Tap Tempo for BBD

POTL · Post by **POTL** » 05 Aug 2020, 21:23

Hello.
The idea behind Tap Tempo in analog modulation and delay pedals is not new, but still hasn't been covered in detail at the DIY level.
I looked through a lot of commercial products such as JHS, Chase Bliss and noticed that they all use BBD 3007/5, 3207/5 with a clock as a module (do not give up on them, unlike Electric Druid projects).
Obviously, the main change in the circuit is the replacement of the analog LFO with a microcontroller.

I see 2 obvious options for implementing a similar scheme (but any ideas are welcome).
1) Electric Druid style, the main controls (Manual, Rate, Depth) are implemented on the microcontroller, we get a full set of functions and the ability to flexibly configure presets.
The microcontroller output goes to the point where the depth control output was in the analog circuit. The clock and other components remain unchanged.

2) Sabrotone style.
We only use the microcontroller to adjust the Rate, the rest of the circuit does not change. Manual and Depth are not saved in presets.

As far as I understand, we can program the microcontroller to fully simulate a real LFO and we get 100% (or so) identical sound compared to a fully analog circuit.
But there are points that I cannot understand.
1) Chase Bliss Tonal Recall is a new take on the EHX DMM, but uses a different clock and digital control.
Both effects work from 15V, but as I understand it, the LFO in Chase Bliss will only work in the 0-5V range, while the DMM is 0-15V
In reviews and comparisons, Chase Bliss modulation sounds no worse and there is no feeling that the sweep is 3 times less.
2) Flangers circuits sound much better when powered from 9V (EHX Electric Mistress) or 15V (MXR, ADA, DOD).
Circuits using the original 3101/2 clock and BBD running on 5V sound much the same (IMHO).
I understand that they are using a different clock, but I think the LFO sweep range also has an impact.
I have never seen a commercial flanger working with a watch other than the mn3101 / 2, in principle the only product is the Chase Bliss Specter.
At the same time, Chase Bliss managed to make a delay with lush modulation.
I'm wondering if it's worth increasing the LFO range to 9-15 volts or can I make it sound like the original circuits using only 5 volts?
If not, are there any ways to increase the LFO range, or is it just impossible to assemble a flanger with a lush sound powered by LFO 5V?

POTL · Post by **POTL** » 06 Aug 2020, 08:37

OK
I modulated the standard LFOs
Most circuits have a range of no more than 4V between maximum and minimum values, which means that we can simulate normal LFOs well.
The only exceptions are Flangers, which work without original watches.
Perhaps this is the reason for the lack of commercial flangers with tap tempo

POTL · Post by **POTL** » 06 Aug 2020, 10:38

Another addition.
I tested the LFOs of most flangers and noticed that they have a wider range than other effects.
At least those that don't use the original watch.
Interestingly, there are some interesting exceptions among deep-sounding flangers.
1) The Electric Mistress uses a non-inverting amplifier to boost the LFO range, it goes from about 3V to about 7V.
2) The ADA flanger uses an inverting amplifier to reduce the LFO range from about 10V to about 7V.

In general, all interesting sounding flangers work with an LFO, the range of which starts from 7V

This is bad for Tap Tempo, which can only output 5 volts or less.
But thanks to the Electric Mistress circuit, it becomes clear that with the help of an amplifier we can increase the LFO sweep and achieve the desired result (so far in theory).