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Bose 901 Series IV - EQ doing a buzz sound…

C

Castanheiro

New Member
Hi everyone,

I’m fairly new to the forum but I read very good advices here before :) hope someone can help me understanding what is going on with the EQ and if this is some form of easy repair .

I have a pair of Bose 901s connected to the EQ and having an external power amp integrated with my home theater and receiver. They work really great with an emotiva basx A300. Issue is some while ago the EQ started to do some Constant buzz noise but barely noticeable when you are listening or watching something at like -20db but when you are listening at lower levels you can feel it there.

now the sound is great. Looks like something electrical? It also happens with no rcas connected. As son as I connect it to the Electric plug, it does the buzz.

there are no buzz sound from the speakers. They have like a very faint continuous sound, typical of no signal audio source but connected .

hope someone here could guide me in the right direction
 
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Castanheiro said:
Hi everyone,

I’m fairly new to the forum but I read very good advices here before :) hope someone can help me understanding what is going on with the EQ and if this is some form of easy repair .

I have a pair of Bose 901s connected to the EQ and having an external power amp integrated with my home theater and receiver. They work really great with an emotiva basx A300. Issue is some while ago the EQ started to do some Constant buzz noise but barely noticeable when you are listening or watching something at like -20db but when you are listening at lower levels you can feel it there.

now the sound is great. Looks like something electrical? It also happens with no rcas connected. As son as I connect it to the Electric plug, it does the buzz.

there are no buzz sound from the speakers. They have like a very faint continuous sound, typical of no signal audio source but connected .

hope someone here could guide me in the right direction[/QUOTE . Not sure how set you are on having the original eq. You can add any equalizer you wish. Doesn't have to be a Bose. DBX makes a pretty decent entry level eq. About 175$. Probably cheaper than finding a factory replacement. Someone else may want to chime in with what might be the issue with yours. If it was me, I would "____can" the Bose eq whether it worked or not in favor of something else. Just my opinion. Hope you get it solved.
Click to expand...
 
Hopefully someone will chime in on the issue with your eq. If it was me I would get rid of the Bose eq and replace it with an entry level DBX EQ. In my experience, Bose had terrible electronics. I wouldn't think that the eq would be much different from a wave radio. Poor quality. If your not stuck on originality, go with a different eq.
 
Jason Lafler said:
Hopefully someone will chime in on the issue with your eq. If it was me I would get rid of the Bose eq and replace it with an entry level DBX EQ. In my experience, Bose had terrible electronics. I wouldn't think that the eq would be much different from a wave radio. Poor quality. If your not stuck on originality, go with a different eq.
Click to expand...

Big issue will be the rather extreme amount of equalization which the Bose 901 uses to get anywhere close to flat response. Much more extreme than a Wave Radio is.
 
Hope you are still reading your thread. I am servicing this same equalizer. I have purchased new 901's series IV in 1980 without the eq then. About 10 yr ago I purchased the used matching eq. from a most likely unreputable individual(not stolen, just not well cared for). I am presently planning on refurbuishing this eq in the next few weeks. I downloaded (you can find it on hifiengine.com free after you register) the 901 service manual that includes the eq servicing. I am new to this field but I can work my way around a soldering iron. Maybe I can just write what I have found so far in mine and we could both benefit from each others findings.
 
Hello Castanheiro. I have the same eq series IV and I recapped the thing recently. While in there I noticed 2 sets of resistors installed with the wrong values according to the parts list. Maybe it's an after print mod. They are r105/r305 (spec 3Kohm, actually installed 2,4Kohm) and r127/r327(spec 1,5Kohm, actually installed 1 Kohm). Could you check yours and confirm/infirm what's in yours? Would apperciate very much. Cheers
 
Hi everyone, sorry I have been away for some time! in fact im reading through this now. I will need to open it up to see for sure.
Ill try also to post some pictures of it here
 
@Castanheiro , if you are the original purchaser of the Bose speakers, Bose will repair your equalizer for a rather low flat fee...at least they did for me several years ago. Spoke with rep on phone. May be worth a call for you...
 
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