing preamp that I am using now. I plan to do several changes to my existing one, especially to the remote control section, which might take time. I will get the prototype verified in the first preamp in a reasonable time.Greg, I used that juma buffer design with a BF862 in a 2nd order crossover pcb that I drew. For each channel it has one buffer section for a full range output and 3 buffer sections for the 12dB/oct high pass output (total 8). The buffer sections sound great as expected, so I am sure you will not be disappointed. I might post it in a new thread soon, but I will first have to get ready for all the "what if you change this?" questions. If Nelson and juma and Zen Mod have time for that, I guess I can make time.
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Hi Propitious,
It looks good.
I attach a few pictures of my humble prototype/final version of the preamp from the current thread (noise free!!! that is the one on a piece of mdf; notice I seem to have the same volume control as Juma). Next to it the partially populated buffer with bf862 and cascode (suggested to me by Juma) and my humble made pcb for it (I have noticed that a Dremel tool is great for small PCBs; faster than etching!)
It looks good.
I attach a few pictures of my humble prototype/final version of the preamp from the current thread (noise free!!! that is the one on a piece of mdf; notice I seem to have the same volume control as Juma). Next to it the partially populated buffer with bf862 and cascode (suggested to me by Juma) and my humble made pcb for it (I have noticed that a Dremel tool is great for small PCBs; faster than etching!)
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I wanted to make a 2nd preamp that was mobile for trying out new builds. It has my version 2 pcb layout from post 116 and I used a LDR, Lighter Note volume control from buildanamp.com (his site shows that he now has a later version). For this build I had a pair of Wima 10 uF MKC caps that screamed "Pick me!" (like when we were kids trying to get one of captians to choose me for a basketball game at the schoolyard court) so I used them. Not sure if it sounds better or worse than using 10 uF Silmic2 and small MKC. I burned it in a few days. With R17 set to 240R, the rail voltage is 38.5 VDC and my DMM set to AC shows about 0.3 mV AC ripple. Nothing gets warm. The Antek 10 VAC with 2 x 18 VAC sec. is plenty.
By itself the Lighter Note sounds very good and surprisingly enough gain going to Cubie3 amp on most media. When I also went through the Son ZV9 v2, it also sounded very good but there was a new white noise when I held my ear close to the woofer or tweeter (equal loudness in both and in both channels). I could not hear the noise a meter away from the speakers. My cheap scope did not reveal any clues. The volume of the noise does not change when I turn the volume control up or down. I lowered gain by lowering R11 (post 116) from 4.7K to 3K but no difference in noise. I know Greg found the cause of his white noise when he changed out the 1M R7 going to gatestopper of BS170. I was doubtful that was my cause because I used Takman MF which are very quiet resistors. At a loss, I changed those 1M to low noise Vishay, but there was no change in noise. At the moment, I am not sure what to try next. The slight white noise does not bother my setup, but I have 87 dB/W speakers. I am not sure it the white noise would be annoying on 97 dB/W speakers.
By itself the Lighter Note sounds very good and surprisingly enough gain going to Cubie3 amp on most media. When I also went through the Son ZV9 v2, it also sounded very good but there was a new white noise when I held my ear close to the woofer or tweeter (equal loudness in both and in both channels). I could not hear the noise a meter away from the speakers. My cheap scope did not reveal any clues. The volume of the noise does not change when I turn the volume control up or down. I lowered gain by lowering R11 (post 116) from 4.7K to 3K but no difference in noise. I know Greg found the cause of his white noise when he changed out the 1M R7 going to gatestopper of BS170. I was doubtful that was my cause because I used Takman MF which are very quiet resistors. At a loss, I changed those 1M to low noise Vishay, but there was no change in noise. At the moment, I am not sure what to try next. The slight white noise does not bother my setup, but I have 87 dB/W speakers. I am not sure it the white noise would be annoying on 97 dB/W speakers.
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Looks cool Propitious!
Interesting that you are reporting noise as well. I am curious whether you can lower it even more. In my setup there is some residual noise close the the tweeter (not comparable with what it used to be with the dodgy 1M resistor), but I am not bothered by it anymore in my listening position.
Meanwhile, I have literally yesterday finished the prototype of the buffer suggested to me by juma. I do not think I should pollute this thread with that buffer. I will just report that it sounds very nice. It has some "effortlessness" about it. This is always a good sign.
I have some issues with the volume control (get hum at low settings) though. So now I listen at high settings (above 12o'clock, not a problem as there is no gain) and control the volume from the computer. I need to investigate that.
Interesting that you are reporting noise as well. I am curious whether you can lower it even more. In my setup there is some residual noise close the the tweeter (not comparable with what it used to be with the dodgy 1M resistor), but I am not bothered by it anymore in my listening position.
Meanwhile, I have literally yesterday finished the prototype of the buffer suggested to me by juma. I do not think I should pollute this thread with that buffer. I will just report that it sounds very nice. It has some "effortlessness" about it. This is always a good sign.
I have some issues with the volume control (get hum at low settings) though. So now I listen at high settings (above 12o'clock, not a problem as there is no gain) and control the volume from the computer. I need to investigate that.
juma: Thank you very much for the ideas. I will try them when I get time again, which might be a few days. As I said, everything is great in my system, but I will try other changes for others who might have very efficient speakers.
Greg: When you are done with the buffer, please start a thread on it. I will probably contribute to it.
Greg: When you are done with the buffer, please start a thread on it. I will probably contribute to it.
Hi Juma,
Since I am typing on a phone, I will try to make it short. I am using Sewa as an amplifier (7w follower basically). I used BoZ as a preamp. Then I modified BoZ and made it look more like Aleph L or Zen itself, added Schade feednack and some other changes, except that it was left resistor loaded (1k resistor as CCS). It sounds better thqn just a Boz (with Irf 630)
I plan to ultimately build a tube pre, but before that I would like to try a thing or two with solid state. So I would like to try a pre that you decribed here, but with a few changes.
1. I would like to use Boz PSU 60v regulated-possible or too much?
2. I don't have the bf862. Instead, I have 2sk170 bl, BF245c and some BC parts (550 but I have to check, I am not at home now).
Can I utilize these parts without much fuss?
Thanks
Since I am typing on a phone, I will try to make it short. I am using Sewa as an amplifier (7w follower basically). I used BoZ as a preamp. Then I modified BoZ and made it look more like Aleph L or Zen itself, added Schade feednack and some other changes, except that it was left resistor loaded (1k resistor as CCS). It sounds better thqn just a Boz (with Irf 630)
I plan to ultimately build a tube pre, but before that I would like to try a thing or two with solid state. So I would like to try a pre that you decribed here, but with a few changes.
1. I would like to use Boz PSU 60v regulated-possible or too much?
2. I don't have the bf862. Instead, I have 2sk170 bl, BF245c and some BC parts (550 but I have to check, I am not at home now).
Can I utilize these parts without much fuss?
Thanks
Hi Vix,
adjusting a circuit to your requirements is doable but it needs building the prototype and optimizing it. Unfortunately, I don't have enough spare time for that right now.
I think you'll be better served with something like this:
MOSFET-trioda Mju folover verzija - Solid State - diyAudio.rs
(set R5/R25 to 10k in order to raise the gain to about 13 dB)
adjusting a circuit to your requirements is doable but it needs building the prototype and optimizing it. Unfortunately, I don't have enough spare time for that right now.
I think you'll be better served with something like this:
MOSFET-trioda Mju folover verzija - Solid State - diyAudio.rs
(set R5/R25 to 10k in order to raise the gain to about 13 dB)
The only active part you need is this:
http://www.mikroprinc.com/proizvodi/poluprovodnici/tranzistori/fet/bs170/index.php
Kelco - Proizvodi - Rezultat pretraživanja
and it costs 10 cents a piece. The rest is trivial...
http://www.mikroprinc.com/proizvodi/poluprovodnici/tranzistori/fet/bs170/index.php
Kelco - Proizvodi - Rezultat pretraživanja
and it costs 10 cents a piece. The rest is trivial...
