by what to replace the TL072?

seb83 · 20th May 2007, 11:01 AM

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

seb83 · 21st May 2007, 06:56 PM

Hi everybody

nobody has any idees??

Thanks

richie00boy · 21st May 2007, 07:06 PM

I don't think changing the op-amp is going to do anything to your hum or lack of adjustment problem. Fix those (if they are possible to be fixed), then see about changing chips.

sreten · 24th May 2007, 10:12 AM

Hi,

If may not have much effect as alluded to above, but in my amplifier,
full of TL072s, replacing critical positions with NE5532s made an
appreciable difference to noise, and cured some input problems.

You do not need anything better than NE5552s.

/sreten.

AndrewT · 24th May 2007, 10:39 AM

get rid of the parametric gubbins and let the music through.

seb83 · 24th May 2007, 08:01 PM

thank you everbody for your answers

One more thing, sreten . you said that you replace your TL072s by NE5552, ok, but, I think you wanted to said NE5532? I'm right? because I did'nt find any datasheet about NE5552....

Sorry if I'm little stupid

richie00boy · 24th May 2007, 08:48 PM

Yes he meant 32.

zeppy2033 · 31st July 2007, 03:56 AM

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.

morinix · 3rd August 2007, 07:48 PM

LF412 - that is what I use.

Tengsimon · 8th August 2007, 03:35 PM

I don't think that change the op the hum disapear.

20th May 2007, 11:01 AM	#1
seb83 diyAudio Member Join Date: May 2007	by what to replace the TL072? 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

21st May 2007, 07:06 PM	#3
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	I don't think changing the op-amp is going to do anything to your hum or lack of adjustment problem. Fix those (if they are possible to be fixed), then see about changing chips. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

24th May 2007, 10:39 AM	#5
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	get rid of the parametric gubbins and let the music through. __________________ regards Andrew T.

24th May 2007, 08:48 PM	#7
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	Yes he meant 32. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

31st July 2007, 03:56 AM	#8
zeppy2033 diyAudio Member Join Date: Jul 2007	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.


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21st May 2007, 06:56 PM	#2
seb83 diyAudio Member Join Date: May 2007	Hi everybody nobody has any idees?? Thanks

24th May 2007, 10:12 AM	#4
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, If may not have much effect as alluded to above, but in my amplifier, full of TL072s, replacing critical positions with NE5532s made an appreciable difference to noise, and cured some input problems. You do not need anything better than NE5552s. /sreten.

24th May 2007, 08:01 PM	#6
seb83 diyAudio Member Join Date: May 2007	thank you everbody for your answers One more thing, sreten . you said that you replace your TL072s by NE5552, ok, but, I think you wanted to said NE5532? I'm right? because I did'nt find any datasheet about NE5552.... Sorry if I'm little stupid

3rd August 2007, 07:48 PM	#9
morinix diyAudio Member Join Date: Jun 2006	LF412 - that is what I use. __________________ Regards Robert

8th August 2007, 03:35 PM	#10
Tengsimon diyAudio Member Join Date: Jun 2004 Location: Taipei	I don't think that change the op the hum disapear.

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