[KonstantinN]

The lazy way to correct for voltage offset independently in L or R channel.(there are other ways, of course!)

(In my case the offset was rather high in one channel, 17mV, while very acceptable in the other. A little trying and failing, and I ended up with less than 1mV offset by reducing the resistance in (what I call) R3 in the drawing to ca. 1.4k by (from 1.5k) by adding an Rx=18k in parallel. The Idle current was accordingly increased by less than 2mA (of 57mA originally), a totally insignificant change IMO. I don't know if this could be of interest to any of you. You can see the added resistor in the photo).

I must not forget to say thanks to all for an interesting thread, Olaf

(this is also a kind of test posting, since it is my first)

This is also my first post here even though i am a long time lurker.
Following the direction of chetlanin and bla-bla’s comments, i zeroed DC offset of my LC output by soldering 4 variable 50k resitors in parallel to the 1.5k resistors (R25, R28,R29,R32) on the schematic.

A bit of nipples turning - hooray! 0mV DC in both channels!

And a note about Muses8920 opamp for the Lovely Cube - it sounds great! With good recordings - better than 2111 to my taste for width and depth of the sound stage and instruments separation and positioning. Unfortunately it comes at the cost of less engaging vocal and emphasizing of bad recordings imperfections. Had anyone tried Muses01 in the Cube ABing with 8920?

 

[penmarker]

What you can try is getting some substantial heatsinks for the output devices and put in a Burson V5 or V6.

The only reason for the heatsink suggestion is because the Bursons don't like high temps. My V5 works fine, however some people reported their opamps burnt in class A designs. The spec also rates the operational temp only up to 55 degrees C if im not mistaken.

 

[francisdemarte]

Amazed and glad to see this thread is still active 8 years after it was started Rock on!

 

[Cidious]

I'm still rocking my Lehman clone. As you can see it underwent a lot of customisations and tweaks through time. But this is practically how I ran it for over a year. Sometimes rolling some opamps.. Got a Burson V6 Vivid incoming. Look back in this thread for the customisations that I made and why.

As far as I can remember

60VA transformer (biggest that could fit. from 40VA to 60VA)
Mundorf 4700uf PSU caps
Panasonic FM PSU caps
ELNA Silmic II at the opamps
Resistors are audio grade ones in signal path.. need to look up what types.. blue and red hahaha
Zener PSU mod
Some bigger electrolyte caps at the PSU
Matched all voltage regulators and resistors. everything PERFECTLY matched
Clarity bladiebla caps at the signal input positions
Black wima caps in signal path
and for Opamp decoupling I used these small black drops which I forgot the name of.. Some luxury stuff.. I rolled quite some caps in and out and they sounded best.

I mainly run the Lehman with my Mad Dogs and my (heavily) modified DT770 (has nothing DT770 in it anymore. 45MM Tesla drivers and similar dampening to the DT1770 with some tweaks here and there. Lovely set of cans. Got a set of MrSpeakers Aeon closed incoming. So I took another look over the amp to see if everything is still performing as I want.

Current Setup
Laptop -> USB -> UFEEL USB004 (signal purifier) -> QED Custom USB cable -> Topping DX3 Pro + Linear PSU -> QED signal lines -> Lehman BCL clone headphone amp + 2xOPA111VM or 2xOPA627BM + UFEEL MK902MKIII dip8 adapter -> Mad Dogs or DT770 Tesla mod cans

Replacing the opa with Burson V6, adding MrSpeakers AEON closed cans, Maybe trying Topping D50 DAC since they are so darn cheap in China. €140 with 11.11, 12.12 or 1.1 discount haha. That's worth to try.

 

[Cidious]

Got me a Burson v6. Lord what fun! I'd say 20% audio performance improvement over the dual single opa627bm or dual single op111vm.
More refined and defined. Less noise and everything just sounds more confident and controlled. Bass is tight and thick. Highs are defined but not harsh. Mid a little laid back on the Vivid. But it pairs well with the dual AKM 4493 DAC I'm running with.

I don't think there is much more I can tweak out of the Lehman. This was another great upgrade. Worth it. Total cost of my unit might not be very budget friendly anymore but certainly top notch.

 

[mikaelmark]

What will be the result, if using a lower value for the DC coupling cap´s, for example: 1uF instead of 1,5 – 1,8uF?

I found information about how to calculate/determine the value, and if decreasing/lowering the value, it may generate more distortion and that the headphone impedance may change the minimal capacitance value needed. It also say´s a higher capacitance value is ofter preferred.

So, should 1uF be enough for this LBC-amp? And what will the result be versus using original value?

https://www.eetimes.com/document.asp?doc_id=1274884

 

[KonstantinN]

What will be the result, if using a lower value for the DC coupling cap´s, for example: 1uF instead of 1,5 – 1,8uF?

f3dB = 1/(2*pi*R*C)
Reducing the blocking capacitance value you decrease amount of low-frequency signals that will pass it. For LC 1uF is still fine, It means that 3Hz input signals will be decreased by 30%. The lower the frequency of the signal, the more signals will be decreased.

 

[mikaelmark]

f3dB = 1/(2*pi*R*C)
Reducing the blocking capacitance value you decrease amount of low-frequency signals that will pass it. For LC 1uF is still fine, It means that 3Hz input signals will be decreased by 30%. The lower the frequency of the signal, the more signals will be decreased.

Ok, so you do´nt think it will reduce an hearable amount within the hearable frequency range over 20Hz? How many dB lower will it go/block?

And are there any pros. if choosing lower value and any cons. if choosing very high value, let´s say more than 2uF?

 

[Cidious]

Popped in a Burson V6 vivid.. Felt like the sound quality improved by about 15 over OPA627BM and OPA111VM.. Couldn't believe my ears.. Then a bit later I got a Sparkoslabs SS3602 discrete opamp.. and another 5-10% improvement over the Burson V6 to my ears... and then I rolled back to dual OPA111VM and OPA627BM to verify... and they can't come close...
The Burson costs about €65 and the Sparkoslabs €80... but... I'd say WORTH IT

 

[lawrence2357]

Hey all I just bought one of these used and I'm very impressed. Assuming it came stock, what opamps should I try? I'm using HD560, HD580 and HD650. (I'm assuming there's no point in trying to drive my HE6!) For the 560s I'd like a little taming of the highs, the 650s already sound good so just a bit more "quality" if that's possible. The 580s are as you'd expect in the middle so something suited to them would be nice too but I could probably live with one or the other. I don't want to do any other mods, recent posts refer to extra heat sinking for Burson opamps so I'd rather avoid that.

Oh I'm also thinking of using it as a preamp, are the opamps in circuit when used like that?

I should also start a new thread for my other amp I just bought, an Iota Audio Reference, wow that's something else. Virtually nothing on the web just a passing reference that they are available.

 

[Cidious]

Opamps that I found very suitable for most of my headphones were opa2111vm (or dual 111vm) opa627bm Burson V6 (discrete) and Sparkos SS3602 (also discrete)

The Burson V6 is a very good opamp for it's price. And you can have a vivid and a classic to roll for different music styles / headphones. But obviously it won't come cheap. Vivid being more clear and analytical and defined. Classic being more musically pleasing and organic but less detailed. Both of them very good opamps and bring clarity and control.

A step above that (also quite a bit more expensive) is the Sparkos SS3602. It's practically the end game. Best of both worlds of the Burson V6 versions. Without any significant weak sides. Very well balanced, neutral and great detail and control. Sounds effortless.

I'm running Sparkos SS3602 now but I'd be happy to use the Burson V6 too if I didn't have the Sparkos laying around. As for the aforementioned IC opamps.. they are better than most other IC opamps... But in terms of clarity they just can't compete with the discrete ones.. I'd never go back to IC for the headphone amp.

I hope it helps. All depeneding on budget I guess.

 

[lawrence2357]

Thanks for that Cidious, the previous owner is selling me his collection which are:

"the original stock chinese op2134 which was a bit nasty, a proper Texas Instruments 2134PA, and pairs of op 602AP, 637bp and 797anz which I think need that adapter which is also there."

Do you know if any of these are any good? I'll keep an eye out for some second hand discrete ones.

 

[zxzxzx207]

I was just wondering. Does any one have a high resolution picture of the sticker at the bottom of the amp? Mine didn't come with one and I want to print one out

 

[Cidious]

Thanks for that Cidious, the previous owner is selling me his collection which are:

"the original stock chinese op2134 which was a bit nasty, a proper Texas Instruments 2134PA, and pairs of op 602AP, 637bp and 797anz which I think need that adapter which is also there."

Do you know if any of these are any good? I'll keep an eye out for some second hand discrete ones.

Uhm I didn't really personally like any of those on headphones. 797 does well in my DAC's IV stage but not so well in my headphone amp. 637bp I haven't tried but read and heard 627bp is better. 602AP I don't know. and original 2134AP is ok but nothing to write home about. I would look for 2x627BP or 2(x)111VM or 2604AP. and if you can afford maybe one of the Burson V6 variants. they are about 20-25% better than the best IC opamp that i've tried. It really lifts the veil of things and makes the sound more effortless somehow.

 

[zxzxzx207]

In case someone needs it in the future, I remade the label at the bottom of the case.