Ceriatone Forum

Hi, I `m having trouble getting a good clean out of my OTS 50. Even when running the pre low(say 4 and below) and the master at full. I`ve checked out all of the preamp tubes. And I compared it to another OTS 50 at a local store here in St. Paul (Willies Guitars) That one sounded not only louder but extremely clean, even w/ the pre running at 6-7.  I`m running fairly vintage  output humbuckers and mini-hums into the normal channel. Any help would be greatly appreciated, thanks in advance!

if you have the master at full your going to get distortion.

How long have you had it? It will improve enormously when you have 30hours plus run time on the tubes with improved brightness and articulation, but break up will not really be affected. If what you describe as a 'good clean' is zero break up, you should get that without a problem, this is a very clean amp even up to 8 on master (not on O/D obviously!). What happens with pre at 8 and master on 3? What about pre on 3 and master on 8? That should tell you whether it is a pre-amp problem or not.

NOT with a low preamp volume  :o

   Could you further elaborate on the master distorting at full volume please. I assumed it worked like a Fender type circuit( pre and master volume). Thanks again in advance!

Hi

It doesnt work like fender.

For max clean, you set vol relatively high, keeping master low.

The most headroom is like clean at about 2 or 3 o clock, while master at 11 or so.

Thanks!

Nik

even with the preamp low your gonna get distortion with the master full. its inevitable, tubes breakup when they're pushed like that

 Thanks evryone, I` found out the guy who owned it before me never had the pwer tubes biased properly.   

My OTS is biased from the factory with standard JJ tubes. and the clean volume is at about 4 but if i crank the Master up to 10 it gets really dirty

Thanks for all of the info everyone! I ended up putting a spare set of Mesa Boogie 6L6GC(STR-440`s) in the amp and biased to about 23mv.  I also took the advice of running the master lower and the pre at around 7. Sound way better!   The only thing I`m wondering is that on my master volume there isn`t much range. Once I get past 3-4 it doesn`t increase in volume a whole lot until around 9-10. Does anyone else have this same problem?

i get that with all my tube amps. after 3 you just get more breakup on the powertubes

    I`ve never experienced that w/ other master volume circuits. Why does it act that way w/ this particular amp? Thanks again!

This is due to the fact, that the fender preamp/tonecontrol circuit puts out much less volts that a Dumble preamp.
In a typical fender (blackface) preamp circuit with a 10k mid pot or 6,8k fixed resistor, there is much more signal dampening, than in a Dumble-style preamp.

A dumble preamp/tone circuit has a 250k mid pot and puts out 10-20 dB more signal to the poweramp. Its ALMOST like haveing a fender pre with the middle pot up full AND the preamp gain at full power.

There you have it !! ;-)

  Thanks for the info. But  Ijust got back for trying another( newer) Overtone Special 50 and the amp stayed totally clean when either running the pre low 2-4 or 6-8 and the master low or full volume. I`m wondering if this amp has had the J. Zucker mods.

I don't think the JZ mods will have a great effect on the amount of break up, it didn't with mine when I converted it. One thing that will is the valve type in V1 for the clean channel and V2 for the OD channel. If you want less drive try a 5751 or Ay7 in V2. Also a 5751 in V1 will lower the overall gain for both channels.

PAB ON will drive the clean into break up a lot earlier. Make sure you have it turned off, the switches are counter intuitive (pedal postion is OFF)!. You'll know its ON if the tone controls have no effect.

Thanks for the info about the different preamp tubes. I have JJ 12 AX7`s in all 3 slots. I noticed that the other Overtone I played through had been tubed w/ Groove Tube 6L6GC power tubes and GT preamp tubes( not sure which ones though). That amp had a tremendous amount of gain in the overdrive mode. I thought maybe someone just adjusted the internal trim pot at full. One other ? I have is, how should the phase inverter trim be set? Mine is  set at exactly half (12 o`clock). is that correct? What exactly does the trim pot effect anyway? Thanks again in advance.

I ended up taking my OT Special 50 to a local tech to have the J Zucker Tweaked Mods installed and biased properly. Should have it back in a couple of weeks!

Hi

23mV is kinda low?

Thanks!

Nik

What's a good range to bias then?

35mA is standard for most blackface fenders so i would probably go with 37mA
30-42mA is a round figure for most 6L6's

Nik recommended me 35 - 40mV

Got the amp back rebiased properly,and the J Zucker mods. Definetly a lot better w/ the changes.  I probably am going to have it upgraded to a 100 watts when I get some more $

i would just keep it at 50 watts. 100 watts wont be much louder it would be easier to keep it normal.
im adding a tube rectifier to mine eventually and making it switchable from tube to solidstate.   

Thats a layout I'd like to see!

the reason I eventually want to upgrade to 100 watts is for the clean headroom.  Right now if I need more clean headroom, I end up running a slave amp( Crate Powerblock) into another cab. It actually gets a great sound, but would like to not have do deal w/ all the extra cables.

I have an unmodified OTS 50 (July '08) and I have all the clean headroom I can stand.  I run my preamp vol between 4 & 5 and my master anywhere from 2-6 depending on the venue. I have no problem keeping this baby nice and clean. The tone I get is very much like Larry Carlton's clean except for the "deep" switches on his Dumbles are actually "deep" not mid boost. Had this amp been modified before you got it? Check the cap and resistor values on V1 against the layout from ceriatone.com. Other than that... good luck.   Bill

 Thanks Bill for the info. I always seem to run my clean fairly loudly. And the only 50 watt amp that seems to have enough clean for me is my Heritage Colonial. So I`ll probably end up having it upgraded to 100 watts as soon as I can afford it.