Today my Fostex 127e went hmmmmmmmmmmm

Godzilla · 2nd July 2007, 01:31 AM

Playing thru the SI amp and a portable cd player as the source.

Hope the drivers are ok. I will troubleshoot later in the week.

I recently connected my small Infinity powered sub. But even with the sub unplugged (wires still in the SI terminals), the speakers just go hmmmmmmmmmm. Turning the volume knob doesnt change the sound.

No music plays at all. Would anyone know what this could be?

OzMikeH · 2nd July 2007, 01:57 AM

not the speakers, WOuld probably be your ampo because the volume doesnt vary.

Geoff H · 2nd July 2007, 01:57 PM

Rest easy, it is the amp. Speakers on their own can't hum. It sounds like the amp has gone DC, feeding ripple to the speakers.

Leave the speakers disconnected when you power up the amp next to avoid toasting the voice coils. Measure the voltage at the amp output. It should be close to zero.

Geoff.

Seraph · 2nd July 2007, 02:57 PM

Guessing the chip may be fried and that may have been due to excess current draw through the SI ground. Infinity grounding scheme may have created a high current ground loop through the SI. Check the small ground choke separating the analogue and power grounds in the SI. Are the ground tracks and connections in tact?

ronc · 2nd July 2007, 03:17 PM

the speakers just go hmmmmmmmmmm.

Maybe they are humming cuz they dont know the words.

ron

Godzilla · 2nd July 2007, 03:20 PM

>>> Check the small ground choke separating the analogue and digital grounds in the SI. Are the ground tracks and connections in tact?

I will try to check that. I have confirmed it's the amp. It hummmmms on the Pioneer/Piezos too. Luckily, the speakers are fine (the Pioneers that is. Havn't yet checked the 127s).

Yeah, the variable was the Infinity subwoofer. It did work the first few times i used it. Then i let it sit for a week or so and when i turned it on everything hummmmmmmd.

I hope the SI amp can be made to work again. I'd like to modify it. If not, i'm glad it only cost $30.

Thanks,
Godzilla

Taperwood · 2nd July 2007, 06:31 PM

I suspect your sub toasted your SI. There is something about the way some speakers are grounded that the T-amps do not like. I tried searching in the Class-D forum but could not find it. I know it's there somewhere. Sorry I can't be more specific, but it's something to do with the ground and how the T-amps are built.

Doug

chrisb · 3rd July 2007, 03:07 AM

might be too late for this current SI amp, and I certainly hope the drivers are OK., but you might want to check out our dear friend Ed Schilling's website/forum regarding the magic box to make safe this type of connection:

http://www.audiocircle.com/circles/i...?topic=38384.0

Taperwood · 3rd July 2007, 04:55 AM

Quote:

Originally posted by chrisb
might be too late for this current SI amp, and I certainly hope the drivers are OK., but you might want to check out our dear friend Ed Schilling's website/forum regarding the magic box to make safe this type of connection:

http://www.audiocircle.com/circles/i...?topic=38384.0

Yeah, that's the solution. Here's Ed's explanation from his website:

http://www.thehornshoppe.com/Magic%20Cable.html

ghpicard · 4th July 2007, 01:35 PM

Short and sweet answer: bridged output amps shouldn't have anything but floating loads. A powered subwoofer should have a way to "float" the inputs otherwise it will short one of the "halfs" of the bridge to ground. It will depend on the specific amp what will happen.
Many subwoofers plate amps have a visible bridge between the (-) input to "ground" that can be removed for this specific case of bridged amps.
I'm sorry Jeff but I think the amp went south...

Gastón

2nd July 2007, 01:31 AM	#1
Godzilla diyAudio Member Join Date: Nov 2005 Location: New York	Today my Fostex 127e went hmmmmmmmmmmm Playing thru the SI amp and a portable cd player as the source. Hope the drivers are ok. I will troubleshoot later in the week. I recently connected my small Infinity powered sub. But even with the sub unplugged (wires still in the SI terminals), the speakers just go hmmmmmmmmmm. Turning the volume knob doesnt change the sound. No music plays at all. Would anyone know what this could be? __________________ www.zillaaudio.com/bib/bib.asp www.ZillaAudio.com

2nd July 2007, 03:20 PM	#6
Godzilla diyAudio Member Join Date: Nov 2005 Location: New York	>>> Check the small ground choke separating the analogue and digital grounds in the SI. Are the ground tracks and connections in tact? I will try to check that. I have confirmed it's the amp. It hummmmms on the Pioneer/Piezos too. Luckily, the speakers are fine (the Pioneers that is. Havn't yet checked the 127s). Yeah, the variable was the Infinity subwoofer. It did work the first few times i used it. Then i let it sit for a week or so and when i turned it on everything hummmmmmmd. I hope the SI amp can be made to work again. I'd like to modify it. If not, i'm glad it only cost $30. Thanks, Godzilla __________________ www.zillaaudio.com/bib/bib.asp www.ZillaAudio.com

3rd July 2007, 03:07 AM	#8
chrisb diyAudio Member Join Date: Aug 2002 Location: victoria BC	might be too late for this current SI amp, and I certainly hope the drivers are OK., but you might want to check out our dear friend Ed Schilling's website/forum regarding the magic box to make safe this type of connection: http://www.audiocircle.com/circles/i...?topic=38384.0 __________________ you don't really believe everything you think, do you? community sites t-linespeakers.org, frugal-horn.com commercial site planet10-HiFi

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2nd July 2007, 01:57 AM	#2
OzMikeH diyAudio Member Join Date: Mar 2007	not the speakers, WOuld probably be your ampo because the volume doesnt vary.

2nd July 2007, 01:57 PM	#3
Geoff H diyAudio Member Join Date: Oct 2006	Rest easy, it is the amp. Speakers on their own can't hum. It sounds like the amp has gone DC, feeding ripple to the speakers. Leave the speakers disconnected when you power up the amp next to avoid toasting the voice coils. Measure the voltage at the amp output. It should be close to zero. Geoff.

2nd July 2007, 02:57 PM	#4
Seraph diyAudio Member Join Date: Mar 2007	Guessing the chip may be fried and that may have been due to excess current draw through the SI ground. Infinity grounding scheme may have created a high current ground loop through the SI. Check the small ground choke separating the analogue and power grounds in the SI. Are the ground tracks and connections in tact?

2nd July 2007, 03:17 PM	#5
ronc diyAudio Member Join Date: Mar 2003	the speakers just go hmmmmmmmmmm. Maybe they are humming cuz they dont know the words. ron

2nd July 2007, 06:31 PM	#7
Taperwood diyAudio Member Join Date: Apr 2005 Location: Bremerton, WA.	I suspect your sub toasted your SI. There is something about the way some speakers are grounded that the T-amps do not like. I tried searching in the Class-D forum but could not find it. I know it's there somewhere. Sorry I can't be more specific, but it's something to do with the ground and how the T-amps are built. Doug

4th July 2007, 01:35 PM	#10
ghpicard diyAudio Member Join Date: May 2005 Location: Buenos Aires	Short and sweet answer: bridged output amps shouldn't have anything but floating loads. A powered subwoofer should have a way to "float" the inputs otherwise it will short one of the "halfs" of the bridge to ground. It will depend on the specific amp what will happen. Many subwoofers plate amps have a visible bridge between the (-) input to "ground" that can be removed for this specific case of bridged amps. I'm sorry Jeff but I think the amp went south... Gastón

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