Tweed ODS vs D'Mars ODS vs Carolina ODS

[Joel]

To avoid contaminating DennyG's very fine build log thread (http://el34world.com/Forum/index.php?topic=22527.0) I thought I'd ask my question here.

I've been reading a lot about these amps designed by Geezer and Tubenit, and I believe that these threads contain the latest up-to-date versions of these amps;

Tweed Overdrive Special - http://el34world.com/Forum/index.php?topic=9636.0
D'Mars Overdrive Special - http://el34world.com/Forum/index.php?topic=17305.0
2017 version of the Carolina Overdrive Special - http://el34world.com/Forum/index.php?topic=21803.0

Basically what I'm asking for is a descriptive comparison of them, since I think it'd be a bit much to ask for an audio comparison (unless anyone has all three and wouldn't mind?).  Also noting that Mr. Tubenit has described each as the best amp he's ever built/played... I get the feeling he's not totally impartial  And honestly, who could blame him?  It'd be like asking a parent to pick a favourite child.

I currently prefer a rich clean tone or a slightly overdriven tone when playing.  But those overdrive tones in DennyG's demos do sound fun.  But, like anything else, I tend to analyse the options to death before committing my hard earned coin and time into a project - hence my request.

Opinions appreciated.

[SILVERGUN]

Reading tubenit's own descriptions of each amp is the best way to tell the differences between his different designs.
If you use the search function and read through the many comments he has made regarding those different designs it should give you the comparison you are looking for. I wouldn't rely on anyone else's opinion since he is the only one who has had all 3 amps in front of him, but I can tell you this..
 
I have been pleasantly surprised by the rich clean drive that is available with just a 2 gain stage preamp, and even found that my Dumbleized Bassman will harmonically feed back on the clean channel.
 
If you are willing to settle for a non channel switched amp, you can get a very rich, clean sound without all the additional circuitry on the 4 gain stage designs.
 
If you want those heavily overdriven tones that dennyg is demo'ing, you'll have to go will a 4 gain stage'er.
 
Some of the magic is found in the mid boost functions, or PAB (Pre Amp Boost)
If you look at it from a different perspective it is only a boost because we are all so used to the tonestack being such a big loss of signal.
On the TOS, he implemented the Tweed style tone control, which is way less lossy than the normal Blackface or Marshall'ish mid-scooped tone stacks.
Without all of the signal loss between stages there winds up being plenty of rich clean drive available from just 2 gain stages.....add 2 more gain stages to that and you have the ability to go over the top as shown by dennyg.
 

[tubenit]

If wanting cleans not TOS. Best fenderish cleans are Carolina Overdrive.  Best Marshall cleans D'Mars.

[Joel]

Thanks for the replies guys.  Appreciate it.

Thanks Tubenit for the succinct summary.

[tubenit]

There are some sound clips for the D'Mars that you can check out.

Here is one by DaGeezer who built the D'Mars preamp and ran it into a power amp using 6AQ5's.  His playing is incredible, IMO.

https://soundcloud.com/dageezer/dumars-noodles1-0

Here are a sound clip of my D'Mars running into 5881's.  It would be a good example of the clean tone with it

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

I don't have any sound clips of the Carolina Overdrive Special. I think it has comparable cleans but more fender sounding.  The clean to OD has greater contrast on the COS also.

I think both of them are very sweet amps for clean tones.

With respect, Tubenit

I guess another consideration is Doug carries a D'Mars layout board that uses a passive effects loop.  I don't think you "need" a active FX loop with this amp if you are using a Carbon Copy Delay or a Boss digital delay.  Those both sounded just fine to me in the passive effects loop.  The 2017 COS doesn't have a Hoffman designed layout board and does have an active FX loop in the design.

Depending on what tone you're looking for with either the D'Mars or the COS, I think any of these speakers would sound great:   Emminence Pro Delta 12,   Emminence Cannabis Rex,  Emmience Texas Heat (more Fenderish tone)  or Warehouse ET-65.   The Pro Delta 12 has the cleanest most neutral tone.  The Warehouse ET-65 perhaps has the smoothest OD tone with the Cannabis Rex as a close 2nd for the OD tone.

[dennyg]

Joel - i'd be interested in your goals for your next project.  I say that because I chose this amp as my 4th build for a few specific reasons unrelated to a specific tone.  Basically I wanted to build my first PP amp, use a small pentode gain stage and explore it's tonal qualities, and put to test layout concepts I'd learned in previous builds using P2P/term strips.  I really didn't expect this to be the most versatile I've ever played, not to mention build - huge bonus! 

The TOS was a fairly complex build for a 4th amp, but I would assume that you're interest in any of these 3 (and both the COS and D'Mars are more complex even than the TOS) suggests that you've got at least as much as experience as I had going in.  Tubenit even tried to gently talk me into an easier next project but I'm hard headed.  My only advice is layout is critical for these amps - I spent a month planning the layout but it paid off big time. 

[Joel]

Hey thanks for the further info Tubenit.  Regarding the FX loop, I'm not a huge loop user.  I built an amp with one once, and barely even used it.  I'm thinking passive would be just fine with me (and it'd reduce the tube count by one!).  I assume that I could just graft the Hoffman D'Mars passive loop in place of the COS active loop?

Thanks for the speaker recomendations.  I'm a WGS fan.  And they are cheaper to buy here in Australia than Emminence.  The plan is to build this as a head cab and run it into my existing 2x12 WGS ET-65 and Retro 30 combo (which sounds awesome with my JTM45 clone).

Dennyg: goals for this project?  Merely to build a good versatile amp.  This design caught my eye, and the sound clips sold it (your clip was one).  It will join my very short build wishlist - the other amp being a Supro S6464 combo.   I've built 7 amps so far, but currently have 3.  The first was an AX84 champ style.  The next two were increasingly complicated evolutions of it, then I gutted and built a Bassman micro (Rob Robinettes design) with active FX Loop (Merlin), which has in turn been gutted. 

1. JTM45 clone - my first "big" amp.  I built it from a "kit" sourced from a local amp builder.  Head cab and speaker cab from scratch.  It's probably cleaner in tone than most normal JTM45's.  I used some old G.E 7581A output tubes that are marked as 7581A/KT66.  Apparently they are more 6L6 than KT66.  And the WGS ET-65 and Retro 30 2x12 doesn't give the same speaker breakup you'd expect from Greenbacks normally used with Marshalls.  Not that I'm disappointed, I love the way this amp sounds.  But if I push it into overdrive the walls in my house shake and I knock down the wifes pictures.

2. Hoffman single channel AB763 Deluxe Reverb in a combo with WGS ET-65!  This one was built from scratch.  It has a beautiful sound - with a touch of that bias wiggle tremolo and a bit of spring reverb... yummy.  I use 5751's in it to give the volume and gain knobs some more useful clean range.  I also found the dimed gain and volume gave a harsh overdrive too, so the 5751's tame that.  Two pics at the end of this thread: http://el34world.com/Forum/index.php?topic=21047.msg223090#msg223090

3. The Micro-bassman has been torn down and made into a Tweed Princeton clone.  I designed and wound the power and output transformers for it, because buying transformers wasn't "from scratch" enough!  Transformer winding is rather time consuming, so I don't think I'll be doing that again.  This amp is paired with a 10" Tone Tubby San Raphael.  The Tweed Princeton has a very nice clean tone.  Not a fan of it's distorted tones though.  Not sure if its the amp or speaker at fault.  Some pics here http://el34world.com/Forum/index.php?topic=21737.msg236156#msg236156

I don't expect to be building this amp for a while yet.  Research, planning, buying, building, playing.  I think I enjoy the research and the logistics of planning and buying parts as much as building and playing. 

[tubenit]

I assume that I could just graft the Hoffman D'Mars passive loop in place of the COS active loop?

Yes, of course. That would be fine.

I am attaching the very latest schematic for the Carolina Overdrive Special 5879 plus.  I moved the tone control for the OD to prior 5879 pentode. It helped an already smooth overdrive just get creamier.

There is an ExpressSCH version of the schematic showing the B+ rail on a 2nd page & a corresponding layout without FX here:
http://el34world.com/Forum/index.php?topic=21804.0

With respect, Tubenit

[Tone Junkie]

Tubenit  what did the 15k resistor after the OD pot and before the 5879 tube do for the sound .
Thanks Bill

[brewdude]

Looks like it adjusts the taper of the pot(?).

[tubenit]

Yes, it adjusts the taper. Ironically, I found the tone I liked the best involved only needing a slight amount of gain between the previous triode and the 5879 pentode.  The 5879 has a FAT warm tone.

With respect, Tubenit

[Joel]

Tubenit, would you mind explaining the operation of the cathode circuit on V2a?  What's it do?

[tubenit]

http://el34world.com/Forum/index.php?topic=22287.msg237647#msg237647

[Joel]

Wow!  You're good.  You had a reply already posted before I even asked the question!   

[Joel]

I've been going over the schematic - particularly the FX loop.  I'm thinking of building this "fitted for but not with" FX loop.  So I'll install all componentry and tube socket, but leave the tube out and route the wiring as per the no FX schem.  Which led me to think about the FX level pots.  So I re-read the section on FX loops in Merlins Preamp book.  Could the FX loop be simplified and built without the level pots?  I'm thinking of just using fixed resistors in place of the FX Send, FX Return and leaving out the FX level entirely.  Is this feasible?  Could it be done better?  Thoughts?

[tubenit]

I've been going over the schematic - particularly the FX loop.  I'm thinking of building this "fitted for but not with" FX loop.  So I'll install all componentry and tube socket, but leave the tube out and route the wiring as per the no FX schem.  Which led me to think about the FX level pots.  So I re-read the section on FX loops in Merlins Preamp book.  Could the FX loop be simplified and built without the level pots?  I'm thinking of just using fixed resistors in place of the FX Send, FX Return and leaving out the FX level entirely.  Is this feasible?  Could it be done better?  Thoughts?

I don't know what this means?   

If you are talking about wanting a simple passive FX loop, then you don't need pots.  Just have send and receive jacks.  Use something like a Boss digital delay,  Carbon Copy Delay or a Digitech reverb pedal.

If you're wanting to simply bypass an FX loop, then use a DPDT switch.

If you're wanting to have fewer pots in the FX loop then used a fixed resistor to ground for send  (try 22K maybe?) and 82k to ground for return and then use a 250ka pot for FX level.  My experience is the FX level pot is needed in an active FX.

With respect, Tubenit

[Joel]

I may have been trying to compress too many thoughts into one paragraph...  I was tossing up the idea of building in the capability of an FX loop but bypassing it to begin with. 

But this is what I was aiming for;

If you're wanting to have fewer pots in the FX loop then used a fixed resistor to ground for send  (try 22K maybe?) and 82k to ground for return and then use a 250ka pot for FX level.  My experience is the FX level pot is needed in an active FX.

Thanks for the tip. 

[SILVERGUN]

More discussion here:
http://el34world.com/Forum/index.php?topic=10208.0