Small clone thin in the bass

[Ed G.]

I have a question on the small clone chorus. I built one some time ago from the tonepad site, I wasn't that big into chorus, so I never scrutinized the tone before. But now the band I'm in will be using chorus, so I was listening to it, and I found the effect output was low and thin compared to the bypassed tone.

Seems like that's a common complaint with this pedal, but I couldn't find any real answers for it. So I started mucking around with it.

First, I found the tone was slightly brighter than bypassed, so I increased the 6.8k resistor on the "pre-emphasis" opamp side. It warmed up the sound a bit, sounds about the same as bypassed now.

Bumping up the 33k resistor on the "de-emphasis" side increased the volume a bit, about the same volume as bypassed on most of the strings, but still sounds thin on the bass strings.

I know changing the .01 and 6.8K on the "de-emphasis" side will affect the treble rolloff, but I'm not sure about how to increase the bass.

I've already changed the .033 input cap to .1.

I'm just not sure what more to do at this point.

[nordine]

i did this mod, and worked out great,
just fine tune it, so it matches your linkings

at first opamp, take that .01 cap, and make it bigger, start with 223, then 333, then even 473

now, the 473 gave me huge tone, but distortion... between a 223 and 333 is the magic... good luck!

[Mark Hammer]

Nordine is right.  The .033 input cap is fine, providing a rolloff around 22hz with the 220k resistor to Vref.

The pre-emphasis and de-emphasis networks, though, (the .01uf/6k8 combos) may well be causing you problems, since they are intended for managing the noise on the delay side but do so by being applied to the whole signal, where they also impact on the dry signal.  Stock, the .01/6k8 pair on the first op-amp provides a rolloff below 2.3khz!  That's pretty high.  Of course, since the BBD has limited signal handling capacity, and since that first stage applies a gain of almost 6x to the input signal you do want to keep the BBD from getting smacked with a big bass transient such that BBD-distortion is kept i check.

What you might consider is increasing the value of the .01uf cap in the first stage, as Nordine suggests, but decreasing the value of the 1uf cap that feeds the delay side.  In other words, you recover more of the bass in the dry signal in that first op-amp, and selectively trim it back in the delay path only.  So, for instance, use a .033uf cap as suggested (bass rolloff around 709hz), but drop the 1uf cap on the output of that op-amp to maybe .1uf or .22uf.  You may need to tinker with the .01uf cap in the feedback loop of IC1b to get a desirable tonal balance. The general strategy of using a different toneshaping for the wet signal than for the dry signal is reasonable, though.

[Ed G.]

Thanks guys!
I will try, and I'll post the results.

[marlin]

i did this mod, and worked out great,
just fine tune it, so it matches your linkings

at first opamp, take that .01 cap, and make it bigger, start with 223, then 333, then even 473

now, the 473 gave me huge tone, but distortion... between a 223 and 333 is the magic... good luck!

Sorry, but what capacitor are you refering to exactly?

[Mark Hammer]

If you look at the Tonepad document for the Small Clone, you will see a 6k8 and .01uf pair coming from the inverting pin on the first op-amp.  If that cap is increased to 473 (47nf, .047uf), the rolloff on the bass end drops down to just a hair under 500hz.  Given the gain of that first op-amp, and how much signal lives down in that region, it is no wonder the BBD started to clip.

If one chooses to decrease the gain of that section in order to "protect" the BBD from being overdriven, maintaining overall volume balance would require upping the value of the 33k feedback resistor in the output stage, or perhaps reducing the 10k input resistor there a bit (e.g., 2k2).

[George Giblet]

You can change the eq by playing with the the pre-emphasis/de-emphasis but personally reckon this is going down the wrong path.

Leave the pre-emphasis/de-emphasis network as is. 

Level: You first need to tune the effect level.  If the level is low it will sound weak and any further refinements will be swamped by the volume drop.  You can increase the output level by reducing the 10k on the last opamp, or by dropping *both* the 20k and 22k values by the same factor.

Filtering: The filtering on the small clone has a peak at high frequencies - most people like that. You can mellow out the unit by changing the 15n on the first filter stage to 6.8n and changing the 470p to 1n.

Delay time: The third area to make changes is the delay time.  You can play around with the 150p, say changing it up or down a few values.  What this can do is move the peaks and notches around to more favourable positions.  The the objectional sound does not change by changing this cap it is likely the filtering is not your liking.

I suspect the level drop and high frequency peaking makes the bass sound weak as there is virtually no bass cut in that unit.

[villeristi]

Dear Mr. Ed... Did you get it done? I'm dealing with the same issues on my clone-clone. The unit sounds really good but the low end response is'nt the same as bypassed...