Vintage HiFi Audio Forum

Audio Discussion => DIY => Tweaks => Topic started by: OldiesButGoodies on September 23, 2012, 10:51:54 PM

Title: Sunfire True Sub - Help Fixing Auto On
Post by: OldiesButGoodies on September 23, 2012, 10:51:54 PM
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

Title: Re: Sunfire True Sub - Help Fixing Auto On
Post by: Reverend on September 24, 2012, 08:33:03 AM
Any ideas on how to troubleshoot this?

Yeah, give it to Tom and Anders to fix.   8)
Title: Re: Sunfire True Sub - Help Fixing Auto On
Post by: OldiesButGoodies on September 24, 2012, 09:13:28 AM
Where is the fun in that?
Title: Re: Sunfire True Sub - Help Fixing Auto On
Post by: thuffman03 on September 24, 2012, 09:35:30 AM
Get rid of the POS sub and get a real sub.  Like a JL Fathom.   :laugh:
Title: Re: Sunfire True Sub - Help Fixing Auto On
Post by: OldiesButGoodies on September 24, 2012, 10:04:59 AM
OMG,  did Huff just say what he wrote?  The pope may excommunicate him!
Title: Re: Sunfire True Sub - Help Fixing Auto On
Post by: thuffman03 on September 24, 2012, 01:07:34 PM
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!
Title: Re: Sunfire True Sub - Help Fixing Auto On
Post by: OldiesButGoodies on September 24, 2012, 01:38:32 PM
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.
Title: Re: Sunfire True Sub - Help Fixing Auto On
Post by: Anders on September 24, 2012, 05:41:17 PM
Maybe it just needs to be kicked in the right place ;)
Or maybe a percussive re-alignment.
Title: Re: Sunfire True Sub - Help Fixing Auto On
Post by: Kingman on September 26, 2012, 06:33:52 PM
Get rid of the POS sub and get a real sub.  Like a JL Fathom.   :laugh:
...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.
Title: Re: Sunfire True Sub - Help Fixing Auto On
Post by: OCCD on September 27, 2012, 04:14:32 PM
Anders and I know what the problem is... 8)
Title: Re: Sunfire True Sub - Help Fixing Auto On
Post by: OldiesButGoodies on September 27, 2012, 09:16:30 PM
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 (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.

 ;D

Title: Re: Sunfire True Sub - Help Fixing Auto On
Post by: Reverend on September 27, 2012, 09:23:55 PM
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.
Title: Re: Sunfire True Sub - Help Fixing Auto On
Post by: Anders on September 28, 2012, 01:27:29 AM
Maybe the flux capacitor isn't fluxing properly  :laugh:
Title: Re: Sunfire True Sub - Help Fixing Auto On
Post by: MacGeek on September 28, 2012, 04:22:38 AM
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.
Title: Re: Sunfire True Sub - Help Fixing Auto On
Post by: OldiesButGoodies on September 28, 2012, 09:47:48 AM
Macgeek,  that is a brilliant suggestion. 

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

Quote
...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!


:P :P :P :P :P


PS: On a related note,  I may drop by ater to pick up a 22uf cap.  Love ya!
Title: Re: Sunfire True Sub - Help Fixing Auto On
Post by: thuffman03 on September 28, 2012, 10:04:59 AM
Or, some pre-amps have switched rear panel outlets.

You should never plug an amp into the back of a preamp.  Bad things will happen to the preamp power supply.  Magic smoke could be let out.
Title: Re: Sunfire True Sub - Help Fixing Auto On
Post by: OldiesButGoodies on September 28, 2012, 10:12:39 AM
Sunfire subs do require their own power station,  preferably connected to a separate light pole transformer several streets over,  to minimize hum (that and a prayer to the Gods of hum at least daily).   But Macgeek's idea could be made to work. 
Title: Re: Sunfire True Sub - Help Fixing Auto On
Post by: MacGeek on September 29, 2012, 07:00:30 AM
A/C power management, including switching, can be a pain.  McIntosh and maybe other companies used to make a power strip (MAC was an R-612).  Six outlets rated at 15 amps that plugged into the wall with a beefy power cord.  On the opposite end of the strip is a second power cord that plugs into a switched outlet on an amp or receiver.  When the amp is turned on, a small a/c signal from the switched outlet passes to the power strip activating it.  Anything plugged into the strip comes on when the switched outlet is on.  Audio Classics has one listed for just over $100.

Belkin makes a power strip with a current sensing outlet.  Plug an amp or preamp into the current sensing outlet and when the amp is turned on, the rest of the strip is activated.  It's about $30 at home centers, K-mart, etc.

Both my analog audio rig and home theater have about a dozen a/c plugs to manage.  I am using both of these devices with excellent results at relatively low cost.  I do have to note, my amplifiers are currently activated via 12v triggers, so the gear plugged into the power strips draws less current than the amps do.  However, before the 12v triggers, I did use these devices to switch the amps

Title: Re: Sunfire True Sub - Help Fixing Auto On
Post by: OldiesButGoodies on September 29, 2012, 09:07:50 AM
MG:

I recently updated the receiver that drives my home theater rig to an Onkyo TX-NR1009.  This receiver has every bell & whistle currently available except a switched outlet or a 12v signal for zone 1 (strangely, it has zone 2 and zone 3 12v triggers - strange design decision - hoping a firmware update will change it).  I am going to try the Belkin as a solution for that problem - thanks. 

OBG
Title: Re: Sunfire True Sub - Help Fixing Auto On
Post by: MacGeek on October 01, 2012, 06:57:59 AM
I got my Belkin strip for free.  Log onto your electric suppliers website and check to see if there is an energy audit, or whatever they may call it.  I did the audit on line and in return, a few weeks later, received a box full of stuff, including the Belkin, a couple of LED nightlights and around 10 CFL light bulbs.  I'll guess about $50 worth of useful stuff for free, not even a shipping charge.
Title: Re: Sunfire True Sub - Help Fixing Auto On
Post by: bigdealz on July 05, 2018, 05:12:08 AM
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


Can you share the details about the hum fix.  I've been doing some research and think I may need to replace my caps.  My sub will frequently start humming at 60 hertz, when it hums I can turn down the sub volume all the way and get no noise and no sound.  I can lower the crossover setting and minimize the hum.  Unplugging the sub from outlet or rca will get rid of the hum and keep it away for a while after I plug it back in.  I've also recently found turning the lights on and off can also get rid of the hum.  I tested with a cheater plug and that didn't help, actually the sub has a bit of noise when not playing, so it was worse that using the grounded plug.  I don't believe this is a ground loop.

After getting the hum fixed I'm also interested in changing the auto power on to something with a remote trigger from my receiver.

I'd like to document the fix if this works so other can use it.  I also like the JL sub swap, I think I may try that in the future if I can fix the amp and if the sub ever needs replacement.