[El Condor]

Quote:

Originally Posted by SonicDawg /img/forum/go_quote.gif Hmmm... to me the LM4562 beats the DY2000/2604 by quite a margin. The bass quality improved quite a lot in my setup, though I must admit that the highs get a bit clearer, but it shouldn't be too glaring.

Something to consider too, it might be the quality of your recordings. Now that I have better equipment to listen to music with, some recordings are becoming difficult to listen to because they have been badly mastered/produced; highs are harsh and unpleasant (sometimes only certain passages, sometimes the whole record). There's not much we can do about that except using low-fi commercial products to listen to music.

 

[deuginthesky]

Quote:

Originally Posted by schuang /img/forum/go_quote.gif Just got my Zhaolu 2.5A and has been playing with it for few days now. I think the manufacture is populating the wrong value of 6 WIMA caps (4700pf around OPA and 2200pf form inputs to ground) on mine and therefore the LPF frequency is rolling off around -3dB @20KHz (no problem for low freq, though). I have traced out the LPF circuitry and run simulation for it. The correct value should be 47pf around OPA and 470pf between inputs to ground, just as it has indicated on the PCB. With right caps value, the frequency response are pretty good: -3dB @1Hz & 79KHz. I have not tried the mod yet but the simulation shows me on the right direction. No wonder it sounds dull. Sean

So the yellow cap close to each OP AMP has to be replaced as well as the 4 green caps close to the Nichicon bipolar green caps. Am I true ?

 

[ast]

Quote:

Originally Posted by SonicDawg /img/forum/go_quote.gif Hmmm... to me the LM4562 beats the DY2000/2604 by quite a margin. The bass quality improved quite a lot in my setup, though I must admit that the highs get a bit clearer, but it shouldn't be too glaring.

I switched back to 2604, much better! donno if system compatibility is an issue here. I have 2.5C and only swapped out the TWO 2604's from the Headphone module. Last night at home I played around many times between LM4562 and 2604, and I confirmed what I hear. With LM4562, the "ssss..." or "ccc....." sounds from the teeth are extremely pronounced, with Shure E500 especially other headphones are not so obvious. With 2604 those sound are still audible, but MUCH natural and sounds they are supposed to be. I comppared with my Lavry DA10 as well just to make sure the source/headphone are in good shape.


So LM4562 is not for me. what other easy mod can improve the headphone amp portion of Zhaolu 2.5C ????

 

[ast]

Quote:

Originally Posted by El Condor /img/forum/go_quote.gif Something to consider too, it might be the quality of your recordings. Now that I have better equipment to listen to music with, some recordings are becoming difficult to listen to because they have been badly mastered/produced; highs are harsh and unpleasant (sometimes only certain passages, sometimes the whole record). There's not much we can do about that except using low-fi commercial products to listen to music.

you are absolutely right. this only happens to one album which is from the 70's. The sizzling treble is always there, with DA10 as well, but with LM4562 they are way too pronounced. So overall I feel more comfortable with 2604.

 

[Crow]

Mod your Zhaolu's faceplate!

I've always thought the stock faceplate looks like plastic (though it's not), so for the past few weeks I've been tweaking things. Obviously I went with the hi-fi look, which often means brushed aluminum--available at most hardware stores. So whip out the sandpaper, drill and saw, dremel, and have at it guys! It was somewhat straightforward--the black piece of aluminum behind the face piece has all the original holes, easy to use as a guide for drilling. IMO toggle switches provide superior tactile response, so the pushbutton had to go. Hex screws were used, they sound better... something about hexagonal resonance

Seriously, I'd encourage anyone to mod that faceplate--if you don't like the original, what's to loose? Google can find you companies that can cut any material to spec... like marble (my ideal mat'l)..... I'm curious to see what kinds of cosmetic mods others have done.... and does anyone know how to neatly etch / print text on aluminum?

Cheers,
Scott

 

[schuang]

Quote:

Originally Posted by deuginthesky /img/forum/go_quote.gif So the yellow cap close to each OP AMP has to be replaced as well as the 4 green caps close to the Nichicon bipolar green caps. Am I true ?

Exactly! I've done the mod and it opens up the high end even my wife can tell the difference (she always told me that all of my amps sounded the same) before and the after.

Before you mod, please make sure the yellow cap marked "WIMA 4700". 4700 is 4700pf, not 47pf (verified with cap meter). You can leave 4 green caps unmod since they only affect a little bit at the high frequency. According to my simulation, input caps (100uf) bypass won't help since it only extents the low frequency to DC (we won't hear down below 20Hz anyway). Let us know how your mod goes!!

By the way, I am using OPA211 and they sound great!! Try them out when they are available.


Sean

 

[cotdt]

That is fine work, Crow. Where did you get that faceplate?

 

[deuginthesky]

Quote:

Originally Posted by schuang /img/forum/go_quote.gif Exactly! I've done the mod and it opens up the high end even my wife can tell the difference (she always told me that all of my amps sounded the same) before and the after. Before you mod, please make sure the yellow cap marked "WIMA 4700". 4700 is 4700pf, not 47pf (verified with cap meter). You can leave 4 green caps unmod since they only affect a little bit at the high frequency. According to my simulation, input caps (100uf) bypass won't help since it only extents the low frequency to DC (we won't hear down below 20Hz anyway). Let us know how your mod goes!! By the way, I am using OPA211 and they sound great!! Try them out when they are available. Sean

On mine, the yellow cap seems to be 470pf and should be 47pf. I am trying to find Wima FKP2 47pF, but they seem very hard to find.
I am wondering about using 47pf polystyrene caps if I do not manage to find FKP2, this kind of cap is said to be good in audio applications, but it may affect the balance of the output stage.
I also have 1000pF polystyrene caps (LCR brand FSC type 160V with 2,5% tolerance) that could replace some green 1000pF Wimas, but still with a possible balance issue.

What is your guess ?

 

[schuang]

Quote:

Originally Posted by deuginthesky /img/forum/go_quote.gif On mine, the yellow cap seems to be 470pf and should be 47pf. I am trying to find Wima FKP2 47pF, but they seem very hard to find. I am wondering about using 47pf polystyrene caps if I do not manage to find FKP2, this kind of cap is said to be good in audio applications, but it may affect the balance of the output stage. I also have 1000pF polystyrene caps (LCR brand FSC type 160V with 2,5% tolerance) that could replace some green 1000pF Wimas, but still with a possible balance issue. What is your guess ?

What a sloppy manufacture! I guess they just get whatever they have and put them in. No QA what so ever.
BTW, I use Silver-Mica on mine and they seems to do the job. Again, you don't have to replace 4 green caps, but the correct value should be 470pf if you really want to. Yellow caps is the bottle neck for the entire signal chain.

Sean

 

[Crow]

Quote:

Originally Posted by cotdt /img/forum/go_quote.gif Where did you get that faceplate?

Ace Hardware, but I've also seen them at Home Depot. They sell it as 2 inch by about four foot pieces, so there are a few chances to get it right. The width was already perfect for the Zhaolu, so no extra cutting there.

Ace also had tempting billets of stainless steel, but there was no way I could machine that myself...

Now all it needs is something on the right side--text or a small insignia or something--to balance it out.

 

[snowball_rx-7]

should get a hold of the guy who did AMB's faceplates.

 

[ckhaber]

Replaced my Zapfilter PSU with the new 56 0hm resistors and guess what,no hum.Also upgraded both power supplies with some Black Gates that i found on sale.Happy camper now with out that dreaded hum.Was going to post a couple of pics but cant seem to get my file down to the max. 25k.How are you guys posting such large files?Chris.

 

[Crow]

Quote:

Originally Posted by ckhaber /img/forum/go_quote.gif How are you guys posting such large files?Chris.

Try http://imageshack.us/
Just upload whatever size image and then link directly to it in your post.

 

[deuginthesky]

Quote:

Originally Posted by schuang /img/forum/go_quote.gif What a sloppy manufacture! I guess they just get whatever they have and put them in. No QA what so ever. BTW, I use Silver-Mica on mine and they seems to do the job. Again, you don't have to replace 4 green caps, but the correct value should be 470pf if you really want to. Yellow caps is the bottle neck for the entire signal chain. Sean

If you look carefully, you will notice that many times, caps are not what is writen on the board. Capacitance is higher, same happens on the headamp board as well as power board (not an issue there, the snubber can handle it).

The 4 black electro caps on the analog stage also have higher capacitance than what is written on the board, I don't know if it badly affects the signal.

I have 1000pF audio grade polystyrene caps (LCR FSC praised by humblehomemadefhi test), is there a way to reduce their capaitance to 470pF ?

 

[cotdt]

Quote:

Originally Posted by deuginthesky /img/forum/go_quote.gif I have 1000pF audio grade polystyrene caps (LCR FSC praised by humblehomemadefhi test), is there a way to reduce their capaitance to 470pF ?

Put two of them in series.