Hello everybody , I'm new in this forum. (excuse my poor english, I'm french ^^ )
I've a SWR SM-400 bass amp, and this one have a good sound.
But I can hear a "hum", even if the Gain and Volume are at "0".
(The GT12AX7 preamp tube is the original.)
I would like to "tweak" this head, because, the 4 semi-parametric band are very hard to tune, and the difference of the sound is very difficult to hear when I tune the equ bands.
I don't search a very High Gain sound, I juste want to find the largest sound, a great round and dynamic bass and the harmonic of the rest of the spectre.
I think to change into first, all the TL072CP operationnal amplifier, by what? I search in a lot of threads, and the choice isn't easy.
AD823, AD828, OPA2134, OPA2604...?
And in the last time, to change the GT12AX7 preamp tube.
If you have comments or ideas to be given me.
Thank you very much
I've a SWR SM-400 bass amp, and this one have a good sound.
But I can hear a "hum", even if the Gain and Volume are at "0".
(The GT12AX7 preamp tube is the original.)
I would like to "tweak" this head, because, the 4 semi-parametric band are very hard to tune, and the difference of the sound is very difficult to hear when I tune the equ bands.
I don't search a very High Gain sound, I juste want to find the largest sound, a great round and dynamic bass and the harmonic of the rest of the spectre.
I think to change into first, all the TL072CP operationnal amplifier, by what? I search in a lot of threads, and the choice isn't easy.
AD823, AD828, OPA2134, OPA2604...?
And in the last time, to change the GT12AX7 preamp tube.
If you have comments or ideas to be given me.
Thank you very much
Filament of the tube.-
seb83:
If the filament of the tube is powered from a AC source like a winding from the main, or separate transformer (most common configuration), this is the cause of the hum you hear. A possible solution, is to convert that AC current, to DC and regulated, in order to feed that filament properly (voltage, current) and free from any interference and sine wave of any kind.
Keep in mind, that the filament is very, very near to the cathode and grid (input) of the tube; that's why the inducted AC couples to the audio signal.
The filament on the high-end mic preamps are feeded from a regulated DC power source.
SWR are valuable amps, one of the best I've heard. Then, ask a technician of your confidence, if you start with the mentioned work. I don't think that changin the opamps the hum desapear. Leave them as they are, and try to change them in the future, as a sound enhancement.
Yes, Pink Floyd, Led Zeppelin, Free, Deep Purple, Yes, Uriah Heep, are inimitable groups.
Regards.
seb83:
If the filament of the tube is powered from a AC source like a winding from the main, or separate transformer (most common configuration), this is the cause of the hum you hear. A possible solution, is to convert that AC current, to DC and regulated, in order to feed that filament properly (voltage, current) and free from any interference and sine wave of any kind.
Keep in mind, that the filament is very, very near to the cathode and grid (input) of the tube; that's why the inducted AC couples to the audio signal.
The filament on the high-end mic preamps are feeded from a regulated DC power source.
SWR are valuable amps, one of the best I've heard. Then, ask a technician of your confidence, if you start with the mentioned work. I don't think that changin the opamps the hum desapear. Leave them as they are, and try to change them in the future, as a sound enhancement.
Yes, Pink Floyd, Led Zeppelin, Free, Deep Purple, Yes, Uriah Heep, are inimitable groups.
Regards.
TLE 2071 series
I did'nt tested yet, but according with datasheets, TLE 2071 series opamps outperforms all the mentioned above.
Has a Slew Rate of 45 V/ms, 10 MHz bandwidth, good stability since it is a direct replacement for the TL series, both intended for audio purposes.
See the datasheet in the web, is one of the best replacements in order to enhance the sound performance of almost any audio device.
Best regards.-
Note: V/ms=volts per micro second. (This server doesn't manage the mu symbol)
I did'nt tested yet, but according with datasheets, TLE 2071 series opamps outperforms all the mentioned above.
Has a Slew Rate of 45 V/ms, 10 MHz bandwidth, good stability since it is a direct replacement for the TL series, both intended for audio purposes.
See the datasheet in the web, is one of the best replacements in order to enhance the sound performance of almost any audio device.
Best regards.-
Note: V/ms=volts per micro second. (This server doesn't manage the mu symbol)
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Hi, I would replace a JFET input opamp for a better JFET input opamp in HiFi gear but remember a bass amp has nothing to do with HiFi. You could try OP249 or the TLE2071/2 as it is a direct replacement. You will change the sonical character of the amp but I guess that is what you're after.
It would be a miracle if the hum would disappear by replacing an opamp but you never know...I think you should look at the filter caps in the power supply.
And check this thread for voicing the SM-400:
http://www.talkbass.com/forum/f15/swr-aural-enhancer-bypass-643201/
It would be a miracle if the hum would disappear by replacing an opamp but you never know...I think you should look at the filter caps in the power supply.
And check this thread for voicing the SM-400:
http://www.talkbass.com/forum/f15/swr-aural-enhancer-bypass-643201/
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