electro-music.com   Dedicated to experimental electro-acoustic
and electronic music
 
    Front Page  |  Articles  |  Radio
 |  Media  |  Forum  |  Wiki  |  Links  |  Store
Forum with support of Syndicator RSS
 FAQFAQ   CalendarCalendar   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   LinksLinks
 RegisterRegister   ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in  Chat RoomChat Room 
Live streaming at radio.electro-music.com

  host / artist show at your time
  mosc Live music with Twyndyllyngs - Bill Fox and Howard Moscovitz
Please visit the chat
 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
Echo Rocket - noise in my echo circuit
Post new topic   Reply to topic Moderators: dnny, Uncle Krunkus, v-un-v
Page 1 of 1 [16 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Author Message
sndbyte



Joined: Jun 26, 2009
Posts: 115
Location: sf

PostPosted: Wed May 28, 2014 10:23 pm    Post subject: Echo Rocket - noise in my echo circuit Reply with quote  Mark this post and the followings unread

Hi,

I just finished building the Echo Rocket and noticed that mine is really noisy. A fuzzy noise that should not be there. So I did some trouble shooting and determined it was the echo portion of the build. If I turn the echo mod level all the way down the synth puts out a clean oscillator with LFO mod. The filter also works perfectly with no distortion. But if I turn up the echo mod level I start to get the noise and the clean sound disappears. The echo functions (delay & repeat) work, it is just that there is the annoying fuzzy noise that accompanies it. I know it should not be there as I have watched Ray's demo video.

Does anyone have any suggestions on why this is happening? I thought it may be a grounding problem but I have checked and every thing is properly grounded. Could a bad component cause this?

Thanks in advance for any help.
Back to top
View user's profile Send private message
sndbyte



Joined: Jun 26, 2009
Posts: 115
Location: sf

PostPosted: Fri May 30, 2014 2:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

So I did some trouble shooting last night and found one of the pins on the echo chip bent under and not connected to the dip socket. I fixed that and the high pitched squealing on the delay pot went away (at the end of the pot's rotation). Unfortunately the noise in the echo did not go away. I triple checked the panel wiring and there was no incorrect connections. I also did some testing on the board and made sure the voltage on the power pin was correct. Right now I can only turn up the delay pot around 25% before the noise appears. What you hear is a wwshhhhh, wwshhhhh, wwshhhhh sound that varies with the length of the delay. Perhaps one of the components is bad...

PS: The filter on this thing is really nice. Much better than the filter on the Noise Toaster.
Back to top
View user's profile Send private message
sndbyte



Joined: Jun 26, 2009
Posts: 115
Location: sf

PostPosted: Sun Jun 01, 2014 10:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

So I spent some time trouble shooting this weekend. I checked component values, voltage and current and I could not find any errors. At this point I think I am just going to desolder everything from the board, throw away all the components and start from scratch (except for the case and front panel I made).
Back to top
View user's profile Send private message
prgdeltablues



Joined: Sep 25, 2006
Posts: 173
Location: UK
Audio files: 11

PostPosted: Mon Jun 02, 2014 2:19 am    Post subject: Reply with quote  Mark this post and the followings unread

Not built this, but seeing as no-one else has responded, and before you start over (it is rather unlikely that resistors or caps are bad, even ICs aren't bad that often, if you got them from a reputable source).

A few thoughts. Does the pulsing rate of the noise vary with the LFO rate? Does it still occur if you have the filter resonance turned all the way down? Have you got the input on mic and the input volume all the way up - that would almost certainly introduce noise, which might only become noticeable if you turn up the echo so that the sound builds. Try on line input and turn the input vol to 0. Even better if you can, ground the input. Is there any electrical equipment around that the circuit might be picking up interference from (fridges. flourescent lights, dimmers)?

If you have a spare PT2399 try replacing that first, then try swapping out each IC in turn.

Have you checked that every point that is meant to be grounded, is indeed grounded?

I know (hollow laugh) troubleshooting is frustrating, but desoldering a whole board is a rather drastic approach - and you could damage the tracks on the board - endless cycle of problems.
Back to top
View user's profile Send private message
inlifeindeath



Joined: Apr 02, 2010
Posts: 315
Location: Albuquerque, NM

PostPosted: Mon Jun 02, 2014 11:56 am    Post subject: Reply with quote  Mark this post and the followings unread

the pt2399 used in Ray's delay circuit is inherently noisy. I recently built his VC delay module and it exhibits the same digital noise. Not much you can do about it, but maybe try different values of capacitors in the filter portion of the delay.
_________________
http://www.youtube.com/user/borisandfef
Back to top
View user's profile Send private message Visit poster's website
sndbyte



Joined: Jun 26, 2009
Posts: 115
Location: sf

PostPosted: Mon Jun 02, 2014 7:21 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for the detailed suggestions. This what I have found so far (I'll check out the other suggestions later once I have access to my workbench... um, I mean the kitchen table).

1. The pulsing of the LFO is not effecting the noise. It only effects it when it is modulating the echo. If the LFO mod is not turned up, there is no effect on the noise.

2. Yes it still happens when I have the resonance all the way down.

3. Input has always been all the way down in my testing and I don't turn the output all the way up as it is too loud for my earphones. I did do a test and when the volume is all the way up the noise is much more pronounced. I found the same result when turning the echo volume all the way up.

4. Mic and line input is turned all the way down. I did a test and turned it all the way up with no input and it seemed to make the noise more pronounced. The input is grounded.

5. Electrical interference may be a possibility. I walked it around my place and I could not tell any difference (kitchen, living room, bedroom). I do live pretty close to a huge radio tower. When I was building my Noise Toaster I was getting radio interference when the cut off freq was all the way up. I could actually heard the voices and music (a mariachi music station and a mainstream pop station). The funny thing is I do not have that problem with the filter on the Echo Rocket.

Additional comment: The fuzzy noise is more pronounced when any of these pots are turned all the way up: volume, echo level, echo and repeat.

I watched Ray's video and I did not hear any of this noise in his demo. I also built a delay unit using the same chip and it was clean with no distortion.

Once again, thanks for the helpful suggestions.
Back to top
View user's profile Send private message
sndbyte



Joined: Jun 26, 2009
Posts: 115
Location: sf

PostPosted: Mon Jun 02, 2014 11:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

This evening I did all my ground testing. I first removed all of the ICs. I then reviewed the schematic and found all ground points. I then marked those ground spots on a copy of the board layout. I went through each of these points in addition to all ground points on the phone jack. Each of these was grounded. In addition I checked each pot to verify that each was grounded (they were). I also checked to make sure each pot shaft on the front of the panel was grounded as well. Of course the panel was grounded. I also checked the switches on the front of the panel and they were all grounded as well.

So right now I am pretty confident that grounding is not an issue (unless of course I missed something).

Next I will try working with new chips. I have an extra echo chip and I am hoping I have all the others.
Back to top
View user's profile Send private message
Uncle Krunkus
Moderator


Joined: Jul 11, 2005
Posts: 4758
Location: Sydney, Australia
Audio files: 52
G2 patch files: 1

PostPosted: Tue Jun 03, 2014 1:17 am    Post subject: Reply with quote  Mark this post and the followings unread

Is there any possibility that all that grounding has completed a ground loop?
ie Is there only ever ONE way back to the main ground connection?
Being so close to a broadcast tower would mean real problems if a ground loop is present, as they act like antennas.

_________________
What makes a space ours, is what we put there, and what we do there.
Back to top
View user's profile Send private message Visit poster's website
prgdeltablues



Joined: Sep 25, 2006
Posts: 173
Location: UK
Audio files: 11

PostPosted: Tue Jun 03, 2014 8:46 am    Post subject: Reply with quote  Mark this post and the followings unread

Unless you find the replacement echo chip solves the problem, then it does rather sound as if noise is getting injected into the circuit, and the most likely culprit is the radio tower and the ground side of the circuit. Might the front panel be acting as an antenna? I'm not sure why it is connected to virtual ground anyway - running off a 9v battery there isn't any need for a safety ground, which is the usual reason for grounding exposed metal parts. I'd suggest disconnecting the panel and all the pot casings from ground. Or take it well away from the tower to test?

Does the noise change depending on whether you are holding the unit or if you touch a finger to virtual ground? Thinking here of noisy guitars and how the noise can be quieted when you touch the strings (which I believe is not you earthing the guitar, but the guitar earthing you - your unearthed body can act as a nice antenna, radiating e-m into the pickups).
Back to top
View user's profile Send private message
sndbyte



Joined: Jun 26, 2009
Posts: 115
Location: sf

PostPosted: Tue Jun 03, 2014 12:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

I actually live 1.3 miles (2 km) away from the radio tower. It is the huge Sutro Tower in San Francisco.

My grounding has only one wire from the PCB to the panel. I ran the wire to the virtual ground point on the board, not the -9 volt point.


Here is a note from Ray's instructions:

The unit's front plate is connected to virtual ground. The battery's positive or negative terminals should NEVER come into contact with the unit's front plate. Attempting to switch the battery's negative terminal with a switching jack that is in contact with the virtual ground will short one half of the virtual ground and will not work.

Grounding issues will arise if the Echo Rockit is powered from a single supply system in which the negative side of the supply is also the system's ground. The Echo Rockit's virtual ground would be at 1/2 the system's positive supply and would not play well with other elements of the system. Battery power or a separate 9VDC wallwart power supply is recommended if used with other pedals to avoid grounding issues.


My next test is to swap out the chips and see if that makes a difference.

After that I will try to add another grounding wire with from the panel to the PCB. I'll also try it with no grounding wire.

I have not noticed any change in the sound when I touch exposed pots or switchs (I have had that happen with other projects in the past though).

If all else fails I'll drive a few miles away from my place and see if there is any change. Perhaps I'll even drive up to the tower and see if the noise gets worse.

Thanks again for all the great suggestions.
Back to top
View user's profile Send private message
alieneYe



Joined: Jul 25, 2008
Posts: 38
Location: Phoenix, Az

PostPosted: Tue Jun 03, 2014 3:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

you say the noise goes away when the Delay Mod Level pot is all the way down. have you tried another 2n3904 (Q3) or checked that the trace from the collector is good?

i suggest this component because typically NPN transistors with cut or unconnected collector pins are used to create noise in various modules.

hope this comes as some help

good luck
Back to top
View user's profile Send private message
sndbyte



Joined: Jun 26, 2009
Posts: 115
Location: sf

PostPosted: Tue Jun 03, 2014 3:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

This is a good suggestion that I had not thought of. I think I have some more 2n3904 chips so I will try it tonight.

alieneYe wrote:
you say the noise goes away when the Delay Mod Level pot is all the way down. have you tried another 2n3904 (Q3) or checked that the trace from the collector is good?

i suggest this component because typically NPN transistors with cut or unconnected collector pins are used to create noise in various modules.

hope this comes as some help

good luck
Back to top
View user's profile Send private message
sndbyte



Joined: Jun 26, 2009
Posts: 115
Location: sf

PostPosted: Tue Jun 03, 2014 11:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

Tonight I first replaced Q3, a 2n3904 transistor. I then replaced all 4 ICs. I powered on the machine and there was no change... I still had the noise in the echo whenever I turned it up past 1/4 of the pot rotation. I then disconnected the ground. If anything that made the noise problem more pronounced. So I reconnected the ground tested it and it was back to the normal noise in the echo. I then added a 2nd ground wire from the panel to the PCB. There was no change in the sound. I disconnected the 2nd ground wire and I now just have the original one ground wire.

I am wondering if the problem could be the pot itself. Maybe I will replace it just in case.

This weekend I will take if for a ride far away from the radio tower and see if that fixes it.

Thanks again for the suggestions.
Back to top
View user's profile Send private message
prgdeltablues



Joined: Sep 25, 2006
Posts: 173
Location: UK
Audio files: 11

PostPosted: Wed Jun 04, 2014 5:23 am    Post subject: Reply with quote  Mark this post and the followings unread

Could you try bypassing the pot completely? I'm assuming it's R41 we are talking about? Connect a wire between point X29 and either X16 (with the Mod shape switch in the Tri position) or X22.

If you do disconnect the pot, before replacing it, try a 1 MEG resistor in its place - again connecting as above - that might help rule out the fact that the pot is attached to the panel as a factor. you could even try various combinations of two resistors as a voltage divider instead of the pot.

I wonder if the noise is actually present at lower delay mod levels, just being amplified by more signal going round the echo loop, as you turn the pot up? Any chance of testing for that, and trying to work out where the noise originates? Easiest with a scope of course, but otherwise a simple opamp amplifier used to probe (probably with a DC blocking cap) at various points eg X1, U3 pin 13...)
Back to top
View user's profile Send private message
sndbyte



Joined: Jun 26, 2009
Posts: 115
Location: sf

PostPosted: Wed Jun 04, 2014 10:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

I tried to use my scope to find any points of noise but could only find some on the delay pot (my scope skill are pretty low, so I may have missed something). I went ahead and replaced the delay pot without any luck. Filter still has unwanted noise. I just watched Ray's video demo and tried to replicate the patches he was using and his sound was clean where mine had the noise I've been trying to get rid of. I think the final test will be this weekend when I take the thing miles away from my place and see if there is still noise on the echo delay. If there still is I'll probably order a new board and start from scratch. Of course I don't want to spend the $ on a new board and components, but it's always fun to build stuff so no problem. I would also be interested to see how the 2 perform next to each other.

I appreciate everyone's help and advice.
Back to top
View user's profile Send private message
sndbyte



Joined: Jun 26, 2009
Posts: 115
Location: sf

PostPosted: Sat Jun 07, 2014 4:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

Today I drove about 10 miles away from my place and tested the echo/delay. I got the same noise as I got at home so I suspect it is not radio interference but a problem with my build of the echo/delay circuit.

I think right now I'm just going to order a new board and start from scratch and see if I have better luck on my 2nd try. If I'm able to get the 2nd attempt to work I will just take the 1st board I built and make something using just the oscillator and filter. What I'd really like to do is combine the noise toaster's VCO with the echo rocket's filter (but I'll try that later).
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic Moderators: dnny, Uncle Krunkus, v-un-v
Page 1 of 1 [16 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
Jump to:  

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
e-m mkii

Please support our site. If you click through and buy from
our affiliate partners, we earn a small commission.


Forum with support of Syndicator RSS
Powered by phpBB © 2001, 2005 phpBB Group
Copyright © 2003 through 2009 by electro-music.com - Conditions Of Use