Hey guys, it was pointed out the volume level had changed between samples. This would have happened when i was swapping the chip over. Apologies for the mistake, hopefully it will still give you an idea of the mod! Cheers (Paul)
Been watching for months now, finally brace enough to try it myself after learning a load of stuff from you. Put my first order in last night at your shop! Thanks big guy!
Some of the differences could be due to the fact that the voltages are likely different now that there are two ICs drawing off of the same power node. You'd have to change values to achieve the same performance per-chip as the original one opamp circuit would have. It's kinda like in cathode bias tube amps - when you double the number of tubes, you half the cathode resistor size.
I haven't heard someone talk about IC stacking since circa 2000 in the Harmony central forums. I think one consensus was that one ic might wear out over the other due to the tiny differences between them.
Have you ever tried (or is it common practice) to solder another socket on top of an IC so you can easily experiment without resoldering multiple times?
I did this in my Peavey VSS 20 in the Superstat circuit and it was a slightly bigger difference in sound and the noise level came way down with the dual 4558dd mod similar to what you did here. It seemed crunchier with a slightly better overall tone. However, the stock volume control isn't quite as effective as it was with one 4558dd. Btw the amp originally came with the 4558d op amp and between the 4558d and 4558dd I noticed very little if any sound difference between the two op amps. Just putting that out there for those that were wondering.
in the end, I suppose it's like twinning up capacitors or resistors. might be very useful for changing the headroom or response in a circuit to match other components.
I've been thinking about doing this with LM13700 in a compressor, but it would seem one has to change outboard resistors and capacitors to compensate for extra power draw, freq response, in/output impedance. Interesting how those two stacked together had some nasty brunt bacon thing happening up in the top end... they did *not* sound happy did they? HAHA! I wonder if it's cuz the TL0xx series have JFET inputs? Thanks for the demo!
The benefit of parallel devices is reduced noise (when done correctly). Devices should be the same model to make sure that they divide current/voltage equally.
Hello Paul. I am complete with you regarding the difference in sound. I think that the stacked version sounds a little bit more muffled or bassy but overall same a with a single opamp. So, I don't think it is worth the effort and having twice as much power consumption. Really good, entertaining and informative videos. Thanks alot and keep up the good work. Greetings from Germany, Thomas.
That Sounded cool like a controlled stacked fuzzing to me even though it lost some volume it stopped when he stopped playing.i would mod the volume and keep it as an extra pedal in a daisy chain.
I came to notice, that the knobs are in slightly different positions in the 1 opamp 2 opamps comparison so distorsion and vloume are actually lower in the 2 opamps part. Also could you make another test with matched volumes? Would be great to hear them at same audio level, since louder is often received as better thanks to the Fletcher-Munson-curve. Thank you, for the interesting content!
It must have happened when i swapped the IC's, I didnt notice that! Im not totally sure that would account for the dramatic volume lose, but the biggest problem is with the noise anyway.
stacking op amps would probably have a bigger difference at higher gain levels with the volume set the same. i suspect youll hear the difference easier as the gain knob gets rotated and itll be heard in "the grain of the gain" more than the total gain
Had same thought. Op-amp would be overdriven, in higher gain. Stacked could maybe 'spread the load' I've got a dual channel pedal. I'll give it a shot, on one side
This seems like transistor matching for creating Darlington pairs ... of which quite a few can already be found inside the op amps themselves. This is kind of like having a filled to the rim glass of tasty beverages and trying to add more by just pouring more tasty beverages on top ... just doesn't work. Drink that tasty beverages and let the riff inspire the quality of distortion.
Next vid should be a single and a dual on an adapter board for a 3 IC test cuz I like the second 1 better, it just needed a jfet od/dist or maybe a (clean) boost/buffer after the dual ICs... something. I like the identical dual ICs and I also liked the mismatched pair.... that "noise" you dont care for can be the secret bread and butter sauce for a new dirt pedal!!
Because you can, does not mean you should... This mod adds further reduces the function of power/ground bypass tp the upper IC due to additional inductance.
I never heard about placing two op-amps in parallel nor saw it in real circuit or schematics.Buffering the output of any op-amp for extra current using maybe more than one it is common solution but this circuitry never has been used.One critical parameter of any op-amp is the Slew Rate that is the time that takes its output to follow the signal changings of the input.For example the LM324 is the worst of all and must be used only in DC comparating circuits so is useless for any audio applications.J-Fet input as TL08x series are fine.
You have increased the current capacity by two. This may not have any benefit for your circuit. This has the ability to shove excess amperage to the Amp stage.
This is kinda stupid, they are just fighting against each other because of the difference in offset voltages. At the end of the day it's just like a single opamp with a drastically reduced lifespan.
