Ceriatone Forum

Here is a Overtone Layout

This is probably a dumb question....but that is the schematic, correct?
Is there a front panel layout anywhere that discusses the controls and what they do, as well as the internal trim controls????  (i guess something like a MANUAL)???

No, that is the amps component layout.  There is no manual but the folks here can help you if you have any specific questions.  The controls are labeled on the layout and the amp faceplate pretty much resembles any Dumble ODS control panel.  There are plenty of pics on the www.  As for the 3 internal trimmers......2 of them I wouldn't bother adjusting and the OD trimmer is set to taste. 

Warning!!
Be very aware that there are voltages that can KILL you in there so DO NOT go poking around unless you are absolutely sure you know what you're doing.   

Hi everyone,

Does anyone have a 'schematic'  ? The layout is handy but  a schematic is handy for fault finding

Would appreciate one if anyone has a copy

If you find one...let me know. ;)

About the schematic, I cannot imagine someone building an amp without one, so I suspect Niki has one. If he wants to post it then that should be up to him. Personally, for my project using Niki's kit, I drew up a schematic by following the circuit in the layout posted here. My project has a different power supply, different transformers, slightly different grounding scheme and is 100W, so it does not exactly match the pre-built Overtone that Nike sells. I have no problem sharing it on this forum if it is OK with Niki.

Hey...could someone show a closer pic of the front of the control panel and explain the contols?  (besides the obvious "input" and the tone controls)
Thanks....

I have a kit on the way, and am just very anxious...I know i love the dumble sound cips I've heard, but other than that, I'm not familiar with the control panel and features.

Thanks so much!

A few questions about the layout:

It looks pretty straightforward except fo the 3-pin devices labeled "5K" near wire B-25, "100K" near wire B-8, and "10K" on what looks like the "FET" daughter board.  Are these some kind of center-tapped resistor?  I've never seen something like that.  ???

Also, about the "FET" circuit.  Is the actual FET the grey blob in the middle of that daughter board?  If it is, I've never seen a 4-pin JFET or MOSFET like that.  I thought FETs are 3-port devices:  gate, drain and source.  ???

There are two connections to a "choke".  I'm assuming that the choke is an inductor mounted to the other side of the chassis as is the output transfomer.

I guess the "7812" is a 12 V voltage regulator device.

Just wondering.  If I can get these answers, maybe I'll actually feel inspired to CAD this as a circuit schematic in AutoCad.   ;)

Those are trimmer pots. It's like a regular pot but these are used inside the amp.
http://www.allelectronics.com/cgi-bin/category/470100/Trimmer.html (http://www.allelectronics.com/cgi-bin/category/470100/Trimmer.html)


Sorry don't know about that.  ???


Yes that's it.

Yes

Ahhh, thank you!  :D

That fourth lead is just a case ground. It's the lower left FET lead on Niki's layout. The FET is not marked but I am expecting a NTE452 when my kit arrives.

I'm using 022699 (Fender Twin) choke, along with Fender Twin output and power transformers. (I'm making the 100w version)

This is different from the generally accepted dumble layout. Are you guys interested in getting closer to what the "standard" is?

What is the "standard"?

Aren't all of those amps tweaked in a some way.
To me, the goal is to make it sound good, whatever the layout is.

 ;)

???
Niki's is the closest I have seen to an 80s ODS. If you don't consider actual component values, (you said 'layout') and realize Niki's is 50w (50w power supply etc) , whereas the real one was 100w, his layout is nearly exact. The only other things I can think to change would be to add the 50/100 switch and LED and remove the Impedance selector.

Are you thinking about a 90s ODS or a HRM?

Ohhhhh Yes!! I am so very interested....Ummm.   Which standard might that be....??  Do tell.

Which is the OD Trimmer- :-[

It's the 100k trim pot at the input of V2.

V2 is the center tube-correct ;D :-\
And thanks Chris.

Yes, the center preamp tube.
 :)

I learn slowly, Interested in how you guys tweak it too, but only the good tweaks :)
Thx
Burnie 8)

I found a data sheet on the NTE452 JFET:

http://www.nteinc.com/specs/400to499/pdf/nte452.pdf (http://www.nteinc.com/specs/400to499/pdf/nte452.pdf)

Happy reading.  ;)

Oh man...thanks....
but...uh....er....what the hell is it?  (and can you play any lynyrd skynyrd with it?)

You can tweak the bias of the FET with the 2.7K resistor from "Source." The original had an 8K there.

What does the fet input do differently than the regular input..I know Iknow ::) ::) ::)
But I have another question that might be more enjoyable...Have you or anyone thought about about transformers as in improving the tone of the Overtone or is that not something you guys think about.
My questions come from one who has no real electronic expertise so cut me some slack okay!! ;D :)

Yeah, it's hard to believe that the holy grail "model"  :-X of this vintage (80s? 90s?) actually has a :o solid state device in the preamp stage.  Look no further than the Boogie MkII for a Fetron device in V1 (that can be replaced with a warmer 12AX7).

When tube amps are cranked to their sweet spot, output transformers probably impart their own unique contribution to the sound coming out of the speakers.  Here's a nice article about Mercury Magnetics' OTs for Marshall original plexis and reissue plexis.  Sounds like they also make retrofit models for Fenderish amps as well.

http://www.legendarytones.com/guitouttrans.html (http://www.legendarytones.com/guitouttrans.html)

Mercury Magnetics:

http://www.mercurymagnetics.com/pages/mainframe.htm (http://www.mercurymagnetics.com/pages/mainframe.htm)

I didn't know th MK II Boogie used a fetron but my MK I (they didn't really say that, that's just what people call them) came with one. I still have it and it was never installed. Mike Bendeneli (sp?) told me they used them when guys CRANKED the amps so far they would go so wildly microphonic you couldn't play them. The fetron isn't a tube so it isn't microphonic. At volumes most mere mortals play at a tube sounds better to most people. Larry Carlton did use the fetron on some recorded solos back in the day though.

A note on  the overtone layout.  The original Dumble on which the overtone is based had the preamp tube sockets rotated 180 degrees. Where Nik has indicated #1, the Dumble has #6.  The hookup is nearly identical either way.

There is a new layout !

I compared the April 1 layout with the Jack Zucker modifications and the new layout per May 26, 2008.

The new layout follows all proposals of the Jack Zucker modifications (JZ mod) exept for:

1. JZ mod proposal: 2 X additional 50uF 350V parallel to the 2 X 100uF 450V
    April 1 layout: no additional caps
    May 26 layout: no additional caps (no change to old layout)
    Reason for non-adoption: not known per today

2. JZ mod proposal: 2 X 470 Ohm 5W instead of 2 X 1 KOhm 5W
    April 1 Layout: 2 X 1 KOhm 5W
    May 26 layout: no change
    Reason for non-adoption: EL34 compatibility
    ....and it was stated before that this would not really benefit sweeter
    cleans either

3. JZ mod proposal: 4.7uF 25V instead of 1uF 25V
    April 1 layout: 1uF 25V
    May 26 layout: 5uF 25V
    Reason for non-adoption: near adoption but not known per today why
    not exactly

4. JZ mod proposal: 4.7uF 25V instead of 2.2uF 25V
    April 1 layout: 2.2uF 25V
    May 26 layout: 5uF 25V
    Reason for non-adoption: near adoption but not known per today why
    not exactly

5. JZ mod proposal: 2 X 330pF instead of 2 X 220pF
    April 1 layout: 2 X 220pF
    May 26 layout: 2 X 390pF
    Reason for non-adoption: not known per today

Maybe someone (for example ampkits  ;)) could shed a light on points 1. and 5 ?

Hi Chris,

This is Jerry i am building 4 Overtones for Hugh Faulds. The two trimmers on the main board get left alone? thanx   Also I noticed I was sent two black an one red bias ports. The drawing shows it in reverse. Is the star ground one of the PT bolts or seperate. Pic looks seperate. Thanks for your help Can I bug you more down the road?

jerry dyer
surreal amplification

The right hand trimmer on the main board is the one that controls the OD channel level and is the one you'll experiment with most. The PI trimmer (left hand end of main board) is set and forget The trimmer on the satellite board that contains the FET, controls the level for that input. Most owners don't use the FET input much but you might want to just set it to a sensible level and leave it, I have mine at 9 o'clock.


That won't matter, just use the  red one in the centre. They are just measuring points.


Separate bolt with 3 or 4 solder tags. Don't tighten it up until all your joints are made. It works as a big heat sink if you do and a low power iron will struggle.

HTH

hey thanx      I just havent seen a PI trimmer. hhhmmmnnn! interesting. 

also are there supposed t obe plugs for the unused switches on the back? thanx

Hi,

  Yes, screws are provided to cover the holes.

  I just dont see a point for 1/2 power switch on the overtone.

  Perhaps my ears are in their golden years (heh).

  We do install on request, however.

  Thanks!

Nik

Just wondering which layout is correct?
This one is a bit different than the one from the order page I've been using
Why is it different?

Read all the posts on this forum (and on ampgarage.com as well) like the rest of us have done over time and you will get all relevant information there is on the Dumble subject.

Also take a listen to peoples sound clips on this forum and find what you like.