Hi there,
could somebody please help me with following stuff?
I´ve got a so called SPL Vitalizer (one of the first models from the 90´s). It´s a nice thing but quite a little bit noisy. The opamps used there are all on sockets, so I could easily exchange them. My problem is that I´m a bloody beginner and I dont know which opamps I could try instead. The opamps are:
TL071CN, TL072CN, TL074CN and LM13700N
Thank you in advance,
Rudolph
could somebody please help me with following stuff?
I´ve got a so called SPL Vitalizer (one of the first models from the 90´s). It´s a nice thing but quite a little bit noisy. The opamps used there are all on sockets, so I could easily exchange them. My problem is that I´m a bloody beginner and I dont know which opamps I could try instead. The opamps are:
TL071CN, TL072CN, TL074CN and LM13700N
Thank you in advance,
Rudolph
TL071, TL072, and TL074 are single, dual and quad versions of the same opamp. They are pretty low-noise to begin with but there are ones with better specs. A common upgrade for audio is the OPA134, OPA2134, OPA4134 single dual quad family. Also the OPA132, OPA2132, OPS4132 family. (I'm not sure on the relative merits.) These are not all that expensive. I would guess that using all from the same family to attempt an experimental upgrade of the TL07x family would be the most conservative approach.
The LM13700N is a "tranconductance" op amp. The applications on the data sheet suggest it's use for current controlled amplifies, current controlled filters and other control circuits. Although, it looks like it is fairly noisy, relatively high distortion device, I'll bet that in your Vitalizer it is not in the signal path but rather supplies DC voltages to control the functions that the unit performs. With luck the unit was designed such that it does not contribute to the Vitalizer's noise and distortion figures. On top of that, there may very well not be a psart that could be substituted without altering the functionality of the Vitalizer. I suggest you leave this item alone unless you or someone else who realy (I mean REALLY!) understands how the thing works can determine whether there is any potential improvement in this area.
From the description, of this product, it looks like it is big bundle of filter elements most likely realized by many, many capacitors. These could well be a noise source equal or greater than that of the opamps. You could try replacing them with the same values but higher quality, but the improvement might be marginal at best. I triesd something like this with something called a Phase Linear 1000, but it was hopeless -- the signal simply passes through so many RC filters, gain and attenuation stages that the unit was just inherently noisy regardless.
The LM13700N is a "tranconductance" op amp. The applications on the data sheet suggest it's use for current controlled amplifies, current controlled filters and other control circuits. Although, it looks like it is fairly noisy, relatively high distortion device, I'll bet that in your Vitalizer it is not in the signal path but rather supplies DC voltages to control the functions that the unit performs. With luck the unit was designed such that it does not contribute to the Vitalizer's noise and distortion figures. On top of that, there may very well not be a psart that could be substituted without altering the functionality of the Vitalizer. I suggest you leave this item alone unless you or someone else who realy (I mean REALLY!) understands how the thing works can determine whether there is any potential improvement in this area.
From the description, of this product, it looks like it is big bundle of filter elements most likely realized by many, many capacitors. These could well be a noise source equal or greater than that of the opamps. You could try replacing them with the same values but higher quality, but the improvement might be marginal at best. I triesd something like this with something called a Phase Linear 1000, but it was hopeless -- the signal simply passes through so many RC filters, gain and attenuation stages that the unit was just inherently noisy regardless.
Well the noise has to come from somewhere??
So where does it come from....
The 2 main noise sources are the thermal noise of the resistors... which I doubt will be higher than the 18nV/sqrtHZ.. the other source are the active devices... you can get 3nV/sqrtHZ instead of 18nV/sqrtHZ if you use opa227 instead of TL072 .....
Than again 18nV/sqrtHZ is -92dB ref 100mV (20KHz BW).. noise shouldn't be a problem... do you use a propper input level?
So where does it come from....
The 2 main noise sources are the thermal noise of the resistors... which I doubt will be higher than the 18nV/sqrtHZ.. the other source are the active devices... you can get 3nV/sqrtHZ instead of 18nV/sqrtHZ if you use opa227 instead of TL072 .....
Than again 18nV/sqrtHZ is -92dB ref 100mV (20KHz BW).. noise shouldn't be a problem... do you use a propper input level?
if the opamps are socketed, get rid of the sockets and solder the replacement opamps right into place -- the exception would be if the sockets had gold wipers or machined pins.
make sure that the power supply pins are bypassed with 100N or 10N capacitors, placing the bypass caps as close as possible to the power supply pins as possible.
consider tackling the power supply -- if it uses standard 3-pin regulators you might want to explore the lower noise discrete component regulators (search this forum under Sulzer, Super-Regulator, ALW etc.)
jack
make sure that the power supply pins are bypassed with 100N or 10N capacitors, placing the bypass caps as close as possible to the power supply pins as possible.
consider tackling the power supply -- if it uses standard 3-pin regulators you might want to explore the lower noise discrete component regulators (search this forum under Sulzer, Super-Regulator, ALW etc.)
jack
Wow, you guy´s are fast! Great board!
Thank You all.
Maybe a few words more about the Vitalizer. The parts used there are all of very high quality. As I can see, there are no electrolyte´s in the signal pathway and the PSU is also of very high quality. The resistors, well - I don´know. But SPL is known for well engeneered stuff.
The unit that I have is from 1995 and has a S/N ratio of 78 db. SPL produces the same Vitalizer Jack today, but thay claim it was reengeneered and has a S/N ratio of 86 db. I don´t beleave they did very much changes because in the 90´s there were companies which tuned this Vitalisers to make the S/N better.
I like this thing, because it does wonders to older recordings and even to better recordings when listening at low lewels (in the evening). I plugged it between my preamp and active studio monitors and I do hear some faint noise when it is silent. Well maybe I should try to attenuate the output of the Vitalizer and crank up the input because I never see the peak-LED´s blinking on it.
Thank You all.
Maybe a few words more about the Vitalizer. The parts used there are all of very high quality. As I can see, there are no electrolyte´s in the signal pathway and the PSU is also of very high quality. The resistors, well - I don´know. But SPL is known for well engeneered stuff.
The unit that I have is from 1995 and has a S/N ratio of 78 db. SPL produces the same Vitalizer Jack today, but thay claim it was reengeneered and has a S/N ratio of 86 db. I don´t beleave they did very much changes because in the 90´s there were companies which tuned this Vitalisers to make the S/N better.
I like this thing, because it does wonders to older recordings and even to better recordings when listening at low lewels (in the evening). I plugged it between my preamp and active studio monitors and I do hear some faint noise when it is silent. Well maybe I should try to attenuate the output of the Vitalizer and crank up the input because I never see the peak-LED´s blinking on it.
Yup. The OPAx227 and OPAx228 families are a possability as well. From the application, I suspect that in most cases the opamp is being used at unity gain, which means the OPA227 is preferred, but if the gain is >5, the data shgeets say OPAx228 is prefferred. **Check the datasheets as I might have that bassakwards!!** While you are looking at the datasheets, note that these families have some limits on the input currents that can be used without damaging the device - you are probably safe - but check. The data sheets app notes also contain info on how to get the best results from these devices so read them a couple of times.
It's not my intent to send the guy off to buy new equipment, but I think that kind of application is potentially better achieved with digital rather than analog technology. If I were interesting in something like this I would be looking for a digital version working at 24/96 or better.
@ sam
The problem is, that there is nothing similar in the digital world! I know a lot of this hardware/software "Exciters" and "Spectralizers" but they do not the same thing. They all sound harsh. A Fletcher-Munson correction with digital equalizers (OK, I´ve heared only the software solutions) also does sound "unnatural". And I can ensure you that I´m not an analog freak.
sam9 said:
The problem is, that there is nothing similar in the digital world! I know a lot of this hardware/software "Exciters" and "Spectralizers" but they do not the same thing. They all sound harsh. A Fletcher-Munson correction with digital equalizers (OK, I´ve heared only the software solutions) also does sound "unnatural". And I can ensure you that I´m not an analog freak.
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