Sunfire True Sub - Help Fixing Auto On

[OldiesButGoodies]

I am slowly removing imperfections from the Sunfire True Sub Mark IV sub.  The recent output cap replacements were a huge improvement - the hum appears to be gone and it sounds cleaner and tighter.  The next frontier is the auto-on circuit.  It takes a while for this cube to detect there is music playing and kick in.  I have to significantly pump up the volume in the pre or go fiddle with the potentiometer in the plate amp so it wakes up (the latter erases the level setpoint,  so it is a bit of  pain).   Any ideas on how to troubleshoot this? 

Thanks,

OBG

[Reverend]

Any ideas on how to troubleshoot this?

Yeah, give it to Tom and Anders to fix.   

[OldiesButGoodies]

Where is the fun in that?

[thuffman03]

Get rid of the POS sub and get a real sub.  Like a JL Fathom.   

[OldiesButGoodies]

OMG,  did Huff just say what he wrote?  The pope may excommunicate him!

[thuffman03]

OMG,  did Huff just say what he wrote?  The pope may excommunicate him!

All I know is if I did not already have two Sunfire True Subs, I would own a JL Fathom.  Tom had one in his shop and it kicked @ss!

[OldiesButGoodies]

I remember that sub - went to the Carver boys in FL in exchange for a - maybe a Sunfire Tube Pre?  It was amazing what it could do - I remember listening to Laurie Mayer's Black Lining on it.  Incredibly solid bass. 

Maybe some day when I grow up I will get one.  For now I just want to get the Sunfire to wake up when I need it to.

[Anders]

Maybe it just needs to be kicked in the right place
Or maybe a percussive re-alignment.

[Kingman]

Get rid of the POS sub and get a real sub.  Like a JL Fathom.   

...Tom's right in one respect...the Sunfires shake themselves to death. Currently have 4 and all but 1 are in need of service or will need it soon. Got a plate amp at VHF right now. The Fathom is a little pricy though. I heard the Epic subs do a great job at a reasonable price but that's just cross talk on the forums.

[OCCD]

Anders and I know what the problem is...

[OldiesButGoodies]

Actually,  after auditioning this sub in PR I would buy this before the Fathom (in terms of value it is a better deal):

http://www.hsuresearch.com/products/vtf-15h.html

And a tip for slowing down walking sunfire subs:  plop a stack of granite samples on top with blue tack in between layers,  make him do heavy squats if he wants to walk.

I am pondering separating the plate amp from the box and putting it in an external chassis,  away from the jumping bean.  Would need to have a blank plate machined in 1/8 stainless steel,  would probably be expensive and only make a minimal difference,  but it does sound like a fun project. 

I am waiting for Anders et al to share their take on how to tame auto on.  I am thinking an infrared detector that senses when I am in the room and turns it on a set minimum time using a 555 circuit or better yet, until I tell it to revert to off.  That or Anders could tell me what magic condenser or resistor or rheostat or peaking coil controls the sensitivity.  That is what a brother would do.

 

[Reverend]

And a tip for slowing down walking sunfire subs:  plop a stack of granite samples on top with blue tack in between layers,  make him do heavy squats if he wants to walk.

F that.  Go to Dick's and pickup a pack of hockey pucks.  Problem solved.

[Anders]

Maybe the flux capacitor isn't fluxing properly 

[MacGeek]

Why not by pass the auto on , hard wire the sub to always be on (or install an on/off switch) and plug it into a current sensing outlet.  Or, some pre-amps have switched rear panel outlets.

[OldiesButGoodies]

Macgeek,  that is a brilliant suggestion. 

But I did find this piece of info in the interwebs:

...the auto on-off time is set by a single resistor-capacitor combination. R40 and C18. These are 5.2 megohms and 22uF. You will find these at the bottom-left corner of the quad jfet opamp U2 (MC34004). The 22uF cap looks to be a higher quality that all the other electrolytics.

Time to open that baby up again!

PS: On a related note,  I may drop by ater to pick up a 22uf cap.  Love ya!