Xiansheng 708B headphone tube amp | Page 23 | Headphone Reviews and Discussion - Head-Fi.org

dcheming · Feb 2, 2007 at 9:44 PM

"I just ordered a brand spankin' new Music Hall CD-25.2 from Underwood HiFi at a more than excellent price!"

Nice!

That should indeed be quite a bit better than your current source and that round display on the front panel kind of matches with the window in the 708B.

"I'm also going to have him throw in 4 mirror imaged Burr Brown OPA-627 opamps to replace the inexpensive 2604 opamps in the stock unit."

That's going to help a lot. They should be mounted in sockets so you'll be able to do some opamp rolling if you want to change the flavor later on. One nice thing about this player is that there's a lot of space inside so you'll have quite a bit room for things like film caps, clocks, dedicated power supplies, chassis dampening, etc.

So what's the estimated delivery time?

Chops · Feb 2, 2007 at 11:08 PM

Quote:

Originally Posted by dcheming /img/forum/go_quote.gif
"I just ordered a brand spankin' new Music Hall CD-25.2 from Underwood HiFi at a more than excellent price!"

Nice!

That should indeed be quite a bit better than your current source and that round display on the front panel kind of matches with the window in the 708B.

"I'm also going to have him throw in 4 mirror imaged Burr Brown OPA-627 opamps to replace the inexpensive 2604 opamps in the stock unit."

That's going to help a lot. They should be mounted in sockets so you'll be able to do some opamp rolling if you want to change the flavor later on. One nice thing about this player is that there's a lot of space inside so you'll have quite a bit room for things like film caps, clocks, dedicated power supplies, chassis dampening, etc.

So what's the estimated delivery time?

Hi Derek,

Yeah, I'm really looking forward to getting this cdp. And those new opamps are supposed to really help out a lot.

And you're right about there being a lot of room in these units. Depending on how difficult it looks to be in there, I might just go ahead and do a lot of those upgrades that Underwood does. Maybe I can talk Walter into writing up a list of the components that he upgrades. He mentions most of them (brands and values) on his site in the "Modifications" section. And guess what, he uses Rikens in his mods, and PC as his source! I can just go off of his mods, but do them a little at a time when funds permit.

As for its arrival, the player will be shipped out on Monday from Atlanta, GA and the opamps will also be shipped out on Monday, but from Canada.

dcheming · Feb 2, 2007 at 11:43 PM

"but do them a little at a time when funds permit."

This is the way to go since you can just work your way down the list of goodies as your wallet permits. Just stick with the simple stuff first like resistors, caps, diodes, wire, RCA jacks, etc. Of course you'll want to get used to the sound of the player before you start changing things.

"And guess what, he uses Rikens in his mods, and PC as his source!"

I also noticed the picture of the RIKENs when I was browsing his site earlier. I wonder how these compare to the Audio Note tants? I would love to put some RIKEN resistors and better opamps in my cd player now that I'm almost done with the 708B mods. It would be nice to install some more M-Caps, but on the inputs to the opamps also. Some Schottky diodes in the PS section would be a nice
simple mod too.

"As for its arrival, the player will be shipped out on Monday from Atlanta, GA"

So then you should have it by next weekend hopefully.

dcheming · Feb 3, 2007 at 1:22 AM

Quote:

Originally Posted by Chops /img/forum/go_quote.gif
Nice volume knob, too. Does that actually fit in the stock recess? Pretty slick.

This knob is from Rat-Shack. I thought the style matched since it's a tube amp and it almost does fit in the recess. It's for a 1/4" shaft so I had to wrap a single layer of electrical tape on the shaft of the ALPS to get it to be centered properly. I'm going to try to shave a bit of its OD off using my drill press as lathe to get it to actually fit into the recess.

Chops · Feb 3, 2007 at 2:11 AM

Quote:

Originally Posted by dcheming /img/forum/go_quote.gif
This knob is from Rat-Shack. I thought the style matched since it's a tube amp and it almost does fit in the recess. It's for a 1/4" shaft so I had to wrap a single layer of electrical tape on the shaft of the ALPS to get it to be centered properly. I'm going to try to shave a bit of its OD off using my drill press as lathe to get it to actually fit into the recess.

Ah... So you're going to attach the knob to a drill bit, turn the drill press on and hold some sandpaper around the rim of the knob to file it down some? Pretty nifty!

dcheming · Feb 3, 2007 at 3:00 AM

Quote:

Originally Posted by Chops /img/forum/go_quote.gif
Ah... So you're going to attach the knob to a drill bit, turn the drill press on and hold some sandpaper around the rim of the knob to file it down some? Pretty nifty!

One step above that, I used my Ghetto Lathe

:

I took off about 0.008" and the knob does indeed fit into the recess now, but I didn't shorten the ALPS shaft enough to allow the knob to go much further in than it already did before. I really don't want to cut the shaft even shorter just to fit this crappy Rat-Shack knob, so I'm going to look for a better quality knob in this style to work with first.

Chops · Feb 3, 2007 at 5:57 PM

Just put in another order of parts for the little 708B at PC.

Input/Output:

TANTALM - 62762 10R 2 watt $12.95 x2
TANTALM - 62712 1K 1/2 watt $4.75 x2

PS:

DIODES - 56739 Vishay-Telefunken SF4007 $0.35 x2

Anode Resistors:

KIWAME- 66220 33K 2 Watt $1.05 x2

The rest:

PRP - 50324 1K0 1 Watt $0.65 x2
PRP - 64726 1M0 0.5 Watt $0.45 x4
PRP - 70164 200R 0.5 Watt $0.45 x2
PRP - 62501 220R 1 Watt $0.65 x2
PRP - 50094 100R 0.5 Watt $0.45 x4

Miller-8 · Feb 3, 2007 at 10:20 PM

I have one of these anyone know how to stop it making horrible noises when you plug the headphones in?

Also is it possible to have sound just come out the headphones rather than both the headphones and speakers? Just now I have to turn my power amp off when I want to listen to headphones.

Chops · Feb 3, 2007 at 11:30 PM

Quote:

Originally Posted by Miller-8 /img/forum/go_quote.gif
I have one of these anyone know how to stop it making horrible noises when you plug the headphones in?

Also is it possible to have sound just come out the headphones rather than both the headphones and speakers? Just now I have to turn my power amp off when I want to listen to headphones.

Mine doesn't make any noise when I plug my headphones in or out, so I don't know.

The preamp output can not be muted, at least not in stock form. So unless you feel like modding the 708B, you'll just have to keep powering down your amp.

Miller-8 · Feb 3, 2007 at 11:40 PM

I am asking about mods here.

dcheming · Feb 4, 2007 at 12:07 AM

"I have one of these anyone know how to stop it making horrible noises when you plug the headphones in?"

Are you referring to the loud pops and crackles as you first plug in the headphones? I built a 1/4" TRS plug that has a 300Ω resistor in each channel that goes to ground. I keep it in the HP jack of the amp while it's warming up and remove it when I finally do plug in my headphones. There is only a very slight click heard upon insertion of the HP when using the dummy-load plug this way.

"Also is it possible to have sound just come out the headphones rather than both the headphones and speakers?"

As Chops said, you'd have to install a little switch to mute the pre output.

zer061zer0 · Feb 4, 2007 at 4:54 AM

Miller, I would suggest that u switch off the power amp. I did exactly wat u have done. Unless u woud like to try adding a switch..

Miller-8 · Feb 13, 2007 at 6:59 PM

I'm going to do my first mod - the volume pot. I know a lot of people have fitted an Alps Blue, i was wondering if the Alps Black RK40 would fit ok? Or a TKD?

Chops · Feb 13, 2007 at 8:37 PM

Quote:

Originally Posted by Miller-8 /img/forum/go_quote.gif
I'm going to do my first mod - the volume pot. I know a lot of people have fitted an Alps Blue, i was wondering if the Alps Black RK40 would fit ok? Or a TKD?

Don't know for sure if the Black Beauty would fit or not. Probably so, but awfully tight, and probably overkill for this particular amp.

drarthurwells · Feb 13, 2007 at 10:10 PM

Has anyone replace the Chinese rectifier 6Z4 tube with the USA 6X4?

You need to switch two wires in the tube socket.

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.

Changing my rectifier tube in my preamps, from a Chinese tube to a USA 5Z4 tube, improves the sound considerably.

Old USA 6X4 tubes are readily available.

Will some report on which wires to switch in the tube socket? I will send a GE 6X4 to someone wishing to try this for $7 total shipped anywhere, if they report on the result.

dcheming

100+ Head-Fier

Chops

500+ Head-Fier

dcheming

100+ Head-Fier

dcheming

100+ Head-Fier

Chops

500+ Head-Fier

dcheming

100+ Head-Fier

Chops

500+ Head-Fier

Miller-8

100+ Head-Fier

Chops

500+ Head-Fier

Miller-8

100+ Head-Fier

dcheming

100+ Head-Fier

zer061zer0

100+ Head-Fier

Miller-8

100+ Head-Fier

Chops

500+ Head-Fier

drarthurwells

Headphoneus Supremus

Users who are viewing this thread