carpenter said:
I tried 3 or 4 at random from both Fairchild and OnSemi bought from Mouser. I didn't see large difference in the measurements between any of them. The jury rigged circuit is still on a perfboard.
So the listening has not proceeded yet. It is interesting that with the pot one can dial in any number of harmonic profiles, and possibly that will allow some adjustment as to what it sounds like. I was running them in the circuit above at currents between 5-10ma.
Idss is off the charts - around 50 ma - so be careful not to use too high a voltage and exceed the thermal rating (10V is too high, 5-6V would be better)
You also use the J310 for the output buffer, but I did not try that as I had the Toshiba parts readily on hand.
Bob
Use this circuit below instead, the pot connection was wrong in the previous post.
For lower (or higher voltages) when you adjust for lowest distortion, you will get less (or more) gain. I tried this circuit with voltages from +18V to +40V and had results of gains from x 1.5 to x 4
Bob
For lower (or higher voltages) when you adjust for lowest distortion, you will get less (or more) gain. I tried this circuit with voltages from +18V to +40V and had results of gains from x 1.5 to x 4
Bob
Attachments
Following the advice from reverend Zen Mod 
three months ago I tried J310/JBOZ as a preamp for F5. The results were very good. They were posted and discussed on a local Serbian forum. Id was 10-11 mA. J310 were from ON Semiconductors (Idss 35 mA). Preamp's gain was 2.1 V/V
Here is the schematic:
three months ago I tried J310/JBOZ as a preamp for F5. The results were very good. They were posted and discussed on a local Serbian forum. Id was 10-11 mA. J310 were from ON Semiconductors (Idss 35 mA). Preamp's gain was 2.1 V/VHere is the schematic:
Attachments
juma said:Following the advice from reverend Zen Mod
Here is the schematic:
I remember that you was non-believer ......
Telstar said:
When you talk about the answer to that one, you need to consider the distortion side (if that's important to you). What I mean is although it may be OK from a level perspective, in many cases distortion goes way up when driving low level loads( 5-10K versus 50-100K) especially at high levels (music peaks).
If nothing else it would be interesting to try it both ways, with and without buffer, especially since it's so easy. The buffer powered by a single voltage supply needs a bias at 1/2 the supply voltage, and this case it is provided for free.
On the circuit shown *with* the buffer output, I noticed a slight increase in distortion at loads of about 5K. I did not yet test without the buffer, but will later.
When's the last time you saw a distortion versus load curve for a preamp?
juma said:
No, I use very short and fast interconnects: 80-120cm made with solid core mundorf silver/gold wires.
Big coupling cap, roger.
BFNY said:
It is VERY important to me. I'm very sensitive to distortions, even the so called "good ones". Otherwise i would have already built the original circuit posted by Nelson in the first page of the thread.
juma said:BFNY, you'll notice that your version of J310/JBOZ has about 4 times higher output impedance than the one I did and overload effects kick in earlier, right?
It wouldn't be too hard to check since you have a THD meter. I rely on CRO and my ears only
I assume so, and I think i'll try your version.
It would be interesting the measure THD, though.
juma said:BFNY, you'll notice that your version of J310/JBOZ has about 4 times higher output impedance than the one I did and overload effects kick in earlier, right?
It wouldn't be too hard to check since you have a THD meter. I rely on CRO and my ears only
What I posted was only one of maybe 15 versions of the circuit tested. In actuality I used adjustable HP power supply, and adjustable 5K pot on top and 1K pot on bottom to give infinite possibilities.
The buffer isolated version, with a 22 ohm output resistor was the one that showed a distortion increase below 8K(it was not precisely the same as the schematic). It had a total output impedance of around 75 ohms, so it's not entirely predicable the distortion from your version would be OK driving 10k. I'll adjust my test rig to your values and post the results.
Bob
juma said:
BL grade. My criteria was the onset of change in distortion, so in this case it means the distortion versus load is rock solid until you hit a load point, then it starts to increase. That is the point I named. In this example, it went from say .020 % THD to .023%.
I did not mean to imply it went from .02% to 10% or anything like that.
Bob