homemodder,
exercise caution before relying on whatever measurements. Toshiba has made low noise JFETs since the 2SK30 (it`s still very usable), like 2SK147/2SJ72-2SK369, 2SK117, 2SK170/2SJ74. Due to the complex nature of noise, figures and graphs need to be interpreted carefully. Also, datasheets do not unambiguously show sonic properties.
exercise caution before relying on whatever measurements. Toshiba has made low noise JFETs since the 2SK30 (it`s still very usable), like 2SK147/2SJ72-2SK369, 2SK117, 2SK170/2SJ74. Due to the complex nature of noise, figures and graphs need to be interpreted carefully. Also, datasheets do not unambiguously show sonic properties.
Why don't you build Syn08's design? It has the same input stage and is slightly quieter. The Vendetta is hard to build. Syn08's design will be easier. Since you appear relatively 'clueless' about fets, I do not recommend going further with one of my designs. I will have you 'on my doorstep' in no time. Please, for me. 
I could do Syn s design I guess, but I liked the vendetta, its quite simple and elegant, I want to try something as simple as possible but with performance to match the lp12. By simple I mean lowish parts count. Have used jfets in amps before in cfp s with bjt as inputs but when it comes to these very low noise circuits youre right, have to dig up my books. No problem, Ill have a look at the analogue forum. John the chinese cloners have about all your design schematics, they floating around their forums, gotta be more carefull.
Lumba, actually Im quite happy with the sanyos, I tried them in 2 circuits similar to Nelsons b1 and prefered them over toshibas 2sk170, in a power amp I couldnt pick up any difference though.
Lumba, actually Im quite happy with the sanyos, I tried them in 2 circuits similar to Nelsons b1 and prefered them over toshibas 2sk170, in a power amp I couldnt pick up any difference though.
On the subject of low noise FETs and BJT's - does anyone know what parts are used in the Rode NT1-A? I found this which I take it is from the designer:
Jim Williams
"I designed it with super low noise Hitachi transistors and a Siliconix rf jfet. As you can see it has German Roederstein metal film resistors and Wima polypropylene film caps. As it is there is little to do to improve it. It was built “modified”.
Anyone know the part numbers for the actives?
Jim Williams
"I designed it with super low noise Hitachi transistors and a Siliconix rf jfet. As you can see it has German Roederstein metal film resistors and Wima polypropylene film caps. As it is there is little to do to improve it. It was built “modified”.
Anyone know the part numbers for the actives?
It does seem that the -A version was improved for lower noise as indicated in this later post by the designer:
"No, this is an early chinese prototype. Note the cheap chinese caps,
resistors and metal can transistors. Not at all what I designed into
it. Replace the fet with a Toshiba 2sk170, note pinout differences."
http://www.audio-forums.com/showthread.php?t=17500&page=2
He did say that he used an RF JFET in another statement, perhaps he revised it in the -A with the 2SK170.
No surprise in the parts used for the low noise version.
"No, this is an early chinese prototype. Note the cheap chinese caps,
resistors and metal can transistors. Not at all what I designed into
it. Replace the fet with a Toshiba 2sk170, note pinout differences."
http://www.audio-forums.com/showthread.php?t=17500&page=2
He did say that he used an RF JFET in another statement, perhaps he revised it in the -A with the 2SK170.
No surprise in the parts used for the low noise version.
Thanks John, interesting point, do you know which or if both FETs will provide the 5 dBA low noise spec?
IOW is one better for noise and the other for distortion?
Condenser mike input stages rely more on low leakage and low capacitance, than short circuit noise. Of course, short circuit noise MIGHT be important as well, in some highly refined situations, but usually it is not as important as low capacitance and leakage.
The optimum fet is usually high 'Q' Gm/ciss, and with relatively low 1/f noise.
The optimum fet is usually high 'Q' Gm/ciss, and with relatively low 1/f noise.
I have heard, that this RF diodes are one of the best available diodes for audio applications, but unfortunately no longer manufactured, i. e. only available as NOS part.
Where are detailed datasheets online and what is the naming of the manufacturer? Which currently available diodes are suited for a replacement?
The other thread in this case is the NUCLON thread go to
http://www.diyaudio.com/forums/tubes-valves/88197-nuclon-my-first-hybrid-guitar-amp.html
Thank you for advices.
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Hello fellow DIY'ers. This may seem suspiciously like a new thread, for that, I apologize. I am in need of help in updating and upgrading an old Parasound HCA 600 power amp. It will be used as a back-up for my SET 300B.
As it is, I'm currently using a First Watt M2, which I love, but I need to raise some cash by selling it. I'm hoping I can do enough upgrades on the old amp to make it a viable standby. The old amp still works, but it's a bit noisy, I'd like to make it quieter and more resolving.
I can do the work, if someone can guide me on what to replace, and with what. Your help would be immensely appreciated.
Thanks and regards,
Dan
As it is, I'm currently using a First Watt M2, which I love, but I need to raise some cash by selling it. I'm hoping I can do enough upgrades on the old amp to make it a viable standby. The old amp still works, but it's a bit noisy, I'd like to make it quieter and more resolving.
I can do the work, if someone can guide me on what to replace, and with what. Your help would be immensely appreciated.
Thanks and regards,
Dan
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