what do you guys think about this one:
High-end Stereo Class A Headphone Amplifier Board Amp PCB base Lehmann circuit | eBay
looks the same to me.
High-end Stereo Class A Headphone Amplifier Board Amp PCB base Lehmann circuit | eBay
looks the same to me.
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In my experience, the classic Lehmann circuit was an almost total disaster for SQ. I blogged about it here : Bargain beaut - headphone amp - diyAudio
I cannot believe this is anywhere near classA as claimed - if it were so then the 10R emitter degeneration resistors in the output stage would be lower in value by maybe an order of magnitude or more.
I cannot believe this is anywhere near classA as claimed - if it were so then the 10R emitter degeneration resistors in the output stage would be lower in value by maybe an order of magnitude or more.
My Lehmann Clone Finally Just Went into the Trash Where it Belongs!
This thread made me pull my Lehmann clone, which was built upon a blue PCB a few years ago, from a stack of projects that I had thrown over in the corner for trash in the near future.
After blowing the dust off it and connecting it to my recently purchased Niles SI-2100 Class D power amplifier, I was instantly greeted by some low-level hum with the volume all the way down.
So I did the ground rerouting as suggested in this post thinking it may be a ground loop:
http://www.diyaudio.com/forums/head...z-hum-lehmann-linear-clone-2.html#post4267890
The ground rerouting in that post was a total waste of time and didn't make any difference with the low level hum, so I tried connecting all input and output grounds to the same point on the signal ground(op-amp) side of the board.
Still...there was low level hum, so I concluded that the LM317/337 on-board PS wasn't up to the job of keeping the hum(or ripple) out of the super-duper discreet "diamond buffer" section of this design.
Just for kicks...I tried this Lehmann clone with my plasma TV and cable box hoping for the best.
As soon as I turned the TV on, there was even more hum and other crazy noises amplified by this POS Lehmann clone to the point it was unlistenable.
It was at this point...I disconnected my Lehmann clone and threw straight it in the trash where I should have thrown it several years ago.
This got me thinking, so I tried my simple LM317/337 PS with Calvin's discrete buffer and experienced the same type of low level hum even though it only has a theoretically gain of one.
Switching over to my clone of Salas' DCSTB cap multiplier PS resulted in ZERO hum with Calvin's buffer, though I didn't waste my time lowering the voltage to see if it would lower the low level hum problem with the Lehmann clone.
So...there are 2 things that should be learned here ladies and gentlemen:
1. Don't waste your time and money on these "Lehmann Clone" kits with a on-board LM317/337 PS from eBay and Aliexpress unless you like a little 60 or 100 Hz "hum" to go along with your lower-level musical enjoyment. I don't but you may!
2. Don't even think about using a LM317/337 PS with a discrete amplifier design. These old regulators just aren't up to the job. Perhaps something that I should post over in the PS forums.
This thread made me pull my Lehmann clone, which was built upon a blue PCB a few years ago, from a stack of projects that I had thrown over in the corner for trash in the near future.
After blowing the dust off it and connecting it to my recently purchased Niles SI-2100 Class D power amplifier, I was instantly greeted by some low-level hum with the volume all the way down.
So I did the ground rerouting as suggested in this post thinking it may be a ground loop:
http://www.diyaudio.com/forums/head...z-hum-lehmann-linear-clone-2.html#post4267890
The ground rerouting in that post was a total waste of time and didn't make any difference with the low level hum, so I tried connecting all input and output grounds to the same point on the signal ground(op-amp) side of the board.
Still...there was low level hum, so I concluded that the LM317/337 on-board PS wasn't up to the job of keeping the hum(or ripple) out of the super-duper discreet "diamond buffer" section of this design.
Just for kicks...I tried this Lehmann clone with my plasma TV and cable box hoping for the best.
As soon as I turned the TV on, there was even more hum and other crazy noises amplified by this POS Lehmann clone to the point it was unlistenable.
It was at this point...I disconnected my Lehmann clone and threw straight it in the trash where I should have thrown it several years ago.
This got me thinking, so I tried my simple LM317/337 PS with Calvin's discrete buffer and experienced the same type of low level hum even though it only has a theoretically gain of one.
Switching over to my clone of Salas' DCSTB cap multiplier PS resulted in ZERO hum with Calvin's buffer, though I didn't waste my time lowering the voltage to see if it would lower the low level hum problem with the Lehmann clone.
So...there are 2 things that should be learned here ladies and gentlemen:
1. Don't waste your time and money on these "Lehmann Clone" kits with a on-board LM317/337 PS from eBay and Aliexpress unless you like a little 60 or 100 Hz "hum" to go along with your lower-level musical enjoyment. I don't but you may!
2. Don't even think about using a LM317/337 PS with a discrete amplifier design. These old regulators just aren't up to the job. Perhaps something that I should post over in the PS forums.
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A couple of years ago I made one with good quality components and I matched all; sand, resistors... I did some mod on the PSU regulation and spent a lot of time experimenting with several caps and OPAs.
I had no problems with noise or hum.
It's an interesting amp to learn.
I had no problems with noise or hum.
It's an interesting amp to learn.
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i m not sure what is going one here, with all the negative feedbacks i read here about these clones, i got this :
Lehmann HV-4 Headphone Amplifier Kit as i said, with its shitty components came with the kit ! the whole kit ( board+components+shipping ) was about 30 something dollars, but surprisingly it turned out quiet good actually, of course i replaced the shitty coupling caps with solen but other than that no tweaking what so ever, right out of the box, no noise no hum whatsoever and the sound quality is amazing very well balanced.
so i m not sure if this individual seller actually knows what they doing or i got lucky, but they have quiet interesting boards in their shop and i got myself another one of their boards just for fun, see how the other one will turn out.
blackdod, how do you like the sound quality ?
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Aatto, you're "Lehmann HV-4 Kit" link above doesn't work for me.
My example used the older blue board like in this kit:
Kit Headphone Amplifier Board AC 15V-0-15V Reference Lehmann Circuit Design | eBay
I didn't use the same quality components that blackdod used with his example.
I did use Dale RN55 resistors to replace all the 1/4W Chinese resistors and larger Dale 1% 10 ohm emitter resistors for the BD139/140s.
I didn't use any coupling caps on the inputs since my sources didn't have any DC on their outputs.
For the power transformer, I used an old and reliable Rat Shack 12V-0V-12V 3A unit.
Initially, I used the supplied 1kuF 'lytics for the 6 caps in a row across the board.
Using 2kuF on the outputs of each of the LM3xx regulators is dumber-than-dammit since it's a well known fact that these old LM317/337 regulators will oscillate like hell with that much capacitance on their output pins.
So for curiosity, I reduced all 6 'lytics down to 220uf but there was no change in the hum.
At this point I unsoldered all 6 of my new Nichicon 220uF caps from the board and threw the board in the trash!
I don't have the time or patience for troubleshooting kits that should work the first time if assembled correctly.
Increasing the volume to get above the hum, I found my Lehmann clone's sound quality was fair at best despite trying about a dozen different op-amps. Some of these op-amps are some of the best sounding singles (OPA627 & ADA4627-1) on the planet when used in other applications, but made little difference in the sound of my Lehmann clone.
Whether or not the yellow boards you guys are using are "improved" in some way(s) to reduce the hum I don't know.
Nor will I be finding out since I don't plan on buying a yellow(or any other color) board and finding out.
My example used the older blue board like in this kit:
Kit Headphone Amplifier Board AC 15V-0-15V Reference Lehmann Circuit Design | eBay
I didn't use the same quality components that blackdod used with his example.
I did use Dale RN55 resistors to replace all the 1/4W Chinese resistors and larger Dale 1% 10 ohm emitter resistors for the BD139/140s.
I didn't use any coupling caps on the inputs since my sources didn't have any DC on their outputs.
For the power transformer, I used an old and reliable Rat Shack 12V-0V-12V 3A unit.
Initially, I used the supplied 1kuF 'lytics for the 6 caps in a row across the board.
Using 2kuF on the outputs of each of the LM3xx regulators is dumber-than-dammit since it's a well known fact that these old LM317/337 regulators will oscillate like hell with that much capacitance on their output pins.
So for curiosity, I reduced all 6 'lytics down to 220uf but there was no change in the hum.
At this point I unsoldered all 6 of my new Nichicon 220uF caps from the board and threw the board in the trash!
I don't have the time or patience for troubleshooting kits that should work the first time if assembled correctly.
Increasing the volume to get above the hum, I found my Lehmann clone's sound quality was fair at best despite trying about a dozen different op-amps. Some of these op-amps are some of the best sounding singles (OPA627 & ADA4627-1) on the planet when used in other applications, but made little difference in the sound of my Lehmann clone.
Whether or not the yellow boards you guys are using are "improved" in some way(s) to reduce the hum I don't know.
Nor will I be finding out since I don't plan on buying a yellow(or any other color) board and finding out.
try this :
GZLOZONE Lehmann HV-4 Headphone Amplifier Kit
no doubt these Chinese boards are a gamble, but sometimes it worth it, for 20-30 bux you won't feel that bad, i always burn in anything i buy with some cheap headphones or speakers, so if anything goes wrong i wont blow any precious stuff
GZLOZONE Lehmann HV-4 Headphone Amplifier Kit
no doubt these Chinese boards are a gamble, but sometimes it worth it, for 20-30 bux you won't feel that bad, i always burn in anything i buy with some cheap headphones or speakers, so if anything goes wrong i wont blow any precious stuff
Well I bought a clone with all components but I got curiosity and finally I spent enough money to leave it to my linking.
Pcb is of a normal quality but if you abuse it you'll probably take off the pads.
I don't know what brand are the resistors but in my case they were at 1% and I used some in non-critical places.
Caps. I checked volt/cap and all is Ok but I wasn't sure and I decided to use originals brands and others series (Nichicon Muse and KW and Mundorf Mcap and Mlytic).
Sand... here I used original components also in the place of the ones that come with the kit.
Unfortunately, some places are famous for selling fake sand and caps.
I never did the amp with the kit components so I can't say how it sound but giving you some care and changing various details you can have a "decent" headphone amp.
I'm not going to argue whether Lehmann's design is good or not. I have other very superior amps and they all have pro and cons.
My intention was to leave the amp to the maximum level with extremely precise measures without much alteration of the design.
Pcb is of a normal quality but if you abuse it you'll probably take off the pads.
I don't know what brand are the resistors but in my case they were at 1% and I used some in non-critical places.
Caps. I checked volt/cap and all is Ok but I wasn't sure and I decided to use originals brands and others series (Nichicon Muse and KW and Mundorf Mcap and Mlytic).
Sand... here I used original components also in the place of the ones that come with the kit.
Unfortunately, some places are famous for selling fake sand and caps.
I never did the amp with the kit components so I can't say how it sound but giving you some care and changing various details you can have a "decent" headphone amp.
I'm not going to argue whether Lehmann's design is good or not. I have other very superior amps and they all have pro and cons.
My intention was to leave the amp to the maximum level with extremely precise measures without much alteration of the design.
I have made headphone amps with LM317/337 regs and even 7815/7915 regs and they were dead quiet. Hum comes from ground loops and is not necessarily caused by the voltage regulator. Ground loops are mostly preventable with due diligence. But sometimes, even with all the dilligence, planning, proper design, you can still get hum because there is a part somewhere that is touching something you did not account for.
Hum can also come from EMI pickup from a trafo or mains too close to the input stage or wires. I battled with hum on an M2 amp for months. Redid the ground wiring, tried different PSU topologies etc. After moving the trafo outside the case, hum went away. M2 uses a small signal transformer for VAS stage. It picks up stray mag fields like flypaper catches flies in a dumpster. So it turns out people shield their signal trafos. But I don't think an amp should be designed so that it is intolerant of mag fields from its own power supply.
Dynalo and Kevin Gilmore amps seem to be obsolete, so they can be quickly eliminated as far as considerations for future builders.
The AMB Labs Beta22 here in America should be a worthwhile alternative to these Lehmann clones though at a much higher price.
How would you compare the Beta22 to the Lehmann clone in terms of SQ being you have both?
The AMB Labs Beta22 here in America should be a worthwhile alternative to these Lehmann clones though at a much higher price.
How would you compare the Beta22 to the Lehmann clone in terms of SQ being you have both?
X, I'm so glad that your headphone amps using LM317/337 regs were dead quiet. I think I may even sleep better tonight knowing that.
Having used these outdated and subpar performing regulators with other discrete designs, I can WITHOUT A DOUBT attest that the hum was due to the PS and NOT ground loops.
Substituting a different PS with these discrete circuits, like the Salas DCSTB, eliminated the hum INSTANTLY!
For op-amp circuits, the LM317/337 seem to be more than sufficient because of most op-amps' rather high PSRR.
Tying all grounds to the same point on the PCB practically eliminates the chance of "ground loops". That's why I went to the trouble of doing so on my Lehmann clone and making sure the power and signal grounds only connected at one point. This isn't my first experience or rodeo with grounding problems "X".
So...you go on thinking the LM317/337 and 78/79 series of regulators are all fine and Dandy(which happens to be my nickname). For some applications, they may be more than sufficient, but they're no match for a quality PS like Salas' DCSTB.
Now...let's bust out the whiskey and soldering iron and build something like Juma's Easy-Peasy Capacitance Multiplier that you and Prasi are so hip on!
Bye "X".
I wish you had withheld this revelation. Puts all your sonic claims in a different perspective
Well, we have a Dynalo SuSi with new components so I wouldn't eliminate it for future building and Dr. Gilmore often evolves his designs.
Beta22 is a nice amp, but I think that it's a more complicate building (and remember that 2sk170/2sj74 are obsolete). For beginners or newbies I think that a Lehmann clone is a better way to learn and practice... In this sense also comes to mind the Zen HA clone too.
I can't compare a Lehmann with a Beta22 because they are different animals. Beta22 power is terrible if you compare with a Lehmann and I don't refer at use a simple resistor on the out put to take measures. If you have a planar like a Hifiman or Audeze you can feel how work both amps and his respective Psu.
Second point is what is better? An input with Jfets devices or a Diamond Buffer with OPAs? I haven't answer for this questions... I feel better using Fjets but I know that out there exits nice Opas like Opa627 and Muses. However I think that the best way to know pros and cons of both design is to try them out and experiment with them.
About Psu, each person has their own tastes about it. We all know designers who prefer slow diodes, other fast...
I have Psu's with regulators like the LM78XX or LM337/317 that are quiet. For example my Lehmann clone or my Pass Ha. Another thing is that you use an oscilloscope to determine what they are. Obviously, there are better designs and more sophisticated and elegant but probably more complicated.
Attention, it's my opinion, I don't want opened a discussion with this.
Beta22 is a nice amp, but I think that it's a more complicate building (and remember that 2sk170/2sj74 are obsolete). For beginners or newbies I think that a Lehmann clone is a better way to learn and practice... In this sense also comes to mind the Zen HA clone too.
I can't compare a Lehmann with a Beta22 because they are different animals. Beta22 power is terrible if you compare with a Lehmann and I don't refer at use a simple resistor on the out put to take measures. If you have a planar like a Hifiman or Audeze you can feel how work both amps and his respective Psu.
Second point is what is better? An input with Jfets devices or a Diamond Buffer with OPAs? I haven't answer for this questions... I feel better using Fjets but I know that out there exits nice Opas like Opa627 and Muses. However I think that the best way to know pros and cons of both design is to try them out and experiment with them.
About Psu, each person has their own tastes about it. We all know designers who prefer slow diodes, other fast...
I have Psu's with regulators like the LM78XX or LM337/317 that are quiet. For example my Lehmann clone or my Pass Ha. Another thing is that you use an oscilloscope to determine what they are. Obviously, there are better designs and more sophisticated and elegant but probably more complicated.
Attention, it's my opinion, I don't want opened a discussion with this.
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The newest generation of Headamp GS-X still utilizes the classical Jfet-Input Single-Ended Dynalo topology, and four separate channels to make a balanced amp. There`s a lot to try and modify even with such simple topology. But the THAT340s in the Gilmore open-source design for IPS is perhaps not a good idea, should avoid them.
My favorite PSU is a laptop SMPS followed by DC step up (which also provides regulation), followed by Juma's easy peasy cap multiplier (knocks ripple and hum down by -45dB, but more importantly provides a 20sec soft start ramp up to eliminate turn on pop), followed by a CRCRC (2.2mF for small 100mA bias amps and 22mF for 1.5amp bias) to clean up all residual noise. With this setup, the 60Hz peak (normally at -80dB with the best linear supplies), is now barely visible at -125dB. Noise floor is flat a -130dB over all audio range 10Hz to 30kHz.