Adding a Blend to a Diamond Compressor "Clone"

[HadMatter217]

Hi everyone,

I'm looking into building a compressor, and I've designed a sort of hybrid between the Diamond and Warden compressors. It's basically the gain stage from the Warden with the discrete LDR and LED replaced by a NSL-32 with the LED being driven by an opamp circuit that's pretty similar to the one used in the Diamond, but with an attack Pot added. Then, I included the Tilt EQ, because I really like the sound of the Diamond's EQ. Not that it matters, but I also kept the Diamond Compression indicator, but converted the green side to a millenium bypass So what I have is some weird 5-knob hybrid of a Warden and a Diamond, and I was hoping to add a Blend knob, since I really like being able to blend the dry signal with the compressed signal.

So that's the background on what I'm working on. Now for my question: Should blend the dry signal into the compressed signal before or after the EQ? My initial thought was to do it after using an inverting amplifier going into the blend stage, but since there's a decent amount of phase shift in the tilt EG between one extreme and the other of the tone pot, I wasn't sure if that would cause too much destructive interference with the dry signal. The other option is to blend it before the EQ using just a buffer for the blend, but I wasn't sure if I want the dry signal to go through the EQ. Does anyone have any ideas or previous projects where they added a Blend circuit to the Diamond?

[knutolai]

When requesting help about a circuit it very helpful to post your schematic. It's hard to get a sense of the circuit you are describing without doing multiple google searches/investigating.

[rankot]

When requesting help about a circuit it very helpful to post your schematic. It's hard to get a sense of the circuit you are describing without doing multiple google searches/investigating.

Agreed.

[duck_arse]

agreed, plus welcome.

[HadMatter217]

The portion of the circuit that's relevant to the question is just a tilt EQ. My question, more generally is can you blend an unshifted or inverted signal into one that has a non-constant phase shift, and what would the effect of that (variable, depending on positon) deconstructive interference be, from an audio point of view, vs just trying to send a blend of the compressed signal and the dry signal through the EQ (which would itself be a blend of a slightly shifted compressed signal and an unshifted dry signal). The rest of the details were just intended to give an idea of what I was aiming to do overall with this pedal. The other circuits don't really matter all that much for the sake of my question.

The Diamond schematic is here, as well as frequency and phase plots for the Tilt EQ.: http://revolutiondeux.blogspot.com/2012/06/diamond-compressor.html

[iainpunk]

i haven't experimented with your particular compressor, but i do have experience with the "really cheap compressor" and i used a modified BMP tonestack (also a tilt control, but without the mid scoop) as a "mixer".

where you would normally have the input, i fed the compressed signal and where normally the ground would be is where i put in the (boosted up to 2 times) clean signal, so i could have clean high and compressed low or vice versa. both clean and compressed had volume controls as well.

[iainpunk]

i haven't experimented with your particular compressor, but i do have experience with the "really cheap compressor" and i used a modified BMP tonestack (also a tilt control, but without the mid scoop) as a "mixer".

where you would normally have the input, i fed the compressed signal and where normally the ground would be is where i put in the (boosted up to 2 times) clean signal, so i could have clean high and compressed low or vice versa. both clean and compressed had volume controls as well.

here is a simplified drawing, i think this is more useful than a normal mixer

[HadMatter217]

Thanks for the reply. That seems like a really interesting concept that I might consider. I think that's way more knobs than I'm trying to do, but would the idea be that if you only wanted the compressed signal, you could turn the clean signal all the way down? This seems like an interesting idea, for sure.

[iainpunk]

if you turn down the clean signal, you have a normal big muff style tone control, without the mid scoop. that means that there is a 5dB loss over all and you take out more treble or bass depending on the setting, but that can be resolved with putting the compressed volume knob higher or using simple boosters instead of buffers

[HadMatter217]

That makes sense. I'll definitely consider this. I always liked the Big Muff EQ. I think either way, it makes sense to blend the dry signal in before the EQ, since no one has really been able to answer how the variable phase shift would negatively affect the tone. Thanks for the suggestion.

[iainpunk]

i dont think filtering makes any difference in destructive interference, you will always have some of it when mixing, and i don't think it's very noticeable with first order filters, like in your original schematic.

cheers,
Iain