Ceriatone Forum

made 4 easy changes that made an incredible difference.

   1. Changed the resistor in front of the lead drive from 150k to 220k (In my amp this leads to a 100k pot. In older ceriatones the pot is probably 250k. It should be changed to 100k)
   2. Changed the suppressor caps on the v2 socket from 270pf to 390pf (I didn't have 330pf)
   3. Clipped the 15pf cap on the master
   4. Clipped the cap/resistor across the effect loop

http://www.sheetsofsound.net/demos/ceriatone-tweaked.mp3

Took ya long enough. ;) ;D 

sounds good, but then again it allready sounded pretty decent :-)

I'm curous: what do these changes do soundwise? bettrer tone control better pot respons? alter the sound? In what way?
I know sopme of you guys have a lot of technical expertise, but some of don't. Onviously I'd be interested to learn as much as possible on improving the ODS. I would have to find someone with a soldering iron though.

Jack, Nice tone!

However, I would need to carefully A/B it with your previous clips to understand the difference. Also, it sounds like you are mixing in the delays differently than before?

Mine is a January model, I wonder which version is it? ???


M

The changes I'm after are to get the OD to sound more like the robben OD and to open up the clean sounds so they are not so peaky. Also, I find that with the stock circuit I have to turn the tone control way down on the guitar and keep the treble and presence at 10 O'Clock so ideally I will have more useable tone control range.

Gathered from ampgarage and the brownnote forums, I am armed with the changes necessary to make this amp sound more like robben's dumble ala *ludotone or *uchs or *arole-ann.

When I'm done, I think you guys will find that the amp sounds much more delicious and it's only a few bucks in parts. Hopefully Nik will incorporate the changes back into the production model.

In addition to the values, I'm using carbon film resistors in certain audio-path areas and specic types of caps in other areas to make the tone more musical.

Stay tuned!

Yeah, but if you had a g12-65, you wouldn't have to worry about that, since it tames the highs....but you say that its too dark? ???

Sorry Jack, I'm not really sure what you're after? Something in between a g12-65 and RWB?



excellent work given that you say that you are not an electronics expert.

I'm too lazy to open up an amp and my usual amp tech is too grumpy to be visited. :D


Marin

I've been using emi wizards which are brighter and I really like them. The last 2 clips were done with the wizards. I also have a 2x12 cab coming with greenbacks.

Jack, one more question, what is the voltage of the 330pf?

All parts rated for 500v unless otherwise specified.

Latest Tweaks:

    * Changed the treble cap from 330pf to 390pf (like dumble)
    * Tacked a 1uf cap across the 2 2.2uf cathode bypass caps. (Awaiting 4.7uf from mouser)
    * Changed the 150k resistor before the ratio control to a 180k
    * changed the 2.2k PS dropping resistor to 3.9k. (Awaiting a 3.3k from mouser)
    * Changed 1k power tube screen grid resistors to 470ohm

Another round of HUGE improvements. (Clips later). Additionally, it's no longer ice-picky for jazz stuff in the clean channel. Very sweet cleans out of the amp that rival the boutique cleans out of many other amps I've played.

When my mouser order arrives, I'm going to do the complete gamut of changes I've gotten from Gil and Scott and this thing's going to be a monsta!!!

Hi Jack, nice of you to share your tweaks, with all tonesamples you're providing it's really good to follow how things end up.
Thanks!

Yes, thanks Jack. Please post your final menu with a clip - I have an Overtone and plan to mod it based on your info.

I'll post a clip tonight or tomorrow with the latest tweaks. I'm now at the point where I can't go any further until UPS shows up with my order from mouser with parts. Unfortunately, I forgot a couple parts in my first order so I ordered about $5 in parts last night (along with $5 shipping) which will arrive a day or two later. The main tweaks now are the V2A and V2B cathode bias circuits and plate resistors and V1B cathode bias circuit. I'm going to try beefing up the power supply caps from 50UF (a tad light) to 75UF which should give me a little tighter bottom in the OD channel at the expense of possibly making the cleans a little more stiff. It's a balancing act.

The amp sounds so good now but I know it can be even better. I hope Nik makes this part of the standard circuit because it will remove complaints folks have about it being too aggressive and bright. Basically, when these changes are done, the amp should kill because the transformers appear to be incredible quality.

+ one more on the recipe ;D 
Great clips!!!

Jack,
I'm a new guy here and I've recently won an OTS on eBay. I consider myself a lucky dog! I've emailed Nik and he sent me mods, many of which are things you're doing.

I'm not real good at reading schematics so was wondering if it would be too much to ask if you could mark up/circle or otherwise notate a copy of the schematic and then post it so we can all see what areas of the board you're going to for the changes. For example, I can't seem to find the cathode bipass/preamp caps (the 2 - 2.2 uf ones) for the life of me... Blind, I guess...

Oh, and let me add that you're a very masterful player. Love your clips, my friend. Do you play out at all?

Cheers -
Ken

Hi Ken,

That's a good idea. Using photoshop I'll mark up the schematic when I get some time. Does anyone know what Nik uses to generate the schematics? Visio or something else? Maybe I can get the original files and replace the component values and then hilight them?

As far as I know Nik uses CAD.

I think Nik is a little reluctant to let anyone get their hands on the original files. When I asked for a .dwg or .dxf so I could print a large version he was a little cagey as to what software he used.

Hey Jack -

Awesome. Yes, when you have time to work it, I believe it would be a real help to many of us here that are a little overwhelmed by a layout or a schematic.

BTW, is there a concern for getting zapped while doing some of these mods? I've heard where if you have the amp off and then flip the standby on, the major current reserves are drained. Is that true? I'd like to avoid getting a nasty surprise while in the unit snipping and soldering away!!

Thanks!
Ken

Hi kenster...I'm a newbie to electronics and I'm planning on performing the modification to my Overtone.  I'm doing a lot of reading on discharging caps...the caps can store enough voltage to kill you.  So we do need to be very careful when poking around in the amp.
Here's some info that I found....

http://studentweb.eku.edu/justin_holton/caps.html

http://www.schematicheaven.com/mods/capdischarge.htm 

Good luck!!!

Hey poipounder57,

Thanks for those links. That makes me want to think twice about just jumping in and doing this so quickly. How effective is it to flip the standby on while the power is off in the OTS? Even Nik says that's all you have to do. Jack, do you have anything to add to this discussion? What procedure do you use to get the charges out of the chassis before you work on it?

Cheers -
Ken

My amp tech told me that if when you turn off, you turn the standby off then count to ten before switching the mains off that should do it. But to be on the safe side get your meter out and see what voltage you've got on the big filter caps.

I just measured the voltage across the big caps and I noticed something interesting.
When I switch off the amp ( and it doesn't matter if the off switch goes first and the standby after one minute )... somehow the caps gets discharged, no action needed.
I don't know why or how... maybe it's the design of the amp.


...but don't take my word on this, please measure the voltage yourself.
 ???

What Nik has been telling me. You made a case for switching the standby off last ( a minute should be ample time to discharge capacitors) doing as it's intended to do.

That makes me feel much more comfortable.

Thx!
Ken

Yes, but I'm trying to say that even if you switch off both switches at the same time the caps still gets discharged.

 ???

mcinku -

Yes, I understood and I should have worded things a bit differently. My bad....

It may well be in the basic design to drain the current regardless of which way you switch the power off. I'd err on the side of switching the standby off last just to be smart. I've done that on amps in the past - leaving the standby on while switching the power off - and you can actually hear what sounds like current draining off thru the speakers.

Your test validated that and combined with what Nik is saying, I'm ready to jump in this weekend.  ;D

Cheers!
Ken

But be warned... this may be the case with OTS but don't think it's the same with other amps.
I just have to say this, for any other guy who might be reading this.


BTW as far as I know, when you leave the standby switch on and you are listening to the volume which is fading... This is not necessarily the draining caps thing but it could be also the 6L6 (or any other power tube) heater is getting colder. So if the heaters get colder before the caps gets drained... you could still have the charge in there.
 ;)