Author Topic: Madbean Current Lover 2015 - sweep frequencies  (Read 664 times)

Mcentee2

Madbean Current Lover 2015 - sweep frequencies
« on: May 30, 2018, 10:40:38 AM »
Hi all,

I have a new Madbean Current Lover 2015 and the sweep didn't sound very "sweepy", so have got my multimeter out that is capable of frequency measurement and have the following at the *lowest* point of the Clock trim, ms times are worked out using "ms=stages/(freq in khz * 2)"

High: 620 khz = 0.82ms
Low:  170 khz = 3.01ms

These numbers go through the LM 311 Pin 7 and into the MN3007 Pins 2 and 6, and the low side freq of 170 khz seems a bit high, leading to a very narrow sweep of 0.82 - 3.01 ms.

With Filter matrix on I get even worse on the low end, but I know that the circuit LFO and "Filter/Matrix" are different :)

Range Fully CCW: 600 khz = 0.85 ms
Range Fully CW:   266 khz = 1.92 ms

I was expecting something more .8ms  - 7ms or so, freqs 70khz - 600khz for a MN3007 1024 stage bbd

I also have a Boss HF-2 as well and that seems to operate "by the book", with sweeps from 40 - 500 khz so I know my multimeter is ok.

Voltages measured today with a 9.2v Battery, pdf figure is first, my figure is second. I have put a * next to the ones I think are "dodgy":

IC1   4558   
1   4.59   4.46
2   4.59   4.47
3   4.18   4.05
4   0   0
5   4.51   4.38
6   4.55   0
7   4.53   4.42
8   9.13   8.87

IC2   MN3007   
1   9.13          8.86
2   ~4.45   4.27
3   ~4.85   4.75
4   41mV   380mv *********
5   0   
6   ~4.45   4.37
7   ~4.2          4.87
8   ~4.2          4.9

IC3   CD4049   
1   9   8.8
2   4.5   4.38
3   4.5   4.38
4   4.5   4.38
5   4.53   4.38
6   4.5   4.35
7   4.5   4.36
8   0   0
9   4.5   4.36
10   4.5   4.36
11   4.5   4.36
12   4.5   4.36
13   ignore   
14   4.5   4.28
15   4.5   4.33
16   ignore   

IC4   CD4013   
1   4.53        4.34
2   4.53        4.34
3   varies   4.7-5.3
4   0   
5   4.5        4.35
6   0   
7   0   
8   0   
9   0   
10   0   
11   0   
12   9        0  ****** are these two a typo ?
13   0        8.75  ***** are these two a typo ?
14   9        8.75

IC5   LM324   
1   varies   7.46
2   ~4.2   4.07
3   varies   4
4   9   8.69
5   0   
6   0   
7   7.8           0   **********   Looks very odd!
8   varies   2
9   varies   2
10   varies   2
11   0   
12   ~4.2       3.9
13   ~4.2           3.9
14   varies   4

IC6   LM311   
1   0   0
2   varies   
3   varies   
4   0   0
5   9.14   8.69
6   9.14   8.69
7   varies   
8   9.14   8.69

IC7   4558   
1   4.55   4.36
2   4.55   4.36
3   4.55   4.36
4   0   
5   4.51   4.3
6   4.55   4.3
7   4.55   4.3
8   9.14   8.67


I have checked some components around those areas but all seem ok, I will continue to check values, but any guidance would be appreciated.

Thankyou

Mcentee2

Re: Madbean Current Lover 2015 - sweep frequencies
« Reply #1 on: May 31, 2018, 06:54:56 AM »
Solved :)

Another symptom of what turned out to be the problem was the Control Voltage coming off Pin 2 of the LM311 only varied between 1.0v - 2.2v (9v supply) or 1.3v - 3.1v on a 12v supply), giving very little sweep.

After reading various threads on the EM3207 etc on DIYSB forum from the brilliants guys here, I tracked it down to the builder using a 10k Lin pot for the Range control instead of a 100k Lin pot !!!!

Swapped it out now, and the LM311 Pin 2 CV now reads 1.1v - 8.8v  (on a 12v supply) during flanger sweep (not static matrix mode)

After Clock trim adjustment I can get the lowest 4013 Pin 1 clock rate at 70khz on the knuckle , high is about 1000 khz (yes 1 Mhz!!)* with no chirping or drop outs, giving a delay range of 0.51 - 7.31ms, perfectly in Electric Mistress territory.

Whether or not the MN3001 can provide an "audible" signal at that speed re gain and fidelity, or whether there is any dry guitar signal at that height is another matter, but I am impressed the signal doesn't "click" out and back in at the top at that speed  :)

The one thing left I can't yet investigate without a scope would be to look at the clock rate (Or better "delay time") sweep in terms of VCO / MN3007 in terms of shape. I know the EM LFO is triangular, and I know the EM "perfect" shape for the resulting delay time perception is "hyper triangular" (sharp at the top, rounded at the bottom).

Does anyone already know what the Current Lover and/or EM3207 sweep shape is vs the Electric Mistress as it wasn;t clear from the other threads on the EM3207 ?

Listening to this now really shows the greatness of the whole circuit, with the added volume stage tacked on the end and, to my ears more crucially, the retention of the high end of the signal through the pedal, stunning!

DrAlx

Re: Madbean Current Lover 2015 - sweep frequencies
« Reply #2 on: May 31, 2018, 02:50:44 PM »
It's a hyperbolic sweep in frequency.  In other words the delay time rises and falls linearly. Explained here... https://www.diystompboxes.com/smfforum/index.php?topic=116836.msg1083340#msg1083340

Mcentee2

Re: Madbean Current Lover 2015 - sweep frequencies
« Reply #3 on: May 31, 2018, 05:22:52 PM »
Thankyou @DrAlx, I must have learnt something whilst trawling all yours (and others) posts whilst researching this circuit as I understand your thread link in words very well, not maths :)

As my pedal is Madbean CL and not a vintage EM it allows me to think of various "improvements".

One of which is to somehow shift the delay time spread to longer times to mimic more of the chorus side of the circuit.


A toggle to take it back to EM times would work well.

Your other threads suggedt I might simply get this from changing the clock cap from 22pF to 47pF ) thereabouts, but I was also thinking of the type of Manual control found in my Boss HF-2 and using that as an "LFO/VCO" base control voltage shift that the LM311 ranges up and down from.

That is all supposition at the moment as I need to look at and understand how that Manual control works, I am only half way through it at the moment.



Mcentee2

Re: Madbean Current Lover 2015 - sweep frequencies
« Reply #4 on: June 02, 2018, 04:01:42 AM »
Still working on this.

If I change the cap for a c47pF it does indeed increase the while range so I get nearer 14ms, however the low end is still at about 1ms, so it basically sounds very deep, but any range setting is related to the lowest delay at one end and ranging upwards, and it makes it very warbly, I don't need that much range but want it starting at a higher ms.

I am looking for something akin to a Manual control where I can shift the "centre point", or at least move the short delay longer, and then range around/from that with the LFO/VCO.

I was thinking about all the posts I read describing the  original EM as very "chorus-like", but the ms delay spread always starts at the smallest end <1ms, and any range onto Chorus times 7ms upwards seems a huge spread which wouldn't make it "a very wide deep chorus" as chorus have a narrower range for subtlety?

Is there something else that accounts for this Chorus description?

The other thing I would like to tweak is to tame the top end coming out of the circuit, I know this is a thing that is desired by some, but it is very bright in my set up, and a little shaving of treble would help!

Looking at the circuit, the volume stage is a simple non-inverting opamp buffer/gain with a 100pF low pass filter so could I just change the 100pF feedback cap with one that cuts off whatever treble I am happy with ? Is there any other untoward change this would cause, or is there a better place to put a pot/cap treble control, maybe before the buffer, rat style ?

« Last Edit: June 02, 2018, 10:55:00 AM by Mcentee2 »