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The "Lovely Cube" Headphone Amp (Lehmann Black Cube Linear Clone) - Page 83

post #1231 of 1240
Quote:
Originally Posted by Tribbs View Post


WHAT 200 Ohm resistor???

The two resistors to be replaced with zener diodes are 1.1K ohm resistors: R306 and R308 as designated on the PCB of the Lovely Cube amplifier.

At number 2 and 3 at the drawed schematic, it say´s there should be trimpots at 200 Ohm with the 1K resistosr, so they will be equal to 1K1. But I guess this will not refer to the Zener mod!?

 

 

 

/ Mikael Markstrom

post #1232 of 1240
No! As far as I know, you can't have both modifications.
Either #1 OR #2 and #3.

If your DC offset is <20mV you don't need #2/#3.
Edited by Tribbs - 2/18/15 at 4:07pm
post #1233 of 1240

I've just gotten around opening my Lovely Cube Premium and I see that some components aren't the same as the others. The op amp is also different which is the LM 4562NA.

 

**added: How will the LM4562NA fare with a dual OPA627AP?

 

 

 

 

  


Edited by penmarker - 2/18/15 at 2:09am
post #1234 of 1240
Quote:
Originally Posted by penmarker View Post
 

I've just gotten around opening my Lovely Cube Premium and I see that some components aren't the same as the others. The op amp is also different which is the LM 4562NA.

 

**added: How will the LM4562NA fare with a dual OPA627AP?

 

 
 

 

 

 

 

  

 

Quote:
Originally Posted by penmarker View Post
 

I've just gotten around opening my Lovely Cube Premium and I see that some components aren't the same as the others. The op amp is also different which is the LM 4562NA.

 

**added: How will the LM4562NA fare with a dual OPA627AP?

 

 
 

 

 

 

 

  

I hav´nt tried the LM4562, altough I´m having two pcs in my shelf.

 

As far as I know, they are high end, at the same level as OPA627, even the LM4562 is much cheaper. It measuring will is used in some high end equipment such as the newer version of the Benchmark DAC1.

 

It should be well suitied for this headphone amp. The only downside may be it can feel a bit clinical/ sterile/ boring and not so much musical soul.

 

But both OpAmp´s are of much higher grade than the standard OPA2134 used in BCL - that one also measuring well but some say it sound like putting the head in a bucket; a narrower sound stage.

 

As the OpAmp is the heart in an amp, it´s a personal option what sound the best - it also affect the sound more than the DAC-IC in a DAC. My personal favourite playing in the same league as LM4562 and OPA627 (they should even be a bit better), that I´ve used widely is the TI THS4032 or two mono THS4031 with 0,1uF caps soldered to them so they will not oscillate. They´re really nice!

 

 

/ Mikael Markström

post #1235 of 1240
Quote:
Originally Posted by BlaBlaBla View Post
 


Do not plug in your headphones. This offset is almost to big for speakers!

 

1. Pull out tantalum capacitors and measure Vout. Regulator can work without Cadj (tantalums) and LM will show good Vout voltage if tantalums were bad. If you have multimeter in the same time, you can measure capacitance on pulled out tantalums. But watch out for polarity. Tantalum capacitors will blow of if there is reverse polarity for more than 2% of nominal value.

 

Yes. It is strange if measure resistance over R2 and get ringing. Probably blown tantalum. If there were zener diode instead R2 resistor, it would protect tantalum because zener diode wouldn't allow voltage over its nominal value (12V, 13V or any voltage that your zener has). Also zener wouldn't allow reverse voltage that usually kills tantalum capacitors.

 

2. If Vout is still bad (without tantalum) then you can cut out old LMs and install a new one. Leave nodes (legs from old LM) in PCB. Measure Vout again.

 

3. If Vout is still bad then you try to see what is happening with capacitors after regulator (FC). Simple test is, after turning the amplifier on, to check voltage on capacitor cap (top position where cross is - where capacitor pops if it is under great overvoltage or stress). Two capacitors must have very very low voltage on their cap (two capacitors connected after positive LM317) and two must have negative voltage close to Vout (two connected after negative LM337).

 

 

So if using a higher wattage zener, may it be enough with only 2 zener diodes (just single 1+1, not paralell 2+2), such as 13 Volt 5 Watt 1N5350B, or are they not gonna work fine in this amp replacing the standard 1K1 resistors?
 
/ Mikael Markstrom
post #1236 of 1240
Quote:
Originally Posted by mikaelmark View Post
 

 

I hav´nt tried the LM4562, altough I´m having two pcs in my shelf.

 

As far as I know, they are high end, at the same level as OPA627, even the LM4562 is much cheaper. It measuring will is used in some high end equipment such as the newer version of the Benchmark DAC1.

 

It should be well suitied for this headphone amp. The only downside may be it can feel a bit clinical/ sterile/ boring and not so much musical soul.

 

But both OpAmp´s are of much higher grade than the standard OPA2134 used in BCL - that one also measuring well but some say it sound like putting the head in a bucket; a narrower sound stage.

 

As the OpAmp is the heart in an amp, it´s a personal option what sound the best - it also affect the sound more than the DAC-IC in a DAC. My personal favourite playing in the same league as LM4562 and OPA627 (they should even be a bit better), that I´ve used widely is the TI THS4032 or two mono THS4031 with 0,1uF caps soldered to them so they will not oscillate. They´re really nice!

 

 

/ Mikael Markström

I contacted the previous owner earlier today and he confirmed that he swapped the stock OPA2134 to the LM4562 and forgot to switch it back. It sounds perfectly fine by me. I love soundstage but have a hard time discerning them properly. Up until now, all of the music I've heard from earphones/IEM/headphones sounded like they were a wall of music from the front instead of a parabolic shape (left and right sounds sound far away but gets closer to my face as they come to the middle, as opposed to front channel being further away). I've tried all setups from low to high end, it's just not very realistic to me even binaural sounds. Maybe I'm putting my expectations too high but that's how I've been hearing things.

 

The amp is fantastic, paired it up with an AK240 playing The Eagles DSD with the HD650 sounds heavenly. I really can't believe the quality of sounds I'm getting from this unit, and I got it for only around US$100 used. It was in perfect condition too.

 

post #1237 of 1240
Quote:
Originally Posted by penmarker View Post
 

I contacted the previous owner earlier today and he confirmed that he swapped the stock OPA2134 to the LM4562 and forgot to switch it back. It sounds perfectly fine by me. I love soundstage but have a hard time discerning them properly. Up until now, all of the music I've heard from earphones/IEM/headphones sounded like they were a wall of music from the front instead of a parabolic shape (left and right sounds sound far away but gets closer to my face as they come to the middle, as opposed to front channel being further away). I've tried all setups from low to high end, it's just not very realistic to me even binaural sounds. Maybe I'm putting my expectations too high but that's how I've been hearing things.

 

The amp is fantastic, paired it up with an AK240 playing The Eagles DSD with the HD650 sounds heavenly. I really can't believe the quality of sounds I'm getting from this unit, and I got it for only around US$100 used. It was in perfect condition too.

 

Nice!

 

As your LM4562 are socket mounted, you can always try with different OpAmp´s and see what you prefer.

 

I notice you´re from Malaysia, so you maybe can get OpAmp IC´s easier than here in the west.

 

Then when you are satisfied, I suggest you consider to solder the OpAmp as sockets are not the best for high end audio - I´m happy to see the incoming audio signal are soldered without sockets. And the 4 pcs 10 Ohm Dale CW-2B may get some bad sound if they´re not non-inductive as the NS -serie Ayrton Perry.

 

Also, be aware of that kind of 1/8 to 1/4 adapter, as it can really degrade the sound if the quality of it is poor.

 

I will not scary you, but those things are what I notice can reduce the sound quality.

 

 

/ Mikael Markstrom

post #1238 of 1240
I'm interested in getting the Audio-GD Moon opa, but someone pointed out how they measure badly. I'd attach the link here but I'm on my phone.

The 1/4 inch adapter is good quality so it's fine. There is a local person selling a bunch of op amps including Sun, Moon, Earth, dual 627AP, and 627BP.
post #1239 of 1240
Quote:
Originally Posted by penmarker View Post

I'm interested in getting the Audio-GD Moon opa, but someone pointed out how they measure badly. I'd attach the link here but I'm on my phone.

The 1/4 inch adapter is good quality so it's fine. There is a local person selling a bunch of op amps including Sun, Moon, Earth, dual 627AP, and 627BP.

Measures are one aspect, that can tell if a IC etc make good sound quality - but today´s OpAmp´s, DAC´s etc are mostly so high grade the small differences in THD, SN ratio, dynamic etc a normal hearing person can´t be heard any difference between them.

Then we have the listening qualities, and they will differ between person´s and what music listening to, some prefer other qualities then some do; some like a warm sound, maybe with a heavy bass, as other´s prefer a clean sterile sound with a lot of treple. Some want big soundstage with good instrument separation as other´s just prefer a "right in the face" sound.

 

So it´s difficult to say what OpAmp is the best, but just google for the Texas Instrument´s THS4032 (stereo) or THS4031 (mono), as many people like it so much and also prefer it above the OPA627 - I have implement it in many of my gears as CD-player´s, Squeezebox, DAC´s, headphonea amp´s, X-Fi sound card´s etc, and like it a lot!

 

But if you want seriously good sound quality and want to mod your Lovely Cube, I suggest you first of all consider to change the two blue cubed DC blocking cap´s for the incoming signal and maybe also the parallell yellow at side of them, as they may affect the sound a lot. You can also replace them with good copper or silver wire´s, if you are sure you will not have too high DC current to your headphones. In my amp´s, I have used Audyn True Copper 1,5 uF (about $80 pair) parallelled with Russian Teflon FT-1 (about $4 pair). Bought some extra of both of them to get a lower price, so I can sell if you are interested.

 

Then consider to change the blue polarized electrolyt´s, at least the two nearest the OpAmp, as the signal will go through them. I used Elna Silmic II for those, and four Nichicon Muse KZ for the power supply (altough I know many use the popular Panasonic FC).

 

You can also replace the two big 4700 uF cap´s to better one´s, I used 10000 uF Mundorf M-Lytic (about $30 pair), wich I also have some extra spare to sell.

 

All depends on how much you´re willing to invest for your good sound and what headphones you are using (my phones are Sennheiser HD800, HD600, recabled HD650 and AKG 702).

 

 

/ Mikael Markstrom

post #1240 of 1240

Thanks Mikael, you're the real deal. Unfortunately I'm putting my purchases on hold for now. Just secured myself a new job and I'd love to pay off all my loans and debts first. 

 

I have to say, even without modding anything, the amp is amazing. I'll read through the mod logs other users had tried, especially the improvements from capacitor upgrade. Just curious, what other amps do you currently own and use to drive your headphones?

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