Xiansheng 708B headphone tube amp
Feb 13, 2007 at 11:49 PM Post #346 of 415
"Has anyone replace the Chinese rectifier 6Z4 tube with the USA 6X4?"

I'm planning on doing exactly that pretty soon. I'm just going to build a temporary adapter using a 7-pin socket and some short lengths of 18ga solid core to avoid having to modify the PS PCB at first. If the 6X4 makes a noticeable improvement then it would definitely be worth it to mod the PS board to use it permanently.


"You also need to drill a hole in the top cover to the top of the 6X4 has clearance - may need to glue a washer in place on the top cover, to surround the hole and protect the tip of the tube."

This wouldn't work since you have to slide the case on from the back. The only way to try to make it fit it is to lower the PS board as low as possible on its mounting screws. I'm looking for a low profile 7-pin socket to replace the stock one with to help get some extra clearance too.
 
Feb 13, 2007 at 11:58 PM Post #347 of 415
Quote:

Originally Posted by dcheming /img/forum/go_quote.gif
"Has anyone replace the Chinese rectifier 6Z4 tube with the USA 6X4?"

I'm planning on doing exactly that pretty soon. I'm just going to build a temporary adapter using a 7-pin socket and some short lengths of 18ga solid core to avoid having to modify the PS PCB at first. If the 6X4 makes a noticeable improvement then it would definitely be worth it to mod the PS board to use it permanently.


"You also need to drill a hole in the top cover to the top of the 6X4 has clearance - may need to glue a washer in place on the top cover, to surround the hole and protect the tip of the tube."

This wouldn't work since you have to slide the case on from the back. The only way to try to make it fit it is to lower the PS board as low as possible on its mounting screws. I'm looking for a low profile 7-pin socket to replace the stock one with to help get some extra clearance too.


I forgot about sliding on the cover from the back - I took my cover off when I got the amp and have never used it since. Makes changing tubes easy.

I'LL BUY YOUR TEMP ADAPTER WHEN YOU ARE THROUGH WITH IT.
 
Feb 14, 2007 at 12:03 AM Post #348 of 415
"I took my cover off when I got the amp and have never used it since. Makes changing tubes easy."

Hah, yeah me too, I haven't had it on since the day I got the amp. I'm thinking about crafting some aluminum side panels and going with an easily removable mesh top for ventilation. The tip of the 6X4 could then stick through if it's too tall.

"I'LL BUY YOUR TEMP ADAPTER WHEN YOU ARE THROUGH WITH IT."

Well I could easily make two of them. It would probably add about 3/4" to the height so the tube would stick out quite a bit just to let you know.
 
Feb 16, 2007 at 4:16 PM Post #351 of 415
Can anyone suggest a replacement for the 6Z4 rectifier tube? Can you use a 6X4? If not why not? How about a russian 6Ts4P?
 
Feb 16, 2007 at 4:57 PM Post #352 of 415
Quote:

Originally Posted by Miller-8 /img/forum/go_quote.gif
Can anyone suggest a replacement for the 6Z4 rectifier tube? Can you use a 6X4? If not why not? How about a russian 6Ts4P?


Dcheming just wrote this last night.

6X4 Rectifier Modification
 
Feb 16, 2007 at 6:26 PM Post #353 of 415
Yeah i already read that, doesnt explain whether there are any tubes you can just slot straight in as replacements or why the original tube has different pin locations.
 
Feb 16, 2007 at 7:56 PM Post #354 of 415
Quote:

Originally Posted by Miller-8 /img/forum/go_quote.gif
Yeah i already read that, doesnt explain whether there are any tubes you can just slot straight in as replacements or why the original tube has different pin locations.


There are no other tubes that will work in the existing circuit.
 
Feb 16, 2007 at 10:14 PM Post #355 of 415
Quote:

Originally Posted by Miller-8 /img/forum/go_quote.gif
Yeah i already read that, doesnt explain whether there are any tubes you can just slot straight in as replacements or why the original tube has different pin locations.


It's very hard finding much info on the mini 6Z4 rectifier and the same goes for finding info about its equivalents. All the new 6Z4 tubes that I've seen for sale appear to be the same low quality one I already have. So as far as I'm aware there's no other viable option for a drop-in improvement.

The 6X4 on the other hand has plenty of info available and has many nice NOS versions. It's a little tall for this application, but I don't mind that since I always have the top case off anyways. The mod to the socket in the 708B is required because in the 6X4 one of the anodes and the cathode are connected to different pins than in the 6Z4.

6z4and6x4pinoutsxo5.jpg
 
Feb 17, 2007 at 4:44 PM Post #357 of 415
Quote:

Originally Posted by Miller-8 /img/forum/go_quote.gif
Have you noticed a sound improvement so far?


It's in the other thread that I already mentioned (and linked) to you earlier.
 
Feb 18, 2007 at 3:49 AM Post #359 of 415
Quote:

Originally Posted by regal /img/forum/go_quote.gif
Would any of these chinese amps be an serious upgrade over my maxed out millett hybrid


Maybe a bit better, but not a serious upgrade IMO. I feel that a maxed out Millett would be better than a bone stock 708B, but if you were interested in modding it at all it might be a different story. I did a quick comparison between my 708B with Auricaps and ALPS and a Millett with diamond buffers at a friends house a few months back and they were very similar sounding. The Millett had tighter and deeper bass and the 708B had better midrange.

However, it was just a quick test and CD player wasn't the greatest. I'd like to be able to borrow his Millett and listen to it in my system for a few days. I've also done a lot more modifications to my 708B since then so I'd like to know how they compare now.
 
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