Tascam m600 mixing console OpAmp help - Page 1
Forum section: electronics / beginners

author: LuisLDias
author_rank: Contributor
timestamp: July 29, 2016, 10:50:54 pm
content: Hi everyone!Hi everyone!I bought recently a Tascam M600 mixing console not for the console itself, but for the project and the opportunity. I´m an electrical engineer and I am working on wind turbine commissioning. I've some knowledge in electronics, but not a lot.I need to replace some of the amp-ops, but some of them are not available any more.They use the:M5218LNJM2041NJM5532For me at all look quite similar, can I just change all of them to NE5532?Of course they have a different pin out, but a will use a small adapt board because of the package. But just looking at the specifications are they any similar?As Dave says the audio industry have allot of the fool things on it. Almost everyone is saying that the NE5532 is not good enough. They use the OPA2604 or the LM4562. Are they really good for the money? I don't know nothing about noise... the if a change to a jfet op-amp will I have problems with gain or noise?I will put all the data sheet if you need an add the schematics also.LM4562https://dl.dropboxusercontent.com/u/63475761/lm4562.pdfM5218Lhttps://dl.dropboxusercontent.com/u/63475761/M5218L.pdfNJM2041https://dl.dropboxusercontent.com/u/63475761/NJM2041.pdfOPA2604https://dl.dropboxusercontent.com/u/63475761/opa2604.pdfNE5532https://dl.dropboxusercontent.com/u/63475761/ne5532.pdf

author: dmills
author_rank: Super Contributor
timestamp: July 29, 2016, 11:03:58 pm
content: Nothing at all wrong with the 5532, they are used by the thousand in many of the highest end mixing consoles ever manufactured.They do not make wonderful I/V converters on DAC outputs, but for AUDIO, as opposed to RF type edge rates they do just fine.It is fair to say that most any record made in a major studio has audio that has seen the insides of dozens of the things (SSL desks are full of them).Now they are quite power hungry, so you may need to watch available power and cooling, but for the performance, you cannot beat the price.Audiophillia gets uptight about them because they are cheap and old, but with the proviso that they make poor reconstruction filters, they still get it done just fine.I commend a copy of "Small signal audio design" to your attention for much on opamp choices in pro audio.Incidentally, the low hanging fruit in desk modifications is usually cleaning the connectors, followed by the grounding, followed by the power arrangements, electrolytic caps, and then a long way back everything else.Regards, Dan.

author: JPortici
author_rank: Super Contributor
timestamp: July 29, 2016, 11:30:36 pm
content: Quoteand yet they get crazy for tubes

author: dmills
author_rank: Super Contributor
timestamp: July 30, 2016, 12:09:21 am
content: yea, but toobs are not old they are 'Vintage'.Sigh.To the OP, it would be worth checking the supply voltage, some of those old parts will take +-22V which is a fair bit more then a 5532, just worth a check, an as I say, I am not sure I would start with the opamps.Regards, Dan.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: July 30, 2016, 12:13:02 am
content: NE5532 is OK,available in SIL as NJM5532and NJM2114 is a better option. An old trick when using NE5532, NE5534 and NJM2114 is to add a 100nF film cap directly between the supply pins.CheersAlex

author: JPortici
author_rank: Super Contributor
timestamp: July 30, 2016, 01:10:35 pm
content: Quote from: Alex Nikitin on July 30, 2016, 12:13:02 amNice.Thanks for the link i needed a bunch of those for repairing a 70's teac mixer that ahs been sitting unused for ages.when i looked a couple of years ago they were like 5€ each

author: singapol
author_rank: Frequent Contributor
timestamp: July 30, 2016, 01:28:17 pm
content: Quote from: LuisLDias on July 29, 2016, 10:50:54 pmYou are replacing NE5532 because someone said it's not good.Are you replacing because mixer is not working or for the sake of changing.What about your own thoughts and listening impression of the stock mixer?

author: LuisLDias
author_rank: Contributor
timestamp: July 30, 2016, 03:05:43 pm
content: I'm replacing because some of them have failed. But the mixing console as a lot of noise first I will replace the electrolytic caps then the ic's. Some of the channels need new ones so I will replace all of them so that they remain similar.Them I will make a ground modification because the ground is 1 small pcb trace 1.6 long.There are any problem changing normal op-amp's two jfet input amp? This change will change just the gain?I don't care if someone say's I think that is stupid at this point to spend like 5€ per Op-Amp

author: dmills
author_rank: Super Contributor
timestamp: July 30, 2016, 04:18:50 pm
content: Depends, in a low Z circuit a jfet opamp will usually exhibit more noise then a bipolar one (and in a high impedance circuit the reverse is true), it has to with the ratio of current and voltage noise of the input stage. Distortion is also a variable here, so it is not as simple a decision as you would expect.Changing the opamps should not change the gain (Which is always set by the feedback network), but may change distortion levels and can always cause stability problems if you fit something that is not suitable.Usually the noise is more an artifact of overall topology then particular opamp, a 22k resistor is often noisier then a decent opamp, and usually the only places it matters are in the preamps and the bus summing amplifiers (That exhibit lots of noise gain due to the nature of a virtual earth stage).Regards, Dan.

author: LuisLDias
author_rank: Contributor
timestamp: July 30, 2016, 06:25:31 pm
content: Can I clean pot's in the ultra sonic cleaner? Or there are any better way?

author: dmills
author_rank: Super Contributor
timestamp: July 30, 2016, 06:43:46 pm
content: I have seldom had much luck long term with cleaning pots, even if re lubricated correctly with something designed for contact lube (NOT WD40!) they always seem to go crackly again in annoyingly short order.Crackles can often actually be down to leaky coupling caps putting DC on the track, so check that first.A top tip for cleaning knobs and such (Not the electronic parts), pillowcase or sock, add knobs, zip tie closed then bung in the washing machine, much easier then faffing about with a toothbrush.

author: LuisLDias
author_rank: Contributor
timestamp: July 30, 2016, 07:55:22 pm
content: Quote from: dmills on July 30, 2016, 06:43:46 pmthe washing machine is a good one! Thank!The pre amp schamatic

author: dmills
author_rank: Super Contributor
timestamp: July 30, 2016, 09:43:02 pm
content: That looks entirely conventional.I would be surprised by failed opamps, but a phantom power accident could take one of the input transistors (Two more diodes clamping to the negative rail in the same manner as D101,102 do to the positive rail would make the thing substantially more immune to P48 screwups).If pin 1 on the mic connector is really wired as shown, there are probably better ways, but the presence of the P48 might make that slightly trickier then it should be.The mic gain pot is a slightly obscure Reverse Log type, like hens teeth to source those things.Can anyone see what C108 is supposed to be doing, it looks mostly like an excuse to screw up the impedance balance to me?Regards, Dan.

author: StillTrying
author_rank: Super Contributor
timestamp: July 30, 2016, 11:18:06 pm
content: Quote from: dmills on July 30, 2016, 09:43:02 pmThe matching C109 & R119 are also connected to a low impedance point - the output of the op amp.But I'm not very good with that balanced stuff, looks a bit like spaghetti to me.

author: dmills
author_rank: Super Contributor
timestamp: July 31, 2016, 01:08:52 am
content: How did I miss that?The opamp output is still only low Z while it has loop gain, but yea I can now see the matching.Incidentally, that opamp is inside the loop, so be a bit careful if you replace with something too different in GBP or corner frequency, it might take off.Regards, Dan.

author: singapol
author_rank: Frequent Contributor
timestamp: July 31, 2016, 03:39:25 am
content: Quote from: LuisLDias on July 30, 2016, 07:55:22 pmThis is the mic preamp circuit so I would get same transistor and opamp. 2SC1844 is a low noise high 400 hfe. The alternative can be BC550C but check pinout is same or not ( C=400 -600hfe). NJM2041 is low noise version of generic NJM4558 or other 4558. +/- 22V. You can use OPA2604 fet front end dual opamp but of course you think it's too expensive. It's your choice to make. The output coupling cap is a bipolar e-cap 22uf 16V. I will also pay attention to this cap. There is also the input cap 10uf/63V.(You can change or leave it alone.) Since there are many units I can understand your cost concerns.PS: You can substitute NJM2041 with NE5532 but there are subtle differences.Also note BC550C max. 50V vs 2SC1844 max.60V. Can use safely?

author: LuisLDias
author_rank: Contributor
timestamp: August 14, 2016, 10:14:26 pm
content: Do you guys think that something similar do this work?

author: Brumby
author_rank: Unknown
timestamp: August 15, 2016, 12:13:12 am
content: Quote from: dmills on July 29, 2016, 11:03:58 pmIt is amazing how many times I've had faults and noise disappear after a round of mechanical treatment. Cleaning contacts, removing contamination, repairing broken wires and running over some suspect solder joints....

author: dmills
author_rank: Super Contributor
timestamp: August 15, 2016, 12:35:07 am
content: Truth....A gauge insert points being a special favorite for attention, together with ribbon cable busses.Regards, Dan.

author: singapol
author_rank: Frequent Contributor
timestamp: August 15, 2016, 04:15:34 am
content: Quote from: LuisLDias on August 14, 2016, 10:14:26 pmYes, provided the in- line pin outs are the same with the original device.

author: LuisLDias
author_rank: Contributor
timestamp: August 15, 2016, 02:50:21 pm
content: I put the 8 pin matching but that pcb look well design or not? I never did one. It's dual supply but a add the 2 cap on the power rails, and 1 GND pad on the upper left side. I need to find one ground point on the board and connect trow a wire. Are there any better way?

author: Hideki
author_rank: Frequent Contributor
timestamp: August 16, 2016, 10:15:22 pm
content: Ideally, pin 4 on SV1 (you can rename that silly Eagle default name) should go to the cap (C2) before going to the opamp pin. Traces for pin 2 and 7 could be moved a little further away from the other pins.I would use SMD components, but you don't have to.

author: SunkenCity
author_rank: Newbie
timestamp: May 22, 2017, 07:48:30 pm
content: How did this work out for you? I'm thinking of doing some similar stuff to my m600. I can't seem to view the pictures and schems you posted be cool to see these.Thanks,Clayton