anyone done "3 legged dog" from runoffgroove.com??

[rx5]

anyone? Ive done mine but just 1/4 turn from the 1M gain pot and "OSCILLATION !?!?!?!?" :x  done my project in a perfboard and yes ive done it cleanly...short wires,etc... my chip is HEF4049BP... is this chip buffered?? how many classes (buffered/unbufferd)??are this chips??

another thing, can the J201 N - Jfet be sub'd by 2N5458 N - Jfet??


tnx...

[Bill_F]

I could never get mine to stop oscillating. To bad because I really like the way it sounded.

[gez]

It looks as though your chip is buffered.  Buy one that has a 'UB' somewhere in the code (unbuffered).

[Paul Marossy]

I built it a few months ago. There are two secrets to the oscillation thing:

1. You need the unbuffered CD4049 chip, it has "UBE" at the end.
2. You have to use a fresh battery! If you try using a battery that's putting out 7.5 volts or so, it will squeal like nutz!

It sounds good otherwise. I use a wall wart to avoid the squealing problem.  I built exactly per the layout at RunOffGroove.com

[rx5]

yup.. I think its the buffered type.... got another here:CD4049UBCN maufactured by: F <dunno what company maker it is>...but still got oscillations... maybe the battery...i think its about >7V but not greater than 8V..... i tried the last stage modd by changing the 1M feedback res to  330K and it now sound fine... but the GAIN (1M pot) sound like a tone control...hehehe  :lol:  minimum resistance:no output , 1/4: its like treble boosted distortion, halfway to max resistance: sounds like more bass ..... ive been comparinr it to the Double D circuit.....seems like the same but with buffered outputs....

another: can J201 be substituted by 2N5458??? or what are close replacements to this J201??? cant seem to find J201 Jfet here....

[Joep]

The the 2n5458 wil work, you may need to adjust the resistor (8k2) between the 9v and the drain, to get around 4,5V at the drain of the fet. See also the DD schem.

Hope this helps.

Joep

[gez]

The way this is set up input impedance increases as the resistance of the gain pot increases, so the .01 cap between the drain of the input buffer and the input of the first inverter stage IS acting like a tone control - it cuts lows when the pot is at lowest resistance, gradually re-introducing them as the pot resistance increases.

You have a few options.  One is to increase the cap value so that ALL the signal is passed all of the time (this might sound a little 'wooly' mind).  Another is to replace the drive pot with a 1M resistor and then connect up a pot (1M?) between the .01 cap and the input of the inverter.  You can then make the .01 cap smaller so that things work the other way round - as the pot's resistance decreaces, gain increases and lows are cut.  Different cap values will give you different amounts of cut.

[Paul Perry (Frostwave)]

Try a 100microfarad cap across the battery. Can't hurt!

[Nasse]

I looked at the schematic and there was those large resistors from inverter input to ground. They may be part of what makes this circuit sound special but are they necessary or cause any problem?

[Nasse]

Never happened to me but did you remember to connect unused inverter inputs to ground or V+ , 4049 has six inverters

[rx5]

tried to rewire the Jfet input circuit... got rid of 8.2K from the drain..<connected the drain staight to V+>......then replaced the 470ohm with 8.2K and i get my output from Source.... coupled it with .01uF to a 1M pot with clockwise leg to ground and mid leg to input of the inverters... changed the 1M pot <feedback/gaIN 1st inverter..to 470K> ..... now it works great....  im goona add another jfet at the output of the inverters to buffer it...

and i ulways use electro caps for the supply rails.... :wink:

[rx5]

The the 2n5458 wil work, you may need to adjust the resistor (8k2) between the 9v and the drain, to get around 4,5V at the drain of the fet. See also the DD schem.

Hope this helps.

Joep

yup.... thats the important part of jfet operation when you connect a resistor from DRAIN to V+....... I rewired again my ciruict to the original.....tried replacing the 8.2K between DRAIN and V+ to 10 pot..adjusted it till i got +4.5V...... got a resistance reading of 4.03K..... i seriesed a 3.9K and 100Ohms to get close to it.... now it works like a charm but i didnt use the adjustable 1M gain as the feedback element of the first inverter..just used 470K(same as the Duble D) .......

and yes, there are two types of CD4049... my first one was buffered so it oscillated s much.... i now use the unbuffered (CD4049UB).... now it really works...  important part is that you should get 4.5V at the DRAIN leg....i used 2N5458 cuase i cant seem to find J201.....

hope this clears up the problem.....