Superlux HD-681 modifications

[Deleted]

driving a HP balanced is not very beneficial because the drivers themselves don't have a center contact.

Of coarse there are low level signals in HP's too but the HP circuit is and will be the same for all signals that is low-ohmic.

screening (as in keeping outside induced 'noises' out of the signal path) is NOT needed for HP signals.

the funny part of noise generated by electronics is that it is totally random.
When driving balanced some noise will be in phase and cancel each other out, some will be in counter phase and amplify each other.
It being random lowers the effective noise floor as the signal is always in counter phase and thus always amplified.
Therefore balanced driving is good for S/N ratios.
Noise from the source of course will be amplified and treated as a signal.

Sometimes when you want very low noise amplification 4 to 6 transistors are used in parallel just for making lower noise levels at the input stage.

a shielded cable has MORE copper in at least 1 wire thus lower ohmic.
You want low ohmic wiring in low ohmic HP's (HD681) so the biggest part of the applied voltage falls over the driver and not the wiring.

we are talking 0.1 to 0.3 dB in loss of levels here.(over the whole freq range at the same time no part of the freq range will be produced louder nor weaker)
Not a big deal and hardly (if) noticeable.. but very measurable.

the cables will have ohmic resistances around 0.2 to 0.4 Ohms..
The inductor used in the filter already is good for 2.5 Ohms to put things in perspective.
In total still less than 10% of the whole circuit (32 Ohm driver)

[clausdk]

Mar 5, 2010 22:14:59 GMT @solderdude said:

driving a HP balanced is not very beneficial because the drivers themselves don't have a center contact.

Of coarse there are low level signals in HP's too but the HP circuit is and will be the same for all signals that is low-ohmic.

screening (as in keeping outside induced 'noises' out of the signal path) is NOT needed for HP signals.

the funny part of noise generated by electronics is that it is totally random.
When driving balanced some noise will be in phase and cancel each other out, some will be in counter phase and amplify each other.
It being random lowers the effective noise floor as the signal is always in counter phase and thus always amplified.
Therefore balanced driving is good for S/N ratios.
Noise from the source of course will be amplified and treated as a signal.

Sometimes when you want very low noise amplification 4 to 6 transistors are used in parallel just for making lower noise levels at the input stage.

a shielded cable has MORE copper in at least 1 wire thus lower ohmic.
You want low ohmic wiring in low ohmic HP's (HD681) so the biggest part of the applied voltage falls over the driver and not the wiring.

we are talking 0.1 to 0.3 dB in loss of levels here.(over the whole freq range at the same time no part of the freq range will be produced louder nor weaker)
Not a big deal and hardly (if) noticeable.. but very measurable.

the cables will have ohmic resistances around 0.2 to 0.4 Ohms..
The inductor used in the filter already is good for 2.5 Ohms to put things in perspective.
In total still less than 10% of the whole circuit (32 Ohm driver)

Ok now if I recable a 600 ohms headphone, and I still want low resistance in my cables right ??

And if low ohms is wanted and shielding is useless, why don't we just use a household wire with ground for our headphones, the much thikker wire should provide a very low resistance right ??.

[Deleted]

HD681 is not 600 Ohms so let's go further on the cable discussion in the 'I got a plan' thread you started.

[Deleted]

Hi Frans,
IIRC you once said that you intended to audiophonically (? measure the various headphone cables that were sent to you during your recent filter installations. Did you do this, and if so did you find anything of interest? The reason I ask is that I thought the cable that I installed made an immediate improvement, even with my crappy soldering. Anything to add?
Dave.

[Deleted]

Hi Dave..

I have (just measured inductance, capacitance and resistance) these 3 make up the transmission line that conducts the the electric signals.

The outcome looked surprising until I did calculations on it..
This made all the measurements fit.

Will get back to it.

[clausdk]

Not the prettiest thing in the world but it is the first..



Thanks to Frans for the leather.

They will get prettier over time, this is just my first prototype.

[MaN227]

keep up the good work claus

now if I only had my very own set to play with ...... sigh

[Deleted]

now if I only had my very own set to play with ...... sigh

How long have you been waiting now Chaz, seems a long time!!!

[clausdk]

Ver 2.0





He likes them


what do you think ??

[Deleted]

Nice work looks good to me Claus, well done

[clausdk]

Thanks, I am still trying to figure out how to make them the best way..

It is very soft and hangs down, the midle part is just leather, I have just stiffend the ends with some plastic, I am going to use a thinner and more flexible one next, this one broke in two, it can not be seen, but it annoys me..

I am not sure if it can be seen on the pic, but the outer edge is embossed, I used some strong nylonstring, which also adds strength and rigidity to the band..

Next one will be for Frans, who has donated the leather..

Remember by donating leather you will get a free headband..

Chaz:If you cut up the coat and stips it from the lining inside, then cut as big pieces as possible, to the LETTER weith limit, maybe we could look into that..
I know exately how yours is gonna look..

[clausdk]

Ok now try this guys..







Make two equal sizes, like a golf ball..



transform the balls to saussages and wrap them around the phones, then you work the cotten thing up under the cup, and put it together again



put on a good song..

And prepare to smile.

[tripmaster]

Hi Chaps

A few weeks ago Puffin sold me his spare 681s, that is after Jerry had his mitts on them!

I must say after knocking up one of Fran's filters...I've been completely hooked!

I held off posting my first message as I wanted to wait until the everything loosened up before posting my opinion.

I would really like like to change the ear pads, and it would be great to have a metal finishing kit if they are still available?

For the modest outlay this combo must be one of the bargains of the year!

Thanks

Richard

[jkeny]

Claus, I tried putting in some wadding as you show but the bass went away - I either used the wrong wadding - it was finer than what you show in your pics & not as open or I used too much. I took it out & the bass returned.

I was worried that it might have been my rewiring which I did at the same time as the wadding - I used 4 core cable from a mouse to rewire them in balanced configuration. I also took out Frans filter & put it in an external box (the mouse itself) so I could change the caps from ceramic to polypropylene 1uF caps & also I wanted to put a pot in place of the 39 ohm R so I can dial in the amount of HF attenuation (within reason)

One other thing I have to report - I told a friend about these cans & he bought a stock pair. He believes they are very, very good but as hard to drive as his AKG701s. He makes the point that they need a good HA otherwise the HF sounds harsh - he's running his stock & has played with the equaliser in Foobar to attenuate the HF around 7K & better equalise the the freq range. He prefers the unit stock but on his Aikido HA.

What do you think - anybody got a stock pair running off a good HA?

[clausdk]

Mar 10, 2010 23:50:53 GMT jkeny said:

Claus, I tried putting in some wadding as you show but the bass went away - I either used the wrong wadding - it was finer than what you show in your pics & not as open or I used too much. I took it out & the bass returned.

I was worried that it might have been my rewiring which I did at the same time as the wadding - I used 4 core cable from a mouse to rewire them in balanced configuration. I also took out Frans filter & put it in an external box (the mouse itself) so I could change the caps from ceramic to polypropylene 1uF caps & also I wanted to put a pot in place of the 39 ohm R so I can dial in the amount of HF attenuation (within reason)

One other thing I have to report - I told a friend about these cans & he bought a stock pair. He believes they are very, very good but as hard to drive as his AKG701s. He makes the point that they need a good HA otherwise the HF sounds harsh - he's running his stock & has played with the equaliser in Foobar to attenuate the HF around 7K & better equalise the the freq range. He prefers the unit stock but on his Aikido HA.

What do you think - anybody got a stock pair running off a good HA?

I just run them from a Meizu SL8 or my Philips GoGear
also through the Ibasso D10, and that is a fine mix..

I have loaned my filter to a fellow danish head-fier, som I am filterless at the moment, but I do not miss it TBH, will be fun when it returns home and see if it is better than now.

My vatte/wool, It is the kind of #wool/Vatte" that are use to clean fishtanks, it is a wonder drug..


The Details has gone crazy, it is truly amazing

You are going pretty hardcore

BTW if you look closely you can see that, I had to solder afterwards

[jkeny]

Mar 11, 2010 0:14:38 GMT @clausdk said:

.....................

The Details has gone crazy, it is truly amazing

This is what you hear with the wadding in place?

You are going pretty hardcore

I like to explore the potential of a device I'm not finished yet - I will be running these from a balanced source so that shoul dbe interesting

BTW if you look closely you can see that, I had to solder afterwards

It's safer to unsolder anyway to do this job as it's difficult to control the headband while trying to put in the wadding & you risk pulling the wires off the small pcb inside the cans

[clausdk]

Yes the dampning made the details go berserk..


If you desolder first it would be much easier..

But I had the time

[clausdk]

And if you you change resistance and caps with a click.
It would be the coolest thing on earth.

[MaN227]

Mar 10, 2010 19:15:32 GMT @clausdk said:

He likes them


what do you think ??

we interrupt this thread for something "of an almost human nature" ;D

that is a beautiful child you have claus

ok now what about that stuffing , put it where? lol soz

[covenant]

Mar 11, 2010 0:14:38 GMT @clausdk said:

Mar 10, 2010 23:50:53 GMT jkeny said:

Claus, I tried putting in some wadding as you show but the bass went away - I either used the wrong wadding - it was finer than what you show in your pics & not as open or I used too much. I took it out & the bass returned.

I was worried that it might have been my rewiring which I did at the same time as the wadding - I used 4 core cable from a mouse to rewire them in balanced configuration. I also took out Frans filter & put it in an external box (the mouse itself) so I could change the caps from ceramic to polypropylene 1uF caps & also I wanted to put a pot in place of the 39 ohm R so I can dial in the amount of HF attenuation (within reason)

One other thing I have to report - I told a friend about these cans & he bought a stock pair. He believes they are very, very good but as hard to drive as his AKG701s. He makes the point that they need a good HA otherwise the HF sounds harsh - he's running his stock & has played with the equaliser in Foobar to attenuate the HF around 7K & better equalise the the freq range. He prefers the unit stock but on his Aikido HA.

What do you think - anybody got a stock pair running off a good HA?

I just run them from a Meizu SL8 or my Philips GoGear
also through the Ibasso D10, and that is a fine mix..

I have loaned my filter to a fellow danish head-fier, som I am filterless at the moment, but I do not miss it TBH, will be fun when it returns home and see if it is better than now.

My vatte/wool, It is the kind of #wool/Vatte" that are use to clean fishtanks, it is a wonder drug..


The Details has gone crazy, it is truly amazing

You are going pretty hardcore

BTW if you look closely you can see that, I had to solder afterwards

Claus,
Is the fish tank material filter wool? If it it's a very cheap solution.
I was thinking about getting some long-fibre wool like they use in speaker cabinets. But if fishtank filter works then its a trip to Pets-r -Us this weekend!

[clausdk]

Claus,
Is the fish tank material filter wool?

Yes it is, cheap and good..

[clausdk]

this one is for solderdude..









I ran out of glue

So I will finish it up tomorrow and send it your way..

A thanks to Frans for donating his old jacket for my experiments..
I hope it will be worth it

More to come just wantes to show you guys a ½way picture

[audiofil]

Just a quick update on my HD681 modifications.

I mentioned earlier I was planning to dampen the cups with Dynamat and rewire with dual entry.
Here are my findings...

Originally I've cut the stock cable and mounted a female plug to allow comparisons between various cables.
I've tried the stock, a Vandamme starquad and some RCA-terminated ICs with adapters.
The Starquad cable seemed the best, although after prelongued listening I've found the differences to be only slight.
I suspected that the differences were so small because of too many soldering connections from amp to the headphone drivers.

After rewiring with dual entry (Vandamme Starquad) I felt that the sound opened up considerably. Because comparisons are now impossible without re-soldering another cable, I am aware that my impressions are subjective and I'm comparing the sound I'm hearing with the sound I'm remembering.

Throughout the modding I've used the same 3 tracks (from Chesky's Ultimate Demonstration cd) to have a sort of objective reference and I do hear differences with the new cable. Spatial cues and overall texture seems better defined now. Depth in particular is, to my ears, a lot more obvious than I remember it before the rewire.
That's the cable mod....

Dampening
I had ordered last month a sheet of Dynamat Extreme from a Romanian car-audio shop and used cut pieces form that.
The initial dampening:
- small piece on the magnet
- thin piece (a ring of about 5mm) on the larger cup that holds the driver
- larger piece on the external cup (with punched holes).
- removed the stock paper ring and put inside a generous piece of wool.
The sound had changed considerably... for the worse. There was a bass and high end roll off and the sound signature shifted towards a "bathroom reverb" kind of setting.
In effect of that - I removed all the Dynamat dampening and rethought the process.
I think the Dynamat material is too thick and has an aluminum foil glued on one side. This probably accounts for the wrong acoustic tuning of the cups.

Second (and final) dampening:
- left the small dynamat piece on the back-magnets
- I stuck small and thin blue tack sheets (7-8mm square pieces) on both cups and on the front (under the foam disk, on the margins). First I've put 4 and then 8 pieces in a sort of a star pattern.
- small piece of wool inside the cup, underneath the grey paper ring.

The sound: I like it very much!
The differences are not radical as the Dynamat mod was, but to my ears the HD681 sound definitely better and more balanced.
There is a bit less bass energy (which I felt was too much), the mids seem to be brought back in business and the highs appear sweeter.
Soundstage and imaging also appear more precise.
I haven't noticed any differences concerning size - samed width and depth, only better defined.

Unfortunately I don't own a digital camera anymore.
I'm sure that pictures would have explained much better the mods.
Feel free to comment.
Any questions or suggestions are welcome.

[jkeny]

I too noticed too much/too dense a wadding inside the can's cups caused the bass to disappear & messed up the sound, much like what happens in a speaker cabinet - this probably needs to be tuned to your own tastes.

[clausdk]

Why bother with dynamat ??
If some filter wool is used the force of the sounwaves, will be broken up an have less effect on the cup.
Do not use cotton or sheaps wool it is much to dense, the filter wool does not fckup the bass in any way, it makes it tighter, but it does steal a bit volume so you have to dial a bit further on the pot 5% or so..