Too much delay on Glam Chorus

[Ralfg]

Hi Everyone,

I've build the Glam Chorus and it seems to be sounding more like a slapback than a chorus, too much delay.  I heard an audio sample of it on You Tube and it sounds great.  Mine though has just a touch too much delay.  I double checked the values of everything and it doesn't look like I put in any incorrect components.  I tried a different PT chip and got the same results.  Anyone else have a similar problem?  I don't really know much about this circuit, is there a way to reduce the delay time on it?  I checked the voltages compared to whats in the build doc and mine are a bit, are higher by almost a volt.  Is this just a result of a power supply that's giving just a bit too much juice and increases the delay time?

Thanks for the help and info that you can provide.     

[Jebus]

Hey!

I don't have schematic on hand right now, but on PT2339 -based pedals the resistance from the ICs pin 6 to ground determines the delay time, so check that out.

[madbean]

Yeah, R19 needs to be 2k. Please double check that (or tell us the color bands on it). Can't really comment on the over-voltage w/o your actual voltages listed.

[Ralfg]

Thanks guys,

R19... the one I didn't check.  It measured 1.8 k, swapped it out with a resistor that measured beforehand at 2K.  Then I measured again once it was on the board and got 1.8K.  I was measuring from pin 6 because I couldn't get the volt meter lead on the end of the resistor because its too tight.  Not sure why this would be the case, double checked my solder connections and they look good to me. 

I noticed my meter was messed up because it just measured 12 volts at the power supply, so I tried a different one and got basically the same voltages as in the build doc.  Rechecked R19 and still see the same value at about 1.88K.   

Swapping out the resistor made a really big difference, the delay is less pronounced and it sounds more chorus like.  Still a slight delay.  How is this controlled through R19?  How does this value affect the delay?  If I were to play with it or put in a trimmer would it make a difference?

Thanks for all the help.

[Jebus]

Hey!

Your multimeter is running out of battery.. 

Higher resistance there means longer delay time. You can try to reduce R19 if you are sure all the other values are correct.

[Ralfg]

Haha... That would explain that. Learn something new every day.

Thanks for all the info and help.

[Boba7]

The problem is if R19 is lower than 1k, the PT2399 could lock up when you power the pedal.

There are ways to put a very low value (like 100r) along with a small anti lock-up circuit, but I've never done it. Some chorus like the Little Angel or the Jenny Greenteeth do that I think.

[Boba7]

Also I've experienced big changes in delay time with the same resistor value and different PT2399's...

[sharpan.sv]

Is it possible to use ht8970 in place pt2399? Looks like pinouts exact the same, but delay time with 2k resistor is about 29 ms instead of 50 with pt2399

[midwayfair]

Is it possible to use ht8970 in place pt2399? Looks like pinouts exact the same, but delay time with 2k resistor is about 29 ms instead of 50 with pt2399

Probably (you shouldn't have the distortion problems of that chip over the PT at this delay time), but the problem with going to a shorter delay is locking up. No idea if the HT will be more resistant to that. The actual resistor values used to reach an appropriate delay setting are irrelevant. If the problem was simply that the resistor was too big, you'd change the resistor not the chip.

[sharpan.sv]

I've tried this. Sounds nothing like slapback anymore, but chorusing very weak and depth pot needs to be set almost at max. Maybe with some LFO tweak it will be good