Baby "D"

[B]

Hello all! I'm new here. My name is Chris, I have been lurking for a while now and never had anything to offer to the discussions, So I just kept myself quiet. But I just finished a project that some people might be interested in (I think?) Basically In my quest for the perfect bedroom amp, I have married an ODS preamp to a Fender Champ power section. Not really all that clever, But still fun none the less.

This is technically the second amp I've ever built, The first was a paralleled V1-Dumbleish tonestack- v2-Fender Champ output section affair, that whilst sounded good, just didn't do it for me. So I gutted it.

Basically, It is very "D'lite" in the preamp, It is fairly straight ahead with no complex switching, kind of "set and forget."

The amp also has a mixture of values for caps and resistors in the preamp that sound good to me.

It is built with all 716 caps, And metal, Carbon film resistors (because that is what I had) Also, I ran out of real estate and improvised the tonestack location.

I won't lie and say it sounds like a perfect repro of the ODS sound, But it definitely has some similar voicings to it. I'm really surprised at actually how tune-able the amp is to my different guitars.

Anywho, Attached is a schem drawn with the pcb express program and some pics.

Any and all suggestions are thoroughly appreciated!!
-Chris.

[IMG:640:480]http://i430.photobucket.com/albums/qq21 ... byD007.jpg[/img]

[IMG:640:480]http://i430.photobucket.com/albums/qq21 ... byD001.jpg[/img]

[IMG:640:480]http://i430.photobucket.com/albums/qq21 ... byD008.jpg[/img]

(anyone in the Reno/Tahoe area who'd care to take a listen or help me record some clips would be my hero!)

[CHIP]

Cool build. Like to hear some clips. I built a Champ clone a while ago, maybe I'll have to do some tweaking!

[ChrisM]

Nice little amp, tight and compact.

You may have seen this already but this might interest you
https://tubeamparchive.com/viewtopic.php?t=3068

[KT66]

Great looking build Chris. You asked for suggestions, so here are some I thought of ( mind you, I havn't built an ODS yet, but I am an avid reader of this forum).

Add the bright switch - if you don't have enough real estate use a pot w/ a push/pull switch.

Make the local feedback on CL2 switchable w/ an on/off/on SPDT so you have 22M, 44M, or none.

Make the bias fixed, or you could use a DPDT and have both types.

You could try global NFB injected into the cathode of CL2, but you would have to change the cathode cap arrangement ( see AA764 Champ).

I would go higher than 20U on the first PS cap, you might be concerned about the motorboating thing, but I know from experience that 2 X20U in parallel or a 30U is fine, so 40U should be ok too. You could also try a choke, and make it switchable. ( In case you can't tell, if you are afraid of switches, you should stay from one of my amps lol.)

In a class A circuit like this one a tube rectifier adds no sag, so if you made it SS ( you could use a Weber copper cap, or if you use 2 diodes you will need a resistor to bring the voltage down if you wanted it the same) you could use the 5V tap to power a relay for the overdrive.

Or don't do any of that and just enjoy your amp.

Again, great job - would love to hear some clips.

[topbrent]

welcome to AG!

[B]

Thanks to all for the welcome!! Unfortunately I don't have a means of recording any clips right now. But hopefully soon!

Add the bright switch - if you don't have enough real estate use a pot w/ a push/pull switch.

I will try that, Thanks!

Make the local feedback on CL2 switchable w/ an on/off/on SPDT so you have 22M, 44M, or none.

The local feedback is on a switch, But just a SPST on/off

You could try global NFB injected into the cathode of CL2, but you would have to change the cathode cap arrangement ( see AA764 Champ).

I have thought about a little NFB, But it seems the big mods on the AA764 is to remove it, or at least put it on a switch, Then proceed to turn off the NFB and forget all about it.

I would go higher than 20U on the first PS cap, you might be concerned about the motorboating thing, but I know from experience that 2 X20U in parallel or a 30U is fine, so 40U should be ok too. You could also try a choke, and make it switchable. ( In case you can't tell, if you are afraid of switches, you should stay from one of my amps lol.)

Correct me if I'm wrong, But I was under the assumption the 5Y3 couldn't "handle" anything bigger than 20uf, I would like to try a choke when the Misses lets me come off the wallet!

In a class A circuit like this one a tube rectifier adds no sag, so if you made it SS ( you could use a Weber copper cap, or if you use 2 diodes you will need a resistor to bring the voltage down if you wanted it the same) you could use the 5V tap to power a relay for the overdrive.

Changing to Diode rectification would for sure allow me to up the PS filter caps, as well as open up the octal socket for one day building a 2X6V6 ODS with some of the trimmins. And that is a really good idea to use the 5V heater taps as relay power supply.

Or don't do any of that and just enjoy your amp.

Again, great job - would love to hear some clips.

I plan on tweaking this thing to death, Kinda' my guinea pig.

Nice little amp, tight and compact.

You may have seen this already but this might interest you
https://tubeamparchive.com/viewtopic.php?t=3068

I did see that! It is awesome, and he managed to fit it ALL in there!! Amazing stuff! Mine is crammed into a Champ sized chassis that I bent up at work, But boy, is it TIGHT in there. Also, The amp lives in an 80's harvard reverb amp that I practically stole, I know some people think they're great, But it wasn't my cup o' tea.

Thanks again!!
-Chris

[heisthl]

Congratulations on a project well done. Those Champ sized amps can be a real challenge - I don't do very many anymore but here's as far as I could take it in that size package - 5 preamp tubes

[talbany]

Henry

Gutsy call putting that OPT that close to the Preamp tubes ...Gotta give Mercury a little credit there...Nice work are those tube covers powder coated red or anodized...They are cool..

Tony

[Bob-I]

Add the bright switch - if you don't have enough real estate use a pot w/ a push/pull switch.

I will try that, Thanks!

I was able to squeeze a switch above the pots and between them on a Princeton chassis. I had to abandon the cicken head knobs and go with pedal sized knobs, but I like it better than push pull pots.

You could try global NFB injected into the cathode of CL2, but you would have to change the cathode cap arrangement ( see AA764 Champ).

I have thought about a little NFB, But it seems the big mods on the AA764 is to remove it, or at least put it on a switch, Then proceed to turn off the NFB and forget all about it.

Well, this ain't a Super Reverb

One of the keys to the Dumble smoothness is the GNFB. Folks remove it on the Fender's to make them more gritty in the mids. The Dumble tone needs to be smooth IMHO.

[B]

Well, this ain't a Super Reverb

One of the keys to the Dumble smoothness is the GNFB. Folks remove it on the Fender's to make them more gritty in the mids. The Dumble tone needs to be smooth IMHO.

Good point, My reasoning is sometimes pretty flawed.


Actually, Heisthl, Henry if I may, your builds are definitely what inspired the build. Truly magnificent, Especially the one with fender style reverb, I've thought about reverb, But think I'll go the one tube route. Also, I built mine to someday be a fender piggy back style setup, Just smaller, Hence the slope faced chassis. Which incidently is a pita to work with.


Thanks again guys!
-Chris

[Guitarman18]

Nice work B.

I did exactly the same thing in order to get to grips with the ODS type amps, although I kept getting issues with motorboating when the gain and OD volume were turned up. I put it down to limitations of the SE output and spent ages trying to work around the issue. I then built a 100 Watter and never looked back.

Have your had any similar experiences with motorboating? If not, maybe I should revisit my amp.


Thanks for sharing.

Cheers,

Paul.

[Structo]

Nice!

I'll bet it sounds great!

[B]

Nice work B.

I did exactly the same thing in order to get to grips with the ODS type amps, although I kept getting issues with motorboating when the gain and OD volume were turned up. I put it down to limitations of the SE output and spent ages trying to work around the issue. I then built a 100 Watter and never looked back.

Have your had any similar experiences with motorboating? If not, maybe I should revisit my amp.


Thanks for sharing.

Cheers,

Paul.

Hello Paul, Actually, I've heard (read) about motorboating issues, And it seems really prevalent in SE amps. I just changed the preamp to output coupling cap (the .047 cap on my schematic) from .02 to .05 and have noticed the amp has just the slightest motorboating as the note fades. I was trying to let a little more bass content through the amp, as of right now I'm just running a P.O.S Fender 10" that came stock in the Harvard Reverb donor. But other than that, I have not had any real issues, at least none that have manifested themselves at apartment levels.

-Chris.