Blueprint compared to Mobius Strip

[zgrav]

I have built both of these VFE pedals and like them.  For the Blueprint, my pedal has a very low level of background sound -- sort of a hi-frequency harmonic  - that is present with any of the delayed signals from the PT2399.  And the pedal is otherwise very, very quiet which is the only reason I can hear the other sound.  I have changed out the memory chips and it does not seem to make a difference.  I am guessing it is part of the modulation circuit that the BP uses, since there is no similar sounds from my Mobius Strip pedal even using both of the delay channels.    Wanted to ask if anyone else has noticed this.

[Aentons]

I have a VFE regular production Blueprint and I don't hear what you are talking about. With mix and level and depth all the way up, the only thing I hear is a very, very low to midrange sort of vacuum cleaner type oscillation sound. It's not noticable at all during repeats.

[zgrav]

Thanks for the reply.  We might be talking about the same noise, except I know this is coming from the echo part of the circuit since it goes away when the repeat ends.  Almost sounds like a noise gate kicking in to cover a very faint fuzzy harmonic of the repeated signal.  I'll swap out a few more 2399 chips to see if I can find a quieter one.

[Aentons]

It sounds like you are describing the normal  noise on the repeats that is present at long delay times, which is inherent with the PT2399. Is it there when you have the delay time at noon or lower?... or to put it another way, is it more pronounced with longer delay times?

The very faint hum type sound I described is really only present when there are no repeats happening so it sounds like we are likely talking about two different things.

The VFE designs usually push the boundaries of some components, sometimes to an extreme. The PT2399 associated noise is allowed in the design of the Blueprint in order to push the delay time to an extreme for that chip. I'm not sure if the Mobius Strip is designed for longer delay times, or if it has different filtering, so the nosie may not be present there for that reason

[zgrav]

It is a just a very low noise level on the PT2399.  Only noticeable when I am doing some very soft playing with notes fading to silence.  Overall I am happy with the pedal, and the modulation options on the delay are useful.  Not as clean as my old Boss DD-2, but I never expected it to be. 

[zgrav]

UPDATE  --

I had set this pedal aside for a while and did a bit more critical listening to the noise.  The low background fuzzing and harmonics was also in the dry signal but not very noticeable until it was getting repeated in the wet signal.  I had used a TLE2074 quad op-amp on the board that I swapped out for a TL2074 chip and the noise went away.  I put in a different TLE2074 chip and the noise was there again, so I went back to the TL2074 and all is well.  From the datasheet I thought those chips were interchangeable and the TLE2074 had better specs.  Not sure if I just have 2 bad TLE2074s, or if they are not always a better sub for the TL2074.     Either way, I am happy that this pedal finally cleaned-up nicely.

[zgrav]

I will add that the most likely explanation is that my two TLE2074 chips are out of spec since they work but are noisy, since those are the chips called for in the build document.

[Aentons]

my two TLE2074 chips are out of spec since they work but are noisy

Where'd you get'em?

[zgrav]

Most of my 2074 chips in my inventory are old, and likely came from RadioShack, Mouser, or Digikey. 

[fair.child]

2074, you can get free samples from TI. I used them for testing and my BLP build and worked really nice.