[Knijsterbek]

I performed the "Spritzer mod", which consists of the re-location of 2 150K resistors in the feedback loops per channel, plus changing the values of 2 resistors per channel to fix the low gain issue.
For the re-location of the 2 resistors in the feedback loops, the originals have to be removed.
For the gain issue, I left the original 560 Ohm resistors (R5 and R6) in place and parallelled them with 330 Ohm pieces which makes 207 Ohm total (Spritzer replaced them with 200 Ohm pieces).
 
I have not been able to make A-B comparisations, but I experience much more control after the modification of the feedback loop.  It is always hard to describe these changes to others, because as long as they are "heard" and not measured, they remain subjective.
 
According to Spritzer, resistors should be metal film and rated 1/4 watt 350V.
 
Here is a picture of one of the 2 identical plug in boards (one left, one right channel) after the mod.
 

 
 
Spritzer, what about the gremlins?
Should I lower the gain again?
 

 

[BoilermakerFan]

Here are the pics of the new, improved tips:
 

 
 
 

 
 
 
 

 
 
 
 
 
As you can see, a huge improvement in the shape and size of the opening and they are tight, very tight on the 001s, so they stay in with no headband.
 
 
Now, off the SR-001 portable amp, the drivers are very bass heavy and the mids and highs are a little more recessed than when I use the stock tips and headband and really jam the drivers in my ear canals.  The tips do move the driver out of the ear a good 3mm which make the sound sig tilt to the dark side compared to my SR-Lambdas.  But I think the amp is part of the issue.  I plan to mod it and probably mod the tips just a tad more to bring them in closer.  Whenever I get my hands on a set of 003s or a 003 cable I can run them off an eXStatA and see how they really sound. 
 

 

[Germs]

Is the original 727 flawed and it is better to buy a second hand 717, or the 717 has the same issue ?

 

[padam]

The 717 does not have the same issue.

 

[Sim1]

Quote:

[...] Whenever I get my hands on a set of 003s or a 003 cable I can run them off an eXStatA and see how they really sound. [...]

 
I think you can find or create the tiny PCB acting as original edge connector in SRM-001 and then use SRE-725 extention cable (or just a small part of it ended with 5-pin plug) to make a nice adaptor instead of full cable replacement. That should be rather easy and headphones would still remain usable with portable amp.
 
 

 

[BoilermakerFan]

Quote:

 
I think you can find or create the tiny PCB acting as original edge connector in SRM-001 and then use SRE-725 extention cable (or just a small part of it ended with 5-pin plug) to make a nice adaptor instead of full cable replacement. That should be rather easy and headphones would still remain usable with portable amp.
 
 

Thanks.  The 001/003 cables are easily removed right at the drivers.  Nothing at all like their big brothers. 
 
 

 

[MrGreen]

Quote:

Here are the pics of the new, improved tips:

What am I looking at here? How deep do they go? Are they molded for the pinnae as well?

 

[BoilermakerFan]

Quote:

What am I looking at here? How deep do they go? Are they molded for the pinnae as well?

Uh, yeah.  How else would they stay in?  They were molded with the drivers inserted into my ears like the stock tips where on them with foam protecting the screed. 
 
The top of the ear mold fits under the Helix at the Fossa triangularis.
 

 

[visualguy]

 
Quote:

The 717 does not have the same issue.

 
What's the issue with the SRM-727 in terms of sound quality? I read here about the mod, but what's the impact on the sound?
 
The 727 without the mod sounds fine to me with the SR-007, so I'm curious about what the problem is that I haven't noticed so far.
 
The SRM-007ta (unlike the SRM-727) doesn't drive the SR-007 particularly well - there's a noticeable lack of control in the bass (flabby bass) on some music, and there's a slight lack of dynamics, although it isn't nearly as bad as you would think by reading comments here...
 
Anyway, what's wrong with the 727 from a sound (not amp design) perspective?
 

 

[padam]

It was been discussed several times before, the 727 uses no feedback in the output stage so it does have a different sound which some might or might not like.
 
Audiod wrote a direct comparison a while ago

 

[visualguy]

 
Quote:

It was been discussed several times before, the 727 uses no feedback in the output stage so it does have a different sound which some might or might not like.
 
Audiod wrote a direct comparison a while ago

What do you mean by "different sound"? Different from what?
 
The comments by audiod don't match my experience at all. He says that "The 727 sounds lifeless on the O2's and never really opens up". Huh? There's nothing "lifeless" about it...
 
I have a KGSS and a 727 which I compared using my SR-007 mk1. When both are warmed up, they sounds very similar. I find that the KGSS is slightly better, but the improvement in sound is very marginal.
 
Like I said, the 007ta is noticeably less good, although not horrible by any means, but the 727 is pretty equivalent to the KGSS in my experience.
 

 

[Teejaay]

anyone know where to buy o2 pads black at a good price.

 

[cascode]

Quote:

Here is a picture of one of the 2 identical plug in boards (one left, one right channel) after the mod.

 
Thanks for posting the photo - that makes it very clear. It's actually easier than I'd imagined - and easy to remove, so worth the experiment regardless.
 
Is this mod particularly recommended when the amp is used with SR-007 headphones?  Most of the posts I've read have been from people using it in that combonation.  Would those who have heard it also recommended the mod if the amp is partnered with lambda headphones?
 
 
 
 

 

[Knijsterbek]

I have no Lambda pro headphones, but with Sigma pro the amp sounds fine to me.
 
I would like to know about the gremlins of the gain mod as Spritzer mentioned.

 

[padam]

Quote:

 


What do you mean by "different sound"? Different from what?
 
The comments by audiod don't match my experience at all. He says that "The 727 sounds lifeless on the O2's and never really opens up". Huh? There's nothing "lifeless" about it...
 
I have a KGSS and a 727 which I compared using my SR-007 mk1. When both are warmed up, they sounds very similar. I find that the KGSS is slightly better, but the improvement in sound is very marginal.
 
Like I said, the 007ta is noticeably less good, although not horrible by any means, but the 727 is pretty equivalent to the KGSS in my experience.
 

I meant the 727 is obviously different from the 717 and as I wrote there is nothing wrong if you like the 727 sound, some others like it as well but Spritzer does not. I might get one 727 later on to see if the mod makes a substantial difference and I could compare it with my friend's 717 as well.