F-50 clean channel volume/noise problem

[skamor]

I have just purchased a used F-50 combo which has a couple of issues that need to be dealt with. The amp will be used primarily for big band jazz, and the most serious problem for me is therefore the apparent lack of "clean power".
I used to own a (60W) Mark IIB, and expected the F-50 to be comparable in loudness. It is, but only on the lead channel; on the clean channel I have to set both the gain and master to 1:30 or higher in order to reach gigging volume for comping, and a clean solo would require maxing out the guitar volume as well. On the lead channel, a gain setting of 12:00 and master between 9:00 and 10:00 cuts through easily for solos.
The second problem is noise, there is an annoying amount of hiss on the clean channel. The level of noise will vary to some extent with different preamp tubes (particularly in V1), and will decrease if I turn down the gain and master controls. So I have concluded that the noise is a consequence of the first problem, i.e. the high gain/master settings that I have to use.
I really need help with this, as the amp is close to useless to me as it is. Obviously, I am hoping for a diagnosis/fix suggestion, but I would also be grateful to hear from other F-50 users with similar experiences and suggestions for work-arounds.
By the way, apart from the problems described above, I really like the way the amp sounds

 

[boss4]

I suggest you to call or email mesa boogie assistance for a professional response. It seems to me its a tube problem but I dont own a F model so I'm not sure. But I can say that my father have a Fender hot-rod deluxe and its hell loud for 40w. Good luck!

 

[skamor]

Thanks for the reply, boss4. I have been in contact with Mesa on the phone but I was immediately redirected to their regional representative in Scandinavia, where I live. The service people there were reluctant to take on the problem, and indicated that it might be inherent to the amp design. I find that hard to believe/accept, but a local tech said something similar when I took the amp to him a couple of weeks back: "the clean channel is very nice and pretty, but the lead channel is bullets and gun-powder".

I really need to find out whether my problem really is an amp design thing or not, and would like to contact Mesa about it again. However, the phone route didn't really work for me the last time, and I was wondering if there existed an e-mail alternative to reach technical support in Petaluma. If anyone on the board has such contact information, I would be grateful if you could forward it to me.

 

[fabien]

It is true that the F50 lead channel is blasting quite early on the master pot, this combined to a steep jump in volume at the start of the run makes it quite difficult to play lead at low volume.
The clean channel has a smother MV taping so there will always be a difference between clean and lead MV settings, unless you play the amp cranked :shock: ... What?... Speak louder, I can't hear you! :lol: That's why you have two separate Masters

My master settings are about 12:00 and 10:00 (clean/lead) with the gain set at 1:00 and 10:30 (again clean/lead)
for a gig, a bit less at practice. We don't play too loud, we have two horns that are not amplified during practice.

That said, the hiss on your amps seems to me like a problem, my amp is dead quiet on the clean channel unless I crank the volume and treble but even then it's totaly usable.

I don't believe it's inherent to the amp design.
Did you try already a full retube with brand new (or known good) tubes, or at least preamp tubes?

Cheers
Fabien

 

[skamor]

Thanks for the reply, fabien. I've been in contact with the regional dealer now, who said they would forward my question to Petaluma. I hope Mesa will come up with a suggestion for a fix, of course, but I'm not holding my breath..

The frustrating thing is that I really like the amp's clean tone, and would be completely happy with the F-50 if it hadn't been for this volume/noise problem.

I have tried new tubes in all positions, and I have a new set of JJ 6L6 (Eurotubes) as well as a new balanced PI tube (also JJ). In the other positions I have either JJ or TAD 7025/ECC83. Of course, having just this one tube amp, it is difficult to selct a known good performer among new tubes, but I think I'm good tube-wise.

btw, do you know which tube is the first in the signal path? V1 or V2, there seems to be different views on this in the forum?

 

[boss4]

Its v2.

 

[skamor]

OK, so I got a response from Mesa, saying that I should expect a difference in volume, and that I should check that the preamp tubes were working properly by swapping them, one at a time....

Not that much wiser, in other words. I do expect a difference in volume because of the added gain stage in the lead channel, but the problem is not the difference but the fact that I can't get enough volume on the clean channel! At least not without wearing my bandmates and myself out with the idle noise.

In a few days I will receive another batch of preamp tubes ( I already have plenty), and I will continue to swap them, if only to select the quietest and best sounding ones. But is faulty preamp tubes really the only conceivable cause of my problems with the F-50? Should I ask my local tech to check other electronic components? If so, which ones? He already spotted and fixed one bad solder joint, maybe I should ask him to check again for other bad ones? Or maybe resolder the whole thing?

Still frustrated, and last night the F-50 started popping, too....

 

[boss4]

I feel your frustation man, I also had my troubles with equipment (fortunately not the recto), and I suspect that maybe its more than just tube problem. Your tech have to get the schematics and take a good look or talk himself with a mesa tech so they can comunicate better.
If you still have the warranty... Good luck!

 

[fabien]

If the problem persists after full retube it would look like another component of the amp is failing. Even after swapping tubes around the chance that you systematically put a failing tube in the same position is nihil. You could have a burned resistor or cap around V2 affecting the clean channel only. Nothing a tech couldn't pinpoint in my opinion.
It does sound like your signal is not properly amplified.
Clean channel with both volume and master fully cranked does generate some hiss but by then your amp is bloody blasting and your dog/cat/canary should beg for mercy and your neighbours beg for a sudden power shortage :mrgreen:
I'm affraid your amp is in need of a complete checkup.

The popping (and crackling) though points to a tube problem. I'd say try again with your upcomming tubes set.

 

[skamor]

Thanks for advice and encouragement, fabien and boss4; to the tech it goes.

 

[jvanoort]

As of last Saturday I am the owner of a Mesa F-50 combo and I experience the exact same 'problem': the clean channel is considerably less loud than the lead channel.
I read about fried rectifier grid resistors and opened the amp up to check mine. They seemed alright and both measured 470 ohm. Solder joints were ok too.
I also ordered a new set of tubes, so maybe that will make a change. I believe that V1 is the clean channel?

Whet do you guys think? Clean is loud, but lead is insanely loud. Is that the nature of the beast?

I emailed Mesa about this and am still awaiting their response. According to the response Mesa sent to the OP however it just might be the way it is...

 

[fabien]

As I said earlier, if your master settings needed to balance both channels are about 12:00 on the clean and 9:30 or 10:00 on the lead and that by then you're blasting at gig volume, your amp is working perfectly.

It all has to do with the difference of reactivity/taping of the master pots.

Cheers
Fabien

 

[jvanoort]

Small update: I just experimented some more and I noticed one thing. I was rather hesitant to crank the gain on the clean channel, perhaps because I associate Gain with crunch. Once I cranked the gain I noticed that the clean channel stays clean and it is insanely loud too!
The gain/volume pots on both channels indeed seem to work just the other way round in regard to sheer volume.

So the solution may be just that: more gain! Just dial in some treble (or pull out the gain knob) for some blackface chime.
My heart is more at ease now, there seems to be nothing wrong with my amp

I did hear some crackling/tingeling noise, so the tube swap may be a Good Thing (TM) anyway

This works the other way round too of course, just in case your cleans are to loud for apartment use: no gain, no pain (Sorry, I thought it was funny )

 

[jvanoort]

It all has to do with the difference of reactivity/taping of the master pots.

This!!!

With the gain at 9 or 10 I could fully crank the clean channel in my home. Yes, very loud, but fully cranked and no earbleed. Disappointing.
But: now the gain reacts the same as the volume on the second channel. Every little bit adds amounts to the volume!

The volume's there alright

I always find it difficult to refer to things as 'gig-volume'. That's pretty relative...

 

[skamor]

Hello again, I thought I'd better offer a status report on my F-50, especially since I was also PM'ed by you, jvanoort. My amp just came back from the local tech, who was given the following task: fix the noise! This because I reasoned that I could live with the funny tapers on the gain/master controls if the amp was less noisy when idle. Try to improve the signal to noise ratio, as it where.
When I left the amp with the tech, the noise (hiss AND hum) was quite bad with the settings used for band practice (gain about 01:30, master about 02:30; not THAT loud...), and the level of it was sensitive to both master and gain controls, with or without a guitar plugged in.
I have now got the amp back from the tech, who - to my disappointment - hadn't completely dissected it, and neither had he completed the task given to him. Instead, he had modified the amp (!) by including a capacitor on a preamp heater. In fairness, the hum is less annoying now, but I still think I deserve better and I have contacted a different technician who seemed to find the problem interesting...
Before sending it away, I will experiment a bit more with the gain and master combinations using the latest posts as guidelines. By the way, when you guys say cranked, you mean ALL the way, right? If not, could you please use the clock references instead?
Next time, I hope to be all smileys, due to an F-50 that works perfectly....

 

[jvanoort]

Hi Skamor,

cranked in the current context indeed means all the way up.
Sorry to hear your problem is not yet fixed. In regard to the volume level try this: turn the gain off (dis-cranked :wink. Then turn the volume way up.
Now gradually add more gain. By doing this I learned that there is enough volume there.

Now you have to find a balance of course. If you find you have to crank the gain to much to get enough volume you might pull the gain knob or add treble to make the tone less tweedy and more blackface like.
It makes kinda sense that you can't have amazing volume without enough gain...

Good luck with your other noise related problem and please keep us informed!

 

[fabien]

I always find it difficult to refer to things as 'gig-volume'. That's pretty relative...

Very true! by gig-volume I meant 'not bedroom volume', so at the volume used to play with a drummer either at practice or on stage. It usually doesn't make much of a difference unless you play outdoor.

 

[TKell]

Hi, I know this is an old thread but I wondered if you had a solutions to this issue?
I have a similar issue with an F50 that ive owned for a while now.
Its impossible to use for gigs as the clean channel will suddenly drop in volume then when you adjust it up, it will jump back again a while later and be really loud.
This happened every 10 minutes id say. Ive swapped all the valves numerous times, I even took it into mesa boogie and John Henry techs to look at and for some bizarre reason they reckoned it didn't happen when with them. I assume it's cause they just left it on and didn't play through it.
Its a lovely amp, but this issue has been bugging me for a while and id love to get to the bottom of it.
Cheers for any help
Tom

 

[Ikke Nik]

Late answer, but better one too late than none. Same problem with my F50. To solve the problem as much as possible I had to change tubes in V2 several times. From a lot of noise to very much noise. Best result was TAD low noise. I really think it is mainly a design problem. My MIII makes much less noise, I can plug in any ECC83 without any problem.