[Ideal]

Quote:

Originally Posted by Agnostic /img/forum/go_quote.gif I tried replacing the 6N3 with a russian 6N3P-EV(EB) but they increased the buzz and didn't improve the sound. Also tried replacing the 6n11's with two Sylvania JAN 6DJ8 but one channel was much louder than the other. Anyway they didn't seem to have a very big effect on the sound signature. .... The Russian 6n23p-eb(ev) is supposed to be a good replacement for the 6n11 I read but my experience with the Sylvania 6DJ8 made me feel sound quality would not improve greatly from replacing the 6n11's.

You couldn't be more wrong!
The 6N11's/6922's do a lot for the sound image, I won't say what I've replaced mine with but I can tell you this, it sure isn't Sylvania.
I like open and dimensional sound, Sylvania and RCA have a closed boxy claustrophobic type sound.

As for the 6N3J, I use the stock one, as I have been unable to find a suitable replacement. You just balance it out by choosing other E88CC/6922/6N11's.

When I tried LM Ericsson 396A instead of 6N3J all I got was buzz, just like you experienced.
I think the 6N3J may be "primed" at it's max operating limit, and that probably exceeds 396A/5670.

 

[mojolo]

would you mind telling us which 6DJ8/6922/7308 tubes you are using?

i have some Amperex Holland Orange Globe Halo O Getters and Philips Holland A-Frames ecc88's/d6j8's. have you any experience with these? (i just ordered the xiang sheng and it is on the way)

For the 6N3, did you try any other versions such as a 6n3p-ev or Sylvania/GE/Raytheon/RCA 5670/2c51 tubes?

I think the date code is also important for these as post 1960's Sylvania 5670 are not supposed to be that great while 1950's Sylvania's (possibly early 60's) are supposed to be better. Same goes for GE and RCA. of course it all depends on how well they specifically match to the xiang sheng.

 

[lordmozilla]

Hey,

I have followed and read your thread and have been very impressed with your modding, and have ended up buying a 708B in order to have a play with headphone amps.

I have been looking at parts to buy and have decided to go with an alps blue velvet pot, but you mention the mundorf ZN caps and would like to get them. However i can only find 250V 0.22uF versions. Or i can get the mundorf supreme caps rated 1200V.

I dont know many audiophile electionic shops but there is this one amplifier valve kits, HIFI pre-amplifiers, speaker kits, upgrade components in the UK, feel free to direct me to another, but they do not seem to stock caps that do not cost too much and have the right rating.

Also for resistors, they stock the Kiwame in 2W but would you recomend getting 0.5W resistors such as the Shinkoh. Are the kiwame good resistors for this use?

These are the changes i was going to do now, and maybe get to tube rolling later on, but i have had a play with it stock and would like to try it differently now.

Thanks for all the real clear pictures and instructions,
Brendan

 

[zer061zer0]

a little update on my XS, which i have recased, not the best of works, but i am very comfortable with the uniform look given to my amps

 

[lordmozilla]

Hey,

Just for reference i have the UK version of the 708B

Nearly finished modding my 708B. I replaced teh front 6n3 with a 6n3p-IV cryo treated (the cryo bit was cheap so ), changed all the audio resistors with kiwame 2W resistors and changed the phono plugs (i didnt think i would but they are really bad). Also changed to pot to an alps blue velvet. Managed to keep the stock volume knob by just mashing up the knob with a screwdriver to make it a tight fit.

Removed the wima caps for the headphone path - not the preamp with LCR 630V 022uF caps.

Also i removed the whole front window assembly as i just didnt see the point.

All that needs doing is replacing the two driver tubes with a pair of matched NOS 6N1P-Vi tubes and adding two 3pDt switches in order to switch between inputs and another to remove the noise from having a preamp plugged in when listening to headphones.

I'm kinda having trouble sourcing these so i'll have to look a little harder. I'm also going to to try to replace the headphone jack but thats for a little later.

also changed the power cord with a tagan EMI shielded cord - the stock power cord really deserved to die.

As for the audio change from stock to modded i dont know, i'm amazed every time I plug my headphones into this amp so i really can't say lol. I'll post some pictures later on if i remember.

 

[dcheming]

Brendan,

Glad to have you on board.

Sorry for being so late, I must have missed this thread since I don't come around here as much as I used to.

"but you mention the mundorf ZN caps and would like to get them. However i can only find 250V 0.22uF versions. Or i can get the mundorf supreme caps rated 1200V."

I wanted to go with the ZN series because they are film 'n foils, but their long size would necessitate mounting them vertically. Doing this will expose them directly to heat from the nearby tubes, especially since the ZN caps are black IIRC. This is why I went with the Auricaps since they are very short and compact so they can be easily mounted horizontally. The Mundorf Supreme caps are even longer, but at least they are white so they wouldn't absorb as much radiant heat. Of course you could also just bend the leads underneath like how I mounted the Dayton film 'n foils on my amp. BTW, Parts Connexion carries 630VDC ZN caps in 0.22uF.


Please do post some pics if you get a chance.

zer061zer0,

I like the smoked lexan cover. I'm considering doing something similar when I get around to building a new cover for mine, but with glass. Have you had any problems with overheating in that case? You could always drill some holes in the case under the PCBs to aid ventilation if so.

 

[Senad]

Could somebody tell if it is possible to remount the original knob on alps blue velvet with some tweaking (I am aware that it doesn't fit)?

 

[dcheming]

Quote:

Originally Posted by Senad /img/forum/go_quote.gif Could somebody tell if it is possible to remount the original knob on alps blue velvet with some tweaking (I am aware that it doesn't fit)?

The original knob is designed to be used on a vol pot with a splined shaft so if you found a RK27 with such a shaft it might fit. Your other option would be to fill in the webbing on the inside of the knob with epoxy or better yet JB Weld, then drill and tap a small hole for a setscrew. If you don't have the tools to do this I could do if you as long as you paid for shipping.

 

[lordmozilla]

thansk for the response, i've gone with some LCR caps that i found, they are ok. I just got my two 6n1p's in the post and man do they make such a difference, the bass is real deep now and much more present, the difference is unbelievable. Compared to swapping the 6n3 they seem to be much more worth it. I'm really surprised because I really expected there to be nothing noticeable as with the 6n3, but the difference is definitely notable.

I've also checked my heater voltage, and my 6n1p was at 6.2V. Now my voltmeter is a cheap old thing, but seems ok to me. I guess power must be quite low where i am pluging it into. I have noticed though that my board difffers in a few places from yours, especially round the PSU, where the resistors are much beefier than the ones in the pictures of the stock ones you posted.

I want to replace the output caps, but i have no idea what to use, can you make any recommendations on capacitance? I'll be using a variety of caps but wouldn't want the bass to dissapear. The stock are 120uF, so maybe just stick with that? What would you recommend from parts connexion?

also what is your opinion on changing the diodes? worth it? Also the two capacitors C9 and C8, do you think there is much point in changing them?

I think i'm going to order some mundorf caps to replace the LCR's and use the LCR's on the output.

Cheers, pics will be up tmrw hopefully.

sorry for all the questions but i am new to audio modding, but i'm loving it allready!

Brendan

 

[dcheming]

"I've also checked my heater voltage, and my 6n1p was at 6.2V. Now my voltmeter is a cheap old thing, but seems ok to me. I guess power must be quite low where i am pluging it into. I have noticed though that my board difffers in a few places from yours, especially round the PSU, where the resistors are much beefier than the ones in the pictures of the stock ones you posted."

Guess you lucked out on the heater voltage issue. The layout of the 220V version is definitely a bit different, but mostly in the PS board and in where the B+ comes into the audio board. Also every time I see the insides of one of these amps the parts are visibly different. Bargain bin level components for sure.


"I want to replace the output caps, but i have no idea what to use, can you make any recommendations on capacitance? I'll be using a variety of caps but wouldn't want the bass to dissapear. The stock are 120uF, so maybe just stick with that? What would you recommend from parts connexion?"

This is a tuff call since one wants to go big uF for good bass response, which invariably means electrolytic, but one also wants the highest SQ for this important component, which means big and expensive film caps. A while back I almost ordered a pair of 100uF Mundorf M-Caps during the 15% sale at Parts Connexion but changed my mind at the last minute. I decided that enough money has been spent on my 708B in the name of experimentation so I'm saving the good stuff for when I build a Bijou amp. So for quite a few months now I've just been using a 7.5uF Solen as an output cap. Sure there's some loss of deep bass but for the time being I feel it's worth the trade off for clarity until I build the Bijou. So it really depends on whether you want to go 'lytic or film here.


"also what is your opinion on changing the diodes? worth it? Also the two capacitors C9 and C8, do you think there is much point in changing them?"

For $0.35 each I definitely think it's worth it to replace the diodes with something like the ones I used. The contribution to better SQ that they make is probably very small, but just having a quality component there makes me feel better about safety. Which is also why I replaced C8 and C9 with something better. Piece of mind for a few bucks is worth it to me.


"sorry for all the questions but i am new to audio modding, but i'm loving it allready!"

Yeah there's definitely something truly enthralling about modifying audio equipment IMO.

 

[lordmozilla]

hey,

thanks for the response. I do have another question :

I'm guetting some small cracking on one channel. weird because its never happened since this morning and i haven't changed anythign last night when it was fine. the other channel actually does crack a tiny bit too. i'm gonna swap the tubes to see if they are the cause.

Cheers

edit 1 : its not the 6n1p

 

[dcheming]

Quote:

Originally Posted by lordmozilla /img/forum/go_quote.gif hey, thanks for the response. I do have another question : I'm guetting some small cracking on one channel. weird because its never happened since this morning and i haven't changed anythign last night when it was fine. the other channel actually does crack a tiny bit too. i'm gonna swap the tubes to see if they are the cause. Cheers edit 1 : its not the 6n1p

Did you try swapping out the 6N3 also?

 

[lordmozilla]

no i'm just at work at the moment, i'll try again when i get bak home. Only had time ot swap the 6n1.

i'm kinda hoping its the 6x4 (or 6z4 i never know which one it is!)

 

[lordmozilla]

The noise problems has nothing to do with the tubes unless its the 6z4 which i can't test. Maybe it's the pot? see the question below :

What are the side effects of removing C101 and C201 ? I don't really understand

another question is i get some noise after 13-14 o'clock which only gets worst. Could this have something to do with the new alps pot? How can it be grounded? does that mean a connection from the screw on the outer case to the ground?

Someone mentioned grounding the pot to the phono output and grounding that to the case with 10x100ohm resistors in parralel. ? Should i just do that and use 1 x 10ohm resistor thats 5W ?

 

[zer061zer0]

Check the solder points to and out of the volume pot and the wires to the RCA