Replacing VTB1 Opamp?

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dickiefunk

dickiefunk

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I'm thinking of trying to mod my VTB1 by replacing the Opamp. It currently has a 4580 Opamp and am thinking of replacing it with a OPA 2134 or Burr Brown INA163. Which would you recommend as being the best Opamp for upgrading from the 4580 and is there anything else worth replacing on it?
 
dickiefunk said:
I'm thinking of trying to mod my VTB1 by replacing the Opamp. It currently has a 4580 Opamp and am thinking of replacing it with a OPA 2134 or Burr Brown INA163. Which would you recommend as being the best Opamp for upgrading from the 4580 and is there anything else worth replacing on it?
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OPA2134 should be safe, it might not be the best, but it's good (much better than 4580), inexpensive, and stable. INA163 is not pin-compatible. It doesn't even have the same number of pins!
 
Thanks for the reply mshilarious. Is it an easy job swapping over the OpAmps in the VTB1 to the OPA 2134? What would I need to do for this? Are there any better OpAmps than the OPA 2134 I could use?
 
Any ideas on these OpAmps and if they would be better or more suitable than the OPA 2134's?

OPA 2132P, OPA 627

AD 797, AD 823, AD 8066

THS 4032
 
I'm using an AD845 in the mic preamp I'm building. Sounds fine to me.
 
The 4580 is a BiFet, if I'm not mistaken.

It's used a lot in the ultra-cheap crap like Behringer and Studio Projects.

Your original idea of the 2134s is fine, but you might also like the 2604 ... a lot of people tend to like that one a lot for some reason. You'll see it in a lot of higher-end gear, and it's very popular for modifications like you're doing.

I'd be really shocked if the SP wasn't surface-mount, though, so good luck if you're going to try and change out that opamp by yourself! :D You'll probably need more than a kitchen knife and a pair of tweasers.

.
 
OK you need to understand some very basics about opamps before you go crazy with swaps. First off is the package you are replacing (I assume it's DIP-8?). If the opamp you are thinking about isn't 8 pin DIP, it will be a much bigger hassle to swap.

Second, 4580 is a dual opamp. AD845 in the DIP-8 package is single, OPA627 is single. OPA2132 is dual.

Finally, superfast, wide bandwidth opamps can oscillate under the wrong conditions. If the VTB's circuitry isn't set up to deal with that, it's a potential problem.

Also you need to make sure you are swapping in a FET input opamp, which 2134 is (and the others mentioned above too, but double check). You don't want a BJT input opamp in the place of a FET input unless you really know the circuit and what you are doing. You can *usually* swap out a BJT input and replace with FET input on a mic input stage, but elsewhere in a circuit (especially in a mixer), the BJT opamps could be necessary to drive the required outputs.

Is it easy to swap opamps? Well, can you solder? Can you desolder without lifting traces? How robust is the VTB1's PCB? Are the holes plated-through? I don't know the answer to any of those questions, but I've swapped many opamps, even when I wasn't that experienced, and it isn't too difficult, but you should get some experience before you jump in. Find an obsolete PCI card with thru-hole components (an old modem should be good for that) and desolder it for fun.

I have swapped the x134 series into many units, always with little trouble and good results. I've used 2604 too, which chess mentioned. They are fairly similar parts, I think 2604 is a bit quieter and 2134 is lower distortion. Both are good, and much better than 4580.
 
Thanks for the replies and info. I spoke to the guys over at Studio Projects and they recommended the OPA 2134 as being the most suitable option for upgrading the OpAmp.
One of my mates is a technician so I'm going to take it to him for the necessary work.
 
dickiefunk said:
Thanks for the replies and info. I spoke to the guys over at Studio Projects and they recommended the OPA 2134 as being the most suitable option for upgrading the OpAmp.
One of my mates is a technician so I'm going to take it to him for the necessary work.
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Assuming it's socketed it would be a doddle to do it yourself. Just make note of the location of the dot on the old opamp and make sure the replacement is oriented the same way.
 
I'm getting the OpAmp changed this week to a OPA 2134. Does it matter whether I choose Burr Brown or Texas Instruments?
 
If you resell it, being able to say "burr brown mod" will probably increase the resale value.

But Burr Brown is actually a part of TI now, I doubt there's any audible difference.
 
Hi! Just had my VTB1 open yesterday and my colleague replaced the stock 4580 OpAmp with the OPA 2134. It was nice to find that every was through the hole so it wasn't too hard a job to replace! I noticed that there was a couple more OpAmps inside - another 4580 and a 2082D . The OpAmp we replaced was at the U1 stage. The other 4580 was at U6 and the 2082D was at U2. I'm guessing that the 4580 at U6 is used as a buffer? Would it be worth replacing these other 2 OpAmps?

Ok now the sound! I can honestly say that changing the 4580 for a OPA2134 has made a difference. Everything sounds clearer and more focused to my ears. I can't say for sure how much of a difference it has made but I definately noticed an improvement and can say it was worth doing (especially seeing as the OPA2134 cost me £2).
 
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Usually with a hybrid tube pre, there is one opamp as the input and first gain stage, and another opamp that follows the tube to drive the output. The third opamp :confused: could be almost anything, without seeing a schematic or even a picture it's hard to say. Reading this page:

http://www.studioprojectsusa.com/vtb1.html

under circuit topology, there are separate input stages for line and mic input. The 2082D is FET, so that is probably the instrument/line input stage. If you don't use that input . . . don't bother with it. Otherwise, you could swap the chip. Actually looking at its datasheet, it's not horrible, although OPA2134 is a bit quieter, and probably lower distortion.

The second 4580 would probably be the output stage. You'd want to leave that as a BJT, 5532 would be an improvement, although there could be something sexier out there . . .
 
Hi. Thanks for the reply. I sent an email to studio projects asking about replacing the OpAmps at U2 (2082) and U6 4580 and they said that replacing them would not be necessary? I do use the line in on the VTB1 so would it be worth replacing this 4580 with another OPA 2134?
Would it be worth replacing the 2082 OpAmp?
 
Hi. How does the 5532 OpAmp compare to the OPA 2134 ? I can't find the specs.
 
I used NE5532s in my green pre. Very nice, clean sound. I can't compare it with the OPA 2134 though I'm afraid.

data sheet here:

http://www.ti.com/lit/gpn/ne5532

The beauty of these cheap IC opamps is that you can buy a few different ones and see which you like best.
 
I would tend to trust SP, especially since they told you that the first replacement would be worthwhile. Very few manufacturers are cool enough to say that, usually they would just say "opening the case can be dangerous and will void your warranty".

If you decide to replace the second 4580, I would use 5532, simply because it's a better output driver than 2134 is.

http://focus.ti.com/docs/prod/folders/print/ne5532.html
 
Thanks again for the replies! I might try the 5532 chip to see if there would be any improvement. I could always put the 4580 back in if it's not suitable.
Thanks for the links for the 5532. There are loads of different 5532 amps. Which one should I go for?
 
I'm pretty sure it's the same amp as in the same circuit but in different packages. As long as you get the right package they should all work and sound the same.

If you get NE5532P then that will be the 5532 opamp in a DIP8 package which is what you need.

RS stock number is 810-188.
 
Cool stuff to read...I don't really understand much of it, though. :D
 
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