Help need on Xindak XA3200MII hybrid pre-amplifier

[Mohan Siribadda]

Hi Diyaudio friends,

Dear Friends,

I have been using this amplifier for nearly 4-years without an issue. However, recently it started to give a crackling noise on one channel and later the sound coming through this channel was intermittent. When I examined the tube layout, I found two types of tubes.

One type is 12AX7 (2nos) and 12AT7 (2nos). According to forums, the out put tubes are 12AT7 and the input tubes are 12AX7

As some forums suggested that this crackling noise may be due to tube failure or dirty tube pins. As such, I removed the tubes and cleaned the tube pots and pins. However, I am not sure when re-fixing these tubes I have connected to the right pots.

As such, kindly advise me where these 12AX7 and 12AT7 are located on the circuit board. When looking from the front, is 12AX7 should be located close to the front or rear of amplifier. In other words, are 12AT7s located close to the rear panel of the amp?

I do hope you would help me to clear this doubt and look forward to hearing from you soon. I have attached the link on the photo of the xindak interior

Thanks for your support!

Have a great day!

Best regards

John M Siribaddana

Google Image Result for http://www.minhembio.com/bilder/bild/?pic_id=251597.jpg

[Mohan Siribadda]

Hi Diyers

I need your help on this. Can anyone help me to get this amp going.

Regards

[ashok]

Chances are that the 12AX7 is closer to the front of the amp. Try to trace where the signal from the volume pot goes. That will be the 12AX7.

You can alternatively check which tube is connected to the output sockets , that of course will be the 12AT7.

[Mohan Siribadda]

Dear Ashok,

Thank you very much. I checked it found that the tubes are located exactly as you have suggested. Now I need to trace why the sudden crackling noise from one channel.

Best regards

Mohan

[tricomp]

You are of course correct about tube placement.
The attached spec's sheet explains where the 12AU7 goes; at the output.

It also says that the amp uses 'five-circles precious resistors'
Now, THAT should really make an impact on sound-quality!

rgds,

/tri-comp

[Mohan Siribadda]

Thank you for sending me the spec and your point is very well taken.

I am now grappled with the crackling noise on the left channel. For your information this pre-amp is connected to two Marantz MA500 mono-blocks and wired to B&W 603S2 book shelf speakers.

I need to isolate where the problems lies along the signal path, need to check whether it is on the Marantz 500s.

What I noticed, when the power is switched on (pre and power) amps, I do not get the crackling noise, but when I play a sound source such as CD the crackling noise appears. Some times one channel is dead briefly and the sound is produced intermittently.

I do hope you can enlighten me how to get about on this to bring back the system fully operational. I do not want to blindly do anything as I do not whether due to this high crackling noise could damage the speakers.

Hope to hearing from you, by the way anyone has the schematics on this XA32000MK11 please let me know. I have tried Xindak, unfortunately they are non-responsive, may be due to Chinese New Year close by.

Thanks for your support.

Have a great day!

[ashok]

Maybe a cold solder or something causing loss of signal or power to one stage. To confirm it is not the tube , exchange the 12AX7's . Put the left tube in the right socket and the right tube in the left socket. If the problem stays in the same channel, try exchanging the 12AU7. If the problem still remains in the same channel then the problem isn't the tube. However if it does move to the other channel then one of the exchanged tubes is faulty.
Remember to turn the power off and wait a few minutes before exchanging tubes !

Check the input sockets too , and also the signals/cables coming into the amp.

[Mohan Siribadda]

Hi Ashok,

Thanks, I will do the tube swapping as you have suggested, I will give you a feedback on this. Your support is greatly appreciated.

Have a great day!

Cheers