[Headamp] upgrading a Lehmann BCL clone

I also think I hear distortion now.. So something is or not going right (maybe I demolished one of the solder holes when desoldering. The resistor holes are bitches so small and in between the big caps) Or the hole system just needs more time to run in. Hissing seems to be more right than left. It is the background hissing amplified by the system already on the track.

What temperature do you guys use to solder? I have a adjustable solder station. Mostly I'm on 350 degrees C to get a quick solder without heating everything up to long.. But maybe I destroyed some parts and bits by soldering on a to high temperature??
 
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I replaced the red wima caps at the LM317 position with the small elna's.. Seemed together with 2 Zener diodes..

Seemed to have introduced a lot of hissing in every song.. the background is now full of hissing. Is this the elna caps that need to run in?

:eek:

Really strange the zeners mod it's an easy and effective one done by a lot of people on another forum...

Regarding Silmics II it seems also strange to me, they do need some burn-in but I've never heard hissing from them.

Can you post a pic?
 
I see I have destroyed one of the solder holes.. ****!

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OK, got it all together again. Just flushed the diode hole with some tin. Guess the inner tube was still intact. Working like a charm.

Also replaced all the resistors with Vishay Dale RCN55 (military grade). Cannot judge the sound yet. But they don't harm. The DC offset was 4mv and 9mv. Now it's just 2mv on both channels. Matching the resistors was childs play.. they were all the same on a few exceptions.. that's what military grade stands for I guess.. HEHE!

Also replaced the LXZs that came with the machine for other LXZs that I ordered (470uf 35V) I have ordered them from 3 different sources. Got two in already.

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Left is the non-glossy kind that came with the machine that didn't sound good to me. Then I ordered some new 470uf 25V to compare with the left ones.. They are glossy but the letters are of poor quality and the little logo next to LXZ is way thicker than on every LXZ I have seen before. To the right is the 35V variant that I ordered. The photo doesn't really show it but the blue color is really faded. I gues they must be really old or also counterfeit.. I placed the 35V variant, but I cannot say anything because I also changed the Panasonic Pureisms for Elna Silmic II 100uf 35V like suggested above. So this wasn't really a smooth move to compare. I think the Elna's are a bit to smooth combined with the Aune T1. But first everything needs a burn in before I make any other changes.

Changing to fast confuses everything. So I need to take a step back and compare more.
 

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End result for today.

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I am probably going to change back the LCR polystyrenes because the Amtrans made the sound REALLY harsh in the top end it hurts my ears and doesn't seem to smoothen out..
 

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Tested the LCRs. Same sibilance.. have to look at other stuff. Maybe Elna's at LM317.. Try replacing them for cerafines. And first putting Pureisms back. Because it wasnt this sibilant. So something changed. and it started when I was changing to the Amtrans. I have to retrace my steps.
 
Its not the opamp. I tried OPA2134, OPA2604, dual OPA111VM with and without adapter. It's something else.

It's distortion. I'm quite lost with the sound now. It's annoying as ****. Maybe I should just order a new board and start over. Maybe the boards contacts are not doing very well anymore.. I tried pushing components seeing if there maybe is a bad contact but no luck.
 
I sleep it over. Maybe it's just some components that need settling a bit.. Had this with the Aune T1 when I replaced some caps.. It sounded terrible and after a day keeping it on and playing some music when I was away it totally restored.. So lets just give it some time before I start changing things again.

Ordered some mundorfs.

I mostly have parts for 2 or 3 more boards now.. so maybe I just start over. I even have a second 40VA transformer.. I could make one extra for at work.

OR I could do Beyerdynamic A1 clone.. with two inputs and input selection to use different DACs..

For now I will just take a rest. It's about 0.30 here (China, no I'm not Chinese, I'm Dutch).

Ordered myself some NOS BB USA OPA111AM instead of VMs.. not sure what the difference is between AM and VM but I will audition. The VMs I got really cheap and were kinda old already. I still have a couple of high quality adapters lying around so swapping some opamps could be interesting too. I just want to learn and improve my device. It's kinda addictive. Tuning the your 'house sound'.

Still looking to replace the ERO coupling caps.

BTW while I type this post, I'm swapping opamps again (thnx for the tip).. and the sound does soften up a bit on the harshness with the dual opamps without adapter.. so this is something to look into.
 
BTW while I type this post, I'm swapping opamps again (thnx for the tip).. and the sound does soften up a bit on the harshness with the dual opamps without adapter.. so this is something to look into.

Since the poor opamp decoupling of the Lehmann it's advisable to use unity gain stable opamps, I've had best results with ADA4627-1B.

Also... did you clean board?

In my initial build only fet opamps gave a decent DC offset while bipolars oscillated with 1V DC offset!

This until I've very well cleaned the board, now I can use bipolars too without oscillation and pretty good DC offset.
 
I definitely need to clean the board more.. I used alcohol to clean it.. but the solder paste just spreads.. This can be a problem.. I think paste also came into the gain switches.. The alcohol doesn't seem to dissolve it very well..

DC offset is 2mV on both channels.. so that is quite good.

But I think cleaning must help my case.. any tips on how to clean the board thoroughly ?
 
Btw the distortion is mostly when power is required from the amp.. upper bass and especially lower mids and the highs are really harsh.

I am thinkin about starting a new PCB from scratch with all the right components from the start. Making an elite version from scratch. SO I know that everything I do is clean and well chosen.
 
Ok. even though it is bed time here. I tried a thorough cleaning with shitloads of alcohol.. and guess what.. The distortion got less! Even though I had no notable DC offset before.

SO.. it's better but it's not gone.

I have decide to populate a new PCB. I practically have all the parts I could wish for. Just need to order a new pcb and some basics.

Will be a clean build. I will use the other board to test things out, after I've cleaned it even more.
 
I definitely need to clean the board more.. I used alcohol to clean it.. but the solder paste just spreads.. This can be a problem.. I think paste also came into the gain switches.. The alcohol doesn't seem to dissolve it very well..

Those switches are a real PITA, I now remember I've had problem with them too, after cleaning (intermittent sound, sometimes distortion and so on), the only solution has been changing them with new ones.

Even now that I've made every care to avoid solvent in them they're starting again to making strange jokes...

I'll probably replace them with a fixed config using wires directly soldered to tabs.

But I think cleaning must help my case.. any tips on how to clean the board thoroughly ?

Isopropyl Alcohool but even better a product like this one:

| RS 400 ml aerosol Precision Cleaner & Degreaser for PCBs |

I usually first spray it, use a toothbrush and finally give a final touch with cotton and isopropyl alchool.

Ok. even though it is bed time here. I tried a thorough cleaning with shitloads of alcohol.. and guess what.. The distortion got less! Even though I had no notable DC offset before.

Fine :)
 
Ok I ordered a new PCB from a Chinese tech guy.

The PCB looks quite interesting and has already implemented some of the improvements going around on the forums I think. Don't have the full schematics rigth now but here is a picture:

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