That's what I was planning to do.
I'll check datasheets and adjust something while duplicating those models, since these are C grade while the Toshiba models refers to BL.
I played with it and lower I could get was 3,5X, but not in a very linear way. Not satisfied, I played with R3 instead, and I'm not sure how to interpret the results of the simulation. It should affect the currents, but dissipation of the 4jfets was basically the same. Hummm...
Distortion follows the output voltage (therefore keeping Vin fixed it seems lower with lower gain) and is very close to the one measured by Papa, except THD20>>THD1. I think the "C" version of Linear jfets improves linearity a bit especially at high frequencies (very important for me). I had to use j74/k170 models.
I also played with the rail voltages, which showed that the 18V chosen value is ideal (shouldn't have doubted that, but hoped to run it lower) and correspond to about 45V for the rails.
Anyway, I do like this circuit very much, I love the offset cancelling behavior (had to add only 7 ohm on upper rail to make it virtually 0 in sim). It looks like the perfect linestage to put in front of an F4.
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I have emailed Linear Systems a couple of times with zero response.
On the other hand, I have traded emails with Central Semiconductor and have received a not-so-polite rebuff.
My gut tells me that money talks and semiconductor companies may tend toward being hard of hearing. You have to shout money-wise.
I have dropped back to punt and ordered some parts from a broker. If it turns out to be wasted money, it will not impoverish me but merely disappoint. If the parts turn out to be useful/genuine, I will buy enough for many DIY projects and call that good. The other option is to switch to BJTs.
At what price? Matched pairs? If not matched pairs, how much do you have to spend to obtain a dozen or so well matched P/N pairs?
The punkydawgs guy on eBay is charging USD $50 for a matched quad of P/N Toshiba parts.
This not exorbitant if you just want to make one or two stereo amps and/or preamps for long-term usage as your main stereo system.
If you want to make quite a few iterations of many different NP DIY topologies, it becomes kind of pricey.
An active DIY crossover with lots of Toshiba buffers will be mucho expensive.
Some people are selling toshibas here too, no need to ebay.
Not matched, you can only choose grade.
4€ each for singles. I'll try to find cheaper. Dunno how many i will get, probably 50 Ps and 50 Ns.
For this preamp a perfect match is not needed, just a "balanced 4", if you get what I mean.
The price of that matched quad isn't bad, and would work too well for it.
I hope the B5 will use something else, cause I will need 4 boards of it.
That will be sweet. Are those the ones that you brought hundreds of thousands into your inventory?
I've used Erno's version -- his with feedback of course -- don't want to dig through a pile of AX to figure out the year:
The All-FET Line Amp | audioXpress
The All-FET Line Amp | audioXpress
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