Deluxe Memory Man, MN3008 building

[Dimitree]

Hi everyone.. I'm building a Memory Man from scratch.. I have some factory schematics, early version and later version (I think everyone got those 2), but both uses 2 x MN3005 bbd.. Newer model uses 4 x MN3008..almost the same sound.. Now, since the MN3005 is really expensive, I'd like to adapt my circuit to the use of 4 MN3008..but I don't know how to do that.. I've read all the datasheet..I know that it should be simple, but I'm not quite sure..
some question:

1) Is the clock driver CD4047 good even for the MN3008?
2) how to adapt the different Clock Input Capacitance (1400pf for MN3008, 2800pf for MN3005)?
3) I need a dedicated Bias for each MN3008, right? If yes, how to do this?
4) ok, now there are 2 MN3005 in the circuit, I need to add another 2 bbd after the second MN3005, but could I just copy the circuit part from the OUTs of the first 3005 to the IN of the next 3005, and replicate it for the other 2 chip? (if so, the bias for the other BBD would be just like the 2nd MN3005)
is really that simple?

Sorry for those question, but I really don't know how to do this part of circuit..
I hope someone can help me
really thanks
Dimitri

[Mark Hammer]

Check out the AD3208 project over at General Guitar Gadgets.  It can use either two MN3205 chip;s or two MN3208.  I realize that isn't the same as an MN3005/3008, but it will give you an idea about how to cascade multiple chips.  And of course, since you can just pull the one chip out and stick the other in, that sort of answers one of your questions, right?

[Dimitree]

Thanks for the reply!

And of course, since you can just pull the one chip out and stick the other in, that sort of answers one of your questions, right?

uhm..not really.. I understand that I could put the MN3008 in place of the MN3005, but now I need to add another 2 on the circuit, so I guess I should copy that part as I said before..

[Dimitree]

this is what I mean:



that would result in 9 trim pots, while the newer Memory Man has only 7.. Maybe it uses a shared bias adjustment?

[Mark Hammer]

You don't really need all that stuff you show in between BBDs, not unless there is something special about what you have planned that you haven't mentioned yet.  True, there IS some signal loss going through the BBD, but that only needs to be made up for once at the output, not between each successive BBD.

[cpm]

i might have some notes from a 4xMN3008 DMM i had for repair
the factory schematic (3005s) was exactly the same until the point of the 2nd and 3rd BBD chip

[Dimitree]

thanks guys!
those notes would be really apprecciate 

No, nothing special planned, Mark  just a full working Memory Man..
So after the cap and the first three resistors of each BBD I could go directly into the next BBD input?

[Mark Hammer]

thanks guys!
those notes would be really apprecciate 

No, nothing special planned, Mark  just a full working Memory Man..
So after the cap and the first three resistors of each BBD I could go directly into the next BBD input?

You can't go directly, since the two complementary outputs from the preceding BBD have to be mixed together, the bias voltage has to be "reset" between chips, and the next BBD rebiased.
In this AD-3208 snippet, you can see that there is a 1uf DC-blocking cap on the input to each BBD.  After that cap has done its work, you can see there is also a DC bias source, via a 100k current-limiting resistor, on the input (pin 7).
You can also see a balancing trimpot on the outputs (pins 3 and 4) of each BBD.  Manufacturers differ in their approach to balancing.  Some find it enough to simply use a pair of equal-value 5% resistors, while others find it worth their while to stick in a balance trimpot and adjust to perfection.  The compromise would be a pair of 1% resistors.  I imagine that if one is aiming for widest bandwidth possible, then a trimpot is the way to go.

[Dimitree]

thanks again for all this help Mark, I really appreciate it..
so, sorry if I'm boring, but I'm still not quite sure about this addition..both for my poor english and for my poor electronic capability..

again..and sorry for that.. is this right?


after U10 there is the existing part of the circuit, the part between the 2 MN3005..etc..

[Mark Hammer]

I finally called up a schematic of the DMM reissue, and now understood what you're attempting to do.  Much to my surprise, EHX uses the gain recovery circuit between BBDs that you showed, although why I don't know.  It seems superfluous to me.  Although, now that I think of it, I guess if they have one half of a 4558 for the gain recovery after the 2nd BBD, that means there is another unused op-amp sitting
nearby the first one, so...... 

The datasheet for the MN3008 shows there is usually no insertion loss, but also shows as much as +4db output or as little as -4db (relative to input, same specs for the MN3005), so I gather that is why the op-amp stage between the BBDs is capable of added gain as well as reduced output.  In other words, it is there to compensate for part-to-part variability so that the S/N ratio and max delay level is the same across all production pedals.  I guess when you crank out as many of these as EHX does, you can expect variation in BBD lots over time.  That approach may provide some benefit to you, but personally I don't see it as essential.

You will also note that while the first BBD uses a pair of fixed resistors for output mixing, the second one uses a trimpot.  If I was the one making this pedal, I might opt for trimpots on all BBDs, or alternatively use a pair of 1% mixing resistors (2k4) on the output of each BBD.

It is worth pointing out that one of the most highly praised analog delays out there is the Maxon AD999, and if you've ever seen gut shots, you'll immediately note just how many trimpots are in there.  There is a bias AND a balance trimpot for each of the 8 BBDs it uses.  So, while some manufacturers find they are satisfied with using a matched-value resistor pair for mixing, and using a single trimpot to derive a single bias voltage used for all BBDs in the circuit, the Maxon approach would suggest that maybe the difference in sound quality resulting from a few more adjustable parts is worth the builder's time and effort.

Datasheets indicate separate bias sources for pin 7 and 8, however the DMM simply taps the bias circuit at one point for pin 8 and a different point for pin 7.  If it works for them, it can work for you.  Essentially, what you would be doing is using the bias circuit that EHX uses for the first BBD, and applying it to all subsequent BBDs in the same fashion.

Does all of this make sense?

[Dimitree]

yes it does..

so, about the circuit between the BBDs, I could use the first schematic I posted, with 4558 in-between..if I'd want a "perfect" circuit, but with a lot of calibration to do..
Otherwise, I could use this last schematic, right? It should work good the same?
in this last schematic I posted I did the bias just like the first BBD on the DMM, as you suggested.

about the trimpot VS fixed resistors, well, if the value of the 2 resistors are well measured and those are almost identical, it should be good even in this way..less trimpots to have 

the important thing is if the last schematic I posted is right..both for the configuration and for the values..

[StephenGiles]

The Yamaha E1010 delay which uses 4 x MN3005, has a low pass filter after each bbd, and each bbd has it's own bias trim. The clock to each bbd is also buffered by it's own TC4049, wired as 2 x 3 inverters in parallel.

The circuit in all it's glory is here in 2 parts

http://www.4shared.com/file/30199724/5425cbd6/1010a.html
http://www.4shared.com/file/30199692/5f70dd1f/1010b.html

[StephenGiles]

The Yamaha E1010 delay which uses 4 x MN3005, has a low pass filter after each bbd, and each bbd has it's own bias trim. The clock to each bbd is also buffered by it's own TC4049, wired as 2 x 3 inverters in parallel.

The circuit in all it's glory is here in 2 parts

http://www.4shared.com/file/30199724/5425cbd6/1010a.html
http://www.4shared.com/file/30199692/5f70dd1f/1010b.html

By the way, I used a 4047 clock for my E1010 build!

[Dimitree]

thanks for this schematic!

I hope I can use a single 4047 for the clock, even using 4 BBDs.. The input capacitance should be the same as 2xMN3005, so I think I don't need buffering the clock, etc..

I think I'll let the circuit as it is, without filtering between the BBDs, to achieve the same "character" the DMM has.. I decided to use the same schematic EHX uses for this part, including the op-amp to attenuate or amplitude the signal between them.. If it won't work, I'll keep the 2 BBDs schematic and buy 2 x MN3005.. 
I hope it will work..
thanks guys

[puretube]

So, after all that has been written on da webz about past times` E-H quality, saving on parts, a.s.o.,
some (or rather almost everybody... [except Dimitri]) think they put a "redundant" opamp smack dab in the middle of a relatively complicated circuit,
one that even inverts the signal at that point?

[Dimitree]

ehm..sorry..I don't understand what you mean  my english is poor, sorry

btw, I've started (and almost finished) the PCB.. Any suggestions about traces within the delay signal section? (for example: not too close, oscillations, etc..)

[Dimitree]

so this is how I'm going to build that part:



I belive that's how EH did (more or less) on the newer version with MN3008..
the blue part is the one I'll add.. Positive input on U3 goes to 1/2 VCC
Please could someone confirm if this way is right?

really thanks

[puretube]

So, after all that has been written on da webz about past times` E-H quality, saving on parts, a.s.o.,
some (or rather almost everybody... [except Dimitri]) think they put a "redundant" opamp smack dab in the middle of a relatively complicated circuit,
one that even inverts the signal at that point?

Make-Up-Gain between 2 chips that nominally got zero insertion loss  ?
see reply #126

[njkmonty]

http://www.diystompboxes.com/smfforum/index.php?topic=92799.0

http://youngpedals.com/Deluxe_Micro_Man_Rev_A.pdf