Gainclone heaven ?

[Scroobius]

Funny that I was discussing the very same with Nick recently and it appears that there are very few balanced / bridged GC's out there. Now that I have heard the difference I would only consider balanced. But of course the problem is that there are not so many source components that offer decent quality balanced outputs. So the only option is to install transformers and then of course you have to start spending a lot of money to get good quality - and even then you are putting something extra in the signal path. From where I am sitting (which is in front of my speakers listening to the Duke in mono ha ha) NOS1 with balanced output into balanced bi amped GC is very special indeed.

On the offset both Nick and I were lucky to be able to get such good offset results. But of course balanced configuration should always work out good because the net offset at the speaker terminals is the difference between the offsets of the two individual amps whereas in a normal config you are stuck with whatever is on the output of that amp.

Happy days - my amp is starting to relax a little now and losing some of the "edge" noted when first fired up.

It would be good to get someone else on board - is anyone out there thinking of balanced GC? if so let us know.

Cheers

Paul

[Scroobius]

I just re-checked mains hum levels in the dead quiet of morning and actually there is some mains hum through my speakers. It is at a low level but it is there with slightly more through the LH speaker. Just the same as Nick's amp when it was here but I cannot comment on the absolute levels (something we will check when I visit Nick soon).

So earthing now is with both channels connected to PE in a star. There is a potential loop with this because the USB input to NOS1 is connected to PE also (but what does this mean with balanced?). So I tried a number of different earth arrangements breaking that loop but the best arrangement is what I have now. It seems that the mains hum is probably not caused by earth loop but by hum breakthrough from the bigger nosier transformers.

From work on the previous amp and Peters input I know that any noise affects SQ because hum/noise rides on top of the signal (not under it) and modulates it. The next thing to try would be different layout inside the transformer box (one transformer on top of the other as in NOS1) and to locate it further away from the amplifier box. Big work and I am not sure I want to do that but for anyone starting a project like this it would be worth considering.

[PeterSt]

Paul,

Assuming this hum is 50Hz mains frequeny, I would consider the transformers to be too close to your further components. Actually they are in my view.
Point of course is that you can't move them away, hence you made it so nice and tidey that the supply box can't be moved away even for trying. I didn't look at Nick's at this time, but he may have the same problem. IOW :

Once you grant yourself lengthening the AC wires from the transformers (which should be harmless I'd say) you can do anything with that extra length. Does it help, then you can always eliminate one connection by resoldering all to the rectifiers. So, now cut it all just inside the amp box and insert 30-50cm there just to try. BUT you will know how hard it can be to "strip" this wire and solder (etc.) it, because of its coating. So on that matter maybe resolder at the recifiers end to begin with (which allows you to put all back in original state when it does not help).

In the mean time this will allow you to stack the transformers for trials.

A first and more easy thing to do might be laying around the wires from the switch (well, the blue/brown you have on top of the one transformer). Although I don't have the experience that such a thing is not allowed, I would never do that. But indeed, I would also never put the transformers next to eachother like this.

A last easy thing to try may be a sheet of mu-metal in between the boxes. So, detach them and put the sheet in between them. But have it twice as high as the box.
If you can get it, that is, and the internet is your best chance (then easy). Expensive stuff though.
Remember : mu-metal (or anything) does not filter; it can guide away (magnetic) radiation. Bounce it into another direction.

... if it is from transformer radiation at all ...

Peter

[PeterSt]

I don't know whether this can be of help :

I can't value your remark about the USB Input to the NOS1 being connected to PE. I mean, on the NOS1 end it is not at all. But if you mean via the PC, then you will be correct. But this is out of my reach of course.
But if you think this is of importance - disconnect the PC from PE.
I don't think it will help - up to creating other problems (DC Offset on the NOS1 end ?), but it is worth a try.

FWIW remember : I have my PC connected to the audio ring just the same, it is connected to PE while my GainClones are not and the NOS1 is not connected to PE as well. And, nothing in the NOS1 is connected to PE for ground; only the cabinet is. Still, connecting the cabinet to PE (hence connect the NOS1 to PE) makes differences all over the place (the cabinet is an antenna and whatever it catches now goes into PE).

Test all without your monitor's switching block connected to the mains (pull out the mains plug). Just to be sure.

Peter

[Nick]

A few thoughts, and a question.

Be careful isolating your pc from PE, beyond the obvious safety points, I did this a long time ago and found that the singnal ground in the pc rose to 79v as the smps drifted upwards. As soon as the pc was connected to PE via another component the voltage dropped but this would have been due to a ground loop. The other thing is that if a ground was connected to the pc (eg monitor d connector) it would give a very feeble spark as the voltage was pulled down to earth.  You pc smps many not behave the same but put a meter from the signal earth of the pc to PE before you try using a disconnected PE as a diagnostic.

I arrived at the star earth signal ground to PE set up in the balanced amp after trying a few permutations. Its a little counter intuitive but it gave the best results here.   

I think the gainclone hum I have here is due to an out of spec tranformer, it humed before it was put into the amp and I have an RMA from the supplier to have it replaced. Even with 103db speakers the hum is not bad and its actually as loud coming from the transformer inside the amp.

As I mentioned by mail I think  Paul, I would try reversing the mains phase of one transformer first. They are very close to one another and the flux runs in opposite directions at their closest point. Assuming the windings have the same direction reversing the phase will make the fields run in the same direction. This may work like stacking the transformers. It a quick arrangement to test and may help. Otherwise Im with Peter regarding the position  of the transformers.

Im planning to take a close look at the ground set up when my new oscilloscope arrives is a couple of weeks.

Peter,

Am I right saying that the NOS is signal ground is connected to PE on the interface via a 100k resistor and a cap in parallel with the resistor  (i'm unsure of the cap value) ?

These components sit between the usb cable shield connection (which routes off to the nos case ground) and the signal ground of the usb lead which in turn sets signal ground....I think.

Cheers nick

[PeterSt]

Peter,

Am I right saying that the NOS is signal ground is connected to PE on the interface via a 100k resistor and a cap in parallel with the resistor  (i'm unsure of the cap value) ?

These components sit between the usb cable shield connection (which routes off to the nos case ground) and the signal ground of the usb lead which in turn sets signal ground....I think.

Hi Nick ... No ...
But if so, you did that yourself. Haha.

But don't get fooled by looking at the USB interface only;
At the cabinet's end the USB shield is disconnected from the chassis per the outwardly bended clip on the connector ...

So totally nothing is (or should be) connected to the chassis. Ok, PE itself.
Can easily be checked for course (multi meter).

Regards,
Peter

[Scroobius]

Whoops sometimes even the most obvious is not (but it should be). The top plates for both the amp box and the transformer box were still in their plastic wrapping never (yet) having been installed. So I unwrapped them and screwed them in place. The mains hum is lowered and is now the same from both speakers. Better for sure but not quite as low as with my previous amp.

The SQ is not quite where I want it yet - my previous amp was smoother but not as good in most other areas. I know just how much difference fine silver makes in the i/c (the RCA i/c's on my previous amp were fine silver and Nick's were great when we tried them with his amp) so that is the first thing to try. If that does not work then I will have to consider surgery (maybe) but it is much work to do.

P

[Nick]

Peter,

Am I right saying that the NOS is signal ground is connected to PE on the interface via a 100k resistor and a cap in parallel with the resistor  (i'm unsure of the cap value) ?

These components sit between the usb cable shield connection (which routes off to the nos case ground) and the signal ground of the usb lead which in turn sets signal ground....I think.

Hi Nick ... No ...
But if so, you did that yourself. Haha.

But don't get fooled by looking at the USB interface only;
At the cabinet's end the USB shield is disconnected from the chassis per the outwardly bended clip on the connector ...

So totally nothing is (or should be) connected to the chassis. Ok, PE itself.
Can easily be checked for course (multi meter).

Regards,
Peter

Hi Peter,

Thanks for explaining. I measure 104k ohm from the usb shield connection point  on the NOS input (the port on the outside of the case) to [ EDIT  the NOS signal ground at the RCA output ground or the velaman psu ground]. This measurement is taken with mains cord, interconnects and usb cord all disconnected from the nos.

I know the whereabouts of the 104 k resistor an it is bypassed with a cap meaning that for ac, pe and signal ground are connected. I have not changed anything electricaly in the ground layout. I cannot see any point where the usb sheild is "lifted" in the cable between the nos port and the card.

I have just broken the shield pe (using tape) after the point that the pe wire runs back to the chassis but before the shield connection reaches the interface. What a difference to SQ.

 Is this the intended arrangement ?

Thanks,
Nick.

Ps 09-z9 sounds MIGHTY, MIGHTY  fine 

[PeterSt]

Uhm Nick,

Can you please show a photo of the USB chassis connector, from above, inside of the chassis ?

Regards,
Peter

[PeterSt]

Nick,

Reading your post better, I think we are talking about something else. Never mind that photo because I think you will find that clip is "bended outward" anyway.

Maybe better take this to email ?

Thanks ...
Peter

[Nick]

Peter hi

I had the same thought see your email in box, it looks a bit unusual in there

Nick

[Scroobius]

I mentioned in previous posts that the new balanced GainClone had taken a big step forward in SQ. But I still had a few reservations namely a slight unevenness in the mid to upper registers and a slight cold hardness in the sound.

Whilst I would never be going back to my old amp I still hankered after its refinement.

Well today I received some fine silver wire in the post. I set to with my soldering iron and replaced the enameled copper wire in the i/c with fine silver.

The result is a complete removal of any doubts I had about my system the SQ is back where I want it  - very refined top end and the slight course unevenness in the mid to highs is completely gone. Mmmmmm I was missing this.

I have to say I am still surprised by how much difference silver makes. My interconnects are only about 10cm long. So why the difference? Surely the electrical properties remain the same as the actual construction of the i/c has not changed. The resistance of silver is not much difference to copper and over the short lengths I doubt that is a factor.

I still think silver / gold etc work their magic at a quantum level. Who knows? - what I do know is that I am totally happy with the SQ now.

 

Paul

[listening]

Here is the actual result of my last weeks effort. The system is build up on commercially available pcbs, assembled and wired as written in my first post.

Nothing special but I tried to get analog in and analog out as near as possible. Therefore the copper rails and the chip are mounted at the bottom of the cabinet.

The pcb at the left side of the transformer is a softstart unit which is not necessary at this time and unused.

Because I'm using very rare Philips Alnico drivers there is no chance to do without a coupling capacitor. I tried a lot (had two well broken in black gates for lease from a friend, which showed the direction) and ended up with a satisfying solution: A (new old stock ) combination of Roederstein KP1832 and NSF Styroflex capacitors.

Georg

[Nick]

Georg hi,

The build looks great ! And an interesting story about the input caps, defiantly best to be safe there  you certainly don't want any accidents with your drivers.

How is the sound ?

Best,

Nick.

[listening]

Hi Nick,

that was he biggest challenge and hopefully I have not to repeat the process too often . After trying oil caps, mica, foil, even vacuum caps and other nice stuff I ended up always with a sonic compromise. Some types work best for rock and jazz others better for classical music. The actual combination is suitable for the long term, works with all types of music and has a delicate and colorfull character.   

Georg

P.S.: Did not try very interesting but very expensive solutions like Duelund or Thel Mica Caps (4,7 MicroFarad!)