gettestudios wrote:After years of researching the "Opamp" looking at reviews as well as listening to the deferences between types, brands etc. I have settled on one.
Before you go mad on OPA rolling, have a really good read of ...
Kingston on GroupDIY had an excellent thread on what is REALLY important for noise & THD; opamps and local decoupling of rails, some questions
Many true gurus chime in. It proves how OPA rolling takes a VERY poor second place to correct earthing, layout & decoupling. It’s a long thread but read the whole thing from #41 to find pearls of wisdom.
What you get is critically dependent on how good the AMEK decoupling, layout & earthing system is. VERY few people can do this properly. JR is one of them though I'm sure he's ROTFL
The console currently uses at an exclusive level, NE5534N/NE5532N.(schematics show TL072's)
Also look carefully at where some idiot .. I mean (pseudo) guru has substituted 5532 for TL072. There's usually some good reason for TL072 .. probably to do with bias current. The best replacement for TL07x is OPAx134.
Note it comes out better than practically all the uber OPAs in Kingston's thread though its spec suggests otherwise. The reason is it is probably the least fussy of the 'modern' OPAs to dodgy decoupling, earthing bla bla. It also has VERY high immunity to RFI.
Da uber OPAs may do better in simple test circuits, but OPAx134 & 553x will often outperform them in complex systems like big mixers.
Also watch bias currents.
553x are npn input with loadsa Ib. Good makers use this to ensure electrolytics are nicely polarised. FET OPAs like TL07x have zilch & many of da uber OPAs have evil Ib cancelling.
Unlike JR, I think the important faults are the ones the customer notices and complains about.
That's cos I was a real DBLT guru in my previous life. Clicks are verbotten on Broadcast Desks. (There's even a test spec based on a BBC PPM) So I will happily put evil electrolytics (nicely polarised) in the signal path.
There's NO evidence that paralleling electrolytics with Golden Pinnae films gives ANY advantage, audible or otherwise.
EQ, I have drooled and studied the SSL and VR EQ's for some time.
EQs, like compressors & limiters, are very personal. If you like it, dun change it.
Take care of the pots, especially any Reverse-Log ones ... unless you have a branch of Ye Olde Unobtainium Shoppe nearby.
MicPre is centered on a Sowter 4057 transformer, transistor and a single IC. Needless to say, since i am expanding to 48 ch, i do not even want to know how much it would cost to have these custom made. I am leaning toward a L1538 based mic pre (still costly) but am open here, ideas and suggestions. I want a clean pre that has little color and handles low end well.
Don't knock da old transformer designs
Though I will never design another one, they do certain things that are nearly impossible with modern stuff .. in particular practical RFI immunity & 'The Phantom menace'
Main practical CONs are $$$, size & weight. Performance wise, a THAT solution can have 1dB NF while the best I've done with a transformer is 1.6dB. Frequency Response is also difficult to get from DC to zillion MHz .. which is why some appear to have better LF cos it is often lumpy and with a bit of 3rd harm. too.
The various THAT solutions are hard to beat for 'clean'
Only change is, U1.1A, U4.1A, U6.1A, U8.1A was originally a TDA1034, I am showing it as a TL072, and i also removed the 33pF comp cap.
Du...uh! TDA1034 is an early name for NE5534. It is a single OPA compensated for 3x gain (hence the 33p for unity gain). TL072 is a dual OPA.
If you want to 'improve' a historical desk from a competent manufacturer, the good mods are those the maker did in later examples. There will be good reason for them.
eg I'd love to see one of Jo Wuttke's last Schoeps mike circuits to see what he changed and what he kept.