Noisy PJB micro 7

[edr]

Feeling a little bit dumb right now and could use some advice.

TLDR pjb micro 7 has background white noise, probably in power amp stage. no idea if there’s a good way to diagnose that further.
Since the seller said the tweeter was busted, I bought a new tweeter but they both sound the same to me and I don’t think they’re the problem.

the other week I picked up a Phil Jones Bass micro 7 used at a killer price as an impulse buy. The store said it was cheap because the tweeter was busted so they disconnected it. It still sounded great without it, so now it’s mine.
Instead of checking out the tweeter myself, I immediately got in touch with pjb and bought a replacement tweeter off of them. It arrives, I connect it up, there’s some background hiss. Not a ton, mind you, but it’s there. Definitely more audible noise with the tweeter connected.
So I swap back in the old one, and it’s the same deal. I swap back and forth like twenty times and can’t find any difference in sound. I really should have held off buying that new tweeter as I have no idea what to do with it.
I’m assuming that the person at the shop heard the (white?) noise, disconnected the tweeter, heard way less noise, and called it a day.

I messed with all of the knob settings, and the noise seems to be independent of the volume controls or preamp or anything else. It’s the same with or without a bass plugged in, same for the aux in. The headphone channel does not suffer from the noise. Haven’t tried the line out yet but I’m assuming the same situation. That’s why I think the noise might be related to the power amp circuit. Not that I know my way around these things.
So,
1: any ideas on how to make the noise issue go away? It’s not loud to the point of unusability but it’s definitely not acceptable for a product like this. Sounds like white noise. Volume wise, it’s a bit louder than a whisper but way less than talking.
2: what do I do with the extra tweeter? I think I could use either of them. Or none. But if I can fix the noise issue I’d love to have the tweeter. I doubt pjb would accept a return on the new tweeter since there’s a thin layer the attachment screws have to pierce when you install it, so it’s visibly not new.

thanks for listening to the ramble and my stupidity! I just want to have a really nice practice amp out of this by the time I’m done.

 

[agedhorse]

This is why I suggest that proper diagnostics leads to a proper repair. If the old tweeter wasn't bad, replacing it isn't going to fix something that wasn't broken. I unfortunately see this all the time.

If two different amps sound the same, have the same background noise floor, chances are good that it's simply the way it's designed. If a third one has the same noise floor, than IMO that would be conclusive.

Maybe you can sell the spare tweeters on eBay?

 

[edr]

This is why I suggest that proper diagnostics leads to a proper repair. If the old tweeter wasn't bad, replacing it isn't going to fix something that wasn't broken. I unfortunately see this all the time.

If two different amps sound the same, have the same background noise floor, chances are good that it's simply the way it's designed. If a third one has the same noise floor, than IMO that would be conclusive.

Maybe you can sell the spare tweeters on eBay?

i sure was naive for assuming the guy at the store knew what he was talking about, and regret not verifying it myself. I’m not very knowledgeable in the amp space at all.
Live and learn I guess.

I’m not sure how high the noise floor is on this, but it’s definitely too high. It’s more audible than on my much larger GKs. I’ll ask in the pjb club if it’s normal to have this much noise, but I’m pretty sure it isn’t.

 

[agedhorse]

Maybe, but again good diagnostic (including testing against another known good unit) is the first step in determining if there really is a problem or that you are just more sensitive than others to the noise.

 

[edr]

Maybe, but again good diagnostic (including testing against another known good unit) is the first step in determining if there really is a problem or that you are just more sensitive than others to the noise.

You’re right, of course. Unfortunately I don’t have another lying around and no easy way to get one. I might just have to live with the noise and call it an expensive lesson learned

 

[agedhorse]

If there ends up being nothing wrong with it, then it's not an expensive mistake. You just bought an amp that you didn't evaluate to see if it would be suitable for your needs, then bought ANOTHER on. You can always sell them, right?

 

[RodRy]

You’re right, of course. Unfortunately I don’t have another lying around and no easy way to get one. I might just have to live with the noise and call it an expensive lesson learned

You may have good luck at the Combo Club (which you have already posted to, that's why I found you here) or the PJB club.

I agree with your earlier statement, it's hard to get two of the same amp to compare. Used to be that you may find a good store that stocked a few, but now?
Best of luck!

 

[iagtrplyr]

Okay, edr, I clicked on the link you left and now understand your dilemma. I’m sure at this point you feel it’s hopeless, but from what I’ve read about how involved Phil Jones is with his products.

Maybe another phone call to discuss what can be done to remedy the situation. I’m sure you wish to spend zero on the endeavor, but a shipping fee might be worth it depending on what they offer you. Don’t give up on the notion that you can get your combo back to specs.

 

[edr]

You guys are super. I sent an email off to the person I was in touch with about the tweeter, hopefully I can find out more soon. thanks for convincing me not to give up!

 

[edr]

They said I can send it in to them but they’ll bill the work $75 an hour. Not that I’d blame them for that.
This is becoming less and less economical as we speak but I think I’d like to get a nice practice amp out of this mess and learn a bit along the way. One of the problems with me always springing for entry level stuff is that any repairs I can’t do myself never seem worth it. But thankfully I can afford it. May as well see what happens.
Edit: I bought this amp for $150, new one runs for 300, I think?

 

[agedhorse]

Maybe you ought to buy new with a warranty, it would be cheaper for you in the long run.

Before you assume something is wrong, be sure that something IS wrong. The quickest way to end up with a set of new problems is to attempt to repair an amp that has nothing wrong with it.

 

[edr]

Never followed up here, so here's the update.
A few weeks ago I finally shipped the amp off to PJB so they could take a look at it.
The person I was in contact with said they'd accept the extra tweeter back and credit it against my repair costs.
No news as to the problem / solution yet, and I know that I'm not making the most economical choices here, but... I just want to bring some conclusion to this.

 

[edr]

They replied, said the noise was within spec, and they fixed an issue with the power cord that was unrelated to the noise.
I guess I shouldn't have gone with the advice of a thread full of fanboys (no offense! I'm sure the higher-end models have a much better noise level than this one, and are generally good products) and investigated more fully myself. Or just not impulse bought the dang thing to begin with.
Oh well! I'll just call this an expensive lesson. Will still probably use it around the house anyway.
Also, how would I measure the background hiss myself?

 

[agedhorse]

Again, it's not an expensive lesson as you have a fully functional amp that can be resold if it doesn't suit your needs. An expensive lesson would be buying an amp that was in fact defective, out of warranty and economically unrepairable.

 

[edr]

Again, it's not an expensive lesson as you have a fully functional amp that can be resold if it doesn't suit your needs. An expensive lesson would be buying an amp that was in fact defective, out of warranty and economically unrepairable.

An excellent point. You've been the voice of reason against my idiocy for this entire thread and I greatly appreciate it.
For the total money I spent, I could have bought it new. It's not a bad amp. I just wish I was smarter about this whole thing.

If I knew what I did now, I could have just reconnected the tweeter it came with, been satisfied with the sound, and realize it really was a steal since the tweeter worked just fine as is, all to the tune of 150usd.

 

[Deleted member 165050]

Is your noise present all the time or just while playing? Asking because I have a similar issue with my Session 77 but it's quiet while not playing, then the hiss appears if you play. As with yours it's not in the headphone out so I'm also suspecting power stage, just wondering if its a characteristic of this specific PJB range (which after all is very budget priced for PBJ). I was thinking of selling mine but maybe I'll learn to live with it...

 

[edr]

Is your noise present all the time or just while playing? Asking because I have a similar issue with my Session 77 but it's quiet while not playing, then the hiss appears if you play. As with yours it's not in the headphone out so I'm also suspecting power stage, just wondering if its a characteristic of this specific PJB range (which after all is very budget priced for PBJ). I was thinking of selling mine but maybe I'll learn to live with it...

As stated earlier, the noise on mine is present always. Even if input is disconnected, even if the amp is muted. I don't think the issue you're seeing is related.



In other news, the amp came back today. The noise isn't bad as long as I'm not actively listening for it. I still like the amp.

Thus ends this saga.

 

[Deleted member 165050]

The noise isn't bad as long as I'm not actively listening for it. I still like the amp.

Same feeling from me for my Session 77 - it's basically a good amp and my noise is only an issue at low volumes, and then only if I listen for it.

 

[Wibble666]

Can’t help thinking that the tweeter isn’t totally necessary for bass... just use it without one. Unlike the micro and session the double four doesn’t even have one but seems to do ok despite that. Phil probably included one more for the auxiliary in requirements than for the actual bass input itself.

my only slight concern would be if there was a crossover split between the tweeter and woofer, but as far as bass goes that probably won’t be an issue here.

 

[Deleted member 165050]

Can’t help thinking that the tweeter isn’t totally necessary for bass... just use it without one. Unlike the micro and session the double four doesn’t even have one but seems to do ok despite that. Phil probably included one more for the auxiliary in requirements than for the actual bass input itself.

my only slight concern would be if there was a crossover split between the tweeter and woofer, but as far as bass goes that probably won’t be an issue here.

The Micro 7 and Session 77 are marketed as full-range with frequency response from 30Hz to 20KHz and according to the PJB site are intended for any instrument rather than just bass... I guess they decided to hit a wider market with those amps.