Hamlet Delay and Preamp: Schematic, build doc, layouts, and demo

[midwayfair]

I don't really know. I do know that PT2399s can vary pretty wildly especially from seconds-sellers like Ebay folks, but usually even at worst you can get get to 25K before the noise becomes noticeable -- it's certainly extremely abnormal for the motorboating to appear with the delay at minimum even with the tone control at 0 here.

Unfortunately we're sort of at the mercy of the chip itself for a lot of things and the chip variability can complicate troubleshooting, but I'm sure you already know that.

[maoriente]

Sorry, the noise with delay at minimum wasn't quite motorboating, more of a white noise, hiss kind of thing.

The motorboating only happened with the delay full on, or close to full on. As I backed off the Delay control, the motorboating would stop but there was a white noise and sometimes other strange noises until I got to about 40k. Then they would quiet down, but a couple of them would be noisy again at minimum.
 
One of them seems to be working well with a 50k delay pot. I double checked the tails bypass with this "quieter" pt, but there is still noise when not playing. Frustrating. Makes me think I have two issues going on, poor PTs and a build error. And I think I already mentioned this, but if I ground the FS1 connection, the noise in tails bypass goes away.

I think at this point I'm going to order a bunch of PTs from Tayda and in the meantime build another vero to see what I get. 

     

[midwayfair]

more of a white noise, hiss kind of thing.

Again, hiss is pretty normal when you start getting above 200mS of delay, but having it at minimum with the tone resistance pretty much anywhere on the dial would be weird. The only thing I can suggest there is double check that you've used 56nF for the tone cap and not 5.6nF. But considering you still have some unusual behavior when the bypass is disconnected, I'm more inclined to suspect the chip.

One thing that might help is if you build a comparison on a known working layout. Unfortunately, while I know of at least two etch layouts (other than the etchable version of my perf layout), I don't remember if anyone else did a build on vero. When I get home I'll try to remember to look through my circuitboard box and see if I still have a PCB (which you can have). If I don't, I'll see if I can get a comparison build to you some other way. Are you in the U.S.?

[maoriente]

Wow, too kind Jon. I'm in Utah.

Recently, I have mostly been using monolithic caps. Some are a bit out of spec so I measure each one and usually end up doubling them up trying to get the exact schematic values. For the tone cap in this build, I paralleled a 473 and a 103 to get the 56n.

I re-cut and re-flowed all the joints yesterday just because. Played it again tonight using headphones and there is definitely some strange noises in the background. No change using a battery supply.   

Even with the best sounding PT, and with the guitar volume turned all the way down, there is a shift in the noise while adjusting the delay pot. It quiets down close to full CCW, and then there is a little bump in noise at full CCW, not nearly as loud as full CW. Adjusting the tone control just masks the noise.         

I just finished up a madbean Dirtbaby (pcb) tonight, I increased the filtering quite a bit per the build doc and also increased C13 from 4n7 to 47n. I already had a seperate PT2399 installed, I'm not getting any of those strange noises on this one. I swapped in a couple of the suspect PTs and they were acceptable. The Dirtbaby is much darker though, but even with the tone control full CCW on the Hamlet, the noise levels are night and day between the two.   

Conclusion: there must be something wrong with my build and not necessarily the PTs.

I'm traveling the rest of this week but will try to knock out another vero the following week to compare.

I'll see if I can record and post the noise before I take off tomorrow. If not, I'll do so when I get back.



 

[maoriente]

Haven't had a chance to build another one just yet, hopefully over the weekend, but here is a sound sample.

I recorded direct to pc from headphone jack of amp, also recorded a Dirtbaby for comparison. (I've increased the filtering on the Dirtbaby making it darker on the repeats that with the stock values)

Hamlet: Max Delay, Max Mix, Max Tone, Min Repeats
https://soundcloud.com/maopedals/hamlet?in=maopedals/sets/delays
Bypass 0-3 sec
Effect On 3-10sec
Guitar Volume turned down 10sec
Rotate Delay knob slowly CCW 15-24sec
Rotate Delay knob slowly CW 24-33sec
Rotate Delay back and forth a little quicker 33-45sec

Dirtbaby: Max Delay, Max Blend, Min Repeats, Rate & Depth Min
https://soundcloud.com/maopedals/dirtbaby?in=maopedals/sets/delays
Bypass 0-3 sec
Effect On 3-10sec
Guitar Volume turned down 10sec
Rotate Delay knob back and forth 10-27sec

[maoriente]

As usual, Jon was right on.

I replaced the 56n tone cap and the noise is gone! 

I had originally paralleled 2 multilayer ceramics in the same holes to get the 56n, I replaced with a single box cap and the noise is gone. My guess is I had a bad solder joint with the 2 caps-per-hole.

I still have some noise with the tails bypass though, I assume I may have the same issue with a couple of the other caps I had paralleled. It's a sputtery kind of white noise with the tails bypass.

Going to dive back in with an audio probe after lunch. 

[maoriente]

So while audio probing in tails bypass, I found noise at the collector of the 2n3904. The base and emitter are clean. The same noise makes it through the 1u to lug 3 of the volume trimmer.

When I remove the charge pump, the noise goes away. I tried a couple of 7660s and a LT1054 with pin 1 lifted. No change.

Same noise when powered with 9v battery too.

The noise is also on PT2399 pin 14, and the Drain, Source and Gate of the 2n5457

Not sure what to make of it. Maybe the charge pump is to close to the PT2399?

Here is the layout I used.


this picture before I swapped out the 56n tone cap(s)

[midwayfair]

I would expect charge pump noise to be a high pitched whine, and I think that's what I'd also expect if proximity were a problem. That's really not the noise I expected from the PT either. If it's coming from the PT it makes sense that it's at the collector of Q1 -- it would just go through the cap back to the collector. You could try lifting the 1uF decoupling cap from Q1 if you want to be able to probe the outputs of Q1 and Q2 separately.

If it is the charge pump doing it, I am not sure what else could be done (especially because I haven't encountered it before). Maybe increase the 10uF filtering capacitor.

[maoriente]

I increased both 10u, neither affected the noise.

So here is the latest:
With FS1 and FS2 closed, the noise is barely detectable. I think there may be some noise way in the background, but it's hard to hear even with headphones.

When I disconnect FS1 and FS2, there is a noticeable increase in hiss. I get these weird noises while adjusting the delay knob too. If I ground FS1, the hiss is somewhat reduced, but still noticeable compared to shorting FS1 and FS2.

Not sure what to make of that.

When I remove the charge pump, the noise seems to be gone altogether. Or it's just so faint I can't tell its there.

The Delay without the charge pump still sounds pretty good, maybe just not as sharp. 

At this point, I think I'm going to run this particular vero at 9v, re-bias Q2 and call it a day. 

I'm going to redesign the vero and try again.

Thanks for all your help Jon.   

     

[snk]

Hello,
I dare to ask a quite dumb question, but i have started studying the (very interesting !) Hamlet Delay Build Doc, but, as english is not my native language, i am not positive about the meaning of one sentence :

C9 provides some final high-pass filtering. Increasing it will retain some additional bass and subharmonic frequencies, but no fundamental guitar information is lost even with a comparatively small capacitor in this position.

Does "retain" actually mean that the capacitor will allow the bass to pass through (like "the bass will be kept in the source signal, remain intact"), or does it mean that the capacitor will block the bass, and doesn't allow it to pass through ? 

I am trying to understand how to further hipass filter a delayed signal, so i am trying to figure out which capacitor value I should have for C3 (input cap) and C9.
- Should I focus more on C3, or on C9 ?
- Why value should i choose in order to filter out the frequencies below 100-150hZ ?

Thank you !

[midwayfair]

Hello,
I dare to ask a quite dumb question, but i have started studying the (very interesting !) Hamlet Delay Build Doc, but, as english is not my native language, i am not positive about the meaning of one sentence :

C9 provides some final high-pass filtering. Increasing it will retain some additional bass and subharmonic frequencies, but no fundamental guitar information is lost even with a comparatively small capacitor in this position.

Does "retain" actually mean that the capacitor will allow the bass to pass through (like "the bass will be kept in the source signal, remain intact"), or does it mean that the capacitor will block the bass, and doesn't allow it to pass through ? 

I am trying to understand how to further hipass filter a delayed signal, so i am trying to figure out which capacitor value I should have for C3 (input cap) and C9.
- Should I focus more on C3, or on C9 ?
- Why value should i choose in order to filter out the frequencies below 100-150hZ ?

Thank you !

Increasing that capacitor will cut less bass. However, that bass is not in a guitar signal.

If you want to cut more bass (high pass), then you could make that capacitor smaller.

"- Why value should i choose in order to filter out the frequencies below 100-150hZ ?"

Use a calculator like this one:
http://sim.okawa-denshi.jp/en/CRlowkeisan.htm

Or, better, experiment by ear.

[snk]

Thank you very much, Midwayfair (as well as for the Hamlet design !), and sorry for the average understanding of your sentence 

If you want to cut more bass (high pass), then you could make that capacitor smaller.

Would you advise to decrease C3 first, and then experiment with lower values for C9, or the opposite ?

[snk]

Use a calculator like this one:
http://sim.okawa-denshi.jp/en/CRlowkeisan.htm

Using the Hipass calculator (it's a hipass filter, right ?), it gives me that the values used in Hamlet set a cutoff point around 72Hz. Is that correct ?
If i set the resistor value to 110nF, it should have the cutoff point set around 144Hz, which seems fine (unless i'm mistaken)

Increasing that capacitor will cut less bass. However, that bass is not in a guitar signal.

I will use it with synths and drum machines

[midwayfair]

Would you advise to decrease C3 first, and then experiment with lower values for C9, or the opposite ?

C3 will affect the bass for the whole delay signal, INCLUDING the first repeat.

C9 will affect every signal AFTER the first repeat.

If you ALWAYS want less bass in the delay, make C3 smaller. Try 47nF.

[snk]

Thank you very much, Midwayfair.
That is very interesting to know.

Will the change have a big influence on the feedback behaviour (like getting faster into self oscillation, or not being able to reach self oscillation) ?

Am I right assuming that a 47nF capacitor with a 10K resistor will make a 330Hz HP cutoff point ?

[maoriente]

Hey Jon, hope all is well.

What's the recommended way to get 10db gain for the dry signal?

Increase the 4k7 collector resistor or decrease the 1k emitter resistor?

Or something else?