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Old 14th November 2008, 12:19 PM   #11
AndrewT is offline AndrewT  Scotland
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what's wrong with 40mW into 100dB/mW headphones. Too damn loud that's what.
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Old 14th November 2008, 02:25 PM   #12
lineup is offline lineup  Sweden
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I second that, AndrewT

SSTART will not be short on power for any HeadPhones > 8 Ohm impedance.
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Old 14th November 2008, 03:06 PM   #13
h_a is offline h_a  Europe
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It's the same as running an Aleph hard, it raises THD. In my humble opinion, if single-ended, then plenty of bias.

Have fun, Hannes
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Old 16th November 2008, 03:13 AM   #14
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Quote:
Originally posted by Cobra2
How much gain does it give (or how do I calculate gain)?

Arne K

Gain = 20dB, plus or minus a smackeral


Quote:
Originally posted by twitchie
250 pieces of J310 on the way to me ... I'll give this one a shot. I can't promise anything before 2009 however

Thanks for this one Grey

P.S. Will it work as a headphone amp?

If you need more current, parallel more devices...jeez, am I gonna revoke your DIY license?
Note that this will increase your gain if you leave the rest of the circuit as-is. My suggestion is to throw as many JFETs into the mix as you like, then resize the load resistor to split the difference between the rail and the voltage at the Gate of the cascode device. As it is, there's about 17V across the load resistor. If you're running a 50V rail, you've got about 35V of output swing, which is substantial for headphones, but comfy for normal preamp duties; the philosophy being to only use a fraction of that. If you double the number of JFETs (at the same bias current), then halve the value of the load resistor. Something in the range of 120 to 150 Ohms would do pretty well. Yes, you can parallel two 270 Ohm resistors to get 135 Ohms and to handle the heat.
You can parallel any number of devices that floats your boat. The J310 is a low capacitance device and the cascode reduces the effect even further, so capacitance won't be a problem. The MOSFET cascode will take the current from quite a few JFETs before it starts getting antsy.
Don't forget to increase the capacitance at the output if you're using it to drive headphones. Think in terms of an electrolytic bypassed with a film cap.
As I've said, I've got a screaming blue million of the J271s and have been toying with the idea of a single-ended, massively parallel amplifier to use a few of 'em up. A scaled down version would do rather nicely for headphones.
One of the nice things about J310s is that they're cheap. Build a SSTART to listen to, then use the leftover parts for Evil Experiments. Who knows, you might come up with something really, really cool.

Grey
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Old 16th November 2008, 04:30 AM   #15
lineup is offline lineup  Sweden
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Grey
I know you know.
But like with may Nelson Pass 'keep it simple' amplifiers
we need to take good care of providing a Clean power supply.

A shunt regulated 50 Volt, with one IRF610 bypass transistor
with enough capacitance filtering
would be one of my options.
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Old 16th November 2008, 08:15 PM   #16
GuidoR is offline GuidoR  Italy
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Me too, I have 100 j310 waiting for a work :

Lineup, I agree with your comment.

Maybe ZenMod can help us...
Master ZenMod, will the Shiny go up to 50V?
Or is beyond the 317 max in-out limit? (but - correct me if I'm wrong - is not a matter of absolute Vout, but only Vin-Vout)

I'm currently playing (very slowly) with a lot of projects

Have a look on this (http://www.diyaudio.com/forums/showt...03#post1643803 (Shinyy is a dual Shiny)
and http://www.diyaudio.com/forums/showt...19#post1627519

Grey,
what about IRF510 instead of IRF610?

Last question:
START: will it drive the F4?

Guido
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Old 16th November 2008, 09:22 PM   #17
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by GuidoR
......
Master ZenMod, will the Shiny go up to 50V?
.....

......
Grey,
what about IRF510 instead of IRF610?

Last question:
START: will it drive the F4?

Guido
- yes - it will work (Shiny) on 50 V for output (look in small "how Shiny works " post

- (even if just my beard is gray ) ........ 510 is OK

- yes - it will drive F4 ...... SSTART is not your Mamma everyday preamp ........
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Old 17th November 2008, 09:51 AM   #18
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oops wrong thread: again

Read it immideattely Grey, J310 ordered.. excelent weekend project! thx..



..but I do miss Fred....no kidding..
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Old 21st November 2008, 11:43 AM   #19
massimo is offline massimo  Italy
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Did anybody think to replace the JFets with a 6DJ8?
35-40 V at its anode will suffice to get a nice operatiing point....


A question for Grey: in the article you mentioned the 2SK246 as a possible subtitute for the J310. It's a direct replacement (despite of the different pinout) or should I change something?.
I have some Toshibas handy.....
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Old 21st November 2008, 04:15 PM   #20
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Today I hooked up a SSTART prototype to a storage osciloscope with a FFT feature..

If I you lower the cascode to about 4.14V, I got a very nice 2nd harmonic cancelation.. .. your milage might avy however, my Idrain were about 20mA/JFET..!
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