MMBFJ310LT1G & BF862 for SOT-23, drain and source are marked differently, but NXP says that they are interchangeable.
Done, made a few other improvements, like the option to use multiple power supplies, popped a few caps in around the place for psu decoupling, and included in pads for the surface mount fets if used.
Those bf862's aren't overly expensive either...
As before the part names are incorrect as I haven't bothered to create the appropriate parts in eagle - I've just used equivalent pinout/profile parts already there.
Those bf862's aren't overly expensive either...
As before the part names are incorrect as I haven't bothered to create the appropriate parts in eagle - I've just used equivalent pinout/profile parts already there.
Attachments
Belated Progress
And here's where I'm at with it now. I've put a slow start on the board, so the turn on thump should be mitigated. Otherwise I hope I've designed a sensible layout...
I bought a bunch of bf862's, J109's and J111's and I've a stash of J310's so perhaps I'll build a few of these to see what the differing jfets sound like (if indeed there's a difference I can pick). So that's an idea to pursue if I fancy it.
Anywho I'll etch I few of these soonish (or seeed them) and see how I go.
And here's where I'm at with it now. I've put a slow start on the board, so the turn on thump should be mitigated. Otherwise I hope I've designed a sensible layout...
I bought a bunch of bf862's, J109's and J111's and I've a stash of J310's so perhaps I'll build a few of these to see what the differing jfets sound like (if indeed there's a difference I can pick). So that's an idea to pursue if I fancy it.
Anywho I'll etch I few of these soonish (or seeed them) and see how I go.
Attachments
Grado Labs | Reference1 & Master1
Spec Input=47K,
no need for a R20 as R19 is 47K.
It is a low o/p at 0.5mV, but this is a MC pre so it should be fine stock values, R15, use a jumper. Would not worry about C15, test to see what it is like. $1500 cartridge, must have fine record collection to go along with it 🙂
Spec Input=47K,
no need for a R20 as R19 is 47K.
It is a low o/p at 0.5mV, but this is a MC pre so it should be fine stock values, R15, use a jumper. Would not worry about C15, test to see what it is like. $1500 cartridge, must have fine record collection to go along with it 🙂
has anyone played around with LTspice on this circuit? I'd like to compare results if possible....
Thanks!
I tried 16 pieces of J310, with 200R bias resistor and 1K drain. 60V power for 0.095 % thd at 1K. Climbs to 0.45 at 20K.
Thanks!
I tried 16 pieces of J310, with 200R bias resistor and 1K drain. 60V power for 0.095 % thd at 1K. Climbs to 0.45 at 20K.
Last edited:
Forgot to mention, the big mosfet is IRFP240.
woops, just noticed max gate source voltage is exceeded.... why does LTspice not flag this error???
woops, just noticed max gate source voltage is exceeded.... why does LTspice not flag this error???
Last edited:
replaced IRF610 with IRF510 (possible model issue) and changed 22.1K resistor to 40 Ohm.
Now, thd is below .1 percent for unity gain with 2V input at frequency of 1K.
Now, thd is below .1 percent for unity gain with 2V input at frequency of 1K.
Attachments
Last edited:
I did a version with a little bit of feedback and got (from memory), um, 0.4% THD? at 10k?
I'll dig it up and post shortly... <edit> included some data that was bad - will repost </edit>
I'll dig it up and post shortly... <edit> included some data that was bad - will repost </edit>
Last edited:
Sim results
Here you go - input is 10kHz @0.5V (1V P to P), out1 is without feedback and out2 is with minor NFB. The log file has the FFT output numerically, and the THD numbers.
I've BJT's in as the cascode element for no real reason other that I read Pass saying he prefers to use a BJT there.
Hope thats of interest!
Here you go - input is 10kHz @0.5V (1V P to P), out1 is without feedback and out2 is with minor NFB. The log file has the FFT output numerically, and the THD numbers.
I've BJT's in as the cascode element for no real reason other that I read Pass saying he prefers to use a BJT there.
Hope thats of interest!
Attachments
THANK YOU! This is of excellent interest!
FYI: The version I posted gives under 0.2% thd at 10K, with 2V input and near unity gain, using that analyzer tool.
I'll try to post an FFT -- just learning LTspice. It is amazing!
Thanks for including the models on the sheet. I will have to figure out how to do that easily. Will try to post something tomorrow.
Thanks again!
FYI: The version I posted gives under 0.2% thd at 10K, with 2V input and near unity gain, using that analyzer tool.
I'll try to post an FFT -- just learning LTspice. It is amazing!
Thanks for including the models on the sheet. I will have to figure out how to do that easily. Will try to post something tomorrow.
Thanks again!
@BigE I reckon your R1 value needs to be about 30k; the dissipation in your J310's will be quite high at the moment I'd say (magic smoke levels!). Hold <alt> and mouse over the part.
I'm also just learning LTSpice (yes it is awesome!) I'll have a play with your model also and see where I get to - great to have someone to bounce ideas off!
I'm also just learning LTSpice (yes it is awesome!) I'll have a play with your model also and see where I get to - great to have someone to bounce ideas off!
Excellent!!!
I was looking for the blue smoke button somewhere.... Turns out that it is within the range for the fairchild to-92 style, but they still need heatsinking. The smd stuff and te ON-semi will just blow up. It's SO good to know about that trick thank you!
The inclusion of the feedback is great! I just don't know how much is ok.
I'll take a look at your model at some point.
Cheers!
I was looking for the blue smoke button somewhere.... Turns out that it is within the range for the fairchild to-92 style, but they still need heatsinking. The smd stuff and te ON-semi will just blow up. It's SO good to know about that trick thank you!
The inclusion of the feedback is great! I just don't know how much is ok.
I'll take a look at your model at some point.
Cheers!
I realize this is an old project but any chance you have any files that you wouldn't mind sharing? I have a cnc sitting yet-unassembled in the box but something that can be etched would be great too! I've got a roll of BF862 as well as a bag of J310 collecting dust. Anyone built the SSTART with some impressions on sound?
Hope that works!
Here you go!
Edit - fail. I'll email you them if you want to PM me your email address.
Here you go!
Edit - fail. I'll email you them if you want to PM me your email address.
Heya - I was looking over that PCB and I can do a bit better these day's, and given jlcpcb costs what it does, I could make a pretty compact 2 sided smd version of the board if you're keen...
I also realised that the designs I gave you have a regulator pcb (led reference for funsies), feeding into a slowstart on the preamp board. Not really a problem, but not particularly elegant. Again, happy to knock out another board if you're interested.
Whats your goal here? I'm even wondering if I go ahead and do a design, and if you're keen we could share a pcb order.
I also realised that the designs I gave you have a regulator pcb (led reference for funsies), feeding into a slowstart on the preamp board. Not really a problem, but not particularly elegant. Again, happy to knock out another board if you're interested.
Whats your goal here? I'm even wondering if I go ahead and do a design, and if you're keen we could share a pcb order.