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Pingushome 13th January 2013 11:27 PM

Lehmann clones
 
Hi,
New to the site but can not seem to find any info on these clones from ebay.
Lehmann BD139 BD140 Preamplifier headphone DIY Amplifier kit | eBay
Any info / tips / comments would be appreciated.
I was thinking of getting one for my home system and wondered if they were any good or if indeed the actually worked and were worth building :confused::confused:
I appreciate I may have overloked a whole string somewhere.:o

jcx 14th January 2013 03:31 AM

it is generally considered impolite to discuss, facilitate clones of current production amps - but discussions of general principles, any peculiar advantages, design choices of a current amp's circuit may be fair game

as a discrete Q "diamond buffered" monolithic op amp gain stage amp it isn't particularly exciting, nothing sufficiently proprietary to prevent discussion that I can see

you can argue over including the output stage in the feedback or not, change bias, roll op amps, use boutique parts...

Pingushome 14th January 2013 09:57 AM

Quote:

Originally Posted by jcx (Post 3324799)
it is generally considered impolite to discuss, facilitate clones of current production amps - but discussions of general principles, any peculiar advantages, design choices of a current amp's circuit may be fair game

as a discrete Q "diamond buffered" monolithic op amp gain stage amp it isn't particularly exciting, nothing sufficiently proprietary to prevent discussion that I can see

you can argue over including the output stage in the feedback or not, change bias, roll op amps, use boutique parts...

Thanks jcx didn't mean to ruffle any feathers just wanted a good affordable headphone amplifier.
That explains why there are no threads on them.
I am only a novice (can follow the instructions of a circuit) so while I find your advice intresting I am afraid it is way beyond me..sorry.
I'll get one of the UK based products as your coments about the circuit being fairly mundane. At least a local product will have a track record and local contactable suppliers. I think that would be safer for me.
Appreciate your advice though and thanks for taking the trouble to explain

maxmba 7th February 2013 08:57 AM

I got this BD139 BD140 amp from eBay and it works well.
Using FFT on my scope i do not see any major harmonic issues at 1000 kHz.
No accurate THD measurements have been done.


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