[BlaBlaBla]

Shielded cables. Both sides of shield have to be grounded, or both sides must not be grounded. If you ground only one side, you will have hum.
 
Quote:

Cable to the pre-out too close to the transformer will cause hum. If it were the alps pot you would also hear it when using headphones.

 

 

[hifienthusiast]

There is no hum through the headphone outputs.
 
The signal cable is a good quality one made by Linn. Using the Linn signal cable, there is no hum from a Creek passive pre amp to the Quad 306 power amp.
 
My Blackcube clone was not made by myself, I will need to open the cover to find out the grounding scheme.

 

[francisdemarte]

Does the hum change to go away when you wiggle the RCA cables? Does it go away when you touch the volume pot or change the volume?
 

 

[hifienthusiast]

The hum does not go away when I wiggle the signal cable, I have even changed the cable to make sure. The volume pot does not affect the hum, the level of hum is constant through the Quad 306 power amp and speakers.

 

[BlaBlaBla]

Quote:

The hum does not go away when I wiggle the signal cable, I have even changed the cable to make sure. The volume pot does not affect the hum, the level of hum is constant through the Quad 306 power amp and speakers.

 
Does your Quad 306 power has power cord with three wires (separated ground) or with two (without ground)?
 
Because if it has two wires and your Lovely Cube has three (ground) - then hum will be always there. You can ground your Quad, or you can remove out third wire from Lovely Cube.
 
 
 

 

[BlaBlaBla]

I replaced resistor R2 in regulators circuit (LM317/337) with two zener diodes (13V, 1.3W). First I was against that, because I did not know how high DC offset would be. Some people say that in their Lovely Cube offset goes above 10 mV... But now, I am satisfied.
 
Here, DC offset is low enough.
 
 

 

 

 

[taiyoyuden]

There are two headphone jacks. Is there a difference between them? Can they be used simultaneously? If so, is there a sound quality tradeoff?

 

[francisdemarte]

Yes there are 2 headphone jack on the pre-built model. There is no difference between them except one of them mutes the line-out and the other one does not. 

 

[alanbeeb]

OK - bottom line folks - is this as good as a real Lehmann BCL? 
Thanks.

 

[francisdemarte]

A couple of people did a comparison in this thread. I believe generally they sound a little different because of differences in parts such as the caps and opamps. Some preferred the BCL others liked the LC. 

 

[alanbeeb]

Is switching Opamps easy - are they socketed or are desoldering/soldering skills required?  

 

[Wingstrike]

Quote:

Is switching Opamps easy - are they socketed or are desoldering/soldering skills required?  

I have a pre-built Lovely Cube Premium and it's socketed. Switching opamps is super easy

 

[Nescafe]

Deleted

 

[alanbeeb]

Just my 2 cents worth on the lovely cube.... I bought a 2nd hand one to try instead of the genuine Lehmann BCL (which I know well from being a previous owner and rate highly) and I have to say I am disappointed.
 
Into the Sennheiser HD565 I am currently using (waiting for Denon AD5000 to arrive) the sound is hard, tizzy, lacking air and space and soundstage is compressed.  The headphone socket on my Sony SACD player does a much better job and is far preferable!
 
I'll have a scan through here to find out about Opamp changes but at moment looks like I will not be keeping it.

 

[francisdemarte]

Quote:

Just my 2 cents worth on the lovely cube.... I bought a 2nd hand one to try instead of the genuine Lehmann BCL (which I know well from being a previous owner and rate highly) and I have to say I am disappointed.
 
Into the Sennheiser HD565 I am currently using (waiting for Denon AD5000 to arrive) the sound is hard, tizzy, lacking air and space and soundstage is compressed.  The headphone socket on my Sony SACD player does a much better job and is far preferable!
 
I'll have a scan through here to find out about Opamp changes but at moment looks like I will not be keeping it.

 
Let's see if it's possible to resolve some of these issues. Find out which opamp is in your LC. What gain setting are you using?