No stubborn guy here Aatto...I personally don't give a big, fat damn if others here have success with their "dead quiet" builds, or not. Can you please understand that???wow, such stubborn guy, does not accept that others may have success with their build. i dont wanna argue with you but just fyi my other lehmann clone works absolutely dead quiet too, no audible hum/noise.
My carefully crafted and assembled Lehmann clones have gone straight into the trash where they belong, since they weren't quiet enough with my EPB fiber optics cable box and my 42" plasma display.
If you're using your Lehmann clone with other sources(like a CD player or music streamer), then it may very well be quiet enough for these sources.
FWIW...I don't really care since there are other headphone amplifiers out there that literally "mop the floor" with these junky a$$ Lehmann clones such as the Schiit Audio Magni 3, which I received a few days ago:
Schiit Audio, Headphone amps and DACs made in USA.
UNBELIEVABLE SQ for only $100.
Good bye Lehmann!!
Does the input impedance of this amp vary with volume control setting? It is the first element connected to ground in the input path and the only thing other than a 10k resistor in series with the opamp input. Is that a good design? Any way to "fix" it if it's not a good design?
I just bought the bare pcb. I recognize that the full kit consists mostly of junk and counterfeit parts. There is no way even the Chinese can sell a complete amp with a genuine Alps pot and other parts for such little money. I intend to populate the board with decent parts and a couple boutique parts such as a bulk foil resistor in the opamp feedback loop. I've heard the difference that can make in other circuits and I think it might be worth the cost even in this crude amp.
Peace,
Tom E
I just bought the bare pcb. I recognize that the full kit consists mostly of junk and counterfeit parts. There is no way even the Chinese can sell a complete amp with a genuine Alps pot and other parts for such little money. I intend to populate the board with decent parts and a couple boutique parts such as a bulk foil resistor in the opamp feedback loop. I've heard the difference that can make in other circuits and I think it might be worth the cost even in this crude amp.
Peace,
Tom E
Parts Express sells this populated pcb and all a buyer needs to do is attach a transformer. It is stated in the specs and in Lehman's own specs that the input imp is 47k, so I guess that's what it is. Everything else I've read says that a volume control in this position will alter input impedance, at least to some extent, and the challenge in any such design is what value pot to use. The BOM calls for 50k, but I'm wondering if that's ideal. A lot depends on output imp of upstream device. I'm taking PC outputs, and I have no idea what that output imp is.
There are two reviews at PE: one review says the amp is quiet, the other complains about hum. Seems like a real coin toss with this design, or perhaps it has to do with connected components.
Peace,
Tom E
There are two reviews at PE: one review says the amp is quiet, the other complains about hum. Seems like a real coin toss with this design, or perhaps it has to do with connected components.
Peace,
Tom E
huh, never seen the PE one, but TBH the board n components look sh$$$y.
as we all discuss it really is a coin toss, i couldn't be happier with mine even though it's all chinese components.
but now even with the good luck i had in the past , i wont bother buying the whole kit, go for the board, and take a look at JLH and nac52 clones as well, people here had better experience with those.
as we all discuss it really is a coin toss, i couldn't be happier with mine even though it's all chinese components.
but now even with the good luck i had in the past , i wont bother buying the whole kit, go for the board, and take a look at JLH and nac52 clones as well, people here had better experience with those.
Finally completed the Lehmann clone amp, and it is absolutely dead nuts quiet through headphones. Volume cranked, and nothing. It's sitting right on top of my computer with no special cabling or shielding. I made one modification to the stock design: instead of taking the pre-amp outputs off the board by way of the narrow traces that run directly under the power supply, I attached a twisted trio directly to the headphone jacks solder pads and ran them along the "quiet" side of the board to the output jacks at the rear of the amp. Now there is no signal path element anywhere near the power supply.
Can't tell much about the sound yet as I just powered it up. Nothing seems bad, but it's too early to tell if it's really good. It certainly has excellent clarity, but I would expect the sound to warm up a little after some hours of play. I have not yet tried the pre-amp outputs, but I measured DC offset at the output jacks and got 1.3 and 1.1 mv without shorting the inputs. Does that seem good?
I don't hear any on-off pops, so I'm guessing DC at headphone jacks is minimal.
Peace,
Tom E
Can't tell much about the sound yet as I just powered it up. Nothing seems bad, but it's too early to tell if it's really good. It certainly has excellent clarity, but I would expect the sound to warm up a little after some hours of play. I have not yet tried the pre-amp outputs, but I measured DC offset at the output jacks and got 1.3 and 1.1 mv without shorting the inputs. Does that seem good?
I don't hear any on-off pops, so I'm guessing DC at headphone jacks is minimal.
Peace,
Tom E
glad to hear you have good luck with yours, i also finished mine about a week ago, getting the preamp out directly from the front head out sounds like a good idea since i get some hum and other noises when i crank it up using it as a preamp. but headphones out is dead quiet.
I got the same results as yours and i like the sound, it is clear and it certainly has a character, nothing to color the sound much may be the character is the flatness.
i used it more as a preamp rather than listening through headphones but i will put it to work once i put a case together.
overall i like it and i m building another one for a friend of mine to use it in a studio environment.
I got the same results as yours and i like the sound, it is clear and it certainly has a character, nothing to color the sound much may be the character is the flatness.
i used it more as a preamp rather than listening through headphones but i will put it to work once i put a case together.
overall i like it and i m building another one for a friend of mine to use it in a studio environment.
Hi guys. This is an old thread would be a pity to let it die. Im trying to build a lehmann copy with a Zero Zone board. The board looks perfect. Ive choosen all the parts but I have doubts about the transformer. What do you thing abouth this two:
https://es.rs-online.com/web/p/products/6718965/
Transformador toroidal RS PRO, Tensión 2 x 15V ac, Potencia 50VA, 2 salidas
or this one:
Transformador toroidal Block, RKD 40/2x15, Tensión 2 x 15V ac, Potencia 40VA, 2 salidas
RKD 40/2x15 | Transformador toroidal Block, RKD 40/2x15, Tension 2 x 15V ac, Potencia 40VA, 2 salidas | RS Components
One is cheaper and more powerful as my first bould i dont need the most fancy components i got just a beyerdynamic dt990pro to move.
Thanks in advance
Im trying to build a lehmann copy with a Zero Zone board. The board looks perfect. Ive choosen all the parts but I have doubts about the transformer. What do you thing abouth this two:https://es.rs-online.com/web/p/products/6718965/
Transformador toroidal RS PRO, Tensión 2 x 15V ac, Potencia 50VA, 2 salidas
or this one:
Transformador toroidal Block, RKD 40/2x15, Tensión 2 x 15V ac, Potencia 40VA, 2 salidas
RKD 40/2x15 | Transformador toroidal Block, RKD 40/2x15, Tension 2 x 15V ac, Potencia 40VA, 2 salidas | RS Components
One is cheaper and more powerful as my first bould i dont need the most fancy components i got just a beyerdynamic dt990pro to move.
Thanks in advance
Hi fellas. Im getting mad looking for that capacitors. I cant find them. Can someone help me? i got these ones for mouser but the pins aren't wide enough:
https://www.mouser.es/ProductDetail...4G%2Bpg2TQWPwjeybDiAhCNBO%2BvLEk8Mub1JePl7Stm
Any alternative?
I got the yellow pcb and they dont fit.
any help will be much apreciated.
thanks
https://www.mouser.es/ProductDetail...4G%2Bpg2TQWPwjeybDiAhCNBO%2BvLEk8Mub1JePl7Stm
Any alternative?
I got the yellow pcb and they dont fit.
any help will be much apreciated.
thanks
Attachments
I dont know about the kit, but the overall design is sound. It is class A into typical 32 ohm headphones, but only just.
One major flaw is that the buffer is NOT included in the feedback loop. This is just absurd - doing so reduces the distortion drastically.
If you want to push it further into class A, replace the two 47 ohm resistors which connect the bases of the output devices to the emitters of the buffer transistors with 1N4148 diodes.
One major flaw is that the buffer is NOT included in the feedback loop. This is just absurd - doing so reduces the distortion drastically.
If you want to push it further into class A, replace the two 47 ohm resistors which connect the bases of the output devices to the emitters of the buffer transistors with 1N4148 diodes.
I have this preamp board but don't have schematic of it, and I've tried it just for fun to be a headphone amplifier. I used the same values as printed in the pcb.
Everything works well, but I heard it sounds smaller than the output of audio jack from a DAC Hat on my raspberry pi.
Could you guys suggest me the proper resistor values to increase the volume to use with 32ohm headphone ? I think output 47k, 100k, 3.3k are too large...
Input is VDC +15-0-15.
Opamp: 2x OPA2604 (From aliexpress, China).
Everything works well, but I heard it sounds smaller than the output of audio jack from a DAC Hat on my raspberry pi.
Could you guys suggest me the proper resistor values to increase the volume to use with 32ohm headphone ? I think output 47k, 100k, 3.3k are too large...
Input is VDC +15-0-15.
Opamp: 2x OPA2604 (From aliexpress, China).
Unfortunately, OPA2604 isn't cut out to drive a 32ohm load to full level (1VRMS), it doesn't have the current capability. So its quite possible the opamp is limiting how loud it'll play.
You could replace that opamp with NJM4580, it has more drive capability. To find out if there is a series resistor between opamp and output limiting the level, you would need to trace the schematic out using a continuity meter. Look to see what's between the output connector at the top (L and R pins) and the opamps. To my eyes, I can't see a low enough resistor value on the board to take that function so perhaps the opamp(s) (pins1 and 7) drive the output directly. Btw, it isn't a Lehmann clone because Lehmanns have discrete output transistors.
You could replace that opamp with NJM4580, it has more drive capability. To find out if there is a series resistor between opamp and output limiting the level, you would need to trace the schematic out using a continuity meter. Look to see what's between the output connector at the top (L and R pins) and the opamps. To my eyes, I can't see a low enough resistor value on the board to take that function so perhaps the opamp(s) (pins1 and 7) drive the output directly. Btw, it isn't a Lehmann clone because Lehmanns have discrete output transistors.
Thank you for your reply.
Yes, this is not Lehmann clone.
I also ordered this item (diy kit) last week, but it takes time to deliver to me.
https://vi.aliexpress.com/item/1005...st_main.4.18751802zhBGje&gatewayAdapt=glo2vnm
Finally, my kit arrived. This KIT is very cheap but also very impressed.
https://vi.aliexpress.com/item/1005...st_main.4.18751802zhBGje&gatewayAdapt=glo2vnm
Well, my volume 50KAx2 seems failed after I unsolder from another board, so I connect directly with the input. The sound is too loud for my cheap headphone Sennheiser HD 202 II, 32ohm impedance (It used 2 single opamp TL070). I lowered the volume from the source (Moodeaudio, dac hat) to 12% only. I think this board can drive higher-impedance headphones.
Without music playing, I heard some noise/buzz. Is it because of no volume control (and it's at max volume) or is the board too close to the transformer?
Can you guys suggest which volume potentiometer is match this setup? 10K, 27K, 50K or 100K? Any improvement, lower gain or output?
TIA.
https://vi.aliexpress.com/item/1005...st_main.4.18751802zhBGje&gatewayAdapt=glo2vnm
Well, my volume 50KAx2 seems failed after I unsolder from another board, so I connect directly with the input. The sound is too loud for my cheap headphone Sennheiser HD 202 II, 32ohm impedance (It used 2 single opamp TL070). I lowered the volume from the source (Moodeaudio, dac hat) to 12% only. I think this board can drive higher-impedance headphones.
Without music playing, I heard some noise/buzz. Is it because of no volume control (and it's at max volume) or is the board too close to the transformer?
Can you guys suggest which volume potentiometer is match this setup? 10K, 27K, 50K or 100K? Any improvement, lower gain or output?
TIA.
