D'Mars 5879 ODS & FX

[tubenit]

Simply put, this version has a VERY transparent sound with very musically sweet harmonics and touch sensitivity.

I have continued to slowly tweak and experiment with this amp for over a year. In it's current state, some of "that" vowel tone has returned to it.

This first post is the NON-5879 OD with an active FX.

This is the "best" sounding amp that I've ever played.  With the more recent tweaks, the touch sensitivity and sustain is just remarkable! The tone and dynamics really change significantly with how one picks the strings.

It has evolved to be a very warm clear clean tone ........... AND a very sweet overdriven tone that is best I've been able to coax out of any amp.  The OD is super smooth sounding, IMO.  I can crank the OD to have almost infinite sustain into feedback.

Originally, this amp had a Hammond 1620 OT which is quite large for a 20w  OT and similar to what you might find with a 30w or 35w. However, it turns out that the 1620 had some high end chime that I didn't care for.

I eventually replaced it with a beefed up 40w OT with heavier laminates.  This began to smooth the OD tone out.  I discovered with the larger and heavier OT that I could increase some of the values of the coupling caps such as the post LTPI caps from .03 to .05.

I think the clean channel sounds like one of the best full sounding warm clean tones that I have ever heard. And there is a nice contrast between the clean and OD channels even at the same volume.  At this stage, I think it sounds 60% Dumblish and 40% Marshall.

I don't understand why changing the FX pots to be more of a variable resistor helped the tone, lessened noise and gave more volume but it did for some reason??  I use a delay (Carbon Copy,  Wampler Faux Echo or Moen Pretty Dolly ...... or a Digitech handwired reverb)  The FX works great and makes a nice master volume also.

The changes have moved the amp from a brighter tone to a fuller warmer tone.  The amp sounds HUGE to me at very modest volumes playing at home.

I have also included a paralleled turret board style.

With respect, Tubenit

[tubenit]

This is a D'Mars with both 5879 OD and an active FX on board.  I have built and am playing this amp now (2-'15)

Relay illustration for this amp is reply #33 on this thread:  http://el34world.com/Forum/index.php?topic=14348.0

Voltages for B+ rail are:   node A/ 367v    node B/365v    node C/338v   node D/257v   node E/249

I went back and forth between a 390p vs. a 500p for the treble cap.  It is in series with a paralleled (.0012 + 680p for)  .00188. I settled on a 390p because it gave a bigger tone spread between it (in series) and the .00188.  Both sounded good though.

With respect, Tubenit

7/18/2015  EDIT:   I've spent hrs and hrs trying to tweak the last ounce of tone out of this amp. Tried tons of different stuff but kept very little of the experiemental mods in place.  This 7/18/2015 is the final version.  It also is the smoothest OD and has the sweetest harmonics.

EDIT: 11/1/2015   I have found two more tweaks.  The most important is the bypass of the tone stack going into the OD section.  It allows a much THICKER and more TRANSPARENT OD tone without impacting the clean tone which remains the same. 

The other tweak is I replaced the 22k of the FX send with a 100ka pot.  That was needed to really push the OD tone and it allowed more versatility to the amp.   I can get a pushed clean tone that is on the verge of breakup ............ OR a really pushed OD tone that has great sustain and harmonics. The 22k gave a more relaxed and cleanish tone that wasn't pushed.  I have the 100ka pot dialed between around 56k to 82k most of the time now.

EDIT:  11/14/2015      I had gotten the clean channel to the place where it lacked headroom so I changed out the plate resistors and cathode resistors in the clean channel.  I also bumped up the .02 coupling cap off V1-1 to .03.  Note that the cathode follower resistor is only 82k.  This was done after reading Valve Wizard's explanations of lower value CF resistors adding harmonics.

EDIT: 12/20/2015  After Willabe experiments with different caps and reported Musicaps as being VERY transparent, I experimented with some in my amp which then brought about a few other minor changes.  This is probably as close to an "opus" as I will ever come up with. 

IF there is any discrepancy between the schematic and layout ............ go with the schematic!

Best tone I've had from any amp.  The clean channel is very touch sensitive and "dimensional" with nice harmonics.  OD channel is not distorted and has smooth OD and very nice sustain.  I'm happy with it.

[MakerDP]

After going back-and-forth on this build for a couple years now, I finally have the parts all on-order or on-hand to do this build. I am going to go ahead and do the 5879 w/effects.

Any updates since last post?

Also, I would like to know, in your experience, which tone caps you felt were the most crucial to tweak in your tone shaping after the build? There are so many of them and I would like to avoid as much dead-end tweaking as possible.

And finally for now... I went with the 272FX PT. Those voltages in the second post... are those with a 300-0-300 PT?

Thanks for your efforts on this amp. I am really looking forward to hearing how this thing turns out in the end!

[tubenit]

No new updates.  You can build the entire amp with Orange Drop PS or perhaps Hoffman's yellow Jupiters.

I would consider replacing just two caps with musicaps.  The first one in the signal chain for the clean channel (.02) and the first one in the signal chain for the OD channel (.01).

With respect, Tubenit

[MakerDP]

Thanks. I'm using OD PS caps and a 20x8x3 chassis with a custom layout.

Have you tried replacing the two cathode followers with a couple of IRF820's to eliminate a tube?

[traynor]

Would love to be able to open the layout and schematic in post 2, (5879 OD with active effects 2-15) Any chance in jpg version for us Mac users, thanks.
Brent

[tubenit]

Here is a GIF version of layout.  Any discrepancy between layout and schematic, go with schematic.  You can look at the schematic on the post for comparisons.

Have you tried using J-schem?   It will work on Macs and open the SCH files.

Tubenit

[traynor]

I used to use it on my Mac but since going to Yosemite it stopped working. I'll look into it, maybe it will work now.
Thanks

[BetterOffShred]

Hope it's ok to post in this one.. 

I'm curious about this amp, and was wondering if you had any decent sound clips of it Tubenit?   It looks pretty cool and I was thinking about sticking it in the project folder for consideration.   Also I was hoping you could indicate which PT and OT you ended up using.   I saw that you went with a beefier OT.  What kind of cabinet do you play it through mostly? 

-Brett

[tubenit]

Here is a sound click:   

http://www.soundclick.com/html5/v3/player.cfm?type=single&songid=11824794&q=hi&newref=1

http://www.soundclick.com/html5/v3/player.cfm?type=single&songid=11842172&q=hi&newref=1

I used a Hammond PT with 300-0-300 & 173ma using 5881's.   I used a Classictone OT   http://www.classictone.net/40-18006.html

Having said that,  you could use Hoffman's 40w OT   #018343

It is in a combo with an Emminence Delta Pro speaker.

My purpose in using the 300-0-300 PT was so I could use a 5Y3GT with 6K6 or 6V6  (330v).  5V4 with 6V6 or 6L6/5881's (360v)  or GZ34  (390v)with 5881's/6L6.

With respect, Tubenit

[MakerDP]

Hope it's ok to post in this one.. 

I'm curious about this amp, and was wondering if you had any decent sound clips of it Tubenit?   It looks pretty cool and I was thinking about sticking it in the project folder for consideration.   Also I was hoping you could indicate which PT and OT you ended up using.   I saw that you went with a beefier OT.  What kind of cabinet do you play it through mostly? 

-Brett

I used the same transformers Tubenit mentioned above (the Hammond and Classic Tone) and Tung Sol reissue 5881's. I tried JJ 6V6's in it and I prefer the 5881's. There really isn't much of a volume difference between the two at all so it's really a tonal preference. The 5881's have slightly more clean headroom though. I am also currently using solid-state rectification but I am considering trying the tube rectifier. I also added a PPIMV which I really like having in an amp with this much power.

I run it through an open-back pine cabinet with a WGS ET-65. Sounds fantastic, especially with a tele-type guitar.

[MakerDP]

Hey Tubenit...

I've been messing with 6U8A tubes and I really like the results. Something to consider that would simplify this build somewhat...

Replace V2a with a MOSFET.
Replace V2b and V3 with a 6U8A

I think you would really like this tube if you haven't played with it already!

Tubenit response:   Thanks for the tip!  I'll read up on this tube.