IPv6Freely
Active member
Through-hole J201s are also readily available on Mouser, now.
Missing Build Docs / Schematics
- Thread starter Robert
- Start date
BuddytheReow
Breadboard Baker
J201 and 2n5457 are close substitutes, but they are not identical.
temol
Well-known member
Value of the drain resistor depends on parameters of the particular jfet and other factors. Looks like 100k is a leftover from transfering tube amp schematics to jfets.
Below I attach screens from ltspice.
You can clearly see the difference between J201, 2N5457 and 2N5458 in terms of gain.
I only adjusted Rd value to get 4.5V on a drain of each transistor. Rs does not change (because people usualy adjust only Rd value. And often it's a trimmer).
Rd for J201 =34.3k
Rd for 2N457 =16k
Rd for 2N458 =11.95k
Rs = 3k
It depends. As a source follower (buffer) - yes. In a gain stage - sometimes.
Feral Feline
Well-known member
IMO, it's the PCBs that have SMD pads that must be soldered and are not (easily) removable.
I like adapters because they are more easily removable.
When you've got a through-hole board and SMD-adapter daughterboards, you can socket the main board and solder the SMD bits to the adapters and shove the adapters in the main-board's sockets — if something goes wrong, remove the adapter with the toasted component and replace it — easy-peasy.
If an SMD-board's component goes bad, you can still remove it, but I would think it's more of a PITB to do so and especially so if the PCB has a mix of THD and SMD.
bowanderror
Well-known member
Those look like quite useful LTSpice plots, how did you set up your command to step through 3 different transistor/resistor combinations?
bowanderror
Well-known member
I use resistor leg cutoffs on my SMD adapter boards & they work great in sockets! Also never had a problem with SMD JFETs & heat, and I use a standard hand iron to solder them.
temol
Well-known member
jeffwhitfield
Well-known member
Mojito Deluxe Overdrive is still missing build docs and a schematic.
michaeldustdevil
New member
any chance of the Mofeta Preamp schematic?... i really want to breadboard it before i build... thanks...
Barry
Well-known member
The schematic is likely in Chuck's Boneyard post on it
dont-tase-me-bro
New member
is the Lo-Fi Machine build doc available anywhere?
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Thanks for these informations...
About the 100 k drain resistor, i mean that what if i have to turn the trimpot to 100k to get the correct voltage at the drain? Is the FET still good?
jeffwhitfield
Well-known member
Nope! Just a pic of his finished prototype.
Barry
Well-known member
Nope! Just a pic of his finished prototype.
Celebrating the Autumnal Equinox with another pedal - The Mojito
This Overdrive is heavily based on the BJFe Honey Beest, a Honey Bee with a JFET booster up front. It was a collaborative effort with HamishR. In his honor, I've cracked a tuber of Foster's Lager (yeah, I know, it's that wallaby-piss export stuff). HamishR had been advocating his modified...
forum.pedalpcb.com
jeffwhitfield
Well-known member
Well, that definitely helps.Celebrating the Autumnal Equinox with another pedal - The Mojito
This Overdrive is heavily based on the BJFe Honey Beest, a Honey Bee with a JFET booster up front. It was a collaborative effort with HamishR. In his honor, I've cracked a tuber of Foster's Lager (yeah, I know, it's that wallaby-piss export stuff). HamishR had been advocating his modified...
thesmokingman
Paid Hater
looking at the calendar and my email inbox and it's been over a month since the release of the acetylene and still no build docs ... got an ETA?
Feral Feline
Well-known member
Is the Lo-Fi Machine PCB going to be available again?
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