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These "Lehmann" clone boards have been discussed many times here before.
Having personally built a couple of these "Lehmann clones" in the past, I would forgot about this sh_tty sounding design and move on to something else!
Utilizing a dual op-amp(OPA2134 or whatever dual JFET op-amp you prefer) for the VGS is one of the limiting factors here vs. using a single op-amp for each channel.
Look for a JLH headphone amp PCB if you're determined to try one of these Chinese clone headphone amps.
The all discreet JLH desing sounds MUCHO better IMHO, but will require a DC servo to keep the offset from possibly "frying" your headphones.
The clone amp would be great if you like changing the op amps a hundred times trying to make it work better.
I would tend to get one of these myself;
HIFI FET INPUT MOS Class A headphone amplifier ALPS ASSEMBLED BOARD GOOD SOUND | eBay
I would tend to get one of these myself;
HIFI FET INPUT MOS Class A headphone amplifier ALPS ASSEMBLED BOARD GOOD SOUND | eBay
huh, i was just wondering how the hell they cloned a 1000$ product into a 30$ kit !
i got another board from the same company i believe and the seller claimed that this circuit is also based on lehmann :
GZLOZONE Lehmann HV-4 Headphone Amplifier Kit With ALPS 27 Type Potentiometer
i put it together with its all crappy components, the only thing i changed was the coupling caps which i replaced with solen ones and man it surprised me, it sounds fantastic, no noise no hum , dead quite and looks like a good design overall, so i got lucky you think ?
i got another board from the same company i believe and the seller claimed that this circuit is also based on lehmann :
GZLOZONE Lehmann HV-4 Headphone Amplifier Kit With ALPS 27 Type Potentiometer
i put it together with its all crappy components, the only thing i changed was the coupling caps which i replaced with solen ones and man it surprised me, it sounds fantastic, no noise no hum , dead quite and looks like a good design overall, so i got lucky you think ?
Just say 'no' to classAB for headphones. As 99% of cans only need peak powers of a few hundred mW, classA is the way to go.
i like that !
i found this for JLH :
NEW JLH HOOD1969 Class A Headphone amplifier PCB
what do you think ?
any suggestions on ebay/aliexpress ?
From my limited experience of browsing (but not buying) amps Zerozone is one of the better guys. The full kit is only about $5 more than the bare PCB, a real bargain. To protect your precious cans I'd AC couple the output rather than rely on trimming the DC offset though.
It really depends on the impedance of your particular cans. I have Superlux HD668Bs which are 56ohm and I put 1500uF. For lower impedance use more, higher use less. So for e.g. 28ohm, try 3300uF.
i got 250ohm, so about 300uf ?
few more questions :
- does the cap have any effect on the sound, i read it effects bass., is the brand effect the sound character , like solen, m-caps ... ?
-is there any more general solution ? like if i want to switch between different impedance cans without worrying about cap value ?
few more questions :
- does the cap have any effect on the sound, i read it effects bass., is the brand effect the sound character , like solen, m-caps ... ?
-is there any more general solution ? like if i want to switch between different impedance cans without worrying about cap value ?
Yeah, 250ohm would suit 330uF (nearest standard value).
There are plenty of guys who hear differences between caps, I'm not one of them (yet). So I use a bog-standard electrolytic. Preferably not a low ESR one unless that's all you have as lower ESR normally means higher leakage.
You can size your cap according to the lowest impedance 'phones you're going to use. The only downside is a bigger (longer) switch-on 'thump' with the higher-Z kinds. This can be minimized though by fitting resistors (say 1k ohm) across your jack outputs to provide the ability to charge the cap with nothing plugged in. Then only plug in your cans a few seconds after powering up.
There are plenty of guys who hear differences between caps, I'm not one of them (yet). So I use a bog-standard electrolytic. Preferably not a low ESR one unless that's all you have as lower ESR normally means higher leakage.
You can size your cap according to the lowest impedance 'phones you're going to use. The only downside is a bigger (longer) switch-on 'thump' with the higher-Z kinds. This can be minimized though by fitting resistors (say 1k ohm) across your jack outputs to provide the ability to charge the cap with nothing plugged in. Then only plug in your cans a few seconds after powering up.
As I stated above, IMO the JLH smokes the Lehmann clones for SQ.
You can "roll" all the dual op-amps you want, but it still won't match the JLH's SQ.
DC offset is a big problem with the JLH and varies wildly depending on the temperature of the output devices.
Better AC couple that one for sure as abraxalito suggests.
yeah i did gave that one a try while back,i was happy with it till i tried this one :
GZLOZONE Lehmann HV-4 Headphone Amplifier Kit
I already bought this one a few weeks back :
GZLOZONE HV-5-TB Headphone amplifier PCB
i wanted to give this one a try since i had good experience with GZLOZONE before and since it's hybrid. there's no info on the board, lol, took a risk 😀
JLH is next on the list 😀
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Hmm...I've never seen that board before. Looks to be quite complex and uses a lot of components.
I have to agree that you took a BIG chance on that one, especially since I don't see a schematic for it.
Best of luck assembling it & working all the bugs out...LOL.
i m very pleased with how it turned out tho, as for this board yeah, i m hoping for the best ( and not preparing for the worst ! ) lol, i ll let you know how it turned out, i ll probably receive it in a week or so.
pic from finished GZLOZONE Lehmann HV-4 amp :
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I believe Sennheiser chose the Lehmann BCL amp to power their HD800 headphones at the launch. You might think they know a thing or two about headphones and amps, so surely the BCL can't be that bad??
Like most kit they can be tweaked to some extent for better sound, primarily the power supply.
Like most kit they can be tweaked to some extent for better sound, primarily the power supply.
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Curious - why would Sennheiser 'know a thing or two' about amps? I used to work for a fairly well-known speaker manufacturer, we didn't know too much about amps. The choice of amps for demos was more often than not made based on commercial considerations, not SQ ones.
it does not mean if they manufacture speakers/headphones they know everything about the amps or the other way around, if you are a painter it does not mean you know how paint was made or how to make it ! but as a experienced painter you know what paint to choose.
Lehmann has a good reputation and i m sure guys at Sennheiser tried different amps before they choose one , or it's like a contract or something.
Lehmann has a good reputation and i m sure guys at Sennheiser tried different amps before they choose one , or it's like a contract or something.