fatboy135
Well-known member
Hi to all, I want to said a few words about the fever of mods. Well if you are modding some of your stuff because it doesn´t sounds as you wants it is totally admisible, even if you are bored at saturday rainy day, ok but don´t think that good mods are as easy as simply just replace components.
Well the matter is the next: I have seen all over the internet a lot of people selling mods for tubescreamers, they usually sell a few IC, the socket and a couple of resistors, well I´m not really a TS expert but I think that I have enough knowledge to said a few things about it.
When you are seeing that a machine has a determinated IC and not other it could be for some purposes, but the mainly is that this specific IC is good proved on that kind of machines. The op amps are in general very unstable elements so you must to have all the parameters well controlled if you don´t want that you op amp begin to oscillate.
Even ne5532, burr brown opa2604, tl072,062, 082 jrc4558 and other equivalent elements seems to be the same and seems to works so fine on ever circuit that is the farest from reality, you could have a circuit working properly with a tl072, you replace it with an op amp bb opa 2604 and it could be the most unstable of the world, even being the bb best than texas tl072
Think that you could see all the op amps externaly the same but its manufactured is totally different. Every op amp has its own offset parameters and its own poles etc..., the circuit design is for minimized the possible colateral effects due the manufactured process.
Ok after that bit explanation I recomend that if you really want to test it you could download the datasheet of the opamps and choose the nearest on features, even with that premise you couldn´t know if the invent will work properly.
Another issue is that changing the output resistors of the TS you are incrementing or decrementing the voltage or the current outputs, dependly if you maintains the relation of the resistors, so you will need to calculate the current and voltage as a voltage divider and go for the opamp datasheet to see if the opamp is able to give all the power without any saturate zone.
Even all that premises you could ensure that your slew rate, noise and bandwith will be maintaned with the new opamp, so you will need to do an exhaustive research to see if there is all the parameters under good conditions
I recomend to do the research with a scope and a function generator, but if you haven´t them you could use a multimeter and a tone generator.
To calculate the rms noise you could use only the multimeter, and for slew rate and bandwith you will need to do a sweeping tone with the function generator or the tone generator and calculate the -3dB
Ok after that tests we have to do the most critical test, and it is the aquiles knee of the op amps, the pole that generates the mighty oscilate. It is very usual that oscilates where produced on high frecuencies, higher than audible frecuencies, so you will need to test the circuit for the oscillate even if the TS sounds totally perfect, there could be the oscillate on high frecuency while the TS sounds very nice. The importance of quitting the oscillate is for some reasons, an oscillate disippates a lot of power that it is not involved on the audio process, an oscillate is the consequence of an unstable environment between the op amp and the circuit designs, if the unstable op amp is used and abused a lot it could drives into a totally failure of it.
Ok so, if you are thinking that replacing an op amp for another one is just to quit it from the socket you are totally wrong, if you don´t care about it just replace and play but if you really want to know if your TS is under all good conditions you will need to spend some time researching with all that issues
Enjoy your mod
Well the matter is the next: I have seen all over the internet a lot of people selling mods for tubescreamers, they usually sell a few IC, the socket and a couple of resistors, well I´m not really a TS expert but I think that I have enough knowledge to said a few things about it.
When you are seeing that a machine has a determinated IC and not other it could be for some purposes, but the mainly is that this specific IC is good proved on that kind of machines. The op amps are in general very unstable elements so you must to have all the parameters well controlled if you don´t want that you op amp begin to oscillate.
Even ne5532, burr brown opa2604, tl072,062, 082 jrc4558 and other equivalent elements seems to be the same and seems to works so fine on ever circuit that is the farest from reality, you could have a circuit working properly with a tl072, you replace it with an op amp bb opa 2604 and it could be the most unstable of the world, even being the bb best than texas tl072
Think that you could see all the op amps externaly the same but its manufactured is totally different. Every op amp has its own offset parameters and its own poles etc..., the circuit design is for minimized the possible colateral effects due the manufactured process.
Ok after that bit explanation I recomend that if you really want to test it you could download the datasheet of the opamps and choose the nearest on features, even with that premise you couldn´t know if the invent will work properly.
Another issue is that changing the output resistors of the TS you are incrementing or decrementing the voltage or the current outputs, dependly if you maintains the relation of the resistors, so you will need to calculate the current and voltage as a voltage divider and go for the opamp datasheet to see if the opamp is able to give all the power without any saturate zone.
Even all that premises you could ensure that your slew rate, noise and bandwith will be maintaned with the new opamp, so you will need to do an exhaustive research to see if there is all the parameters under good conditions
I recomend to do the research with a scope and a function generator, but if you haven´t them you could use a multimeter and a tone generator.
To calculate the rms noise you could use only the multimeter, and for slew rate and bandwith you will need to do a sweeping tone with the function generator or the tone generator and calculate the -3dB
Ok after that tests we have to do the most critical test, and it is the aquiles knee of the op amps, the pole that generates the mighty oscilate. It is very usual that oscilates where produced on high frecuencies, higher than audible frecuencies, so you will need to test the circuit for the oscillate even if the TS sounds totally perfect, there could be the oscillate on high frecuency while the TS sounds very nice. The importance of quitting the oscillate is for some reasons, an oscillate disippates a lot of power that it is not involved on the audio process, an oscillate is the consequence of an unstable environment between the op amp and the circuit designs, if the unstable op amp is used and abused a lot it could drives into a totally failure of it.
Ok so, if you are thinking that replacing an op amp for another one is just to quit it from the socket you are totally wrong, if you don´t care about it just replace and play but if you really want to know if your TS is under all good conditions you will need to spend some time researching with all that issues
Enjoy your mod
