[Bosk]

I want to start replacing those pots. And perhaps get good regulators. Any idea where to get them?. Looks like the power supply caps are smaller now¿?.

I'm actually not sure regarding high-quality replacements for those pots but if anyone here knows where to source some I'd be interested in replacing those on my B4-X.

My stock caps were Rubycons of some sort, but its impossible to know if they were genuine or counterfeit. They looked identical to yours.

 

[Bosk]

Just thought I'd post a photo of my B4-X with my new DX300, and brand new 8-core 99% silver 1% gold CEMA interconnect with paladium-plated plugs. There's now abundant detail with neglibable fatigue, bass is a tad overpowering but I'm hoping that dies down as the new cable burns in.

 

[alvaroenoht]

Just thought I'd post a photo of my B4-X with my new DX300, and brand new 8-core 99% silver 1% gold CEMA interconnect with paladium-plated plugs. There's now abundant detail with neglibable fatigue, bass is a tad overpowering but I'm hoping that dies down as the new cable burns in.

how do you charge the battery?

 

[Bosk]

how do you charge the battery?

There's a cable that plugs into the output socket of the 5500 mAh battery underneath the B4-X, the other end is soldered to the B4-X board where the stock battery was plugged in. I disconnect that cable from the battery and connect the wall plug charger in its place to charge it. Which allows me to keep a spare battery on hand.

 

[povidlo]

I'm looking at Burson V5i opamps for Little Bear B4-X.

I need 2 x Dual opamps, right?

Has anyone ordered from diyaudiostore.com, is it legitimate? It works out cheaper delivered than ordering from Burson directly.

Thanks in advance.

 

[fabien32]

I need 2 x Dual opamps, right?

Yes

diyaudiostore.com, is it legitimate?

I didn't buy from them, but from what I heard they are legitimate

 

[Bosk]

Well somehow I ended up killing my backup B4-X after fooling around with the power-supply, I'm not exactly sure how. One channel is dead and it definitely wasn't an op-amp that was totalled. This is why I bought two amps I guess.

Anyway I stripped the board for parts to keep as backups for my main B4-X, and de-soldered everything. I took a photo of the stripped board which may be useful to others here as a reference. Mine was purchased this January on Ebay so it may be the most recent "revision" as the tubes are different from the earlier version.

As you can see from the PCB, its pretty difficult to tell exactly how and through what the signal reaches the output 2.5mm jack. I also suspect the output signal is going through the second set of 2.2uF film caps (why else would they be there?) but can't tell for sure. I would love to hear anyone's input on that as I'm considering replacing both sets of film caps on my main B4-X.

 

[alvaroenoht]

Well somehow I ended up killing my backup B4-X after fooling around with the power-supply, I'm not exactly sure how. One channel is dead and it definitely wasn't an op-amp that was totalled. This is why I bought two amps I guess.

Anyway I stripped the board for parts to keep as backups for my main B4-X, and de-soldered everything. I took a photo of the stripped board which may be useful to others here as a reference. Mine was purchased this January on Ebay so it may be the most recent "revision" as the tubes are different from the earlier version.

As you can see from the PCB, its pretty difficult to tell exactly how and through what the signal reaches the output 2.5mm jack. I also suspect the output signal is going through the second set of 2.2uF film caps (why else would they be there?) but can't tell for sure. I would love to hear anyone's input on that as I'm considering replacing both sets of film caps on my main B4-X.

Thank you for that photo, I just realize that the balance pots are not in the one at the side of the tubes, right channel is on the side. left channel is below the tube

Attached an overlay that shows the circuit so we can see the connections better

 

[Bosk]

Thank you for that photo, I just realize that the balance pots are not in the one at the side of the tubes, right channel is on the side. left channel is below the tube

Attached an overlay that shows the circuit so we can see the connections better

Fantastic and much appreciated alvaroenoht.

I'm still slightly confused looking at the circuit, would you say the signal passes through all four 2.2uF film caps and all four 27R resistors?

 

[alvaroenoht]

Fantastic and much appreciated alvaroenoht.

I'm still slightly confused looking at the circuit, would you say the signal passes through all four 2.2uF film caps and all four 27R resistors?

yes, the they are in the input and output,, I will try to figure out the schematics... last night I adjusted the pots,, the vcc pot is for the plate current, I adjusted them and sound improved a lot!. perhaps getting a better pots can make a significant difference. ..

 

[alvaroenoht]

Thank you for that photo, I just realize that the balance pots are not in the one at the side of the tubes, right channel is on the side. left channel is below the tube

Attached an overlay that shows the circuit so we can see the connections better

also noticed that the dc to dc converters are designed to be different brands,, is clearly written on the the plate golden sun and morn sun.. I wonder why they are not matched.

 

[DBaldock9]

yes, the they are in the input and output,, I will try to figure out the schematics... last night I adjusted the pots,, the vcc pot is for the plate current, I adjusted them and sound improved a lot!. perhaps getting a better pots can make a significant difference. ..

Take a look back at this post, which contains a circuit diagram of the original B4 amp -
https://www.head-fi.org/threads/portable-tube-amp-from-china.626237/post-14511729
Four posts below that, there's a modified circuit, where the author put regulators on the tube heaters.

The balanced B4-X is based on original schematic, with some changes, to add the second op-amp.

 

[Bosk]

yes, the they are in the input and output,, I will try to figure out the schematics... last night I adjusted the pots,, the vcc pot is for the plate current, I adjusted them and sound improved a lot!. perhaps getting a better pots can make a significant difference. ..

Thanks, in that case I will replace all four 2.2uF caps.

I'm definitely keen to replace the trimpots but don't know what to replace them with.

 

[Bosk]

Oh and just an idea I had, would it be possible to replace the 100K volume pot with two fixed resistors, one for each channel?

That way I could install resistors to provide the volume level I most commonly use on the pot (about 10 o'clock) whilst adjusting it on the DAP, and hopefully gaining a big increase in sound quality as I've read in so many places that volume pots, particularly cheap ones, are great for killing sound quality. I could install a stepped-attenuator but there's really only one volume level my pot is ever set to, two fixed resistors would be far cheaper and possibly sound better.

 

[alvaroenoht]

Oh and just an idea I had, would it be possible to replace the 100K volume pot with two fixed resistors, one for each channel?

That way I could install resistors to provide the volume level I most commonly use on the pot (about 10 o'clock) whilst adjusting it on the DAP, and hopefully gaining a big increase in sound quality as I've read in so many places that volume pots, particularly cheap ones, are great for killing sound quality. I could install a stepped-attenuator but there's really only one volume level my pot is ever set to, two fixed resistors would be far cheaper and possibly sound better.

I dont know the value of the resistors, but I read in this thread that vishay are a good brand