Love my F30 but...

F-30, 50 and 100's

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Cole
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Re: Love my F30 but...

Post by Cole » Fri Oct 14, 2011 6:49 am

Excellent! I look forward to the review.

Anthony50Cal+
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Re: Love my F30 but...

Post by Anthony50Cal+ » Sat Oct 29, 2011 7:09 pm

Dude,

I have an F 30 that has the identical problem. I just changed ALL tubes today but the problem persists. If I crank the "Clean" or "Drive" MASTER past 10 o'clock, the HISS is very obvious. I'm almost certain that it is a ground issue. I intend to take the amp to the shop in the next couple of weeks. I will update to this board with the results.

Anthony 50Cal+
Anthony50Cal+

Amp: MesaBoogie Lonestar Special combo, MesaBoogie F30 Combo

Axes: PRS CE22, '72 Gibson SG Deluxe w/trem
Dillion DR450 semi-hollow (heavily
modified). Ibanez RG 550 (20th Anniversary model)

Cole
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Re: Love my F30 but...

Post by Cole » Sat Oct 29, 2011 9:39 pm

A-50cal+...
Thanks for the heads up. Mine is with a tech as I write. I REALLY hope he can fix this issue. I also asked him to provide me with the details of the "hopeful" fix so I can post it here. I was told I'll have it back next Friday. Until then...

Cole
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Re: Love my F30 but...

Post by Cole » Wed Nov 16, 2011 3:08 pm

Well, got the amp back yesterday. I'm confident the tech is competent. I can't get technical but he gave it a very through going over which included beefing up some components but was unable to cure the noise issue. In his own words, he was "dismayed" he couldn't get it done. He's been an amp tech for a long time has worked on a lot of Mesa's and indicated it was one of the highest gain amps he has ever experienced. So, it's time to put this issue to bed. I'll hang on to it and keep my eyes peeled for another Mesa that is quieter. I'd really like to get a head in the same wattage or slightly higher. Thanks for all the great advice and if you have some suggestions re: a suitable replacement, I'm all eyes.

Graon
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Re: Love my F30 but...

Post by Graon » Thu Nov 17, 2011 4:30 am

I should have brought my F30 to the technician two weeks ago for a complete review and tubes replacement but he was busy. I'm going to bring it tomorrow and take my amp back next thursday.

I gonna make a review about the noise reduction especially as soon as possible.

Graon
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Re: Love my F30 but...

Post by Graon » Fri Nov 25, 2011 4:25 am

Ok, here we go for the review:

Yesterday I took back my F30 after a complete review and tubes replacement by the technician. Now, with the new setup the sound is much fuller and there is almost no hiss :) !

Tubes changes :

Power tubes : 2x EH EL84 paired (checked) with a customized BIAS (add/change of 3 resistances)

Preamp tubes :

V1: Tung-Sol 12AT7W
V2: JJ ECC81/12AT7
V3 & V4: 2x EH 12AX7-EH

Cole
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Re: Love my F30 but...

Post by Cole » Fri Nov 25, 2011 7:32 am

Great news! Sold mine yesterday. I'm confident mine was more than a tube issue. Nonetheless, I'll keep my eyes peeled for a suitable replacement.

haey2
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Re: Love my F30 but...

Post by haey2 » Fri Nov 29, 2013 3:32 am

i would like to inquire from experts here how can i "tame" a bit the gain of the drive / contour channel?

i was advised to use a 12AT7 preamp tube...is there another brand that i should be using to attain this tone? or just use a mesa boogie 12AT7 tube?

also, which preamp tube socket should i place the 12AT7?

thanks in advance... :)

bajaman
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Re: Love my F30 but...

Post by bajaman » Sun Feb 07, 2016 9:07 pm

old thread and late reply BUT I have solved the hiss problem :!:
The Mesa F series as well as the Studio 22, Maverick , Blue Angel, Dual Caliber and Express series all suffer from very high background hiss because they all use a 2 resistor and two capacitor filter right at the first tube stage input - the hiss is caused by the thermal noise of these resistors being amplified by the first tube stage. The resistors also cause an 8db to 11db signal reduction further reducing the signal to noise ratio of the critical input stage. Why did Mesa put these resistors and capacitors here then ? I believe Randall Smith was trying to increase the amplifier's headroom and give a gradually sloping from 2Khz 3db shelving boost to 100Hz and below, which subjectively gives the amplifier a more "punchy" bottom end response. The unfortunate trade off is an obnoxious rise in background noise or hiss. Changing tubes has a very negligible effect on reducing this hiss. The filter is comprised of a 1M5 resistor paralleled by a180p capacitor in series with the first tube stage input. There is also a 1M resistor paralleled by a 470p capacitor from the tube input to ground.

The fix: Remove the 1M5/180p and replace with a shorting link, then remove the 470p and optionally replace the 1M resistor with a 10M resistor. okay that cures the hiss problem now how do we put the bass boost back in you may ask? I designed a replacement filter with only a 1db to 4db insertion loss and inserted it immediately before the third tube amplification stage. The filter I used consisted of a 1M5 paralleled by a 180p capacitor in series and then a 10M in parallel with a 120p capacitor from the tube grid input to ground. This worked well and restored the gradual bass boost and tone of the amplifier BUT without that awful hiss!

Alternative partial fix:
Leave the input filter 1M5/180p in place but reduce the 470p to ground capacitor to 120p and replace the 1M resistor to ground with a 10M resistor. This should reduce the his by 7db but there will still be the thermal noise of the 1M5 in series with the input, however this may not be so noticeable now - worth trying first 8)
Cheers
bajaman

john525
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Re: Love my F30 but...

Post by john525 » Mon Nov 06, 2017 12:20 am

Hey bajaman, thanks for posting this!
I'm considering doing one of the mods to my express 5:25, and I have a couple of questions, if I may...
First, for either of the mods, is removal of the circuit board necessary?
Second, do either of these mods change the tonal characteristics of the clean channel? Apart from the hiss, the clean channel on this amp is gorgeous.
Thanks again!

jkowens
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Re: Love my F30 but...

Post by jkowens » Sun Sep 01, 2019 7:50 am

Hi john525, did you end up trying this mod? I’m curious to hear others results. Particularly the alternate method :D

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