No bass/treble from Yamaha amp

[ifsixwasnin9]

Yamaha AX-596 amp bass and treble never worked. It's about 15 years old. Amp does have sound. What could be wrong? Audio repair store in Baltimore charges $100 for diagnosis and don't know if it's worth it. Could problem be expensive?
It has a Natural bypass switch which bypasses all controls but when I turn it off bass/treble/loudness never worked.
I like the amp a lot and drives my JBLs well.
I have very little money because I'm on disability. Repair could be more than I paid for it new.

 

[Mikado463]

so for 15 years 'it' never worked ??? how the heck did it 'drive your JBL's well' ??

Hopefully the AVR crowd here can help you out .........

 

[TLS Guy]

Yamaha AX-596 amp bass and treble never worked. It's about 15 years old. Amp does have sound. What could be wrong? Audio repair store in Baltimore charges $100 for diagnosis and don't know if it's worth it. Could problem be expensive?
It has a Natural bypass switch which bypasses all controls but when I turn it off bass/treble/loudness never worked.
I like the amp a lot and drives my JBLs well.
I have very little money because I'm on disability. Repair could be more than I paid for it new.

I have had a look at the circuit. It is from the days where there were service manuals published. The first thing to check is that the jumpers are connected between the pre-out and the power amp in. If the tone control is on bypass then the input stage is connected to the power amp bypassing the tone control circuits. So look at the pre outs and the amp in RCA sockets, there should be a metal jumper between them. If there is not, use RCA plugs connected with audio leads. If the jumpers are there, then most likely one of two ICs has failed. The tone control circuit is an IC, and this could have failed, there is also an IC buffer amp in the return from the tone control circuit to the power amp section which could be a point of failure.

If the jumpers are connected, then I doubt the amp is fixable as the ICs are probably NLA by now. The failure of your unit has to be one of those three possibilities.

If the jumper are there, then we can see if the ICs are available.

 

[ifsixwasnin9]

What is "IC"? Jumpers are connected.
If I bought a Loki Mini EQ would that give me bass and treble control? Or would that add more problems and decrease quality of sound?

 

[isolar8001]

What is "IC"? Jumpers are connected.
If I bought a Loki Mini EQ would that give me bass and treble control? Or would that add more problems and decrease quality of sound?

"IC" stands for "Integrated Circuit".
If TLSGuys suspicions are correct (and they usually are), that unit needs repair if the parts are available.
You might pay 100 dollars for a diagnostic just for them to tell you they cant get the parts.

That will surely cost way more than the EQ you speak of which will not decrease your sound quality.
Just insert it with two stereo RCA cables where the jumpers should be on the back of the Yamaha.

 

[TLS Guy]

"IC" stands for "Integrated Circuit".
If TLSGuys suspicions are correct (and they usually are), that unit needs repair if the parts are available.
You might pay 100 dollars for a diagnostic just for them to tell you they cant get the parts.

That will surely cost way more than the EQ you speak of which will not decrease your sound quality.
Just insert it with two stereo RCA cables where the jumpers should be on the back of the Yamaha.

That is his best and cheapest solution, may be. The problem is that if it is the IC driving the tone control circuit that is bad and not the buffer amp, then there will be no output at the jumper terminals. The straight connection bypasses the whole tone control section and the preamp output is right before the buffer amp. So investing in an equalizer has about a 50/50 chance of working.

 

[TLS Guy]

That is his best and cheapest solution, may be. The problem is that if it is the IC driving the tone control circuit that is bad and not the buffer amp, then there will be no output at the jumper terminals. The straight connection bypasses the whole tone control section and the preamp output is right before the buffer amp. So investing in an equalizer has about a 50/50 chance of working.

I have to correct myself. An equalizer in the loop has zero chance of working and the Eq would need both those ICs to be functional. It needs one to give it input and the other to get the output to the power amp.

 

[isolar8001]

I have to correct myself. An equalizer in the loop has zero chance of working and the Eq would need both those ICs to be functional. It needs one to give it input and the other to get the output to the power amp.

He said the jumpers are there (they have to be) and the amp is working other than tone controls....that would mean that an EQ placed in lieu of the jumpers should work.
Some Yamahas like my old CR-1020 had a coupler switch (that was on by default) in addition to the pre-out and main-in.
I can see the IC's causing a problem in that case, but his AX-596 doesn't have a coupler...there has to be a signal being fed to the main-in to get sound at all.

 

[TLS Guy]

He said the jumpers are there (they have to be) and the amp is working other than tone controls....that would mean that an EQ placed in lieu of the jumpers should work.
Some Yamahas like my old CR-1020 had a coupler switch (that was on by default) in addition to the pre-out and main-in.
I can see the IC's causing a problem in that case, but his AX-596 doesn't have a coupler...there has to be a signal being fed to the main-in to get sound at all.

It won't as it is a very odd circuit I have not seen before. When the receiver is in straight mode, the preamp tone control section is totally by passed. The pre out comes from the independent tone control section, and the in goes straight to the power amp. So you could connect another preamp to the power amp via the amp ins, but the preouts will be dead on this unit.

 

[highfigh]

Yamaha AX-596 amp bass and treble never worked. It's about 15 years old. Amp does have sound. What could be wrong? Audio repair store in Baltimore charges $100 for diagnosis and don't know if it's worth it. Could problem be expensive?
It has a Natural bypass switch which bypasses all controls but when I turn it off bass/treble/loudness never worked.
I like the amp a lot and drives my JBLs well.
I have very little money because I'm on disability. Repair could be more than I paid for it new.

Have you tried using the Pure Direct switch in both positions?

Make sure the source cables aren't connected to the Output jacks- I have seen that many times over the decades, with varying results.

Table Of Contents; Features - Yamaha AX-596 Owner's Manual [Page 5]

View and Download Yamaha AX-596 owner's manual online. Yamaha Stereo Amplifier Owner's Manual. AX-596 amplifier pdf manual download. Table of Contents: Caution - Page 6; Notes About The Remote Control - Page 7; Controls And Their Functions - Page 8; Connections - Page 11; Operation -...

www.manualslib.com

 

[highfigh]

That is his best and cheapest solution, may be. The problem is that if it is the IC driving the tone control circuit that is bad and not the buffer amp, then there will be no output at the jumper terminals. The straight connection bypasses the whole tone control section and the preamp output is right before the buffer amp. So investing in an equalizer has about a 50/50 chance of working.

I would bet that the IC might show some other symptom, other than the EQ not working. Not passing sound and distortion/noise are some of them. Did you see part numbers for the IC's?

If there's no output at the jumpers, there would be no output from the output section- there's no switch to send the signal through the pre out or to bypass it. The two easy tests would be to remove one and send the signal to something that can accept it and use a phone or walkman as a source so the signal can be injected at the Power Amp input- maybe a friend can do this for the OP.

 

[highfigh]

He said the jumpers are there (they have to be) and the amp is working other than tone controls....that would mean that an EQ placed in lieu of the jumpers should work.
Some Yamahas like my old CR-1020 had a coupler switch (that was on by default) in addition to the pre-out and main-in.
I can see the IC's causing a problem in that case, but his AX-596 doesn't have a coupler...there has to be a signal being fed to the main-in to get sound at all.

That set of jacks is labeled 'Coupler'.

 

[TLS Guy]

That set of jacks is labeled 'Coupler'.

View attachment 71921

The problem is that the direct switch bypasses the whole tone control section. The preouts come directly off the tone control section. In his situation this obviously is not working. It won't be the passive elements but the ICs associated with it.

 

[isolar8001]

It won't as it is a very odd circuit I have not seen before. When the receiver is in straight mode, the preamp tone control section is totally by passed. The pre out comes from the independent tone control section, and the in goes straight to the power amp. So you could connect another preamp to the power amp via the amp ins, but the preouts will be dead on this unit.

That is very strange !

 

[ifsixwasnin9]

Yes, I've tried Pure Direct switch off and on and get no tone controls.
My CD player is plugged into CD outputs on the amp. Not sure what you mean by "source cables".
I have to go thru manual. Does the manual explain what IC is? I don't know what IC means.
I did use a Carver Preamp for years (and loved it because it had Midrange control) with this Yamaha amp and used Carver tone controls but people here told me that was VERY stupid on my part so I sold the Preamp for $235!
Now I'm thinking of buying an inexpensive EQ but I am on disability and can't afford much because I'm in debt!
I contacted Loki Support and asked if I could use an EQ with my amp and they gave me two different answers: "Yes I can", and "No I can't". They have their heads up their *.

 

[Trebdp83]

Yamaha AX-596 amp bass and treble never worked. It's about 15 years old. Amp does have sound. What could be wrong? Audio repair store in Baltimore charges $100 for diagnosis and don't know if it's worth it. Could problem be expensive?
It has a Natural bypass switch which bypasses all controls but when I turn it off bass/treble/loudness never worked.
I like the amp a lot and drives my JBLs well.
I have very little money because I'm on disability. Repair could be more than I paid for it new.

What kind of devices do you have connected to the unit? How is each device connected to the Yamaha?

Assuming the Yamaha is fully functional, tone controls will not work in a few instances. If the Pure Direct function is ON, tone controls will be bypassed for every input source device.

If there is only a single external device in the system and it is connected to the CD/DVD input ports, turning the CD/DVD DIRECT AMP function ON will bypass tone controls.

If either the Pure Direct or CD/DVD DIRECT AMP function is ON, the PRE OUT/MAIN IN ports are bypassed.

The TAPE MONITOR feature of some units is not present here to use with a connected equalizer. So, an equalizer used here would have to be connected to the PRE OUT/MAIN IN ports. The PURE DIRECT AND CD/DVD DIRECT AMP functions bypass the PRE OUT/MAIN IN ports and must be turned OFF when using an equalizer.

Additionally, when using an external processor or even an older TV with analog output ports connected to the MAIN IN ports, all control functions will be bypassed and volume and any tone settings will be made by the external device.

As always, incomplete system information means anybody attempting to help will be shooting in the dark. It is essential for posters to provide any and all information concerning each and every device as well as each and every setting in a system.

In the time it took me to post, additional information about the system has been posted. More would be helpful still.

 

[ifsixwasnin9]

I have CD player and turntable connected to amp's RCA outputs and amp Preouts connected with jumpers.
I have a mechanical engineering degree and struggled thru EE 101! I hated Penn State with a passion! I worked for USAF in NM at High Speed Test Track and it was a disaster for me. Coworkers were jerks.

 

[isolar8001]

I have CD player and turntable connected to amp's RCA outputs

That would be the amps RCA INPUTS, not outputs.

 

[highfigh]

The problem is that the direct switch bypasses the whole tone control section. The preouts come directly off the tone control section. In his situation this obviously is not working. It won't be the passive elements but the ICs associated with it.

Can you post the schematic? I don't remember seeing a product that blocked the pre outs with tone controls bypassed. I can understand why they might do that, but it certainly makes it less useful.

 

[highfigh]

I have CD player and turntable connected to amp's RCA outputs and amp Preouts connected with jumpers.
I have a mechanical engineering degree and struggled thru EE 101! I hated Penn State with a passion! I worked for USAF in NM at High Speed Test Track and it was a disaster for me. Coworkers were jerks.

And I addressed the connections from the source devices (CD, turntable, DVD, etc)- Source device signal path goes from OUTPUT to preamp INPUT. You may hear the music, but not much will work properly if your signal path is wrong. Out ALWAYS goes to IN. Make sure the connections are correct- I have actually seen people who worked i n AV connect equipment that way and it doesn't work.