drgordonfreeman

I just purchased a brand new Peavey 6505+ off of Musicians Friend.

I've spent the last few days building an isolation cabinet for my Avatar 2x12 loaded with Celestion G12k-100's. The iso cab works AWESOME. I can crank all the knobs on the head to 10, stand right next to the iso box, and I can carry on a conversation with someone at normal indoor speaking levels.

Everything is great on the first channel, which is the clean/crunch channel, when all knobs are cranked to 10.

When I switch to the second channel, which is the lead channel, the amp breaks down. Basically, I can hear myself playing THROUGH THE AMP head, as if there was a miniature speaker inside the amp head, and when I am not playing, a very loud, high-pitched feedback-sounding hum is generated. I even tried moving the iso cab to another part of the house, and the hum was still generated. If I turn the knobs down to 5, everything is normal again. The second I turn any of the knobs on the lead channel past 5, all hell breaks loose.

Anyone have any ideas what's going on?

Marshall Amps

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V-man

That is the terrifying sound of a head that has no load to drive. Not saying that's what's happening to you, but that sound always brings my nuts straight up to my stomach when there is no FX loop to explain the problem.

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twothemax

check your preamp tubes. could be one is on its way out. even though its new tubes can be very tricky.

drgordonfreeman

yea, i was thinking that maybe one of the tubes (pre or power) was going out.

however, i wasn't sure if a bad tube would render all the symptoms i described, or if maybe they were symptoms of a much bigger problem with the amp.

twothemax

to me it sounds more preamp tube. try swapping your preamps with each other and see what happens. just swap their positions.

RussBert

You need to play the head through a regular cab for a while. You will find that you can't run the lead channel settings too high because all hell breaks loose with feedback. Quality tubes will help. Point is, you can't just run everything on "10". Feedback and blocking distortion take over the signal and make the amp sound like shit. No one, I repeat NO ONE runs the lead channel wide open. If you can run the post and pre of the lead channel past 5, you have broken new ground!

My son has been running 5150's for over a decade now. Careful pre-amp tube selection makes a big difference



Here's the tube layout for your amp, which is rather unconventional...

the tube's are laid out like this,

<--- Power Tubes <--- V4 V3 V5 V2 V1 V6

5150II/6505+ Signal Path,


clean and crunch channels
guitar > V1 (one half) > V6 > V3 > V4 > Power Tubes


lead channel
guitar > V1 > V2 > V5 > V3 > V4 > Power Tubes
V3 is for the FX loop
V4 is the PI

Guitar-Rocker

Too much gain for the tube to handle, slightly microphonic tube, pickups that aren't perfect, every little thing adds up. Lately I've seriously been thinking of limiting gain in my amp builds (to keep people happier) when the knobs get cranked to 11, .....to allow the customer to dime the knob, and only get 65% max gain.

drgordonfreeman

Yea, I'll try this to see if it works. It's simple enough to do.



Well, I mean, it is a regular cab. I'm running it through my Avatar 2x12. The Avatar is sitting in an iso box, but that shouldn't affect anything with the amp. All it really does it save my hearing!

Nonetheless, that's really interesting information you posted.

That's crazy that I can run the clean/crunch wide open, but not the lead. Moreover, what about the sound I'm hearing that comes through the amp head itself?

It just seems nuts to me that I wouldn't be able to run the lead channel wide open, when I can do that with every other amp I own. I guess the 6505+ is just different in that regard?



So you think it's an issue of just too much electrical signal (for lack of a better word) slamming the tubes, and the tubes inability to handle it? Let me ask you this, why is it only on the lead channel, and not on the clean/crunch channel?

RussBert

You're missing the point.

If you were to play the amp with the speakers NOT in an iso box, you would clearly understand that you're asking too much. The 6505/5150 series have crazy amounts of gain, and again NO ONE runs the amp wide open!


The 6505 isn't like "every other amp you own" You need to accept that and deal with it. The amp is great, but has it's limitations. This is a case of operator error. Learn how to use the amp properly and you'll be rewarded with great tones


The noise you're hearing occurs with every tube amp ever built. When you run them wide open, you'll hear signal passing through the output transformer. I experience this all the time when I have an amp chassis on the bench for repair, and I run it into a load box. You can always hear the OT as you turn it up

drgordonfreeman

But it's not just with the pre or post knobs. It's with any knob on the lead channel, and the amp does not have to be wide open. The problems are just more prominent when all the knobs on that channel are turned to 10, rather than just, say, one knob.

Example: On the lead channel, I set every knob to 1. Then, I turn the bass frequency knob, for example, to 10. All the problems I described above start to occur. I can barely hear what I'm playing, due to the volume being so low; however, I can still hear feedback, a small amount of sound coming through the amplifier, etc.

Adrian R

Exactly....

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95' Gibson LP Standard
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06' Gibson 67'RI Flying V
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*Some* hearing loss?

drgordonfreeman

What do you think would be a proper remedy?

Marshall Mann

Call GC and have them warranty the amp. If you mess with it (swapping tubes etc), you could void the warranty.

There is no technical reason that you should be unable to run the head with the controls dimmed. But you should expect feedback and noise and lots of it.

Why exactly are you trying to run the amp in this scenario?

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drgordonfreeman

I was just trying it out. I don't really run the amp like that.

However, I'm glad I did, because it seems I've discovered a much bigger problem, as I'm not so sure I would have ever turned any of the lead channel knobs to 10 otherwise.

SuperBeaver

Man that sucks.
Nothing worse than buying some gear and having issues with it.

When I buy used now I just take it straight to a tech and have it checked over for any problems that may be about to raise their ugly heads...

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Ken

Yes, you beat me to it, but I was going to post that the tranny may be the cause, not just a symptom, and needs to be tested. I'm glad in reading further that the issue is just too much gain for the tubes. No one wants to have to replace a tranny, especially when it's working fine all along!

Ken

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1999 Marshall DSL 50
Music Man 65 Reverb late 1970's (?)
Late 1970's (?) Fender Champ
Marshall battery amp
1980 Model 1982A 4x12 cabinet G12H-80's 444 cones
1983 Model 1982B 4x12 cabinet G12-80's 444 cones
PRO 4x12 from the 1970's
Woodson 2x12
1976 Les Paul Standard
Epiphone Les Paul knockoff
ESP Lawsuit Explorer
1979 Chiquita Travel Guitar
1995 Taylor 310

RussBert

This thread is crazy. Nothing wrong with the amp


I dare you to try any high-gain head and set everything to "10" in your iso box...get back to us with the results

Ken

Kinda like a San Diego fireworks show when you think about it....

Ken

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1999 Marshall DSL 50
Music Man 65 Reverb late 1970's (?)
Late 1970's (?) Fender Champ
Marshall battery amp
1980 Model 1982A 4x12 cabinet G12H-80's 444 cones
1983 Model 1982B 4x12 cabinet G12-80's 444 cones
PRO 4x12 from the 1970's
Woodson 2x12
1976 Les Paul Standard
Epiphone Les Paul knockoff
ESP Lawsuit Explorer
1979 Chiquita Travel Guitar
1995 Taylor 310

American Viking

Did you wire the cab yourself?

Intermittent connections will be exacerbated when the amp is at high volume.

drgordonfreeman

lol. Well, it isn't just the gain or volume knobs. It's any knob. I can set all the knobs to 1, and then turn just one knob to 10, and the thing goes ape shit.

For example, I'll turn the volume knob and gain knob to 1, and then I'll turn the mid frequency knob to 10, and all hell breaks loose.



No, it's an Avatar built and wired speaker cab.




I got a return ticket generated, so it's going back in the mail tomorrow. I'm going to exchange it. We'll see how the next one does.

Ghostman

Definitely return the thing. Sucks but that is by far the best option.

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Crate BV120H
Marshall MC412

Dean VMNT Dave Mustaine Signature V - Gears of War
Dean VMNT Dave Mustaine Signature V - Angel of Deth
Laguna LE200GMS Dimarzio Evolution Bridge pick-up
Squire Stratocaster

Vox Tonelab

Marshall Mann

With all do respect Russ, the OP stated that any single control will cause the problem. That would not indicate that the amp has nothing wrong with it to me.

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Marshall Mann

Glad you are getting it sorted out.

Best of luck.

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RussBert

Burn the Witches!

drgordonfreeman

Yea, the new one is already on the way. Supposed to be here tomorrow! I had a return receipt already generated over the weekend, but I was just late posting updates. lol


Thanks.



Thanks a bunch to everyone that posted and contributed in this thread!!!

Ghostman

When you get the new head I'm interested in how the Isolation cab works out for you. Keep us updated!

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I don't play for Fortune, I don't play for Fame. I play because **** you.
Marshall JCM2000 DSL100
Crate BV120H
Marshall MC412

Dean VMNT Dave Mustaine Signature V - Gears of War
Dean VMNT Dave Mustaine Signature V - Angel of Deth
Laguna LE200GMS Dimarzio Evolution Bridge pick-up
Squire Stratocaster

Vox Tonelab

SuperBeaver

If I buy anything and it ain't 100% I take it back.

I refuse to accept any kind of mediocrity. I've noticed anything I order online is more likely to be defective.

I think they send the worst shit out on mail delivery. And I won't stand for it. ****ers.

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Haar '57' T style.
Gibson SG
'77JMP MK II 50 watt 1987
Vintage Modern 2266
Cornford Harlequin
1960AX

drgordonfreeman

UPDATE


I've been playing with the new head all weekend.

When I turn all the knobs to 10 when switched to the lead channel, it sounds like dog shit, but all hell doesn't break loose. None of the problems I described above. Like I said, it sounds like shit, but who cares, as I have no plans to run anything on 10. At least hell isn't raining down from the skies this time around.


The ISO cab works very well, now that I have a properly working head in there.

I keep the volume around 4, maybe 5, and I keep the gain between 5 and 6. All the other knobs are just slightly turned from noon, as I think the head sounds great without a whole lot of additional frequency response.

With the gain at 6 and the volume at 5 on the lead channel, the raw guitar is louder than the cab. It's great. I can get ball busting tone without busting my ear drums.

HOWEVER, I'm still working on lowering the bass transmissions. From the next room over, when the volume is set at noon (5), it sounds like someone is playing a radio at normal volume but with the speakers right against the wall. From upstairs, you can't really hear it at all. I'm working on solutions right now so that all frequencies are kept inside the box, but it's hard, considering bass sinusoidal waves are so long, as well as non-directional. I want to be able to crank the amp and have zero sound waves escape. That's an unrealistic goal, but I guess you only miss the shots you don't take.

I spent about $250 building the ISO cab. I got all the supplies at Home Depot and Target.






A friend of mine who works at one of the Big Four firms as an auditor and audits some of the Bain companies, whose portfolio includes some online musical equipment distributors, says they use the LIFO (last in, first out) method of inventory management. Basically, whenever a product is returned and it's deemed to be not defective, that product is slated to go out on the very next order. That means it's almost a certainty that "new" product you ordered from online is a return from someone else.