So, about a year ago I bought the guts of a JDF2 off eBay. I think it's the older version as it has the transistors marked DMI158 rather than the reissue NKTs. It works just fine (I was actually goofing around with it on Sunday) but it's a bit wooly and gets a touch dark when I roll the volume down.
So, before I order an enclosure to put it in I was figuring I'd like to do some simple mods to it to maybe improve the clarity and versatility, which might change how many knobs are on the enclosure I order.
So, what do you guys like to do to these things? Transistor changes, I imagine, but anything else? Favorite transistors that won't cost me one of my children? Whatcha think?
Quote from: GilmourD on September 03, 2019, 09:36:27 AM
So, about a year ago I bought the guts of a JDF2 off eBay. I think it's the older version as it has the transistors marked DMI158 rather than the reissue NKTs. It works just fine (I was actually goofing around with it on Sunday) but it's a bit wooly and gets a touch dark when I roll the volume down.
So, before I order an enclosure to put it in I was figuring I'd like to do some simple mods to it to maybe improve the clarity and versatility, which might change how many knobs are on the enclosure I order.
So, what do you guys like to do to these things? Transistor changes, I imagine, but anything else? Favorite transistors that won't cost me one of my children? Whatcha think?
If it sounds overly bassy, check out the output cap, usually an incorrect .1uf on Dunlop FF's. Change it out for the proper .01uf to get the bassiness in check. I put a 20k bias trimmer with a small resistor in series in place of the 8k resistor, I have thought of changing it out for an external pot of the same value for convenience. Dunlop was notorious for not biasing their germanium transistors correctly.
Al
Quote from: zombiwoof on September 03, 2019, 10:13:17 AM
If it sounds overly bassy, check out the output cap, usually an incorrect .1uf on Dunlop FF's. Change it out for the proper .01uf to get the bassiness in check. I put a 20k bias trimmer with a small resistor in series in place of the 8k resistor, I have thought of changing it out for an external pot of the same value for convenience. Dunlop was notorious for not biasing their germanium transistors correctly.
Al
Actually, it's the version that has the two trimmers on the board already along with the thermistor (which, I believe, is in parallel). I'd like to add an input pot, like on the Sunface.
I'll check the cap value when I get home.
add a hi pass filter to the beginning. try about a 3.3n and maybe a 10-50 k pot for it, put it in series with the input. that will let you take it from all out fuzz to something more like an overdrive. i have this built into all my guitars, great trick with fuzzfaces
Quote from: pinkjimiphoton on September 03, 2019, 12:43:54 PM
add a hi pass filter to the beginning. try about a 3.3n and maybe a 10-50 k pot for it, put it in series with the input. that will let you take it from all out fuzz to something more like an overdrive. i have this built into all my guitars, great trick with fuzzfaces
+1
It shows the brilliance of the circuit with its soft and hard clipping