Hi

The TLO6x series and TL07x series are functionally equivalent so you should be safe to swap. Where they differ is in performance: The TL06x is a low power device and is not optimised for low distortion, low noise or signal bandwidth whereas the TL07x series is but it draws 1.4mA per amplifier as opposed to 200uA per amplifier. This should not be a problem (each TL074 draws 5.6mA as opposed to 0.8mA of the TL064 i.e. just another 5mA from the power supply).

Most synths have large audio signals so having an opamp capable of higher slew rates will give an improved high frequency response: the TLO6x has 3.5V/us slew rate but the TLO7x has a whopping 13V/us so it can handle bigger signals faster and with lower distortion.

In high gain circuits (e.g. A-119 input stage) the lower gain/bandwidth and higher noise of the TL06x also comes into play - the TL07x is much better here and may be the reason why you hear an improvement as much as for improved slew rate. You may therefore not hear as much of on improvement in the A-134 as it is unlikely to be a high gain circuit.

The more expensive NE5532 can be plugged in place of TL072 in low noise high gain applications but its slew rate isn't quite as good (better than TL062).

Hope this helps
Tony

--- In Doepfer_a100@yahoogroups.com , "mirror_saw7778" <haven1@...> wrote:
>
> After changing the TL064CN in my A119 to a TL074IN and noticing an improved high frequency response and clearer sound I am thinking of doing the same to my A134 VC Panner/Crossfader.
>
> The A134 contains a TL064CN and a TL062CP - are both in the audio path Is it safe to swap these for a TL074 and TL072
>
>
> more info here regarding the IC swap
> http://www.muffwiggler.com/forum/viewtopic.php t=5163
>