Cerwin Vega D9 Hum question

[mjstriker]

So I have a pair of CV D9's hooked up to my PL 400 and have been cranking out some great music. Still saving up for the full White Oak makeover but in the mean time I have decided to recap the speakers with some new dayton caps. All the caps were replaced except one 100uf Non-polar which I couldn't bring my self to pay $30 a piece for some daytons so I am in the process of getting some electrolytics sent. The issue I have right now is that one speaker post-cap has a pretty significant hum. I looked around and some forums talk about a 60hz hum but I haven't found out how to go about fixing it. I compared both crossovers and everything is identical. I re-heated every solder joint to make sure there was a good connection.

At this point I am going a little crazy because I am almost positive there was no hum prior. I even swapped out amp and pre-amp and swapped left and right and the hum stays with the speaker so most likely the crossover. I'm just wondering if I am missing something obvious or maybe I need to start from scratch with the crossover.

On a sidenote the one electrolytic that I didn't replace might have a little bulging on it but to me it is difficult to say and I am pretty sure there was no hum prior.

Thanks for the help

 

[laatsch55]

Do you have any test equipment?

 

[mjstriker]

Unfortunately, I have no equipment except a DMM.

To add, the hum is the same regardless of the volume adjustment.

Unrelated to the hum but I was also wondering how I could go about removing the fuse and the circuit breaker from the circuit? Would this make any improvements in sound even?
This was mentioned in another thread of mine (pretty sure by laatsch55) but I didn't ever get around to it. The fuse I know I could just connect the input and output but for the circuit breaker I wasn't sure if it was that simple. Didn't want to find out the hard way I was wrong.

 

[laatsch55]

I don't think you want to do away with the circuit breaker, saved the mids and tweets on my D-9's A LOT.

 

[laatsch55]

Does your DMM have a frequency counter on it?

 

[mjstriker]

Does your DMM have a frequency counter on it?

Yes

 

[Gepetto]

Unfortunately, I have no equipment except a DMM.

To add, the hum is the same regardless of the volume adjustment.

Unrelated to the hum but I was also wondering how I could go about removing the fuse and the circuit breaker from the circuit? Would this make any improvements in sound even?
This was mentioned in another thread of mine (pretty sure by laatsch55) but I didn't ever get around to it. The fuse I know I could just connect the input and output but for the circuit breaker I wasn't sure if it was that simple. Didn't want to find out the hard way I was wrong.

And the hum goes away when you turn the amp off?

 

[speakerman1]

Does Hum follow speaker?

 

[mjstriker]

Does Hum follow speaker?

Hum follows speaker. Did some more tests and it does not appear with amp turned on. Only appears after I turn the preamp on. I tried switching the left and right on the preamp and it stays with the speaker. Gonna try another set of speakers to double check preamp.

 

[jbeckva]

I don't think you want to do away with the circuit breaker, saved the mids and tweets on my D-9's A LOT.

I was going to say "I did, and haven't had any probs", but then... it's "Lee"... and his tendency to "Mach 8" it is stronger than mine (ey .. my earz are more sensitive .. to PAIN.. ). But seriously... I've had the CB and the LPads bypassed for awhile now, but definitely still keep the fuse in (beefed up with err.. I think.. 6 amp fuses). I've had 'em going pretty good tho with WOPL'd 700's, and so far still going.. .

I can take some pics tonight if you want...

 

[jbeckva]

Hum follows speaker. Did some more tests and it does not appear with amp turned on. Only appears after I turn the preamp on. I tried switching the left and right on the preamp and it stays with the speaker. Gonna try another set of speakers to double check preamp.

That is so strange! Hey do you have any spare speaker wire? If you do, run a temporary line to it and see. Reason being is maybe it's picking up interference on it's current route? Hmmm... real head scratcher here..

 

[mjstriker]

That is so strange! Hey do you have any spare speaker wire? If you do, run a temporary line to it and see. Reason being is maybe it's picking up interference on it's current route? Hmmm... real head scratcher here..

I will try another run of cable. Didn't think of that but sounds like a good idea. Didn't have much time to problem solve yet so will try a few things tonight and report back.

Would appreciate a few pics of the crossover if you get a chance

 

[Northwinds]

Just asking but does each LR RCA jack on the back of your preamp have a shared internal ground??? Or does each RCA have it's own ground? Speaker wire could be the fault but this sounds like a small ground issue. I am by no means as experienced with this stuff as Jer, just thinking out loud

 

[laatsch55]

Put the DMM on frequency count, see whatn freq you're dealing with. That'll give you some idea where to look.

 

[mjstriker]

Honestly don't know if the outputs are common ground. Never checked. It's a citation 17.

Do I check by checking continuity between point (left and right or left of one output to left of another)

The setup really hasn't been changed much except switching around to test a tube amp a couple days ago. The only thing I can think of was when I switched back to the PL 400 I didn't have sound out of the suspect speaker but was getting juice to the amp. Jiggled the speaker wire and had a loud pop and then sound. To be honest can't remember if the hum started after that or after the capacitor change.

 

[speakerman1]

If it is following the speaker it is the preamp. Can you A+B speaker outputs on the pre?



=

 

[mjstriker]

If it is following the speaker it is the preamp. Can you A+B speaker outputs on the pre?



=

I can A+B the pre amp speaker outputs. Will have to wait to after work. What would I be looking or listening for when I do that?

 

[speakerman1]

I can A+B the pre amp speaker outputs. Will have to wait to after work. What would I be looking or listening for when I do that?

What channel you running now? If it goes away when you change them you know which channel is bad. Is it a hum or buzz. Spend your hard earned money. If you had spent the money you may not be having a problem. Could be a cold solder joint picking something up. Ask Lee it took me over a year to save for what I wanted.

 

[mjstriker]

What channel you running now? If it goes away when you change them you know which channel is bad. Is it a hum or buzz. Spend your hard earned money. If you had spent the money you may not be having a problem. Could be a cold solder joint picking something up. Ask Lee it took me over a year to save for what I wanted.

Currently running pre-out to amp so can't a+b unless I connect speaker directly to back of preamp which I can try later. I tried switching left and right on the pre-out and it stays with the speaker

To me it is a hum but I'll try to get a frequency with my DMM.

 

[Gepetto]

Hum follows speaker. Did some more tests and it does not appear with amp turned on. Only appears after I turn the preamp on. I tried switching the left and right on the preamp and it stays with the speaker. Gonna try another set of speakers to double check preamp.

So it could be the amp channel only when connected to a preamp.

Have you physically swapped the speaker wires from the amp, left to right with nothing on the preamp end changed?