[wasupdog]

So, I'm basically done upgrading my rig until I can afford a new DAC that I deem worthwhile upgrading to, which will take a while. I am considering doing the feedback mod to my 727II amplifier. My father is an engineer, but I don't think he has ever really worked with audio equipment. Is it safe to put him on the job, and how long should the job take?

It took me less than an hour including setup and cleanup. You're just removing 4 resistors and soldering 4 new ones in.

 

[AudioThief]

It took me less than an hour including setup and cleanup. You're just removing 4 resistors and soldering 4 new ones in.

Thank you very much. Did you like the results, and do you have any resources I could show my father so he could perform the operation? Bluepirints of sorts

 

[sensui123]

I don't post much..... Been happy with xf2 oo getters Britain made and xf3/xf4 dd getters Holland made for a long time with the bhse. Just landed some nos xf1 oo's..... I had no idea the bhse could scale this much with tubes... The bass, imaging, dimensionality.... It's just a whole other level. Makes me extremely curious now about the metal base Hollands. Some day perhaps... But these xf1s truly are unbelievable.

 

[wasupdog]

 

[wasupdog]

Thank you very much. Did you like the results, and do you have any resources I could show my father so he could perform the operation? Bluepirints of sorts

See pic above. When you open the case these two cards sit upright on the left and right sides towards the front of the case. Rock gently until they pull right out. Remove the 150k resistor towards the bottom. You unsolder it but it's glued to the board so gently try to cut through the glue with a sharp knife or x-acto until it comes off. Now take another 150k/1%/.5watt resistor and solder in like shown above.

It's easier to use new resistors since you can trim the legs to fit. The resistors are going in series so you can just solder it to the leads of the 150k resistor above it. Read the HC thread for more info.

I think the stock 727 is a little raucous sounding. This mod brings the treble and bass under control.

 

[PointyFox]

Edit: Copied from the LCD-4 thread..

Just did the Spritzer BluTac mod to my SR-007A.
I was super skeptical of it. The results actually startled me.
The headphones became much brighter with less mid-bass bloom and slightly less mid-bass impact and more transparent.
Actually a large improvement and now I can say this beats my LCD-4 setup easily. Definitely one of the best headphones in the world.

However! I now get a perfect seal on each side and this causes the drivers to flex when I put on or take off the headphones, a.k.a. "Stax fart".
Is this harmful to the drivers? It's pretty extreme.

Edit: I was told the "Stax fart" isn't known to be harmful. Does anyone know how the BluTack modded SR-007 Mk.2 compares to the SR-009/SR-009S?

 

[Velomane]

Does anyone know how the BluTack modded SR-007 Mk.2 compares to the SR-009/SR-009S?

Also very interested in this.

 

[JimL11]

Does anyone know how the BluTack modded SR-007 Mk.2 compares to the SR-009/SR-009S?

The Stax fart shouldn't be harmful to the headphones on a Stax amp, SRX-Plus or Gilmore amp, which all have bias supply safety resistors. No idea on the other amps.

Tonally the Blutak modded SR-007 Mk2 sounds less bright than the SR-009, and brighter than the SR-007 Mk1, all three compared on a BHSE. Which sounds more "accurate" is a matter of opinion - I prefer the modded 007, others prefer the 009, and some the 007 Mk1, And tonally the Utopia fits in between the modded 007 and the 009. At least, that's the way I hear it.

 

[joseph69]

And tonally the Utopia fits in between the modded 007 and the 009. At least, that's the way I hear it.

This is the way I hear it as well.

 

[statfi]

...The TX2575/TKD 601 series shunt attenuator is IMO at least the equal in SQ to the Slagle AVC and the clear winner on cost, infinitely variable, and package size. Best I’ve found and used so far.

Thanks! Do you have a good link explaining series shunt attenuators?

 

[Jones Bob]

Thanks! Do you have a good link explaining series shunt attenuators?

Just found this link via Google search. Mirrors my experience. https://www.audialonline.com/topics/model-a-volume-control/
Using a TX2575 as the series resistor takes it to another level. These naked Vishay Z foil resistors are the definition of neutral.

Please note, this attenuator is ideally located internally in an amp, at the input of the first gain stage. Used in a separate box with cables, it’s performance suffers.

Running balanced it gets a little different in wiring. Too much to add here, and might confuse some.

 

[statfi]

Just found this link via Google search. Mirrors my experience. https://www.audialonline.com/topics/model-a-volume-control/
Using a TX2575 as the series resistor takes it to another level. These naked Vishay Z foil resistors are the definition of neutral.

Please note, this attenuator is ideally located internally in an amp, at the input of the first gain stage. Used in a separate box with cables, it’s performance suffers.

Running balanced it gets a little different in wiring. Too much to add here, and might confuse some.

Nice! Thanks. I have learned something.

 

[astrostar59]

The Stax fart shouldn't be harmful to the headphones on a Stax amp, SRX-Plus or Gilmore amp, which all have bias supply safety resistors. No idea on the other amps.

Tonally the Blutak modded SR-007 Mk2 sounds less bright than the SR-009, and brighter than the SR-007 Mk1, all three compared on a BHSE. Which sounds more "accurate" is a matter of opinion - I prefer the modded 007, others prefer the 009, and some the 007 Mk1, And tonally the Utopia fits in between the modded 007 and the 009. At least, that's the way I hear it.

The 007 I had, a 2016 model was much better than my previous MK2 which was the black 2012 model. My silver 2015 model sounded very close to a MK1 IMO and had less of the bass bloat and smearing of treble the older Mk2 suffered from. I believe the Stax mafia have rubber stamped the latest 007?

 

[bmichels]

Edit: Copied from the LCD-4 thread..

Just did the Spritzer BluTac mod to my SR-007A.
I was super skeptical of it. The results actually startled me.
The headphones became much brighter with less mid-bass bloom and slightly less mid-bass impact and more transparent.
Actually a large improvement ....?

I have an early SR007 MK1 (and a SR009 ).

--> Does anyone know a Mod for this version of the SR007 ?

 

[SeaWo|f]

The current generation mkii with port mod is viewed as the best version by a few who might be in the stax mafia..

Not sure if your question about modding a mki is serious or joking. But my understanding is that all 007 mods are to get closer to the tonality of the mki?