D'Mars Overdrive Special

[EL34]

Gkar Rumblier

I am definately out of the loop
What exactly does that mean?

[Willabe]

I think he means the "Carr Rambler"?


               Brad     

[EL34]

I still have no idea
What is a Carr Rambler?

Not a Rambler car, I remember those

[Willabe]

Sorry, Steve Carr amp company. The model is the Rambler. 2x6L6, 28w.

Read a couple of interviews with him in Tone Quest Report mag. years ago. Seemed like a nice guy, I seem to remember he lives down in N. Carolina?


              Brad    

[tubenit]

Just offering some info on a couple of "mods" that I've done.  

NOTHING needs to be changed on the Hoffman style D'Mars turret board.  All is good there.

mod 1:  I wanted to see if I could create sort of a "chime" tone stack tone by separating the treble from bass pot but doing so between
             the .02 cap and the bass pot.  This is not really a PAB (preamp boost).  It's more of a "voice" switch. Removing the bass pot
            (sort of) gives a subtle tone change and makes the harmonics a little more vowel tone, IMO.  Not a dramatic change, but a
            useable one for me.  I use this more than not.   mini-toggle

mod 2:  I paralleled a cathode cap on V1-3 and V3-3.  This gives a mild gain boost on both clean and OD. Again it's subtle, but it gives
            a "fatter" gain sound.  I would describe it as fatter more than a volume boost      relay & ft switch

mod 3:  I paralleled a 100uf/100v  cathode cap (with the original 100uf cathode cap).  This tightens up the bass and seems to add a
            little more harmonics in the mid range also.    Having said that,  the original 100uf cathode cap ALONE (not paralleled) has
            more sustain and more "blooming"  than the both paralleled.     mini-toggle

NONE of these increased any idle/floor noise at all. Floor noise remained the same regardless of any of the switched positions.

NONE of this mods are a "must have", but I find them useful. They simply add some subtle tone changes that I like. None of these are a very dramatic tone change compared to the "midboost" ft switch which is a very audible increase in gain and mid tones.

I tried many more mods besides these and quickly removed them.  These seem to be best of what I tried.

With respect, Tubenit

[Geezer]

I still have no idea
What is a Carr Rambler?

Not a Rambler car, I remember those

Carr Amplifiers
 433 W. Salisbury St.
 Pittsboro, NC 27312

http://www.carramps.com/

[EL34]

Cool looking amps!

[moonbird]

You guys hit it perfectly!!

Sorry to be too mysterious. Did not want to get anyone in trouble of draw any flack toward the site is all. Probably much ado about nothing.

However if you get a chance to check out the Carr amp site, they have extensive MP3s of the Rambler. To my tin ear they sound at times very close to Geezers "noddling" in the D'Mars.

[tubenit]

Just an update on this D'Mars OD Special.

Definitely, "my" favorite/best tone of any amp I've built so far.  It has the best harmonics, sweetest very musical tone and smoothest sustain at this point. (The Tweed BluezMeister has comparable smooth OD ....... maybe?).  The amp is very touch sensitive and at some level, reminds me of the HoSo56 (& a couple other builds) in that regard. Very articulate.

I've got the amp so quiet on the clean, that it is significantly quieter at idle than the original VibroChamp or Princeton Reverb I owned. And when you play a chord, it is waaaaay  louder than either of those.  In other words, with the pots set for a volume much greater than the VC or the PR, the amp is quieter at idle.

The quiet idle/most volume ratio is better on this amp than any I've built.  Remember that's with 3 relay switching!

After building it and playing it over the last few wks.  I went back in and moved a few wires around. Re-flowed a few solder joints & that helped the quietness.

This build is complicated enough that patience and persistence are major keys in making it a "WOW" sounding tone, IMO.

I also increased the cathode cap value on the power tubes to 200uf.  I actually have a spdt mini-toggle that allows me to select from 100uf or parallel a 2nd 100uf.  At 100uf, there is the most blooming and greatest sustain. At 200uf, there is a richer bass tone, clearer tone overall and perhaps sweeter harmonics. I play it with 200uf 90% of the time. IF I was only playing lead, I'd probably leave it on the 100uf because the blooming is a tad more pronounced.

The sustain and sweetness on the clean channel is remarkable, IMO.  It has surprising sustain for such a clean and clear tone. Very musically sweet and rich tone.  The clean channel with the midboost has more sustain than many of the early "higher gain" amps that I attempted. However, the tone is clean and clear without grit or distortion.

The OD has a nice "vowel tone" maintaining sweet harmonics like on the clean channel.

I also moved the relay power board on to the side of the amp by the PT.  No problem with that.  I previously had it mounted (inside the chassis of course) above the edge of the OT (which is on the other side of the chassis not chassis thru).  Moving the relay board allowed me to move some of the 6.3v AC wires away from the OT wires.  The result is the amp got somewhat quieter at idle and seems to have better harmonics.  Unfortunately, I am not sure what increased the harmonics, because I moved some wires, reflowed solder joints moved the relay power board all at the same time.  At any rate, having the relay power board on the side of the amp chassis is convenient, out of the way and defintely did NOT add any noise at all.  

At this point, there is NO increase in noise (that I can tell) with the midboost engaged on clean. There still is some increase in noise with midboost on OD.

I am convinced that Doug's relay system is quieter than the previous W_____r  relay board that I tried before.  My guitar volume pot on "8" induces more noise than the amp has by itself.  That's how quiet the amp is. In other words, Doug's relay system with 3 relays was quieter than the W_____   relay board with only 1 relay.

IF you look in the SCH file for the D'Mars ODS ......  I mentioned creating a sort of psuedo "chime" tone switch like I had on my TOS 2CF. While it's not exactly the same, it works and I like this tone the best.  The chime is engaged almost 100% of the time. There is a schematic to show what I did with that. It's controlled by a mini-toggle and easy to wire up.

To sum up the highlights of the amp .................  it is the most musically sweet tone I've ever gotten, with the most tonal options (using the 3 ft switch pedal), & has the best quiet idle/loud volume ratio of any amp I've built.  

I was initially concerned that an amp with this much wiring in this small of a chassis would be unbearable noisey.  Not the case at all!  I should add that my wiring is not that neat looking at all and probably wouldn't impress anyone ........ but the amp is still very quiet.

With all the info now on using Doug's relays,  I wouldn't hesitate to recommend trying them on an amp that would be appropriate for relay switching.  Once you've done it the first time,  it makes sense and seems relatively simple to do.

Some things I tried that made no difference in reducing noise were the following :  ground 6.3v 100 ohm resistors (artificial CT)  to the power tube cathode, ground the PPIMV to the preamp buss wire, & ground the unused pins on the 5879 to the preamp buss wire.

With respect, Tubenit

[EL34]

Nice update

That's where I like to put the relay power supplies
On the side of the chassis far away from all the low signal wires

[SILVERGUN]

WOW
You guys never cease to amaze me....that thing looks almost as good as it sounds!!!

Thank you for showing us the way and I can only look forward to tackling this build in the future 

[sdp1234]

What chassis size would you recommend for this amp with the Hoffman style board?

[tubenit]

I think I used a 20 x 8 x 2.5 .

IF I was getting someone to make one for me from scratch............. I'd like to try a 21" x 7" x 3".


with respect, Tubenit

[tubenit]

OK, this post is (mostly) for Silvergun who has voiced "considering" the D'Mars ODS or TOS.  I'm figuring out he likes to have some "gain" on hand  (per his thread on the turbo wreck amp he's built)
 

In all fairness to disclosure, I did use a VERY VERY mild OD pedal boost on this with a Zenith Drive. The gain was around "1.5" and the level was around "3".  That's it! The Zenith Drive does not have the same OD boost that a Tube Screamer does. It's much less than a TS. It's more of a "more" pedal, IMO.

I had to do that because I have a very difficult time getting a good OD tone recorded because my mic is always overdriven and it comes out too grainy.  However, it should be noted that the PPIMV was set at less than "3" &  IF I had the PPIMV set at 6 or above, it would easily duplicate the sustain & tone that the mild boost from the pedal provided.

Amp vol was "5",  PPIMV less than "3",  OD trim around "5", OD drive around "3" and OD level around "6".  So what I am saying is that I can get even more gain/overdrive out of the amp if I want it.  Midboost was on, but the PAB was NOT on. I can get more gain/OD with PAB on. I used a neck Cruiser (low output humbucking strat p.u.) and then the bridge Fast Track 1 on this clip.

I like this amp because I can get a very clear true clean tone all the way to a "cranked" tone like in this clip.

Excuse the repeated worn out guitar riffs.  The sound clip is around 3 minute and that's probably 2.5 min too long.

Anyhow, check out the sustain on this. I can get almost any note to hold into feedback reasonably easily.

http://soundclick.com/share.cfm?id=11996721

With respect, Tubenit

[SILVERGUN]

OK, this post is (mostly) for Silvergun who has voiced "considering" the D'Mars ODS or TOS.  I'm figuring out he likes to have some "gain" on hand  (per his thread on the turbo wreck amp he's built)

Thanks so much for taking the time to do that ........I can really hear the difference,,,and appreciate the clearness in the OD on that amp...
I'm still trying to dig through the mud on mine (and I love that), and if I could figure out how to work a mic and a 4 track,,,you'd hear the distortion monster that we have built over there.....
I'm ready to start thinking about another build, and I really do love the idea of built in gain (out the wazzu)....I have a TOS board, but I'm not dead set on that being next,,,,,,,I have also realized that BOARDS CHANGE
I have followed the D'mars thread as an outsider, and appreciate the amount of effort that "you guys" have put into that amp......and it seems to me to be the culmination of a lot of previous work........the sustain and blooming is extremely atractive!!
I've been a fan of D'ble's stuff since I saw Robben Ford and Larry Carlton live (separately) sometime around 1994??,,,,so this IS the direction I want to go

I have always gone for a "smooth, liquid, searing, singing" lead tone,,,and one of my teachers even said I might want to try 2 OD units in series going into the front of an amp,,,,but to me it "feels" like I like the OD to happen sooner and later in the circuit (kinda pre AND post OD).......it really felt closer to home when we cascaded the last gain stage on my amp....

There are elements of each amp that I really enjoy, so I'll go back and listen to try to better describe those things that stand out to me on the TOS D'mars, AND TBM.........and I'm not afraid to build anything, now that I have seen what can be done to a ho-hum build....

I trust YOU....and if one of these amps stands out to you as what you would suggest, I am listening.....thank you for taking the time to care
.

[SILVERGUN]

You really got me thinkin.....
I loved the simple circuit build of the T-wreck,,,,and I've got all the parts to do the power section over, plus, I've got another OT...

What do you think about just taking the OD channel of the D'mars,,,,without the switching,,,effects loop,,,,clean channel considerations,,,,and just building it as another experimental platform for me to try to turbo charge, and expand on the theme?......

I'm sure I'm not alone in wondering what could be done to "supercharge" the D'ble topology.....(maybe it's already in there and you just haven't turn the controls up far enough yet....I always start with ALL the controls on 10 and then work backwards util my ears stop bleeding )

Sorry I'm always looking fore MORE gain OD ...It's an illness,,,,,I know I'll grow up someday
I'd rather have my amp do it than rely on a pedal (or 2)

EDIT***I went back and listened to the sound clip again,,,,and actually paid attention to the words on the page and noticed that the OD settings were less thn 50% !?!?!?.......that thing definitely has what I'm looking for......maybe I just want to build the single channel version for simplicity, and because I lack confidence for a more complicated build

[jojokeo]

T, First I'd like to say that I always like to hear your soundfiles and have many times. They're usually w/ background music and mostly playing leads which is okay but not covering chording/combined notes for definition, etc. Also they may have other things like small amounts of reverb, low setting of zenith drive (just mentioned), small amount of compression added into mix, etc. I know that these are for production value but I'd actually prefer to hear just the guitar plugged into the amp only, nothing more - and no song. This may seem like an odd request but for me, it's the only accurate & true way to hear clearly all the desctiptions you talk about it having.

For example, I'd like to to hear clean pristine chords, maybe some double stops, a few short lead or melody licks, let chords sustain for 5 or 10 seconds to hear them trail off occasionally. Maybe a jazz chord progression or country lick, to show it's clean side etc. Then in overdriven mode play some chords fast, then slow, sustain a few at different lengths, hold a single note for 20 seconds (if necessary) both with bending and w/out bending...holding...then add some finger vibrato, quick chording/slow chording, fast picking, light picking, heavy picking, double stops and bends, whatever you can show as far as diversity to help bring out the amp's descriptions. And most importantly, it's not about playing per-se, just demo'ing notes and chords to hear the true amp qualities be put on display. This won't be very good listening for the average person but for us striving to fully get a true measure & understanding of only the amp's tone and diversity, it's of more benefit to me (and others?) this way. If you could do this at some point it would be greatly appreciated, thanks!

[tubenit]

Silvergun,

IF I had to guess, ........... I think you'd probably be the happiest with the original TOS design given the gain that you like.  It will go to a very slight overdriven clean to a pretty intense overdriven OD. That may be the best choice for you? However, until I actually hear you play something .......... I may never be able to give you an educated guess?
 

Jojokeo,

Thanks for your suggestion. I will genuinely keep that in mind for the future. I used to do more of that. I wished I had 1/10th the talent of Geezer in demo-ing how an amp sounds without a backing track. I guess I've resorted to backing tracks because they're very quick and kind of fun to play along with.

With respect, Tubenit

[SILVERGUN]

However, until I actually hear you play something .......... I may never be able to give you an educated guess?

Thanks buddy,,,,I'll work on that......you deserve to hear what has happened on this end..

I've spent the mid morning listening to clips of both you and geezer demo'ing these amps,,,and they ALL sound great

Funny thing,,,,,if you go back 3 months and look at some of my first posts,,,,,I asked the same question about which amp to build,,,and even back then you said TOS...............................guess I really am hard of hearing

Would you also lean towards the TOS because it's an easier build?

[tubenit]

Would you also lean towards the TOS because it's an easier build?

No, I'd recommend something more complicated IF I thought it was a better fit for you. I am confident that you'd be able to handle it just fine.

My best guess is the original TOS is the "best fit" but I don't know cause I haven't heard you play? It is a very good just plug and play amp, IMO. Not much dialing in required.

IF you like a more midscooped sound you can do the TOS with a typical bass,mid & treble design very easily.

With respect, Tubenit

[Tone Junkie]

Sounded good Jeff great sustain I loved the tone , I have to finish this TOS Im working on to get to this one.
Bill

[tubenit]

Just another update.

I have continued to experiment and tweak this amp after playing many hrs on it. Most tweaks I've tried since last update, I removed.

This last group of mods created a few tonal changes that I am keeping :

1)  Amp is even quieter at idle & I did not think it was possible to get it quieter being a high gain amp. Amazingly quiet!!
     I am thinking this is due to separating the mid and bass pots rather than the bass pot going into the mid pot. Not sure why that
     would make a difference but it's defintely somewhat quieter (& I was happy with it even before this).

2)  The amp is smoother when overdriven. It was very good before but would have a tad of grit if the mid pot was turned up. It
     does not have that grit now.  Again, I am thinking that when the bass pot went into the mid pot that this approach added some grit
     when the midpot was around 6 or higher.   Now it's just smoooooth!! No hash or grit.

3)  I tried paralleling some different value pf caps with the 300p across the volume pot. Adding a 150p on a mini-toggle was a nice
     mod. It tightened up the bass notes and made the tone a little fuller sounding.  (no grit or hash added with this mod).  I think this
     would be a useful mod to dial in the 450p with single coil type pickups and the 300p with buckers.  I am learning that on these
     D-inspired amps that the cap values can create a "sweet & musical" spot in tone.  In other words,  450p may sound fabulously
     sweet and musical and full sounding.  Less than that leaves it a little thinner and more than that it loses that "sweet spot".  I find
     similar sweet spots with coupling caps and it is worth the effort to slowly experiment in my opinon

4)  The "traditional Dumblish PAB" simply does not work well on this CF tone stack arrangement. You can sort of create a "chime tone"
     switch by miswiring the PAB,  but it doesn't add a smooth overdriven boost.  However, putting a 220k resistor on JUST the mid pot &
     NOT the bass pot, did give me a very useable overdrive boost that is very very smooth sounding.  I tried 82k to 470k values and  
     selected 220k.  The traditional correctly wired PAB in the CF tone stack also sounded less musical and a little bit harsh & not as  
     smooth as lifting the mid pot with a switched resistor.

     I should note that I had tried a 68k to ground PAB below the mid pot when the bass pot went into the mid pot. Did not like it at all.
     It sounded too buzzy/gritty to me.  Separating the mid and bass pot resolved this.

5)  With the D'Mars on clean ................ there is NO unwanted noise increase when the PAB or midboost is engaged. I can't hear any
     increase in idle/floor noise now.    With the D'Mars on OD ............. the is very very little increase in idle/floor noise with PAB or
     midboost engaged.   In fact,  I am very happy with the idle/floor noise when both PAB and midboost is engaged whether on clean
     or OD.  

6)  The amp has less idle noise, more blooming and sustain & a smoother OD now.  The harmonics, touch sensitivity and musical
     sweetness has remained the same.

An added thought ................ I am wondering if the addition of the 500p across the outside lugs of the bass pot helps eliminate some
"hash" and adds smoothness instead?

Hope this may be of interest or useful to someone.

With respect, Tubenit

[jojokeo]

3)  I tried paralleling some different value pf caps with the 300p across the volume pot. Adding a 150p on a mini-toggle was a nice
     mod. It tightened up the bass notes and made the tone a little fuller sounding.  (no grit or hash added with this mod).  I think this
     would be a useful mod to dial in the 450p with single coil type pickups and the 300p with buckers.  I am learning that on these
     D-inspired amps that the cap values can create a "sweet & musical" spot in tone.  In other words,  450p may sound fabulously
     sweet and musical and full sounding.  Less than that leaves it a little thinner and more than that it loses that "sweet spot".  I find
     similar sweet spots with coupling caps and it is worth the effort to slowly experiment in my opinon

T- I've had experiences where I couldn't find a happy place with a treble cap by itself no matter the value, then found success w/ a resistor in series. Yes, it takes time to find the right combo but as you say it's worth it when you do. For simplicity sakes, start w/ a 47k & 500p. Doing this gives an "in between" effect from all (cap only) or nothing (no cap at all). It also helps minimize the shelving effect (bright/brittleness) in really low settings of the pot rotation.

[tubenit]

cap by itself no matter the value, then found success w/ a resistor in series

Yes, that is a great approach.  I used that on my guitar volumes.

With respect, Tubenit