Lehmann Linear case drawings?

Hi, I'm looking to build a Lehmann Linear headphone amp. I've got no idea where to start when it comes to housing :D
I would get it done by a CNC machine. But I have no drawings...

So does anybody have drawings for Lehmann Linear?

If not do you have any idea how could I make a similar looking case? :D

Thanks.
 

Ian Finch

Member
Paid Member
2010-04-11 4:22 am
Coffs Harbour, NSW
Engineering drawings for the housing or case of almost any electronic audio devices are seldom, if ever, published. The service and technical manuals are commonly available for old equipment but these are about the electronic functions, the components and their locations - the housing is not a spare part, even though it may be shown as part of the assembly.

If you want to copy any case, you'll need the original product in your hands or another owner's detailed measurements that are accurate enough for your needs. That isn't likely to be a simple favour though. Why not post in the Diyaudio headphone amplifier forum where there may be more likely owners to ask: Headphone Systems - diyAudio
 

Accuphasee

Member
2014-09-10 8:57 am
Sound Qualities of Lehman products are erm..."arguable" :p

That said; Why is your focus on making it look the same?
It's just the packaging
arguable? :( it's a class A amplifier! I heard everything good about it :D
But to be honest the main reason I'm looking to build this amp is because its quite easy to build for an amateur.

Engineering drawings for the housing or case of almost any electronic audio devices are seldom, if ever, published. The service and technical manuals are commonly available for old equipment but these are about the electronic functions, the components and their locations - the housing is not a spare part, even though it may be shown as part of the assembly.

If you want to copy any case, you'll need the original product in your hands or another owner's detailed measurements that are accurate enough for your needs. That isn't likely to be a simple favour though. Why not post in the Diyaudio headphone amplifier forum where there may be more likely owners to ask: Headphone Systems - diyAudio
Actually I am not bothered how the amplifier looks, which shape it has.
What concerns me are the holes I'd had to drill for jacks pot and led, since those 3 components (maybe LED isn't) are soldered down directly to the PCB and aren't flexible. So if I were to miss 1 hole, the case would become unusable.

Thanks for the suggestion about posting in headphone systems section. I'll do it if I don't find an answer soon.
 

Ian Finch

Member
Paid Member
2010-04-11 4:22 am
Coffs Harbour, NSW
I think the OP is actually looking for the dimensions of an Ebay copy-kit, perhaps like this: Zero Headphone Amplifier KIT Base ON Lehmann Linear AMP With Alps Potentiometer | eBay

The original product is somewhere around $800 US and this kit costs about $40 US so I guess any kit is a no-brainer as long it actually uses the original components without any further need for matching etc.

I think anyone making their own case would be able to use a ruler or vernier calipers to take centre-to-centre measurements of the sockets and dual volume control from where they are they are located on the PCB - either by direct measurement between pin holes or calculation where they are not central on the socket etc. You can place the parts in the board without soldering to allow for any slight inaccuracy in transferring the dimensions to where they will best fit in the case, allowing for PCB support pillar height.

Draw the vertical and horizontal centre lines precisely and mark with a centre punch to ensure the drill doesn't wander. Then drill a small pilot hole first, say Φ2.5mm, and use a proper drill press and clamp if you expect the holes to end up where you wanted them. Obviously, you must use a larger finished hole size than the mounting bush on the pot or sockets because nothing can be made to align with infinitesimal precision.

Here are the dimensions of RK271 series pot to get you started. The rest is 5 minutes search with Google: http://www.alps.com/prod/info/E/PDF/Potentiometer/MetalShaft/RK271/RK271.PDF
 
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I think the OP is actually looking for the dimensions of an Ebay copy-kit, perhaps like this: Zero Headphone Amplifier KIT Base ON Lehmann Linear AMP With Alps Potentiometer | eBay

The original product is somewhere around $800 US and this kit costs about $40 US so I guess any kit is a no-brainer as long it actually uses the original components without any further need for matching etc.

I think anyone making their own case would be able to use a ruler or vernier calipers to take centre-to-centre measurements of the sockets and dual volume control from where they are they are located on the PCB - either by direct measurement between pin holes or calculation where they are not central on the socket etc. You can place the parts in the board without soldering to allow for any slight inaccuracy in transferring the dimensions to where they will best fit in the case, allowing for PCB support pillar height.

Draw the vertical and horizontal centre lines precisely and mark with a centre punch to ensure the drill doesn't wander. Then drill a small pilot hole first, say Φ2.5mm, and use a proper drill press and clamp if you expect the holes to end up where you wanted them. Obviously, you must use a larger finished hole size than the mounting bush on the pot or sockets because nothing can be made to align with infinitesimal precision.

Here are the dimensions of RK271 series pot to get you started. The rest is 5 minutes search with Google: http://www.alps.com/prod/info/E/PDF/Potentiometer/MetalShaft/RK271/RK271.PDF
Hello, thanks for the detailed answer.

And actually I was looking to buy this £7.7 PCB High End Stereo Class A Headphone Amplifier Amp PCB Reference Lehmann Circuit | eBay

And I'd assemble it myself.
 

Ian Finch

Member
Paid Member
2010-04-11 4:22 am
Coffs Harbour, NSW
Your link is to a pic showing much the same PCB and it should be piece of cake to measure the hole centres and prepare a drawing for yourself. I assume you'll be using one of those Cliff S2/BBB/PC-C switched sockets which are shown on the finished kit, as they're cheap and widely available. Dimensions are on Cliff's website: http://www.cliffinc.com/products/jacksockets/S2.pdf
Bear in mind that whilst this is routine construction for any DIY building, you have the PCB to measure but we don't, so results will depend on your own measurements. You will also need the exact parts used in the full kit to fit the PCB, so this project may be a bit harder and more expensive to build than you hoped for.
 

Accuphasee

Member
2014-09-10 8:57 am
Your link is to a pic showing much the same PCB and it should be piece of cake to measure the hole centres and prepare a drawing for yourself. I assume you'll be using one of those Cliff S2/BBB/PC-C switched sockets which are shown on the finished kit, as they're cheap and widely available. Dimensions are on Cliff's website: http://www.cliffinc.com/products/jacksockets/S2.pdf
Bear in mind that whilst this is routine construction for any DIY building, you have the PCB to measure but we don't, so results will depend on your own measurements. You will also need the exact parts used in the full kit to fit the PCB, so this project may be a bit harder and more expensive to build than you hoped for.
Thanks, looks like this kit you linked might be a good deal, I'll see if it would be cheaper this way rather than hand picking parts.

Thanks.

P.S. Can you recommend a good supplier which has branded components (preferably in EU)? and ships with reasonable shipping rates?
 

Ian Finch

Member
Paid Member
2010-04-11 4:22 am
Coffs Harbour, NSW
Hehe! :D - I live in Oz, half a world away from the EU. However, all those cheap kits come from China and sadly, the costs of European kits would scare you. You will need to buy from China anyway, unless you have plenty of cash to spare on European products and resellers of Chinese kits. Some large chinese Ebay stores do have distribution warehouses in the EU but I doubt small kitsellers would.

Take another approach - buy a kit and assemble it as it comes, listen and enjoy for however long it takes to get bored with it. Then read the headphone forums, decide who is just playing with parts and who seriously knows what they doing by making real improvements and then follow qualified advice rather than "impressions" when it comes to part upgrades.

Much of sound quality is not really about using particular expensive parts or brands but about finding the ones that suit your budget and seem to settle in to a satisfying sound quality after extended listening. We all have different likes and dislikes, particularly with the use of headphones and we need to discover the differences ourselves because they are just as much about our hearing as any parts we use - but that is another story :)
 
Hehe! :D - I live in Oz, half a world away from the EU. However, all those cheap kits come from China and sadly, the costs of European kits would scare you. You will need to buy from China anyway, unless you have plenty of cash to spare on European products and resellers of Chinese kits. Some large chinese Ebay stores do have distribution warehouses in the EU but I doubt small kitsellers would.

Take another approach - buy a kit and assemble it as it comes, listen and enjoy for however long it takes to get bored with it. Then read the headphone forums, decide who is just playing with parts and who seriously knows what they doing by making real improvements and then follow qualified advice rather than "impressions" when it comes to part upgrades.

Much of sound quality is not really about using particular expensive parts or brands but about finding the ones that suit your budget and seem to settle in to a satisfying sound quality after extended listening. We all have different likes and dislikes, particularly with the use of headphones and we need to discover the differences ourselves because they are just as much about our hearing as any parts we use - but that is another story :)
I'm scared of buying kits from china due to lots of counterfeit parts being made today.
But then again, they said it's all genuine and all matched transistors almost too good to be true.

That being said, they have only 3 negative feedbacks and over 350 positive.

I'll listen to someone for a change :p so yeah I'll go ahead and order this kit you linked as soon as i get home in few hrs :D I just hope it doesn't get sold by the time I'm here :(

And probably if I went my way I'd end up paying even more :rolleyes:

P.S. I got the sennheiser HD600, I feel like this amp might be a really good match and I read somewhere that they sound amazing in combination with this amp.