Remove the first uA741CP as shown in post #132.
Install an 8-pin DIP socket.
Insert TL071CP, paying attention to the chip orientation.
Repeat the signal test as per post #132.

If you haven't already, you might want Rabbitbreth to confirm the gain of the powered speaker by physically touching the input and noting the volume of the induced hum.

 

If you haven't already, you might want Rabbitbreth to confirm the gain of the powered speaker by physically touching the input and noting the volume of the induced hum.

yes , did that with first speaker test . white noise

Remove the first uA741CP as shown in post #132.
Install an 8-pin DIP socket.
Insert TL071CP, paying attention to the chip orientation.
Repeat the signal test as per post #132.

My op amps are TL072 's!! not TL 071 ..tell me 'that's ok ....its all going to be alright ' please

 

No. TL072 is not pin compatible with LM741.
Get uA741 or LM741 if that is all that is available. There are hundreds of other single op-amps that are compatible.

 

No. TL072 is not pin compatible with LM741.
Get uA741 or LM741 if that is all that is available. There are hundreds of other single op-amps that are compatible.

bugger !!.. ok . thanks Chips . more waiting . sorry about that

 

You can look up 741 compatible opamps.

 

You can look up 741 compatible opamps.

its ok . just ordered some TL071's . going to take two or three days . no 1' s and No. 2 's have always confused me

 

An old 741 and a TL071 are single opamps. A TL072 is a dual opamp (it has 2 opamps in it).
You should always read the datasheet from the manufacturer.
Guess how many opamps are in a TL074.

 

An old 741 and a TL071 are single opamps. A TL072 is a dual opamp (it has 2 opamps in it).
You should always read the datasheet from the manufacturer.
Guess how many opamps are in a TL074.

yes . I have just been reading up on op amps . 2 channels !! and a 74 has 4 channels ...ok . got my abacus out now ..should have done that before . I was shopping on a few different vendors and somehow fixated on the TL072 and ordered that one .
will the sockets be the same . ?

 

 

View attachment 306484

View attachment 306485

where is the op amp we are working with , on your schematic . ? just trying to understand why i have 5 op amps and what they do

 

The op-amps are in the signal conditioning stages, pre-amp, gain, tone controls, volume.
I have only drawn the power amp stage. There are no op-amps in the power amp.

 

The op-amps are in the signal conditioning stages, pre-amp, gain, tone controls, volume.
I have only drawn the power amp stage. There are no op-amps in the power amp.

ah . pre amp . ok . thanks for that . this harder than French .

 

For an instrument amplifier (guitar and bass) that first op-amp stage is all important.
A guitar pickup is just a passive coil in the instrument. The signal amplitude from the pickup is relatively low and is subject to noise pickup, AC hum interference in the pickup and the guitar lead to the instrument amplifier. If there is no active preamp in the guitar itself, then the preamp in the amplifier itself is critically important in amplifying the signal voltage and not any unwanted noise.

Besides being an electronics enthusiast, I am also a guitar and bass player. Not by any conscious choice of my own, I have migrated towards owning Fender Stratocaster, Telecaster, Jazz Bass, and Fender guitar and bass amps.

 

For an instrument amplifier (guitar and bass) that first op-amp stage is all important.
A guitar pickup is just a passive coil in the instrument. The signal amplitude from the pickup is relatively low and is subject to noise pickup, AC hum interference in the pickup and the guitar lead to the instrument amplifier. If there is no active preamp in the guitar itself, then the preamp in the amplifier itself is critically important in amplifying the signal voltage and not any unwanted noise.

Besides being an electronics enthusiast, I am also a guitar and bass player. Not by any conscious choice of my own, I have migrated towards owning Fender Stratocaster, Telecaster, Jazz Bass, and Fender guitar and bass amps.

well thanks for the education Mr chips .So the pre-amp section filters out noise as well as amplifying the signal? Ive been watching a few guitar pedal shows lately .simple mods one can do to my wah pedal, fix my DD3 , messing about with my four tracks and midi synth stuff . I have a few guitars , my US strat gets played daily ...mostly portable stuff as I travelled alot until the world went bonkers . so have a couple of little amps but got this bass amp for nothing so I thought i might fix it and learn something . Have been playing my bass through a guitar amp or through the DAW but I cant really feel it ...and I want to feel it!!! . A six foot Ampeg rig would be nice but the neighbours will protest I just know it .. they just wont understand .

 

I have to be careful here with what I say because there is always someone more knowledgeable who would not hesitate to correct me. The role of the preamp is to match the input impedance of the pickup while amplifying the signal. The preamp will amplify everything that it receives, including noise and AC hum. There is only so much the pre-amp can do at filtering out "noise".

 

I have to be careful here with what I say because there is always someone more knowledgeable who would not hesitate to correct me. The role of the preamp is to match the input impedance of the pickup while amplifying the signal. The preamp will amplify everything that it receives, including noise and AC hum. There is only so much the pre-amp can do at filtering out "noise".

LOL! the world is full of experts , how blessed we are .

 

I have to be careful here with what I say because there is always someone more knowledgeable who would not hesitate to correct me. The role of the preamp is to match the input impedance of the pickup while amplifying the signal. The preamp will amplify everything that it receives, including noise and AC hum. There is only so much the pre-amp can do at filtering out "noise".

Certainly correct in that the input section, with the controls that determine which bands of frequencies are amplified, tend to not amplify the unwanted signals as much. And certainly the input section must match the very low signal amplitude from the guitar pickup to the amplitude and impedance requirements of the power amplifier section. Every stage of the amplifier has a purpose, and they are not all the same. Not amplifying is functionally the same as filtering, from a different point of view.

 

I have never measured the output level of an electric guitar magnetic pickup but experts say it is much higher than the output level from a record player's magnetic cartridge. Rod Elliot (Elliot Sound Products) says the maximum output is almost 1V.
Another experts posts this preamp with very low gain:

 

I have never measured the output level of an electric guitar magnetic pickup but experts say it is much higher than the output level from a record player's magnetic cartridge. Rod Elliot (Elliot Sound Products) says the maximum output is almost 1V.
Another experts posts this preamp with very low gain:

Reading this threat I was curious, and did some looking around. There are many type of pickups, and various placements - I saw outputs quoted anywhere from 25 mV to 500 mV. And with their large inductance, the load (L+C) has a big effect on the 'brightness' of the sound. Generally recommended loads are in the 250K - 1 M range, with C minimized.

 

Electric guitar payers like a huge mid-frequency peak maybe because their speakers are no good (no tweeters) or because the players and listeners are deafened from listening to loud ROCK "music".