Phase 100 rant, and question: TL022 = TL072 ?

[dschwartz]

now i´m confused!
i have been reading about opamps lately and i came to the conclusion that basically, they´re all the same. Its function is to add, substract and multiply... so..why do 1458´s work better than the other opamps?? iknow that the differences between opamps are:

- current consuption
- Input Impedance
- noise
- headroom (amplification vs rail voltage)
- slew rate
- Clipping shape
- other non-important ratings (Max V, Max I, dissipation, etc etc)

i know slew rate can affect high frecuencies..also clipping shape..
Is maybe the input impedance? is the opamp in a configurantion that the Input Z is set by the opamp itself? not using a Z resistor?

i have just got out of a discussion with a DIY friend that says that opamp type makes a huge difference.. i can´t believe that.. an opamp is an opamp!!! like a calculator is a calculator!!!

[petemoore]

huge difference..
  depends on your perspective I guess.
  Basically all opamps are the same.
  If you notice one sounds better in a certain application:
  Like TL062 cures clicking or pulsing..or has the current consumption you desire...
  Or a high current amp works cleaner say in your otherwise very clean compressor...
  Or you need all the headroom you can get @9v and use an opamp that does rail to rail performance...
  Stuff like that or;
  You notice that the certain different characteristic of the sound of certain opamp is less desirable than the other [what I guess means 'huge difference' to some]...
  'Standard or premium'...when a good opamp does what the specs say it should do...should work fine, I can't see why a phase 100 would have any super-special needs, to get it at least functioning somewhat normally...tick would be the one thing above I can think of that a low current OA might cure.

[the recluse]

My futurlec order came in today and I was able to pull the 4558s out of my GGG Phase 100 and replace them.  I ordered LM1458 but got HA17458s, it's a dual opamp, so...

Anyway, I recently put an HA17458 into my Screamer clone and notciced how much of a difference it made so I was hopeful.  The new opamps seem to bring the phase out a bit more on the 2 and 4 positions, but it's still not quite there for me.  I think my last resort is going to be dropping the value of the resistor that was replaced to prevent oscillation.  The stock value is 15K, the new value is 29K, so I have my fingers crossed that maybe a 22K will split the difference.

I will be building a phaseur fleur soon anyway, so this may end up being a moot point.

[Praying_V]

Just in case, don't forget to mess with the internal trimpot too. 

[the recluse]

I've been playing with the trimmer, but it hasn't provided any drastic results.

When I first built it, I ended up sending it back to JD at GGG so that he could diagnose the oscillation issue.  He had been hearing about the problem from a few people that built the kit, but hadn't had the problem himself.  The fix was boosting the value of R1, which is now suggested in the instructions for the P100 project. 

I hope reducing the value of the resistor does the trick.  We'll see...

[axg20202]

I must have missed this thread. I have built the GGG P100 twice, the second one using the revised board (all new components too). Neither worked and both had the same issue of oscillation in certain switch positions. I gave up on it after many hours of debugging and stripped the boards of their components. It actually gave me great pleasure to bin the boards and move on. To date it is the only build (of many) I have not successfully completed. The question is, is this project actually verified? I think not.

EDIT: sorry, it seems it has been built successfully before. Perhaps it is a case where the required component value tolerances are such that normal variability in components makes it a bit pot luck whether it will work or not? Anyway, it was not fun!

[DougH]

When you are swapping op amps around, try just swapping out the LFO IC's and leave the TL072's for the all-pass filters. If that works, it tells you there is something quirky about the TL072 that will not allow it to work with this LFO circuit. If it's necessary to swap out the TL072's in the all-pass stages, I would think there should be a trim adjustment or something for the control element voltages to get the filters to sweep correctly.

I have a Phase 90 on the breadboard right now with the 4 all-pass stages and LFO implemented with TL072's and it works great. There are differences between the P90 and P100 LFO circuits which could explain it or it could be an interaction between the vactrols and all-pass stages that doesn't occur in the P90 with the JFET control elements.

You guys are making a great case for using IC sockets in op amp circuits though, something I adhere to religiously.

[axg20202]

You guys are making a great case for using IC sockets in op amp circuits though, something I adhere to religiously.

Definitely. I do it for all ICs in all builds. Desoldering ICs is a PITA and the sockets cost pennies.

[ilcaccillo]

I'm also in the Phase 100 nightmare.

I had an MXR phase 100 that stoped working  some time ago. (now I now that problably was a burned vactrol)

I decided then to build a new one.
Everything works fine , except for mode 2 and 4 that have some distortions, can't figure out why.

if anyone could help , here is mu thread:

http://www.diystompboxes.com/smfforum/index.php?topic=73640.msg597554#msg597554


BTW the opamps used in the Dunlop Phase 100 were all TL062.

[jsleep]

I'd like to offer my deepest apologies to everyone who has had trouble with this P100 kit or building from the project on the site.   Specifying the TL072 ICs was a bad mistake on my part.  Also releasing such a complex kit with a PCB with no solder mask probably wasn't the best idea either.  There was actually a couple minor mistakes in the schematic, I have already fixed and reposted that. 

I'm in the process of fixing the kit and project up.  We will be getting new PCBs in next week and the kits and PCB will be up for sale again as soon as they check out okay.

For those of you who had any kind of aggravation with the PCB or kit that you purchased from us, please email and I will do my best to make it up to each of you individually as is best for you.  We'll send you a complete new kit at no charge to any of you who bought the kit and had trouble with it.  To send email me, just go to the General Guitar Gadgets site Contact page.

Thanks,
JD Sleep
General Guitar Gadgets

[Tony Forestiere]

JD Sleep...a stand-up guy. This has got to be the classiest group of folks in the net. 

[ilcaccillo]

JD,
thanks for posting in this thread.

I've sent you an email about my pedal, which I built with a board ordered from you.

It would be great that fixing those errors in the schematic could solve most of our problems.

Hope to hear from you soon

Thanks

TS