Ceriatone Forum

Hi all,

I have my BM50 up and running, fully debugged.  Running in combo w/C-Lator into a 1x12 cab w/Austin Speaker Works KTS-70.  Tubes are TAD 7025 in V1 & PI (v3), and Tung Sol 12AX7 in V2.  Power tubes are Winged-C 6L6.  Tone is far from blowing me away.  Extremely muddy.  With my strat I need to have the mid & bass levels around 0-2 and treble up to at least 7 with the bright switch activated and the presence dialed up to get a halfway decent tone.  Activating the mid boost is pretty much out of the question.  Turns to pure mud.  Sounds like someone threw a towel over the speaker.  With my LP the tone is crap.  Can't eliminate the mud w/o taking the mid & bass controls to 0 -- which sounds like garbage anyway.  I've tried some tweaking with tubes, but frankly given the degree of the muddiness tubes can't account for it.  I've let the amp burn in - but the problem has actually grown worse.  The speaker is broken in.  Hoping I'm missing something.  Got far too much time & $ in this thing to get sound this bad.  Any suggestions out there?  Anyone had a similar issue and managed to figure it out? 

You can try changing the slope resistor (47k) to a higher value, or you can make it adjustable.  On the clean channel the amp seems to like a higher slope value - that will make it sound more scooped.  The drive channel seems to like a lower slope value.

On the overdrive channel, pay attention to the internal tone stack settings.  The internal bass pot needs to be just cracked barely open.  See the note on the layout sheet about setting the post-gain tone stack.

I changed the pre-amp tubes out to NOS RCA 7025 shortplate (V1), Mullard 12AX7 short plate (V2) and a Mullard CV4004 (matched) for V3.  This helped, but did not eliminate the problem.  I'm able to dial in a useable tone regardless of the guitar now, but the mid and bass pots need to be down around 1 or 2, the treble needs to be cranked, and I need to use the bright switches, including the 2 switches on the C-Lator.  This carries its own set of problems, however, as it makes the higher registers on the guitar a bit shrill, so I don't consider it a real fix.  I plan to try a speaker swap to a Celestion Gold to see if that helps, as others have posted that this speaker is particularly well suited to this amp.  However, I'm really frustrated by how the default values in the amp seem to give you a tone that requires near elimination of the adjustment sweep on the pots to make it playable. 

Depending on how the speaker works out, I'll consider trying the slope resistor change which has been suggested (thanks for that).  Can anyone offer insight into how a value change on the bass and/or mid pot might impact this issue?  Here is a link to the layout for the amp from Ceriatone:

http://ceriatone.com/images/layoutPic/OvertoneLayout/OTS-BM-50W.jpg

The mid pot is a 25k(L).  The bass pot is a 500k(A)

Thanks in advance for replies!

I'm also seeking help @ The Amp Garage.  Here is a link to the string over there, to help any reader who may be looking to respond.  Thanks in advance for your help:

http://ampgarage.com/forum/viewtopic.php?p=292963#292963

I ran some models on the tone stack:

1.  The most effective thing to do is to be able to get the slope resistance up.  That will scoop the tone. Mine is adjustable from like 34k to 108k.  Stock is 47k.  Best thing to do might be to keep the 47k slope resistor and add a b50k push/pull mini pot in series to make it adjustable from 47k to 97k.  Install it thru the rock/jazz switch hole - slight reaming is probably required.  Maintain the switching function of the rock/jazz switch but install the components on the p/p pot.  That way you have a slope dial plus the rock/jazz switch.

It really makes a lot of difference.  It's almost like a Marshall/Fender knob.  I did mine a little differently but then realized that I should have done it this way.  Next time I'm in there I'll redo it.

2.  Changing the 330p cap on the mid boost switch - that's the treble cap in the tonestack - to a 300p will change the effective value (in series with the .002 uf) from 326p to 283p.  That widens out the scoop range a little.  It makes the curve more Fendery.

This made a little bit of difference in the breadth of the scoop.  I'm going to try this ASAP.

3.  I might try upping the bass cap to a 0.047.  Even though is seems counterintuitive, it might help to separate the highs and lows some.  Maybe I'll clip another 0.022 in parallel with the existing one and A/B it.

Mine's fairly bassy also. I run the bass knob right at 2, the mid at 5 for strats and lower for humbuckers, and the treble between 7 and 8, presence at least in the middle. The strat sounds a lot better through this amp in general to my tastes - actually it's a really great strat sound, hard to beat.

That's pretty much how I set mine up as well. Great strat and tele sound. When I play my lespaul through it, I use boost pedals in front of the amp with it and adjusted the tone/volume knobs on the pedal to taste. Also have a 10-band EQ pedal setup when using the lespaul. That way when swapping guitars at a gig, I don't have to change the amp settings.

I set up the amp for gigs using the strat and tele. The pedals take care of the lespaul.

I have the 100W version, however.

I'd try different speakers, along with the mods mentioned by TennAmp, espcially the slope resisitor. I have had the parts sitting around to modify mine for like two years and keep forgetting to do it.  The low value stock value really allows alot of low to get through there. Personally, i like the low end, amd run the deep switch on mine which tightens it up quite a bit. i run my bass somewhat higher than most folks do, but, i also run an open back 2x12 and that might make a difference. I run through two Weber AlNiCo 1265's and they sound perfect with the BM.