Mesa Boogie DC-5 Preamp Tube Layout + Advice

[tbonesullivan]

So, I finally got my tube guard for the power tubes, and now I'm finally checking out to see what kind of tubes are in the beast. The PO had told me that there was an EH 12AT7 in the phase inverter spot, but I had it serviced, so it is possible it was re-arranged. This is what I found:

V1: Tung Sol Reissue
V2: Sovtek 12AX7WB
V3: 12AT7 Marked U.S.A. - Looks like an RCA - remnants of orange and red letters
V4: 12AX7A CHINA
V5: EH 12AT7
V6: Baldwin Marked 12AX7 - Sylvania 12AX7WA USA Made

So, I guess, what would people recommend for the DC-5? So far I have liked the sound, though the reverb always seemed anemic on the top end. I've put a sovtek 12AX7WA in there, as I have a lot of barely used ones that I usually put in the reverb spot for dependability.

What about the 12AT7 as the final lead gain stage and FX Driver? Is there any danger? I really haven't had any complaints about the sound, but I have also wondered if I could get a bit more "beef" on the lead channel.  Also I worry that the Sylvania tube is wasted in the Phase inverter spot, but it's got a really big long plate structure, so I worry a high gain spot might go microphonic.

[Lockbody]

The great thing about the DCs is that other that V1, you can experiment with tubes for one channel and not affect the other. Boogie Board member Edward had a nice cocktail of tubes that he liked.

V1: NOS Mullard 12ax7
V2: TungSol RI 12ax7
V3: TungSol RI 12ax7
V4: NOS RCA 5751
V5: NOS RCA 12at7
V6: NOS RCA 12at7
Power: Svetlana "Winged-C"

Of those, I liked the 5751 in V4 (2nd and 3rd gain for Ch1) but I had a DC-5a which had a gainier clean channel vs the later DC-5b. I also liked 12at7 in the reverb (V5) and PI (V6) positions. A 12at7 in the reverb V5 is about the best thing you can do for it. Not much help, though. The reverb in the DCs is pretty weak and nothing special. The 12at7 in the PI will help beef up the tone some.

[tbonesullivan]

I wonder which version of the DC-5 I have. I believe since it's got toggle style switches, that would make it a DC-5b, as the DC-5A had Rockers. I also think the tube definitions may have changed, as the lead channel is V1, V2, and V3 on the tube layout chart I have. V4 is supposed to be Rhythm, V5 reverb, and V6 the PI.

[Lockbody]

No LEDs on the amp to tell which channel is selected and a two-button footswitch that connects at the front means a "B". There are a couple of other indicators, but that's what I remember off of the top of my head. My DC-5a had metal toggles.

A good comparison I read is Texas blues vs jazz comping for A vs B. The B's clean is more like a Mark-based clean. When I bought my DC-10, I had its clean channel modded to rev. A specs. A DC-10 is a great way to beef up the DC-5's tone, FWIW!

V1 is shared. The 5's manual didn't have the tube layout for some reason, so check out one from a DC-3 or 10. vhttp://www.mesaboogie.com/media/User Manuals/Dual Cal DC-10.pdf  The preamp section is the same across all models and revisions.

[tbonesullivan]

AH, I misunderstood. Somehow I thought when you said Ch1 you mean the lead, not the rhythm.

That is the schematic I often see, of course I always get confused when looking at the amp upside down. I really do need to take some new pictures of it. I just waxed the tolex and conditioned the corners. Also got the tube guard for the back, which was missing.

[tbonesullivan]

Ok, so it's all good now. I settled on this:

V1: Tung Sol Reissue
V2: Baldwin Marked 12AX7 - Sylvania 12AX7WA USA Made
V3: JJ ECC83S
V4: 12AX7A CHINA
V5: Sovtek 12AX7WA
V6: EHX 12AX7

I also finally got some good pictures of the beast, complete with the new tube guard for the power tubes, which are Winged C SED 6L6GCs

 

[Caddie]

WARNING:  Big Mesa fan here.  T Bone go here The Mesa Boogie Amp User Forum  Much like the HFC, great source of experienced knowledge, can't say I have ever observed much "bad behavior" over there.  In today's popular terminology its a "Safe Place" for any amp issues, any brand.  

btw - imho (enough acronyms fo y'all?) the Mesa-DC series is their best.   They are getting harder to find.  If you have one don't sell it (unless someone offers "stupid high $$$$") Same goes for the Lonestar Series its Super Dooper too.  

My neurosurgeon and I perform this routine at Neurological Conferences worldwide and Canada!

Back to biz.  The DC & Lonestar Series are great. Why you ask? cuz they don't have the complexity of many Mesa amps that look similar to this

But seriously...Mesa DC and Lonestar.  2 channels, both have their own set of controls.  No shared pots, No pull me / push you pots.  Mesa should hire me.  Why? Put me in engineering: "If THIS nit-wit can figure it out, it's as close to idiot proof as dirt".

Mesa Engineering Team Meeting - marketing guy in black tophat "Hmm...It doesn't have that Mesa feel without loads of push me /pull you stuff on it.  Mr.Sideburns, engineering manager is winding up to kick marketing guy in the nuts.  Pull me side of varmint eyeballs Aunt Bee as she exclaims "OMG  Andy (guy in the red pants & brown vest) did you take a peek at the undercarriage?! Freakin' thang is gigantic!!"

[tbonesullivan]

Well, technically it does have ONE push pull put, which is the boost on the rhythm channel.  They also do make the Express series amps for people who don't want a huge amount of stuff to play with. Some of their amps are just plain insane. The DC-5, and the Maverick I have, both have simple, easy to use controls. No tons of little flip switches to change the gain structure, power amp structure, etc etc etc.