mn3007 vs. mn3207--BBD fight!!!

[gorohon]

I'd like to know what you all think.  Concerning BBD's in general and mn3007 vs. mn3207,  what do you think sounds better and why.  Do low voltage BBD's have less mojo than their higher voltage counterparts?  Or is all this a  phallacy of perception and subjectivity (it's rare or expensive, so it must be good)?  I haven't had the pleasure of hearing all the varieties of BBD's, so your opinions will be welcome.

[Jason M.]

I'm not sure about the MN3007 vs MN3207, but when used for echo, I think the higher voltage BBDs may sound a little different.

For example, the Boss DM-2 uses a MN3005, a high voltage chip, selected for gain at low voltage. The Boss DM-3 is the same circuit, I think, but uses the MN3205 and its complimentary low-voltage clock chip.

I own both pedals, and the DM-2's repeats sound slightly softer than the DM-3. Both units calibrated with a scope. Both run on 9V.
The DM-3's repeats have a "zing" to them.

I recently built an AD-3208 delay and am using 2 MN3205 BBDs for longer delay time. This unit has that same type of "zing" quality to the repeats as the DM-3. Could it be the low voltage chips? I don't know.
I might convert it to use the higher voltage MN3005 chips and up the supply voltage for more headroom to see if there is much of a difference.

There may not be much of a difference with BBDs with fewer stages and shorter delay times, as used in chorus and flangers.

Just my observations and unfounded speculation.

J.

[Mark Hammer]

If I remember correctly, the lower the voltage-series (MN33xx run at lower supply voltage than MN32xx, which run at lower supply voltage than MN30xx), the faster the feasible clock speed listed in the spec sheets.  I'm sure it doesn't happen for the same reasons, but it's a little like the relationship between clock speed and core voltage in CPUs: the older the processor, the higher the core voltage and lower the clock speed.

Of course faster potential clocking is only advantageous for flanging, and means precious little for producing longer delays (in echo units) or for chorus effects (which use, but do not force, shorter delays).  Moreover, the limitations to clock speed for the different series of BBDs is really only about the basic MN3101/3102-plus-BBD arrangement.  The Matsushita clock driver chip provides enough current drive to overcome the input capacitance of the clock-line pins on the BBD...up to a point...after which the clock pulses get very UN-squarish.  If the clock lines are buffered, however, you can push the BBDs much much higher.  The MN3007, for instance, is spec'd for a maximum of 100khz clock speed, or around 1msec at its shortest delay.  Fine for chorus, but not short enough for the more dramatic flanging sounds.  When suitably buffered, though, I have confirmed reports of it clocking up well past 1mhz, which takes us perilously close to (but obviously not past) the "through-zero" zone.  Itis those incredibly short delays that make the A/DA flanger so legendary.

On another track, because of the higher supply voltage, the earlier ones tend to have a higher S/N ratio and wider dynamic range (i.e., more headroom).  Obviously, if the cram a compander chip in there, the headroom differences between series of chips can mean precious little for many sorts of single-instrument inputs/sources.  On the other hand, if the dynamic range of the input signal is either unpredictable, or known to be wide (e.g., mic'd drums, mic'd acoustic piano), then the higher-voltage series is likely to deliver superior performance.

Probably the most desirable aspect of the 32xx and 33xx series (which nobody seems to know about or sell or ever used for that matter) is that they will run off 9v batteries reliably for a reasonable period, and that the power connections are less confusing.