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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Roland Cube 30 Bass or: Putting a sock in it.
Reported as fuzzy sound on the bass guitar E string even at relatively low
levels but otherwise fine sound rendition or backing off the bass control . Feeding a signal generator in then indeed a distinctly fluttery distortion in the range 50 to 70 Hz on top of the wanted output, ok above or below that range. No external speaker output on this cube and before getting inside to scope it or run an external speaker I took the front grille of in case of parasitic rattling but no change. But putting a sock in the front/back vent tube in the speaker surround cured it. Where to go from here ? sci.acoustics.repair ? charge for an old sock ? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#2
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Roland Cube 30 Bass or: Putting a sock in it.
"N Cook" wrote in message ... Reported as fuzzy sound on the bass guitar E string even at relatively low levels but otherwise fine sound rendition or backing off the bass control . Feeding a signal generator in then indeed a distinctly fluttery distortion in the range 50 to 70 Hz on top of the wanted output, ok above or below that range. No external speaker output on this cube and before getting inside to scope it or run an external speaker I took the front grille of in case of parasitic rattling but no change. But putting a sock in the front/back vent tube in the speaker surround cured it. Where to go from here ? sci.acoustics.repair ? charge for an old sock ? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ Interestingly, I have had a similar problem on several Ashdown bass heads. Just as you describe, fuzzy distortion at around 44Hz only, otherwise sounded fine. On each occasion, it has been really bad joints on one of the main smoothing caps - to the point where the cap is effectively not there. With a 'scope on the supply rail, just about full level ripple, but curiously, not a hint of hum on the undriven audio. Only when that string on the bass guitar plucked, or a sig genny put in at that frequency. I completely missed the first one that I had doing it, as it sounded perfectly well on all other material, so sent it back to the shop. He came back a day later armed with a bass guitar, and demonstrated the problem ... Arfa |
#3
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Roland Cube 30 Bass or: Putting a sock in it.
Arfa Daily wrote:
"N Cook" wrote in message ... Reported as fuzzy sound on the bass guitar E string even at relatively low levels but otherwise fine sound rendition or backing off the bass control . Feeding a signal generator in then indeed a distinctly fluttery distortion in the range 50 to 70 Hz on top of the wanted output, ok above or below that range. No external speaker output on this cube and before getting inside to scope it or run an external speaker I took the front grille of in case of parasitic rattling but no change. But putting a sock in the front/back vent tube in the speaker surround cured it. Where to go from here ? sci.acoustics.repair ? charge for an old sock ? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ Interestingly, I have had a similar problem on several Ashdown bass heads. Just as you describe, fuzzy distortion at around 44Hz only, otherwise sounded fine. On each occasion, it has been really bad joints on one of the main smoothing caps - to the point where the cap is effectively not there. With a 'scope on the supply rail, just about full level ripple, but curiously, not a hint of hum on the undriven audio. Only when that string on the bass guitar plucked, or a sig genny put in at that frequency. I completely missed the first one that I had doing it, as it sounded perfectly well on all other material, so sent it back to the shop. He came back a day later armed with a bass guitar, and demonstrated the problem ... Arfa I have also had that fault, we call them Trashdowns around here. I agree with Arfa that it`s probably a dry joint. Roland combos are generally better constructed, or at least, they were! I had a similar fault on a Peavey bass combo, and it turned out to be air fluttering in the bass port, I presume the speaker had somehow deteriorated, a wodge of dacron in the port stopped it temporarily. Ron(UK) |
#4
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Roland Cube 30 Bass or: Putting a sock in it.
In article , Meat Plow wrote:
On Tue, 18 Sep 2007 14:47:28 +0100, N Cook wrote: Reported as fuzzy sound on the bass guitar E string even at relatively low levels but otherwise fine sound rendition or backing off the bass control . Feeding a signal generator in then indeed a distinctly fluttery distortion in the range 50 to 70 Hz on top of the wanted output, ok above or below that range. No external speaker output on this cube and before getting inside to scope it or run an external speaker I took the front grille of in case of parasitic rattling but no change. But putting a sock in the front/back vent tube in the speaker surround cured it. Where to go from here ? sci.acoustics.repair ? charge for an old sock ? Try a different speaker. Well it seems like it could be electronic or mechanical. Putting a sock around a vent will usually make the cone move more and create more distortion, if that is the problem. I can't believe there is a vent, and a 10 inch guitar speaker can't reproduce 50 Hz unless its a HIFI driver. The description about speaker surround, baffles me. greg |
#5
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Roland Cube 30 Bass or: Putting a sock in it.
G wrote in message
... In article , Meat Plow wrote: On Tue, 18 Sep 2007 14:47:28 +0100, N Cook wrote: Reported as fuzzy sound on the bass guitar E string even at relatively low levels but otherwise fine sound rendition or backing off the bass control . Feeding a signal generator in then indeed a distinctly fluttery distortion in the range 50 to 70 Hz on top of the wanted output, ok above or below that range. No external speaker output on this cube and before getting inside to scope it or run an external speaker I took the front grille of in case of parasitic rattling but no change. But putting a sock in the front/back vent tube in the speaker surround cured it. Where to go from here ? sci.acoustics.repair ? charge for an old sock ? Try a different speaker. Well it seems like it could be electronic or mechanical. Putting a sock around a vent will usually make the cone move more and create more distortion, if that is the problem. I can't believe there is a vent, and a 10 inch guitar speaker can't reproduce 50 Hz unless its a HIFI driver. The description about speaker surround, baffles me. greg The vent is clearly seen at lower left on http://media.zzounds.com/media/feed/...CUBE30BASS.jpg looking like a tweeter but the tweeter is mounted co-axially to the main cone. Blocking up this vent means you can turn the bass control up and the volume up without the fluttering noise in the 50 to 70 Hz range. Will take apart tomorrow and scope, external speaker etc. No problems with the reservoir cap solderings -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#6
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Roland Cube 30 Bass or: Putting a sock in it.
Decoupling the negative black lead (not ground) via a 10u polyester cap to
the scope ground the electronic trace was fine at all frequencies and powers. Semi-permanently blocked off the reflex/bass port or whatever that hole is called and the intrusive 50 to 70 Hz induced flutter has gone. Just the normal low level flutter , for low frequency, high power output due to vortexing/cavitation or whatever the normal distortion due to bulk shifting of air mass by a cone is called. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#7
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Roland Cube 30 Bass or: Putting a sock in it.
N Cook wrote:
Just the normal low level flutter , for low frequency, high power output due to vortexing/cavitation or whatever the normal distortion due to bulk shifting of air mass by a cone is called. We call it crapping out |
#8
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Roland Cube 30 Bass or: Putting a sock in it.
Meat Plow wrote:
On Tue, 18 Sep 2007 14:47:28 +0100, N Cook wrote: Reported as fuzzy sound on the bass guitar E string even at relatively low levels but otherwise fine sound rendition or backing off the bass control . Feeding a signal generator in then indeed a distinctly fluttery distortion in the range 50 to 70 Hz on top of the wanted output, ok above or below that range. No external speaker output on this cube and before getting inside to scope it or run an external speaker I took the front grille of in case of parasitic rattling but no change. But putting a sock in the front/back vent tube in the speaker surround cured it. Where to go from here ? sci.acoustics.repair ? charge for an old sock ? Try a different speaker. Just normal "port noise" aka "chuffing" ? Mebbe they need to change the diameter of the port. |
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