Noisy analog filters


When I activate ch1 and/or ch2 analog filters there is noise introduced to the outputs. This doesn’t happen when the fixed filters are activated.
It only adds noise to out 1, 2 and the mix outs. The filters do work but the noise floor increases significantly.


Same behavior here .


I was just about to post this also. They are adding about 10db when turned on; its quite audible…

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There has just been a YT vid posted in the facebook forum, someone testing out some s2400 features including the analog filters and the noise increase is audible there.
I have spoken privately with two other owners who have not posted here and they also experience the same.

I can confirm audible noise as well when activated. Given not too big of deal I didn’t feel the need to post this initially as what I’m sure is a huge backlog of items the Isla team has on their list. Good to throw on their radar though!

There are two trim pots on the audio output pcb to allow adjustment for this.
I leave the cutoff wide open from the factory.

sidenote, in the future, these fixed filters will not be populated on the pcb, I will be doing away with them.

Since we have full envelope control, and the fixed (ch 3-6) filters can be very easily done in sw, it just seems overkill, and we’re not a clone after-all.

in summary, if you want less noise from the filters, you may trim them.


We should be looking for something like this on the board?


no they are much smaller and surface mount.

Will you be removing them from the current boards you have before shipping Brad?


Same question. I ordered in August but would like to have them.

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Just letting you all know I adjusted the cut off on my ch1 analog filter today, unfortunately it doesn’t change the noise/hiss that is added when you activate the filter.

It does enable you to remove the small amount of noise which pokes through and moves with the dynamic cutoff, but the background noise that is there does not change.

Sorry to say that the analog filters are useless to me with this background noise, it will be no loss if they are omitted from future machines. Sadly the filters were actually one of the reasons I and probably many others bought this machine.

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I can understand the disappointment but with the addition of daughter cards down the line hopefully this will take the sting out it.

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Just to be clear are we losing the individual analog filters?

@bradholland will we still be getting the analog filters on all channels for the orders in?

I don’t mind some noise :ok_hand:

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for current outstanding orders, yes.
and until the analogue filter card is made.


Weeee I can’t wait for that thing!

@bradholland Awesome! Thank you so much, cant wait to get this thing. Currently working on an emulator II and it takes a billion years to sample anything.

Just to add a separate datapoint to the discussion, the other day I noticed some hiss and an occasional pop in my setup. Almost by accident I hit the ‘Active’ button on my SP-16’s hardware filter, turning it off. It was the source of the noise.(somewhere between -65 and -70db). Point being I dont think this is a unique problem and while this isnt the exact same filter that is in the S2400 its the same filter that is in the Prophet 6(IIRC its a discrete implementation of an SSM 2044?) but despite marketing blurbs that the filters are low noise, they really arent…

i am not saying this to get up any noses but noise isn’t such a bad thing and part of the old charm, it will find its way into the signal path that many of us wanted (12 bit aint exactly hifi now is it) and give us more to chew on, i have so much analogue and very little is quiet in the true sense of the word - noise in a circuit also helps a filter grip - snake oil? maybe but i dont mind, my tube comps, eq, all sorts are noisy - gimme noise i dont mind

you want a noisy filter to moan about? buy a sherman oooooft ! or a ms20 mk1 which i also have - then think juno and the famed chorus sea swish sea swish ssshhhhhh :rofl:

besides, can’t the filters just be turned off and ran in 48k hifi clean mode? so no probs

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I respect that we all don’t care about noise, that’s fine, I don’t mind some, but with dynamic filter 1 or 2 active on my unit it adds far more noise than I imagine it should.

The static analog filters do not add any noise at all, but perhaps they aren’t actually analog or not the same filter as in the SP12/1200? I don’t know exactly how it is implemented on the 2400 or the 12/1200

I own an SP12, permanent filters, always run it through an ancient cheap mixer with some outboard fx and the signal is far less noisy :man_shrugging:

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