Reisong A10 Single Ended Vacuum Tube Amplifier (Part 2) Balanced Headphone Out Modification

Continue from the previous post about the introduction of this great affordable vacuum tube amplifier, so in this post, I will share my first modification to the layout of this amplifier.

This layout modification is quite radical, because I will put balanced headphone out via 4 pin XLR in this amplifier and defeat the speakers out. The reason for this is this amplifier dimension is small enough for the headphone amplifier compare if I am using the KT88 amplifier here.

We never see Reisong build amplifier for headphones, so I should make one with this unit.

Keep reading.

This what I will doing with this Reisong A10 amplifier:

1. Change from ultra-linear to triode

2. Remove the output common ground

3. Bypass the input selector

4. Replace the potentiometer

5. Fix the solder joint

6. Upgrading the components

7. Install the 4 pin XLR socket

The step 7 can be obey if you want using this amplifier as speaker amplifier instead of balanced headphone amplifier.

Start with the step 1 is changing the default setting of this amplifier from ultra-linear to triode.

The triode will give better sound compare to the ultra linear. The draw-back for triode is the power output will be lower compare when in ultra linear mode.

You can check your speakers sensitivity before doing this modification. If you have speakers with sensitivity above 90 dB, then this modification might be suitable for you.

Because I will using this amplifier for headphones, so the power output will not become the issue.

How to change from the ultra-linear to triode is very simple. Take a look to the output transformer connection to the PCB, then I just need to remove the blue cable and put the jumper wire between point "G" to "P".

Step 2 is removing the common output ground.

I don't know why Reisong A10 is connecting both output ground and joint them to the common ground. With separate the output ground, then each output will not have any connection at all. This can improve the stereo separation and resulting for better sound-stage.

I only remove the jumper at the both negative banana plugs and the cable connecting to the common ground at the PCB.

Step 3 is bypassing the input switch selector.

This step can be obey if you still need this input selector. For me, I don't need this selector at all. The switch can be degrade by time and makes another trouble someday. So I bypass it to just only a pair of stereo input only.

Step 4 is replacing the potentiometer.

The potentiometer will be replace to the better quality. I always using ALPS blue if the space inside the casing is not an issue. I think this is a great way to improve the sound quality by changing the potentiometer for the volume control.

To do this, first of all, the front aluminum knob should be remove by using hex key, then the potentiometer nut can be remove completely.

I also replace the existing signal cable from the RCA jacks to the potentiometer using higher grade audio cable. It is the Canare L2B2AT cable.

I adding another 1K ohm resistor in series between the center pin of the potentiometer to the input at the PCB to preventing the input of the vacuum tube from oscillating.

Step 5 fix the solder joint.

No wonder for the mass production unit like this, the solder joint mostly applied less. Like what I have here, the solder joint at the vacuum tube socket pins are not properly covered with solder tin and for the better reliability, this solder joint should be fix.

Step 6 is upgrading the components.

Like on the previous post, all of the resistors use in this amplifier are all low quality. I try to replace them and all components as much as I can.

The new resistors I use here are combine between Dale and Kiwame.

The capacitor for signal audio are replace using paper-in-oil Russian capacitor. The capacitor for cathode bias are replaced using Panasonic FC.

With all those 6 steps done, I test the amplifier with the same setup before and the sound improvement are get better.

The last step is put the 4 pin XLR balanced headphones socket.

I put this socket at the front panel. The Reisong logo should be remove first.

I have difficulty make the hole on this stainless steel casing, this material rally hard to work with. Latter I just knew that there is a special drill bit for this material.

The concept of this balanced headphones out is the same like what I built here.

I use exactly same resistor divider schematic explained on that post. The difference is those resistors divider is now install inside the unit.

I can't believe the result can be this good. This amplifier is really nice to look at.

I will not express my feeling about how this amplifier sound like in this post. Not yet. I have another things to do with this amplifier.

So see you on the next post then.

Disclaimer: Any statement and photos in this article are not allowed to copy or publish without written permission from the writer. Any injury or loss from following tips in this article is not under writer responsibility.