D'MoSo56 (new idea)

[tubenit]

OK, it's done and it sounds GREAT!!    Very very touch sensitive!!

It is very very quiet at idle. Just a whisper. No hum at all. If you heard the whisper and then I hit a chord, you might be startled at how loud it is with such quiet at idle.

The clean does not sound as clean as the D'Mars clean ............ but I am using 6V6's instead of 5881's and the voltages overall are somewhat lower.  Does it sound like a clean channel?  Oh, yeah .......... definitely.  Not quite black face Deluxe non-reverb clean but headed that direction.

The V1 5879 pentode really surprised me in this amp.  This amp sounds a lot better than the 56T I used to have. But it has some smoothing caps, a different tone stack, an active FX and an enhance cap going into the LTPI.  The overdriven tone of the 5879 is quite a bit smoother than the 56T was and there is NO top end hash. So I am very pleased with it.  

The 5879 will sustain like crazy.  It is very touch sensitive and expressive. Somewhat chimey and has very nice harmonics.  It is not as smooth as the D'Mars  or Tweed BluezMeister.   It sounds more cranked then a buttery smooth overdrive.  Kind of hard to describe the difference but you could hear the difference in person.

Is there a significant contrast between the 12A_7 triode and the 5879?    Absolutely when using a 12AY7 or 12AV7 in V2.  You could easily pick out which one is which with your eyes closed. It is certainly very noticeably different when chording.  I think the contrast is very useful and sure gives a different flavored tone.  I did try a 12AX7 in V1 and it does narrow the gap between clean and 5879 cranked.  12AY7 or 12AV7 is a better choice for contrast between clean and cranked.

I would NOT describe the 12AV7 to 5879 as clean to OD.  Not a good description.  It's more like clean to cranked at the same volumes.     The contrast is significant but not as dramatic as the D'Mars  or the Tweed BluezMeister which actually have an OD channel.

If you're considering building this, I would recommend highly the on board active FX.  It's a really nice feature!  You can dial it to accent cleans or a little more OD cranked tone.  It works as a great master volume. I use a delay in mine, but it works like a boost even without the delay in it. And it works like a master volume also.

I have a NFB switch.  I like the NFB the most.  Disengaging the NFB gives some more tweed tone to the amp. I think the NFB switch could be left out and have the NFB in all the time. However, some people might prefer the tweed accent?

I was surprised that the midboost did not prove to be that useful. I think it could be left out?

Did I have oscillation problems with my layout?  Well, I'm not sure???  With a 5Y3GT rectifier I played an hour with the amp really cranked to the point of my ears ringing.  No oscillation issues at all playing at volumes that exceed what I normally play at.  

Then I put a 5V4 rectifier in.  The chassis was inside facing up about 15 inches from the speaker & I was sitting in front of the chassis within 3 feet with my guitar volume on "10".  I could crank everything pretty much up to "10" except the FX send and level with no oscillation.

However, with everything cranked ............. I can not dial the FX send and FX level both above "7" without oscillation setting in.  In other words, send at 5 and level at 8 or 9 was fine.  Both at 6-7 was fine.  One at 7 and the other higher than 7 would give oscillation. A fix to that might be to use a 100k pot on the FX send or parallel a resistor from wiper to non-grounded side which is probably what I'll do.

The truth is that I can't imagine playing the amp that loud though?

The 5879 was pretty microphonic, so I'll have to try another one.  And the 12AV7 was slightly microphonic too.  So, the tubes and proximity may be the culprit regarding oscillation at cranked volumes?  I'll try different tubes and such and report back.

But honestly, with this amp waaaayyyyy louder than I'll ever normally play it, ............ I had NO oscillation problems at all.  And the amp can get really loud.  It's like Deluxe Reverb loud, IMO.  I'm thinking this is maybe because of the active FX loop which definitely added some gain.

The amp can sound beautiful clean and very cranked   (vs. smooth overdrive).  It's a nice amp.

I'll update the schematic and post voltages sometime later this weekend.  I'll try to get some soundclips up also within the week.

With respect, Tubenit

[tubenit]

OK,  here is the current schematic and I indicated the changes from the original.  There may be some more tweaks down the line & if so I will up date this in a wk or two.


with respect, Tubenit

EDIT:  I've added a picture to show how I would "better" reposition the board to be somewhat easier to wire up and work on.

I should've stated in the previous post, that (at least with the mini-toggle DPDT) that there is NO popping switching from clean (12AY7) to cranked (5879).

[smackoj]

excellent work guys....I love the stuff you do with your love of amps and your willingness to expand the platform...

your quest reminds me of my favorite Tom Petty quote  "If you're not trying new things with your music, you're not going to live where the magic happens"  (paraphrased)

some famous dude said "Get 'er done" but you dudes say "tweak 'er 'till she squeals and then back her off half a frog hair"

 

[tubenit]

OK,  I think I am actually done with the amp!  To borrow an expression from HotBluePlates ............. it sounds "crazy good"!

I think I should have done a better job with the layout as illustrated  in my previous post.  My guess is that I'll eventually move the board out a little bit as it should just take me less than an hour (I think).

Yet,  I can play it waaayyy past volumes that I would play it at normally &  with NO oscillation issues.   I can dime everything  ....... except the FX send on "7.5" with no oscillation problems.  Above 7.5 on the FX send with everything else dimed, I will get oscillation.

Now having said that.   I like both volumes on 4.5 & the FX send at around 5-6 and the FX level at 7.  That is around the most volume that I like.  And the amp just sounds wonderful to me at those settings.

I tried both and decided I like the 12AV7 somewhat better than the 12AY7 in this amp but both sounded good.

There is a significant difference in clean to cranked between the 12AV7 triode and 5879 pentode at similar volumes.  The 5879 really has a chimey cranked harmonically rich tone, IMO.

IF I have anything that I wished would've turned out different, it would be the volume level.  The amp is much louder than I was expecting for some reason?   I actually prefer the 6K6 power tubes with the 5Y3GT rectifier the best & it's still pretty loud & that is what I am currently leaving in the amp.

I don't anticipate any significant tweaks beyond this schematic here.  I'll get around to putting the SCH schematic and layout in the SCH Library of schematics later.  And I'll post some soundclips within a wk or two.

With respect, Tubenit

[Tone Junkie]

Tubnit could you take voltage readings for us .
Thanks Bill
I'm especially curious about your readings at the mosfet cathode follower and 5879 tube.

[tubenit]

Forgot to take the 6V6 screen readings, but here is the rest of them.  The mosfet "plate" connects to node D.

Played this amp until I had blisters underneath my callouses and could barely touch the strings.  I like the amp!

With respect, Tubenit

[Glennjeff]

My fingers look they've been hit by a meteor storm working on this D'Mars tubenit, Zero Sympathy Buddy. Really need to hear some soundclips to get the ears calibrated. Currently Max'd out on tube satisfaction, get back to you when it's sane.

[PRR]

> I can dime everything  ....... except the FX send on "7.5" with no oscillation problems.  Above 7.5 on the FX send with everything else dimed, I will get oscillation.

Counting on thumbs: you have four gain stages; a guitar amp needs two gain stages, three with tone-stack loss.

That's a testment to your skill, that you can have so much gain and not have a humm/hisss machine.

A more detailed calc says you have up-to at-least 4V at "FX Send", which is more than studio gear needs, far more than pedal-gear can tolerate well.

I think I'd try some fixed loss at "FX Send" pot. Like replace 100K pot with 100K fixed plus 20K pot to ground. Then "10" on Send knob is like "5" now. You could run the Send and the Return at "10" and have around the same gain as you have with your S=6 R=7 settings, and a sane level to any FX devices.

OTOH, you could buy earplugs, book bigger venues, and do heavier metal.

[tubenit]

That's a testment to your skill, that you can have so much gain and not have a humm/hisss machine.

Well, .............. no hum or hiss problem at volumes that exceed what I normally play.  With pushing everything towards dimed, yeah it's reasonably noisy with hiss.  However, my statement about no oscillation with everything dimed but the FX send holds true.

I will look at the send pot idea and probably give it a try & report back if I go that route.  Thank you for the idea!

With respect, Tubenit

My fingers look they've been hit by a meteor storm working

Glennjeff,   yeah ............. it gets pretty bad when the finger is painful to even look at. 

[Tone Junkie]

PRR could you draw a diagram of how you would run that 100k resister with the 20k pot to ground. I would find this helpful but I can't quite rap my tired little brain around it.
Thanks Bill

[tubenit]

 

replace 100K pot with 100K fixed plus 20K pot to ground

Bill, you asked a good question.  I don't know if "plus" means parallel or in series?

Having said that, checking the resistance from wiper to ground on the pot ................ I think a 25ka pot with 22k to ground (in series) might be the most useful solution?  (That is based on experimenting with different setting on send and level FX pots) Or maybe a 50ka pot with 10k to ground?

Turns out that dialing the send pot higher and lowering the level pot  .............. VS............. lowering the send pot and having the level pot higher both give useable tone variations.  The higher send pot setting with a lower level pot setting gives sort of a compressed tone.

I can verify now that the amp takes OD pedals really well.  I used my TimZee and the Zenith Drive and both sounded great to me thru the amp.

I found the midboost on chording is not that useful to me because the chord loses some articulation and note distinction. However, the midboost on playing lead and single notes or double stops sounds pretty cool, IMO. There might be more useful uses for that switch though than midboost for other people.

This is truly a fun amp and very expressive, IMO.

You can get the amp cranked using the pentode and get notes to sustain for a reasonably long time (the FX needs to be dialed up also to do this).  However, as I mentioned before ........... it is a cranked chimey tone far more than a smooth tone. Very distinctly different than the Tweed BluezMeister of D'Mars ODS.

With respect, Tubenit

[tubenit]

I plan to start on the amp cab this weekend.  This may prove to be the prettiest cabinet I've built.

I have a really nice piece of flamed maple for the cab top and the front chassis panel cover.  The sides and bottom will be ribbon mahoganey.  The grill cloth might be oxblood with gold or maybe cane weave? I think the contrast between the flame maple and the other woods will give a nice visual appeal using the half blind dovetails.

I'll hopefully get around to posting some sound clips this weekend also.

With respect, Tubenit

[moonbird]

Tubenit --

Well that settles it. I am gonna build this one fer sure. Kinda humg back waiting to see what you thought. Good enough for me. I think I will go with the 6K6s as well. I wonder if this would be a good amp for 6AQ5s? Might tame the loudness a bit.

I did notice that the diagram you made for the PRR suggestion had a 12AU7 instead of 12AV7. Was that intentional? Are you planning to use a 12AU7 for the active FX? 

Thanks SOOO much for the gut shots. Only someone with your skills would have the "guts" to put one up  . It is really great to see how you do stuff.

[tubenit]

I think 6AQ5's would sound superb!!  I didn't have anymore of them though.

Yeah, I settled on 12AU7 for the active FX but the 12AV7 sounds really good also.

I  hope you pay attention to how I would've done the layout board differently.  While the amp is very quiet even at volumes way above what I normally play ............... my guess is that with the layout board further away from the tube & slightly more towards the pots that it would've been even quieter. 

I really like this amp!  IF the cab turns out like I hope, it should be quite beautiful.   

With respect, Tubenit

[moonbird]

Tubenit --

Yessir I am watching your layout "redo" closely. Thanks for the reminder tho ... never hurts!!

I have many 6aq5s - would be happy to send you a couple. Maybe I will do a 6aq5 version just for grins. The plate voltages seem ok but would I need to change any other components aside from a lower impedence OT? What would you recommend?

[tubenit]

Yeah, I'd love to hear what you think of a 6AQ5 version.   I built a 6AQ5 amp years ago and really liked it.  And I know Geezer is quite fond of 6AQ5 tone. 

Thanks on the offer for the 6AQ5.  Since the amp is already built, I'll pass on the generous offer.  Right now I can plug in 6K6 or 6V6 with no rebiasing.  And I can use a 5Y3, 5V4 or GZ34.

I don't know about the OT and impedence issue?  I used an OT with an 8ohm speaker.  Maybe take a look at the Gibson Scout?

http://www.el34world.com/charts/Schematics/files/gibson/GA-17RVT_SCOUT.pdf

With respect, Tubenit

[TIMBO]

Hey T, Is the FX level still working well as a master volume? Thanks

[tubenit]

FX level works great as a master volume.  I tend to set the "volume/gain" pot  &  then increase or decrease the volume with the FX level.

With respect, Tubenit

[moonbird]

Tubenit -

That 305V on the PA plates rang a bell in my mind - so I went to check and sure enough. It is the SAME plate voltage on the 6V6s in the Fender Harvard 5F10 - which many believe had the best clean tone of any amp ever.

Goodness sakes Tubenit - I guess great minds end up at the same places. Pretty doggone impressive if you ask me!!   

[tubenit]

I got a couple of mediocre soundbits done for the amp.  Honestly, the recording does not do justice to the contrast between the 12Av7 triode versus the 5879 pentode.  

The 12AV7 sounds cleaner.  The 5879 has some chime and fullness to it and sounds a little more aggressive while maintaining a reasonably clean tone under "5" on volume pot.

Nothing is changed on the amp or guitar other than simple switching the 12Av7 to the 5879.

The volume knobs were around 4 to 4.5.  At around 6-7, you get some really nice sustain particularly if the FX is cranked.  FX send was 5 and the FX level was 6.

On the soundbit with chording.   Everything is done first with the 12AV7 and then the 5879.  The last chording group has the 12AV7, the 5879 and then the 5879 with midboost and the NFB turned off.

http://www.soundclick.com/player/single_player.cfm?songid=12428140&q=hi&newref=1

With respect, Tubenit

[tubenit]

I apologize for yet another worn out blues tune.  I didn't have much time today and wanted something that I could demo with one take which this was.

http://www.soundclick.com/player/single_player.cfm?songid=12428144&q=hi&newref=1

12AV7 first ................ at 58 sec, then the 5879 ...................at 1:14, then the 5879 with midboost and no NFB.   (All of this was the neck pickup)

At 2:27 (bridge pickup), the 5879 with midboost and NFB ...................  at 4:47,  back to the 12AV7 with no midboost and NFB engaged.

With respect, Tubenit

*  When I have time, I'll try to do something that sounds better than this & is maybe more interesting. 

[Glennjeff]

Really beds in well in a blues mix hey.

Your ears are a lot more refined than mine. When I tried out that front end there was less contrast between the AY and the 5879. Notice you're now using an AV, I have one, cost like $6 and it's a General Electric, looks like it might have had some use. Might try again.

Thanks for all your support here. 

[tubenit]

Well,  I think I'm gonna try something ................... 

I think I'll take the first triode of the 12AV7 and make it into a "hot switch" & see what that sounds like. I'll lose the extra clean tone on the amp, but the 5879 still sounds reasonably clean at around 4.5 on vol. 

Will report back and see what unfolds from this.

Tubenit

[tubenit]

OK, this is cool!   And it's staying in!!

I am renaming it "the 56 PLUS."   Geezer's HoSo56 ........... plus a hot switch gain stage ............. plus active FX on board.  The D'MoSo56 no longer fits since it no longer has the D'Mars front end on it.

I can dial the clean-chime (5879) or the 5879 with 12AV7 gain stage so that you can switch them at the same volume level and there is a pretty dramatic contrast between the two.  

Kind of hard to describe but the 5879 alone is somewhat clean/FAT/chimey .............. and when you switch in the 12AV7 you get an increase in sustain and harmonics and it's somewhat brighter.  This is a really nice contrast to my ears and should be pretty versatile.  The 5879 alone sounds kind of "organic" and is pretty touch sensitive to my ears.  You lose a little of that organic feel when switching in the hot switch but it increases the harmonics significantly.

I'll post a picture of the cab later today, hopefully.   And then a new soundclip when I can showing the harmonics and sustain of the extra gain stage.  

BTW,  I can not hear any increase in floor noise at all.  Amp is very quiet at idle.

With respect, Tubenit

[tubenit]

Needs a brown leather handle and some long screws so I can actually mount the chassis in it.  Chassis is just sitting inside it in the photos not bolted down.

Kind of hard to take a picture of the flamed maple.  Camera flash typically washes everything out.  It's fairly iridescent looking in person.

Sides are ribbon mahogany. And ironically, the piece of mahogany was quite lightweight for some reason.

with respect, Tubenit

[Glennjeff]

Drool.
How did you join the wood?

[tubenit]

Half blind dove tail joints.  Made some errors but overall it turned out pretty nice, I think.

This "hotswitch" gain stage sure worked out great.  I didn't know whether I could adjust the 5879 volume to balance with the 5879 & 12AV7 triode, but it does that really well.  I'm sure a pot before and after the stage helps considerably with that.

Tubenit

[pullshocks]

Tubenit, that is gorgeous

[Tone Junkie]

Very nice my friend.           
Bill

[Willabe]

WOW! Absolutely Stunning!


             Brad     

[Fresh_Start]

Beautiful inside and out!

[tubenit]

Guys, thanks for the nice remarks!

I did some speaker testing with this amp.  I tried an Emminence Red, White and Blues  (that I use for the D'Mars) & a Texas Heat (that I use for the Tweed BluezMeister) and a Cannabis Rex that is in the 56 PLUS cabinet.

I like all of them with this amp.

Texas Heat was my favorite and it had a slightly more compressed sound that made it a little smoother when pushed.  It has a nice top end and the bass is very good also.

However, .......... IF .......... I was a really good player (which I'm not) & wanted to hear all the subtle aspects of playing, I think the Cannabis Rex would be the best.  And my best guess is that the Cannabis Rex would cut thru a mix the best of all of them with the Texas Heat being 2nd.  It seems to express all the articulation of the amp the best to my ears.

To summarize, if you like smooth and compressed ....... the Texas Heat.  If you like chimey with more harmonics, go the Cannabis Rex.

IF I had another Texas Heat, I'd probably put it in the cab.  But, I'll be very happy with the Cannabis Rex as is.

I made just a few minor changes.  The 5879 cathode cap was lowered from 4.7uf to 2.2uf.  It made the 5879 a little brighter and perhaps a little smoother removing a tiny dash of grit.  Worth changing this out.

The 12AV7  hotswitch triode cathode resistor got lowered from 2.7k to 1k.  BIG improvement.  Very smooth sounding now and greater sustain and some sweeter musical harmonics.  I also added a .002 Orange Drop cap in parallel with the .01 off the plate of that triode.

Amp sounds great and looks really decent, IMO.  Very very very fun amp to play!!!

The mid boost switch could be removed with no loss, IMO.   I'll experiment and find another use for that.

With respect, Tubenit

[punkykatt]

Very very nice tubenit.  I like the way you have the speaker baffle tilted back and have the front panel vertical.  I will have to try that next time around.  Where do you get all this nice wood?  Punky

[tubenit]

Where do you get all this nice wood?

Usually at the WoodCraft store here locally.

The ribbon mahoganey sides/bottom for the amp was about $45 total. I'm thinking the flame/quilty maple was maybe around $35? I bought it some time ago. I don't have a good picture of it, but the ribbon mahoganey is just about as irridescent as the maple.

When you consider buying plywood and then tolex and glue and chrome corners, the wood cabs are not much more expensive if at all?

With respect, Tubenit

[TIMBO]

Great job Tubenit  You are the master of tweaks  and this one again you have hit the mark and are happy with the final result but I can't help but think that there can be more to add  as I have found in the short time I have been on this forum that there is an endless array of circuits that can be added to refine the final sound.

Looking over your schem, the thing I like about it is it is simple and gets the job done.

Just one thought, would adding a CF (mosfet)to the AY7 boost/fatten your sound as I have found this in other builds.Thanks

[tubenit]

would adding a CF (mosfet)to the AY7 boost/fatten your sound as I have found this in other builds.

I am wondering the same thing?   

However, I don't have much chassis real estate to work with so it's probably not gonna happen?
 

With respect, Tubenit

[tubenit]

Order to Hoffman Monday am for a leather handle. Got it today Tuesday.  Man, he fills orders fast!

[Glennjeff]

That maple top looks so nice, exquisite (there I can spell that word ).

It appears to be two pieces joined, did you do that? If so How?

My wood working is not anywhere near to that standard but, LEVEL UP, it has to be done. Off to the craft shop.

[tubenit]

Yes, it is two pieces of maple from a left over project. Just glued together, no biscuit joint or anything. Similar to a two piece guitar body.

Remember the cab is half blind dovetail, so it's pretty strong and held together well.  I didn't have enough maple to do an entire cab but I am glad I didn't.  I really like the contrast between the maple top and the ribbon mahogany sides/bottom.

The ironic thing is the piece of maple looked very plain and little to no flame really showing.  I would've rated it a AA maple at the most (vs. AAAA maple being the best).

However, I "popped" the flame on it 3 times.  With a "natural" look, I do this by applying amber analine dye 3 times sanding it off each time back into the natural wood color the best I can. However, the dye does color the softer part of the wood when this is done and adds contrast.

(As a tip, the only thing that I have found that removes water based analine dye off my skin is Windex cleaner. I'm thinking maybe it's the ammonia in it? )

Then I apply Minwax "natural" oil stain on the wood. Result is a fairly iridescent look under lighting. I used Minwax semi-gloss polyurethane for the finish simply because I can put a hot coffee mug or cold drink on the cab with no problems.  Something like gloss Deft Clear Wood Finish allows an even more intense flame to show up but won't hold up with a hot coffee mug as well.

With respect, Tubenit

[tubenit]

I am really enjoying this amp. 

I wanted to do a sound clip showing how this 56T Plus takes pedals.  I am using a homemade overdrive pedal.

http://www.soundclick.com/player/single_player.cfm?songid=12464167&q=hi&newref=1

With respect, Tubenit

[pullshocks]

Thanks for posting Tubenit.  You have got some great tone  with that setup, and your playing was really enjoyable, especially around the 2:15-2:25 mark