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 Post subject: Re: RA100 noisy reverb
PostPosted: Mon Oct 14, 2013 8:44 pm 
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Mark II

Joined: Mon Sep 10, 2012 3:28 pm
Posts: 58
Does it get better/go away when you use the attenuator on the clean channel????

My new RA100 head has noisy reverb as well...swapped some of the preamp tubes with my spare mesa tubes...helped a bit....but really huge difference when I use the attenuator.


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 Post subject: Re: RA100 noisy reverb
PostPosted: Sat Nov 23, 2013 8:36 am 
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Mark III

Joined: Wed Jan 04, 2012 9:32 pm
Posts: 217
I know this seems obvious, but have you tried another outlet or tried it at another location? It would make sense that yours had the same levels of noise that your tech found on the showroom amp. It really does sound like the typical 60 cycle hum from a noisy power source.
The other guitarist in my band played an RA-100 2x12 combo for a long time and it was dead quiet. It had one of the absolute best gain sounds I've ever heard and it was the heaviest amp I've ever lifted.

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Electra Dyne 1x12 combo
Deluxe Reverb Reissue
American Deluxe strat
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 Post subject: Re: RA100 noisy reverb
PostPosted: Mon Jan 06, 2014 9:59 pm 
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Single Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 1847
Location: North Carolina
I now have an RA100. I got it though EBAY. When arrived, reverb cables were not connected. I have changed V6 and that made improvement. With the power soak on, the noise almost disappears.

Comments on the PI tube, if it was the PI tube, noise should be present even with reverb in bypass. In my case the amp is completely silent with the reverb turned off. I have changed V6 with other tubes just to hear if there is a difference. I also have moved the wires so they are not sitting on top of the transformer which has helped to some extent. I will try a jan/ge 5751 preamp tube in V6 to see if that helps. My next approach (if nothing else works) will be to borrow the reverb cable from my Mark IV combo. I believe the transformer issue more than preamp tube. I have replaced all of them except the 12AT7. I may as well get a new one while I am at it.

I also noticed when the reverb is turned up, volume and tone drop out. Sounds the amp is muffled considerably.

_________________
JP-2C, Vertical Recto 212 (V30)
Roadster head, OS Recto slant 412 cab (EVM12L-BLACK LABEL)
Royal Atlantic head , Matching Mesa OS Recto slant 412 (V30)
Royal Atlantic Combo, black face (Cream back G12H75)
Mark V combo (Cream 90W Alnico)


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 Post subject: Re: RA100 noisy reverb
PostPosted: Mon Jan 06, 2014 11:40 pm 
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Single Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 1847
Location: North Carolina
However much I liked the Jan/GE 5751 in v4, it really reduced the noise I was getting with the reverb with it installed in v6. I did try other tubes in the PI position (tubes that are known to be quiet) did not make any difference. I pulled the cables out and still had the noise but not as dramatic. So far the only tube I have not replaces is V3. None the less, with a lower gain tube in V6 reduces the hum considerably. Reverb sounds really good now.

Due to the design of the amp circuitry and considering how sensitive it is, the low level hum is tolerable. As for the other Mesa Amps I have, the Mark V is extremely quiet, audible transformer hum is difficult to notice unless you turn up the volume and gain to stupid levels. Mark IV, not too bad either, but will make similar noise as heard in the RA100.

Noise in the RA does not seem to be channel dependent. I will have to get a replacement tube for V3 and see if anything changes. I may just swap it out with a "known to be quiet" tube and see if there is any difference.

Even with the hum, it does not stop me from enjoying the amp. 8)

_________________
JP-2C, Vertical Recto 212 (V30)
Roadster head, OS Recto slant 412 cab (EVM12L-BLACK LABEL)
Royal Atlantic head , Matching Mesa OS Recto slant 412 (V30)
Royal Atlantic Combo, black face (Cream back G12H75)
Mark V combo (Cream 90W Alnico)


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 Post subject: Re: RA100 noisy reverb
PostPosted: Wed Jan 08, 2014 7:22 am 
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Single Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 1847
Location: North Carolina
The jan/ge 5751 helped to reduce the noise somewhat by limiting the saturation of the reverb. Sounds a little better too.
Noise is still present but at your typical amp noise levels.

I did experiment with the Mark IV combo reverb. I removed the entire unit and plugged it into the RA100 reverb jacks. I was able to move the tank above the amp. Yep, transformer is definitely an influence. Seems that the current location where the RA tank is has the lowest pickup of noise. I also took a closer listen to the Mark V which sounds relatively quiet, Similar noise but not as robust.

I did check grounding on the reverb tank. The powder coated box is not grounded. The suspension springs are but not the enclosure. Perhaps a chassis grounded Faraday box made to fit over the reverb tank may reduce the magnetic pickup noise from the transformer. I will try to make one at work and see if it works.

_________________
JP-2C, Vertical Recto 212 (V30)
Roadster head, OS Recto slant 412 cab (EVM12L-BLACK LABEL)
Royal Atlantic head , Matching Mesa OS Recto slant 412 (V30)
Royal Atlantic Combo, black face (Cream back G12H75)
Mark V combo (Cream 90W Alnico)


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 Post subject: Re: RA100 noisy reverb
PostPosted: Wed Jan 08, 2014 1:58 pm 
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Single Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 1847
Location: North Carolina
Go figure, I took out the new =C= EL34 (one or two of these were rattle makers, disappointed basically), even tried a known to be good EH EL34 and had same results. However, I wanted to retry the KT77 again (fist time due to miss aligned tube, sockets were modified by original owner or defect in casting, found the hard way that tubes can be installed in any orientation) {I am good at making run-on sentences :roll: }..... more to the point, No noise what so ever with the KT77. Could be related to tube type?

_________________
JP-2C, Vertical Recto 212 (V30)
Roadster head, OS Recto slant 412 cab (EVM12L-BLACK LABEL)
Royal Atlantic head , Matching Mesa OS Recto slant 412 (V30)
Royal Atlantic Combo, black face (Cream back G12H75)
Mark V combo (Cream 90W Alnico)


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 Post subject: Re: RA100 noisy reverb
PostPosted: Sat Jan 11, 2014 4:01 am 
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Mark II

Joined: Mon Sep 10, 2012 3:28 pm
Posts: 58
Thanks for the info.....please keep it coming....


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 Post subject: Re: RA100 noisy reverb
PostPosted: Sat Jan 11, 2014 10:29 am 
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Single Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 1847
Location: North Carolina
I would love to get my hands on the schematics for this amp. Not quite sure what preamp tubes run on AC heater circuit. More than likely V6 may be an AC heated circuit. Some preamp tubes will have isolation issues or may be susceptible to cross over transients which causes pickup of hum or static like sounds from the AC supply. The Reverb tank by itself is an antennae. Because of the powder coating or paint of the metal enclosure, circuit ground is not complete. The suspension springs are grounded that attach to the enclosure but seems that the box may not be due to the thin insulating film of the paint or coating. I have removed the tank for inspection, it is as reported the same tank used in the Mark V and Mark IV as well as other amps. The only difference, there is not lid on the box. This in itself may also be part of the issue. Wood does not make for a good shield. Also there was no aluminum foil heat shield on the top surface of the head unit. Those that have the combo, you should not have much of an issue with the noise since the box is complete and sits much farther away from the power transformer.

It is also possible if you have leaky power tubes (power tubes will be AC heated) that may cause the electrical transient noise to be broadcast in the AC heater circuit. Only one tube can cause this issue. Heaters are basically resistive, but there is an associated inductance in the heater element. Triodes and or Pentodes have high capacitance as well as other impedances depending on small signal model. There are many factors that could contribute to the noise level, intensity, or signal degradation. There are volumes of books on this subject. It is next to impossible to condense such that it would make any sense. It would be easier to do the trial and error approach than to understand the physics of the devices and associated affects of electrical transients. Another source of the noise in audio equipment would be the rectifier diodes in the power supply. They are susceptible to damage in the event of no load conditions on the output, the high induced voltage could cause damage to the diodes. In short, noise issue may be related to improper shielding of the reverb tank (lack of signal ground) or related to typical transients (most likely tube related). A faraday box or shield surrounding the reverb tank would be one approach in attempt to reduce the associated noise issue. Wire mesh (chicken wire), metal screen, perforated sheet metal. once constructed, it cannot touch any part of the Reverb tank since it will be earth grounded to the chassis. Signal ground may not be the same as earth ground so to avoid any ground loops (which will add more problems) chassis grounding of the Faraday box or cage and not connected to the ground of the input signal would be best. I may make a project out of this and get a perforated aluminum sheet to make the faraday box and see if there is any difference.

_________________
JP-2C, Vertical Recto 212 (V30)
Roadster head, OS Recto slant 412 cab (EVM12L-BLACK LABEL)
Royal Atlantic head , Matching Mesa OS Recto slant 412 (V30)
Royal Atlantic Combo, black face (Cream back G12H75)
Mark V combo (Cream 90W Alnico)


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 Post subject: Re: RA100 noisy reverb
PostPosted: Sat Jan 11, 2014 10:36 am 
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Single Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 1847
Location: North Carolina
Also to note: I now have all Mesa branded (current production) 12ax7 in the amp (V3 is still the original 12at7). All I hear now is the typical hum that you get with any tube amp. It just sounds different due to the tone of the RA100 when compared to the Mark Series amps. Clean channel is the most noticeable with the hum than the higher gain channel. I can accept what I am hearing as it is not as dominant as it was before. I may do the Faraday box just for kicks. Another note: the amp chassis is a bit more tricky to get back into the head once removed. I found 1inch thick boards (they are actually under one inch in thickness) long enough to stick out of the head cabinet by 4 inches help to work as chassis installation guides when installing the chassis into the shell.

_________________
JP-2C, Vertical Recto 212 (V30)
Roadster head, OS Recto slant 412 cab (EVM12L-BLACK LABEL)
Royal Atlantic head , Matching Mesa OS Recto slant 412 (V30)
Royal Atlantic Combo, black face (Cream back G12H75)
Mark V combo (Cream 90W Alnico)


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 Post subject: Re: RA100 noisy reverb
PostPosted: Sun Nov 01, 2015 1:58 pm 
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Bottle Rocket

Joined: Wed Sep 30, 2015 3:36 pm
Posts: 5
Hi - any resolution to the noise revery problem?
I just picked up a used RA-100 and I'm getting the exact problem.

One question on the head layout: my head shell was custom built (a beautiful hardwood shell) and the reverb connectors face the front of the head. Is this the correct layout? Or should I re-install the reverb unit so the connectors face the back of the head?

Thanks.


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 Post subject: Re: RA100 noisy reverb
PostPosted: Sun Nov 01, 2015 5:38 pm 
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Single Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 1847
Location: North Carolina
My reverb tank has not been removed as far as I can tell, tank jacks are facing front and sit above the power switch.
I get noise with my amp but not quite a reverb issue. However with the reverb on it does seem to enhance it. I have a hall light that is controlled by a dimmer switch. When the hall light is on, the amp is very noisy. When it is off I do not hear it and just get the typical hum I would expect from a tube amp.

If you invert the reverb tank, you may wind up with wires against the tubes.

Would love to see a Hardwood RA100. Can you post pictures of it?

_________________
JP-2C, Vertical Recto 212 (V30)
Roadster head, OS Recto slant 412 cab (EVM12L-BLACK LABEL)
Royal Atlantic head , Matching Mesa OS Recto slant 412 (V30)
Royal Atlantic Combo, black face (Cream back G12H75)
Mark V combo (Cream 90W Alnico)


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 Post subject: Re: RA100 noisy reverb
PostPosted: Mon Nov 02, 2015 12:14 pm 
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Bottle Rocket

Joined: Wed Sep 30, 2015 3:36 pm
Posts: 5
Image
Image
Image

It's so nice that it's too nice... meaning I'm afraid to put a beer on top - even with a coaster.


Thanks for the info on the reverb tank.
I also found out that engaging the power soak on each channel significantly reduces noise.


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 Post subject: Re: RA100 noisy reverb
PostPosted: Mon Nov 02, 2015 6:17 pm 
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Single Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 1847
Location: North Carolina
:P That is really cool. I did not expect to see a tight fit on the chassis. I like the floating face plate too. Have you thought about placing the Mesa Logo on it or is that taboo at the moment.

One thing I found that caused more noise in the amp other than external line noise issues was V3 (SEND/RETURN).(I would not use a 12AX7 in V3, check to make sure V3 is a 12AT7). The Chinese 12AT7 seemed a bit flakey to me. I did get a Mesa replacement but also bought a few NOS 12AT7 since they were the same cost if not less than the Mesa tube. I like the RFT 12AT7 as it seems to be less noisy than the JAN GE 12AT7 or the MESA Chinese 12AT7. It did not seem to matter what tube I used in V6 (reverb circuit) as that did not seem to contribute to the noise.

_________________
JP-2C, Vertical Recto 212 (V30)
Roadster head, OS Recto slant 412 cab (EVM12L-BLACK LABEL)
Royal Atlantic head , Matching Mesa OS Recto slant 412 (V30)
Royal Atlantic Combo, black face (Cream back G12H75)
Mark V combo (Cream 90W Alnico)


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 Post subject: Re: RA100 noisy reverb
PostPosted: Tue Nov 03, 2015 12:46 am 
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Bottle Rocket

Joined: Wed Sep 30, 2015 3:36 pm
Posts: 5
Thanks - I'll give that a try!

On the faceplate question, not sure what I'll do at the moment. I see someone is selling the full RA-100 faceplate, but I'll have to ask him to measure so I don't end up with too tight a fit. We'll see. I'm still looking for a full Mesa head shell so I can take this guy out of my house, too.


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 Post subject: Re: RA100 noisy reverb
PostPosted: Tue Nov 03, 2015 7:28 am 
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Single Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 1847
Location: North Carolina
Based on how tight the chassis is to the custom cab, the RA100 face plate will not fit. With the RA100 shell, there is almost 2 inches between the chassis and each side of the shell. Not quite wide enough to stuff the Roadster chassis into it but almost (thought that would be interesting but no fit). I am wondering if the RA100 chassis would fit a Stiletto shell as it does look similar in shape. Without dimensions to compare no way to tell if it would.

I have grown fond of the RA100 shell. There is also a rear panel that wraps around the back of the chassis similar to the front plate that fills in the gap between the chassis and the shell.

Image

_________________
JP-2C, Vertical Recto 212 (V30)
Roadster head, OS Recto slant 412 cab (EVM12L-BLACK LABEL)
Royal Atlantic head , Matching Mesa OS Recto slant 412 (V30)
Royal Atlantic Combo, black face (Cream back G12H75)
Mark V combo (Cream 90W Alnico)


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