Mesa DC-5 Issue

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zuzek

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Mar 15, 2008
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Location
Netherlands
Hey there,

Since I'm new here, I'll introduce myself first. My name is Geert, 20 years old, student in Holland. I've been into music for as long as I recall and have always geared more towards 'heavy' music. Now Mesa's have been helping me achieve the tone I wanted quite a bit. Prior to the DC-5 I've owned a Studio Preamp, but I preferred a tube-combo for practical reasons. I've only had the DC-5 for about 2 weeks now.

I bought it second handed from a somewhat older guitar player, it worked just fine when I bought it. Everything in proper order and asked when tubes had been replaced, answer was almost a year ago. I still took it cause it was a good price concering how it's not really easy to find one for a good price here.

Had a hell of a time with it so far, tough to find the perfect tone but I'm sticking with it, it's a Mesa anyways. But a few days ago I suddenly heard some buzzing while playing on the clean channel. I immediately put it on stand-by and turned the power off as I didn't want to have any risks and asked a friend what the problem might be. The weird thing with this buzz is that it doesn't occur when I don't actually play but the amp is on, just only when I actually strike strings. Also, when the amp has just been turned on, the buzz doesn't occur. I'd say about 7-10 minutes in it starts happening. The buzz is a bit hard to describe for me, it's not very loud but certainly noticeable and makes recording a bit shitty, I guess it's a somewhat distorted buzz.

Now I'm not totally sure because its hard to find out whether it's buzzing or not when I have the lead channel on, but I believe that the buzz is also occurring on lead (again I might be wrong, it's hard to distinguish this for me). I checked the tubes when the amb was in stand-by, the power tubes look fine and sound fine if I tick lightly on them, the pre-amp tubes look fine although V4 and V5 look like they're burning less than the rest. Ticking against the pre-amp tubes yielded no spectacular events, in other words, nothing strange happened. I've tried swapping V1 and V2 but there was no change in the buzz's volume or occurrence. Also, turning down the gain has no effect on the buzz, just the volume of it (but that's with anything that effects the volume, whether it be the channel master or my guitars volume pot).

Now I'm asking for some help, would anyone know what might be wrong with my amp? Is it tube related or do I have to search elsewhere? Any advice would really be greatly appreciated as I don't have the budget to bring this to a professional tech.

Cheers in advance.
 
My guess is that since the noise is NOT on startup but only as the amp gets played for a while, your issue is still tube-related. Sounds like one of yours are marginal ...though I don't know for certain whether the source is preamp tubes or power tubes.

Consider this:
v1: input both channels
v2: Lead gain stages
v3: Lead gain stage and f/x return as well as final preamp stage for both channels
v4: rhythm channel gain stages
v5 reverb
v6 phase inverter (affects both channels and is the final signal before the power section)

So try to isolate your noise to either one of the channels if you can by starting with v2 and v4. If you can't, then try replacing the v1, v3, and v6 to see if that fixes it. Use the v5 (reverb) if you are short of tubes to try. And of course, you have to be certain that you are swapping with known good tubes. Any known good 12ax7, 12at7, 12ay7, or 5751 will be fine for testing purposes, so long as you KNOW they are good and have not gone microphonic (gone bad). If ALL this fails to address the noise, then try another pair of 6L6s.

Edward
 
Thanks for your reply. Apparently my friend gave me the wrong positioning for V1, and I actually swapped V6 and V5 the first time around. Now I tried the other end, swapped out the reverb for V2 and put V2 in V1. No buzz quite some playing time. Looks like I'll do a full pre-retube anyways since it's second handed. Can't bias myself and don't have money for a tech so it'll do for a while. Thanks again for the help.
 
Good; glad it was an easy fix :)

You can't bias a boogie unless you have a tech install a pot to replace the fixed resistor. You can either replace with Mesa tubes, which are tested to be within the bias range "acceptable" to Mesa, or get some tubes from a reputable dealer that has Boog experience.

Edward
 
Alright thank you for that bit of information, I didn't know DC's were fixed as well (but then again I'm a bit of an amp-noob, that's why I'm here). I'd be very tempted to try SED =C= 6L6GC's as I'm not too fond of the JJ Mesa tubes, but I'm not one to gamble on that, so maybe some other time :). Thanks again!
 
No gamble on the SED Winged-Cs. I like them so much I have them on both my DC5 and my MKIII. Great tube, and better than the Mesa stock IMHO.

Edward
 
No issues whatsoever. And if you're ordering these, you may as well experiment with some NOS preamp tubes. Check out the archives and read up on some opinions and experiences. Of course "great tone" is in the ear of the beholder, but after much experimentation, I've finally derived my "recipe" with a mixture of NOS 12ax7, at7, and 5751s. NOS is neither magic nor "better sounding" by default, but they can make a considerable difference in shaping your amp's voice. Hope that helps you :)

Edward
 
Thanks agaiin. I will replace the power tubes in a few months but I'm on a tight budget so I'm not really going to experiment too much with tubes as I've just put new pre-amp tubes in.

V1 = Tung-Sol 12XA7
V2 = JJ 12AX7 High Gain
V3&5 = Shuguang 12AX7B
V4 = EH 12AX7
V6 = Sovtek 12AX7 LPS

It's a bit punchier and a bit more detail so I'm happy so far, but I'm still trying to find my tone (which is pretty hard to accomplish when you're playing bedroom level).
 
zuzek said:
Thanks agaiin. I will replace the power tubes in a few months but I'm on a tight budget so I'm not really going to experiment too much with tubes as I've just put new pre-amp tubes in.

V1 = Tung-Sol 12XA7
V2 = JJ 12AX7 High Gain
V3&5 = Shuguang 12AX7B
V4 = EH 12AX7
V6 = Sovtek 12AX7 LPS

It's a bit punchier and a bit more detail so I'm happy so far, but I'm still trying to find my tone (which is pretty hard to accomplish when you're playing bedroom level).
I would suggest using a mellower tube in V4(rythm channel) I find the EH's to be a little harsh, and also, I've read you shouldn't use LPS's in combos, as they can become microphonic due to the speaker vibration being so close. If you have no cash I would switch V2(JJ) with V4.
 
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