AMZ FX ANALOG ALCHEMY GEOFX MEF ROG MEF DIY WIKI

Deluxe Electric Mistress V4 or V5

Started by Govmnt_Lacky, August 29, 2012, 08:11:19 PM

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12Bass

#60
November 20, 2012, 09:51:04 AM
Quote from: oldschoolanalog on November 20, 2012, 09:43:15 AM
Read this entire data sheet first. Do the math. The R5107 is the equivalent of a 1024 stage BBD. It has specific clocking requirements in regard to frequency and rise/fall times for the clock you are using. If these are out of spec maybe this is contributing to noise issues. Maybe.
Just an observation.

Was in the middle of composing my post....    :P

If the RD5107A is anything like the SAD1024A, it will be pretty noisy at low clock frequencies.  Plus a ~ 10-15 kHz clock would be much more likely to produce aliasing byproducts.  Would be funny if the problem was nothing more than the clock set too low.  Of course, it shouldn't be producing very useful flanging if that's the case.
It is far better to grasp the universe as it really is than to persist in delusion, however satisfying and reassuring. - Carl Sagan

oldschoolanalog

#61
November 20, 2012, 09:56:23 AM
>In summation, the 512-sample RD5107A can be viewed as equivalent to a 1024-stage device, with the BBD clock set accordingly.  If my math is correct, the above frequencies should be in the ballpark.
>If the RD5107A is anything like the SAD1024A, it will be pretty noisy at low clock frequencies.
+1 totally agree. I am wondering if the clock arrangement used is within the spec for rise & fall times. To check this one would need a 'scope.
Mystery lounge. No tables, chairs or waiters here. In fact, we're all quite alone.

12Bass

#62
November 20, 2012, 10:03:28 AM
Scope would be nice for sure. 

However, audio samples should give a pretty good idea of the BBD clock.  If there's double-tracking or slapback echo, it's way too slow and needs to go up, way up....   
It is far better to grasp the universe as it really is than to persist in delusion, however satisfying and reassuring. - Carl Sagan

oldschoolanalog

#63
November 20, 2012, 10:16:32 AM
The single phase clock input of the R510X BBDs is divided by 2 internally. So... to get the ~34kHz low clock f you need for max delay one would have to have their external clock input @~68kHz.
I agree w/12Bass. It might just be clocked way too low.
Get out the f counter and adjust the clock trimmer for 68kHz or so at the clock input pin for the low end of the sweep. With the EM in "filter matrix" mode this should be an easy task.
My 2 cents.
Mystery lounge. No tables, chairs or waiters here. In fact, we're all quite alone.

Govmnt_Lacky

#64
November 20, 2012, 10:27:35 AM
OK gents... my head is spinning a bit so I just want to clarify.

Using the 5107 BBD in this circuit....

What clock frequency should I set at Pin 1 of the BBD?

@oldschool

According to your post, I should have the circuit in "Filter Matrix" to accomplish this correct? Also, should I set the Color, Range, or Speed controls to any particular setting for this adjustment?

Really appreciate the assistance with this! It has been driving me nuts just starring at me on the shelf!  :-\  ;D
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

Fender3D

#65
November 20, 2012, 10:30:45 AM
RD51s have fs = fc/2, and BW = fs/3, check your filters...
"NOT FLAMMABLE" is not a challenge

oldschoolanalog

#66
November 20, 2012, 10:37:46 AM Last Edit: November 20, 2012, 10:40:34 AM by oldschoolanalog
Start w/68kHz @ pin 1.
In filter matrix mode turn the range pot fully to the end that is the low f side. Speed and color shouldn't matter but put them at minimum to be on the safe side.
Hope this helps.
Mystery lounge. No tables, chairs or waiters here. In fact, we're all quite alone.

Govmnt_Lacky

#67
November 20, 2012, 11:03:48 AM
Quote from: Fender3D on November 20, 2012, 10:30:45 AM
RD51s have fs = fc/2, and BW = fs/3, check your filters...


Could you elaborate on the filter checking?

Still learning about these darn filters...  ::)
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

Jazznoise

#68
November 20, 2012, 12:42:36 PM
We've address both your input and feedback filters at this stage so it's unlikely that this is still the issue. Grab a scope, try and determine the speed you're clocking the BBD at.
Expressway To Yr Null

Fender3D

#69
November 20, 2012, 01:39:42 PM
Quote from: Govmnt_Lacky on November 20, 2012, 11:03:48 AM
Could you elaborate on the filter checking?

the max allowed frequency should be (less than) fs/2,
schematic on page 1 shows basically no filtering (1k is -3dB then ~1dB/oct)
we still don't know what frequency your VCO runs at...
IIRC you somewhat solved this issue lowering the clock capacitor in your micros (thus raising the clock freq.)
"NOT FLAMMABLE" is not a challenge

Govmnt_Lacky

#70
November 20, 2012, 02:39:54 PM
When I designed the layout and assembled the circuit, the only mod that I made was to increase the clock trimmer from 10K to 25K in order to dial in the "what I thought was correct at the time" higher clock frequency. I was going by the 5107=512 stages=twice the frequency mentality. I am seeing now that my initial thoughts were probably wrong  :icon_redface:

I also trimmed the clock frequency according to the info on the factory schematic which calls for 25uS at Pin 1 of BBD with circuit in Filter Matrix mode and Range fully CW. Seeing as I had the 5107, (instead of 5106) I set it to 50uS. There is no mention of frequency in KHz on the schematic. Just rise/fall time.

Tonight, I will connect my Fluke meter and read the FREQUENCY at Pin 1 of the BBD on each end of the 25K pot rotation and report  ;D

Sorry guys.... no oscope at home at the moment and the circuit is not at work  :'(
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

Govmnt_Lacky

#71
November 20, 2012, 06:37:53 PM
Ok campers... for those who are following along  ::)

Range pot set to full CW
Clock trim full CW : 91KHz
Clock trim full CCW : 18KHz

Range pot set to full CCW
Clock trim full CW : 934KHz
Clock trim full CCW : 258KHz

I currently have the trimmer set to 68KHz on Pin 1 of the R5107 with the Range pot at full CW.

Gonna attempt to upload a sound/video clip to hear the noise. I know it will be there as I tried adjusting the clock trimmer before and the noise was there throughout its travel.  :-[

A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

Govmnt_Lacky

#72
November 21, 2012, 11:57:04 AM
OK, massive fail on the sound clip upload  :icon_redface: Wont get into it!

So, I will give my best description of what is happening and if it doesn't get fixed I may just re-etch a newer, better board and start over!!!

With the clock set as above (68KHz) at Pin 1 of BBD, with Color at max, Speed at minimum, and switch in Filter Matrix.

As I cycle the Range pot back and forth it sounds EXACTLY like I am turning the dial on an AM/FM radio with no stations in the area!!  :icon_eek:

When I turn the Speed knob up, I can hear the LFO tick mixing into the signal.
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

Fender3D

#73
November 21, 2012, 12:17:20 PM
Quote from: Govmnt_Lacky on November 20, 2012, 06:37:53 PM
I currently have the trimmer set to 68KHz on Pin 1 of the R5107 with the Range pot at full CW.

What does happen if you raise that 68kHz setting (higher flanging aside)?
Does Tokyo stop broadcastings?  :icon_mrgreen:
"NOT FLAMMABLE" is not a challenge

Govmnt_Lacky

#74
November 21, 2012, 12:22:16 PM Last Edit: November 21, 2012, 12:26:19 PM by Govmnt_Lacky
Quote from: Fender3D on November 21, 2012, 12:17:20 PM
What does happen if you raise that 68kHz setting (higher flanging aside)?
Does Tokyo stop broadcastings?  :icon_mrgreen:

I did notice that when I adjusted the clock trimmer to the higher side (91KHZ) that the sound does start to subside. I looked into making the adjustment however, according to the datasheet, the R510X BBDs have a max clock of 1MHz. Seeing how this adjustment would put me up to 934KHz with the Range pot full CCW, I didn't follow through with it.

EDIT: Just to add to the notes... the test test above was done with NO input. The noise was strictly from the circuit operating at voltage with an output directly to amp.
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

oldschoolanalog

#75
November 21, 2012, 01:27:22 PM
>I did notice that when I adjusted the clock trimmer to the higher side (91KHZ) that the sound does start to subside. I looked into making the adjustment however, according to the datasheet, the R510X BBDs have a max clock of 1MHz. Seeing how this adjustment would put me up to 934KHz with the Range pot full CCW, I didn't follow through with it.
Why not? You would still be within limits. Go for it!
Mystery lounge. No tables, chairs or waiters here. In fact, we're all quite alone.

Govmnt_Lacky

#76
November 21, 2012, 05:13:58 PM
@oldschool

I don't see how I would remain within limits. If I increase the trimmer range then my max clock frequency is going to break 1MHz.

Could you explain a bit?
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

oldschoolanalog

#77
November 21, 2012, 05:25:18 PM
Sorry Greg, I guess I misunderstood what you were saying. :icon_redface:
I have been doing a lot of that lately. Think I'll just shut up for a while. Don't want to create any more confusion.
Apologies.
Mystery lounge. No tables, chairs or waiters here. In fact, we're all quite alone.

Jazznoise

#78
November 21, 2012, 05:30:18 PM
Crank it and see if you notice the BBD's flange going static at some point. The main worry here is wether doing this removes the noise - if it's still there then the problem remains regardless.
Expressway To Yr Null

Fender3D

#79
November 22, 2012, 01:43:07 PM
Quote from: Govmnt_Lacky on November 21, 2012, 05:13:58 PMI don't see how I would remain within limits. If I increase the trimmer range then my max clock frequency is going to break 1MHz.

"1MHz max clock" is not a harmful warning as "max. 15V",
you may raise clock well over its max. declared value, downsides are gain loss and static at a certain point

BTW +1 on what jazznoise said
"NOT FLAMMABLE" is not a challenge
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