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Old 16th March 2004, 10:43 PM   #1
Xbuk is offline Xbuk  United States
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Default Bass Amp Trace Elliot

First post. I am not smart. But I have questions.


I have a Trace elliot bass amp that HISSES really bad. The sound would be perfect if I could get rid of the HISS.

What is a systematic way to find the problem?

IE. what tools? and what to check in order?

And When I find the problem where do I shop for quality parts?

(I am good with a soldering Iron)


As well what are some components in this amp that I could probly replace with known better components.


Last question.. would the power amp section of my fender be diffrent design then the power amp section of my trace elliot. I mean in terms would they make one amp more specific for guitar and one more specific for bass guitar? If so What are some of the things that would seperate a guitar power amp from a bass power amp from a home stereo power amp?

All regarding solid state.


Regards

Xbuk
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Old 17th March 2004, 01:27 PM   #2
Jay is offline Jay  Indonesia
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Okay, I'm smart but I often don't know what I'm talking about

When your TE bass amp hissed, did you use it with a bass guitar? Or a guitar amp? Or a CD??? Did you use a preamp? Did you use a tone control? Did you use "guitar" speaker or hi-fi speaker?

Guitar amps operate in a narrower bandwidth than hi-fi amps because it is designed for guitar only, not for all instruments (and it may have bumps in the higher regions). Bass guitar is supposed to operate in the lower region of guitar frequencies, right? So that hiss, what signal was it trying to reproduce? Surely not cymbal, right?

Electric guitar instrument characteristic is such that driving the amplifier to clipping is preferable to the ears. And only tube amplifier that creates a nice sound right after clipping (due to second harmonics and so on). If your TE amp is solid state, the preamp section might use tubes, or special solid state circuit designed to emulate the tube characteristics at clipping. But because it is a BASS amp, this special feature may not need be available.

I've never heard a BASS guitar amp, and IMSO it is economically not correct to design amplifiers that work only for guitars and not bass guitars. But with bass guitar, you don't need to drive the amp to clipping so solid state is a good approach economically.

If you drive a solid state to clipping (because you don't have special preamp that handle this clipping), the sound will be anoyyingly harsh.

I'm sure your Fender is a TUBE amp. And it seems that you have the preamp as well? Ha ha.. I'm now confused of what I'm going to explain. But of course, there is a possibility that both preamps are different.

About how to solve the hiss problem, assumming that it is not caused by hi-fi speaker, or CD music on bass amp, or something like that, I think you could open the preamp section, and find a coupling CAPACITOR in the signal path, and increase the value. This capacitor usually is less than 1nF. But that's a solution after we know what was happening.

Regards,
Jay
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Old 17th March 2004, 02:15 PM   #3
sreten is offline sreten  United Kingdom
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First you need to ascertain if the hiss is the pre amp or power amp.

If the hiss reduces by playing with the preamp its the preamp.

If its the power amp your pretty stuck.

Next you need to make sure levels through the preamp are correct.

If you have a master volume this should be knocked back
and the correct input and gain level set for your bass.

Still lots of hiss, what happens if you the short the input ? still hiss ?

Given its none of the above inspect the input board for an op-amp.

I reduced the hiss of my bass amp by swapping the input
TLO71/72 FET type op-amp for a NE3352/4 type op-amp.

If op-amps are not used it gets quite complicated.

sreten.
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Old 17th March 2004, 08:40 PM   #4
Xbuk is offline Xbuk  United States
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>First you need to ascertain if the hiss is the pre amp or power amp.

------------------------------------------------


Ok I have done this. and the hiss is from the pre amp. I pluged my bass in to the effects return by-passing the pre amp, as well as the line in input. and the hiss is significantly less. and turned the bass guitar all the way down and its still about the same amount of hiss (not bad).. I plugged it back in to the pre amp. (active input) I have active pickups. turned the bass guitar all the way down and the hiss was much much more as well I pluged in another bass and it was still hissing. SO I have isolated it to the pre amp.

Another thing the pre amp only hisses really bad when I turn up the treblie on the eq section. ( I need need the treblie to get that string diggin sound)

SO which of these things should I try first?


----------------------------------------------

1.

" I think you could open the preamp section, and find a coupling CAPACITOR in the signal path, and increase the value. This capacitor usually is less than 1nF. But that's a solution after we know what was happening."


2.

I reduced the hiss of my bass amp by swapping the input
TLO71/72 FET type op-amp for a NE3352/4 type op-amp.

-------------------------------------------------




More of my thoughts.

Further more I have many class A mic pre amps that are super quiet. (great river). Would it be worth while to build a jack that by passes the trace elliot pre and goes directly into the eq and then the power amp?


Thank you very much

Xbuk
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Old 18th March 2004, 01:10 AM   #5
Jay is offline Jay  Indonesia
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Use of many components along a signal path will certainly create distortion. EQ is one of terrible compensator in the audio chain. The performance will always be better if you replace critical components (usually components in the signal path) with quality parts, or better regulate the power supply.

Changing TL071/TL072 with NE5534/NE5532 IMHO will surely increase the performance (because newer and more expensive op-amps usualy have better characteristics, including Noise-To-Signal ratio). OPA627/OPA637 is a more expensive opamps, but I don't know how much increase you will gain for the money.

In treble processor like EQ, capacitor upgrade from mylar to paper (I hope it is the correct name) is a cheap upgrade but always yield big increase in performance.

If you use a treble pot, check a capacitor that connected from the pot to the ground (This is probably less than 10nF). You can change the cap with better cap or increase the value.

The idea of increasing the value is to increase the treble cut, or sending lower (than before) frequencies to the ground.

FYI, audiophiles tend to use quality parts such that there isn't much to compensate, and added compensator (like EQ or tone control) is not necessary so you get a shorter signal path. But I think your situation is in the middle. I think you can do both approaches.

Regards,
Jay
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Old 18th March 2004, 01:53 AM   #6
sreten is offline sreten  United Kingdom
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Does your bass have active EQ ?

Have you tried turning treble full on your bass rather than the preamp ?

sreten.
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Old 18th March 2004, 03:12 AM   #7
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Try grounding the input first to see if the hiss is really coming from the amp. You wouldn't beleive the amount of RF noise electric instruments pick up (i know, after shielding my guitars' cavity).
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Old 18th March 2004, 05:53 AM   #8
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Here's a silly question:

Do all TE amps of this type behave in this way or is it just yours? Can you check this out at you local music store, it might save you time and efort. If a common problem for TE, then you migh want to contact TE for advice?
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Old 18th March 2004, 12:42 PM   #9
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