Everything You Ever Wanted to Know: Pictures & Diagrams

[tonelab2]

Your turn to call me crazy but I think your right.
Had a close look at photos ODS_124062&63&64 and it seems you are on to something..But still not convinced LNFB is on V1A. I think perhaps there may be an issue with the routing of wires(lead dress) somehow. Can't seem to get a fix which wires go where for conclusive proof that LNFB is on V1A, need better eyesight.

[tonelab2]

O.K.
Had a closer look at the wiring ( my computer monitor is on the blink, the colour yellow looks orange and so does the colour red) and now think you are 100% correct, providing HAD stuck to the colour coding of Yellow=cathodes, Blue= Plates.
The resistors you mentioned are 2x20meg in series and 2x10meg in series (which gives a total of 60meg ). That's how it looks to me with a dodgy monitor and eyesight.

[tonelab2]

O.K Brown looks red on my ol' monitor so it's 2x10meg + 2x10meg.
Makes better sense than 60meg. Even 40meg is to much for my tastes.

Well spotted BTW.

[hipbluescat]

Hello Gil and Bill

I can not thankyou enough.

Especially since the ODS was my next project !!

What speakers were with this amp and who was the speaker box made and configured?

To build this amp would you use 1/2 watt Vishay Dale RN65 series resistors and Xicon MPP series caps ?

What is the difference between the later amps that dumble had built. Pazzo63 wrote

hi, nice pictures ,i m sure that is a nice sounding amp.this is a amp very fender ispired ,but very different from the later ods where have different values of plates and cathodes, power supply, bias ecc.i think it s a one of a kind amp,and probably truely a transitional amp like sweet Mr Ayan wrote.would be nice to see pictures of how this amp has been modded from the GREAT Mr Dumble later on...also would be nice to see pictures of a more recent amps,to compare with older amps,and i m sure that some members have some and show to everybody the GREATNESS of the original builder .I ve read that the MAN is not making ods anymore,so we would not STEAL NOTHING from HIM(i apologize for my english). Dave

Can anyone point me a circuit diagram of a later model ODS.

Can anyone explain how the changes in the later circuit would of changed the tone.

Regards

[Robbie]

Fantastic pics! I had seen these on another website. When I studied the series trimmer on the first OD channel I sketched out the series decoupling cap going to the 120k going to ground then the trimmer (350K) in series with the 68k going to the grid of the first stage. If I have this right this develops a nice low pass filter when combined with the miller capacitance of the first OD tube acting as a pre-od filter. I keep thinking of the nice rich tone of LC of the 80's era. I tried it on my clone and it sounded great!

Robbie

[makrisp]

Can some explain to me what is so new about the pics? I believe and correct me if I am wrong, but are not all these pics listed on Rob Livesey's page under #124?

[tictac]

Looking at the picture of V1 the resistor to the left under the big yellow filter cap is the input grid resistor, probably 22k like Gil said. The resistor bypassed with the 500pf cap is a 220k running from the volume control to the 2nd stage of the preamp.

V1a and V1b are flipped around because the tube socket is 180 degrees from the usual Fender position (pin 4,5 toward the rear chassis) but the circuit is still the standard Dumble fare. The input is not bypassed it's the 2nd stage.

[keithrick]

Looking at the picture of V1 the resistor to the left under the big yellow filter cap is the input grid resistor, probably 22k like Gil said. The resistor bypassed with the 500pf cap is a 220k running from the volume control to the 2nd stage of the preamp.

V1a and V1b are flipped around because the tube socket is 180 degrees from the usual Fender position (pin 4,5 toward the rear chassis) but the circuit is still the standard Dumble fare. The input is not bypassed it's the 2nd stage.

Agreed! I came to that conclusion after some fresh air. I was hoping in my solder fume haze that I had discovered a secret that may have been overlooked!

[glasman]

HAD probably rotated the tube for hum performance (using 6,7,8 as the first stage). It took me awhile to find this, but if you read the bottom of the first page it comments on cascaded stages and hum performance.

http://tdsl.duncanamps.com/sheets/ecc83/ecc83.pdf

Gary

[ayan]

Can some explain to me what is so new about the pics? I believe and correct me if I am wrong, but are not all these pics listed on Rob Livesey's page under #124?

Well, the pictures were new when I posted them because I was the one who took them. If Rob copied them and posted them in his website, then he obviously took the liberty to do so after I put them up in my liitle photobucket site.

Gil

[ayan]

Can some explain to me what is so new about the pics? I believe and correct me if I am wrong, but are not all these pics listed on Rob Livesey's page under #124?

Well, the pictures were new when I posted them because I was the one who took them. If Rob copied them and posted them in his website, then he obviously took the liberty to do so after I put them up in my liitle photobucket site.

Gil

[heisthl]

HAD probably rotated the tube for hum performance (using 6,7,8 as the first stage). It took me awhile to find this, but if you read the bottom of the first page it comments on cascaded stages and hum performance.

http://tdsl.duncanamps.com/sheets/ecc83/ecc83.pdf

Gary

Gary have you ever played with this? Over the years I've come across a few amps done this way, I wonder if its worth doing on a DClone? I would bet it is most noticed on Cathode Follower stages (which the DCLones don't use).

[glasman]

Henry, I have not tried it personnally. But probably will in the future. I just hate to change things that are working

Gary

Hey Gil, welcome back home!!

[Bob-I]

HAD probably rotated the tube for hum performance (using 6,7,8 as the first stage). It took me awhile to find this, but if you read the bottom of the first page it comments on cascaded stages and hum performance.

http://tdsl.duncanamps.com/sheets/ecc83/ecc83.pdf

Gary

Very interesting. It makes you wonder if this is specific to the Mazda tube of 12AX7's in general. I understand the heater reference but I don't understand using the second stage first . I've done that several times just because I have the input on the right instead of the more common left. Maybe I just happened on the RIGHT way to do things

[glasman]

HAD probably rotated the tube for hum performance (using 6,7,8 as the first stage). It took me awhile to find this, but if you read the bottom of the first page it comments on cascaded stages and hum performance.

http://tdsl.duncanamps.com/sheets/ecc83/ecc83.pdf

Gary

Very interesting. It makes you wonder if this is specific to the Mazda tube of 12AX7's in general. I understand the heater reference but I don't understand using the second stage first . I've done that several times just because I have the input on the right instead of the more common left. Maybe I just happened on the RIGHT way to do things

I doubt that it is Mazda specific, even though it is the only place I have seen it mentioned.

WRT Dumble, if you look at pictures of his very first amps, he used pins 1,2,3 as the first gain stage. On later amps (I do not know the cutover serial) he switched to 6,7,9 for the first gain stage.

I think a 50/60 hz hummer test is in order. Input shorted to ground and measure 60 hz level at the output of the second stage.

Gary