vc-lfo build U6 =LT1057? - answered during Muff outage

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vc-lfo build U6 =LT1057? - answered during Muff outage

Post by Pav » Mon Oct 02, 2017 6:40 am

I hope our webmaster is now on the mend - best wishes.

During the Muff outage I asked a question of Synthbuilder and his reply is worth posting to others who might (but do not have to) wish to upgrade .

In the vclfo builders guide V3.2 U9 has been upgraded from a TL072 (bg3.0) to LT1057CN8 dual op-amp. In the UK that is Farnell price 4.50 squid ex vat.

The schematic still has TL072. You tell us to go with the build guide in this scenario - so I will but sonically will i hear anything ?

Synthbuilders response:

The VC-LFO will work with the TL072. However, waveform symmetry along the time axis is not that good at very low frequencies. With the VC-LFO operated at audio frequencies the slewing is not measurable or audible. However, below 0.1Hz you'll notice that the waveforms become more and more skewed, spending more time going up than going down (or vice versa). At very slow sweeps - say one cycle every two minutes - this apparent skewing will be apparent when modulating other things. It may or may not be a problem to you.

If you use the LT1057 the skewing will be massively reduced to a point where it is not noticeable even at the slowest of speeds.

So build it with the TL072 first but use a IC socket. Once in use, if the skewing is not acceptable, then replace the TL072 with the better part.

I have ordered the new part, meanwhile the LFO as first Oakley module is working fine. :hail: Also after a fair bit of re- crimping poor crimping :bang: , is my 2nd the multimix. :nana:
rgds Pav

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