D'MoSo56 (new idea)

[tubenit]

I love the overdrive and FAT tone of the HoSo56 with it's slight chime. And while I could get a beautiful clean tone out of my HoSo56, it had to be done by lowering the guitar volume or volume pot on amp volume.

I love the clean channel of my D'Mars ODS better than any clean tone I've gotten out of an amp.

So I was pondering this am about "how could I maybe get both in one amp?"  A nice clean tone that I could switch for a FAT slightly overdriven tone.   Note the 1MA for the clean volume and the 500ka for the OD volume.

I was thinking two relay switching one between the clean 12AY7 V1a and the 5879 pentode.  And the other relay for the mid boost since I have a strong preference for that on my amps.

Any thoughts?  Think this could be switched on the fly without popping noises?

With respect, Tubenit

[Glennjeff]

I was pondering having both the D'mars and the HoSo56 initial preamp sections in my current build. Was going to look at switching or mixing into the grid of current D'Mars V1b and using the FET cathode(Source) follower instead of HoSo cathode follower. The bias on that valve is a bit different between the two amps so I was wondering about a compromise bias between the two. Wanted to use an EF86 coz the D'Mars already has the 5879 sound.

The relay solenoid switching low level guitar signal may induce hum/ripple/crackle, if so a suitable snubber circuit on the relay solenoid may need to be devised. Just my inexperienced two bobs worth.

Won't know if you don't give it a go.

[tubenit]

Glenn,

Thanks for the thoughts! They are appreciated. 

The bias thought is interesting. One could change the bias on V1-3 to match whichever of the first gain stage and have dual switching simultaneously (if needed)?

Geezer and I experimented with 6AU6 and 5654 (thanks to Sluckey supplying one) in the V1 position on HoSo56's.  I thought those sounded good also as an alternative to 5879's.  It's been a while but I seem to remember really liking the 5654 tone in the first gain stage. I think the max voltage on 5654 plates needed to be watched. 

Don't know about the EF86?  I think that's gonna give ALOT of overdrive and little headroom in the clean channel.

With respect, Tubenit

[kagliostro]

Hi Jeff your brain is an erupting volcano

every few days you've a new good idea 

K

[rzenc]

Hi Jeff!!!

It's really amazing your willing to share one-of-a-kind amps!!!! Keep them coming!!

I relocated the switch so that you can smack the pentode harder. Don't know if this is what you are after??? I kept both pots, there is, before and after the pentode stage so that you can dial how much drive you want.

Hope this helps.

With Respect,
Best regards,

R.

[Tone Junkie]

Jeff I have always found its best to run your input to both tubes at the same time and switch after the fact before tonestack or maybe 2 tonestacks and switch a volume after the tonestack for the clean channel  like you did in the old TOS just a thought.
Thanks for thinking outside the box again Bill

[tubenit]

My goal is to recreate the original HoSo56 sound  .............. AND the original D'Mars clean channel sound  as best as possible with the fewest tubes used.  I love both those amps would love that tone in one amp.


Rzenc,   Your idea is a great idea!  And using the 5879 sort of as a Hoffman "hot switch" is good thinking. I've done that before but it will not allow me to reproduce the original HoSo56 tone which is essential to the effort on this amp design.

Bill,  Not sure what you are saying there??  Got a schematic that you could show, please?  Is this idea going to accomplish the goal that I have stated in this reply.  I'm trying to envision what you are suggesting.

With respect, Tubenit

[Tone Junkie]

Jeff were you have the switch now just run into the 2 tubes just like you have it, and between the 2, 100k resisters and V1b put the switch, that way its exactly the same just a better switching spot. That way you can put the non used channel to ground which in past experiance makes it quieter.
But the volume after the clean channel and possibly 2 tone stacks were just ideas to throw around.
 If you remember your first version of the TOS you had a volume that would switch in just for the clean channel so you had a better chance of matching the two volumes togther.
 Im thinking because one channel is clean and one has a little more gain that would be helpful in this one to.
Just thoughts to throw around you think outside the box alot, I was just joining in the fun.
Thanks Bill

[Tone Junkie]

Yes  Sorry for getting this side tract you had a great idea and I kind of got it going sideways . I was interested because i always wanted to try the hoso56. but i think this idea here that you have is way better. blending a unique lead channel with an exellent clean channel. I must be getting old but I need a good clean channel in every amp I play (LOL).
So thanks for coming up with the idea.
Bill
 

[Tone Junkie]

 Who's going to be first up to give it a try.
Bill

[tubenit]

Bill, thanks for the help with this.  I do think your idea of switching prior to V2b is a good idea.

I am going to seek some input from Geezer on this idea especially since the HoSo56 is his design and is such a great amp.

I "think" this will get the HoSo56 tone reasonably well but not totally certain.  Geezer can probably make a better guess about that.

I've tweaked the schematic already and have drawn up a layout now that I will post later.  I am considering building this for myself.

with respect, Tubenit

[John]

Tubenit, something you've probably already thought about... but IIRC lower voltage for the 5879 was pretty important. Maybe use a voltage divider at the end of the power rail, so you could lower the voltage to the 5879? That is if the standard dropping resistor didn't do it for you.

As with all your excellent ideas, I'm watching closely!

[Glennjeff]

I'm sure that circuit was there, or am I hallucinating schematics.

[tubenit]

OK,  looking at parts I have on hand and then costs of ordering more ................  I can build this amp reasonably inexpensively. So I've just finished ordering parts that I need.

I don't really need a 3rd amp but intuitively I am thinking this might be a winner and very versatile.

So, I will start on it probably next wkend (7/4 wkend)  by building the board and punching out a blank chassis.

Anyone else interested in a collaborative effort over this forum and trading notes and observations and tweaks??  Meaning you're interested in starting this build in the next few weeks?   I've enjoyed doing that with Geezer in the past and found trading information to be quite useful.

I am going to build if first with toggle switching from the clean/5879 OD  &   midboost  and then come back later for relay switching after tweaks are done.

With respect, Tubenit

[Glennjeff]

Will splice the front end onto my D'Mars EL84 during that time frame and tweak as best I can.
Have a spare 5879 and unused socket in place.

Have not put in FX section yet and I think the EL84 version needs that as an essential part of the gain structure.

Notice you've changed bias on V1b, easy to accommodate with some parallel R's and a switch.

All the best.

[Tone Junkie]

Im a few cap and resister boxes and some more of my breadboard items away from testing sadly 2 to 3 weeks out .
Bill

[tubenit]

Well, I went ahead and punched out the chassis today. Turned out nice!

IF anyone is interested in doing this build along with me and trading notes and tweaks ........... this is the chassis I am using. It's an inexpensive blank off ebay.  Since Hoffman doesn't carry chassis blanks, I thought I'd share how I am approaching this. With the chassis being 17" x 8" x 2",  it should have plenty of room to install the relays.

Using a 275-0-275  100ma PT  to use either  6K6's with 5Y3GT or 6V6's with GZ34 or 5V4.  Hoffman's 18w PT & OT should work fine also.

http://www.ebay.com/itm/Tube-Amp-Chassis-17x8x2-12-gauge-/181111392458?pt=LH_DefaultDomain_0&hash=item2a2b1488ca

Getting pretty enthused about this build! 

With respect, Tubenit

[pullshocks]

This looks like just the thing for that gutted out Judybox I bought a while ago.  Just need to order up some caps and a 12 AY 7 (would a 5751 be OK?)  Oh man, how  am I going to fit this with all the  other projects I have lined up?

[tubenit]

I think a 5751 could sound good.  I've used one in that position before and liked it.  The 12AY7 would simply give a cleaner tone  and offer more contrast with the 12AY7.

With respect, Tubenit

[Ed_Chambley]

Jeff, what differences other than micro-phonic issues in the 5879 as opposed to the ef86?  I really like the idea of this build, but was just wondering about your tube choice.  I know you like the tube.  They seem cheap as far as I can tell.  What brand do you prefer as I plan to bet a couple.  I have everything else onhand.

[tubenit]

5879 does not have as much gain as an EF86.  I have 5 RCA's, 1 Sylvania and 2 JAN Phillips.  I can't tell a brand that is better. It's just that some individual tubes sound better than others to me.

With respect, Tubenit

[Ed_Chambley]

5879 does not have as much gain as an EF86.  I have 5 RCA's, 1 Sylvania and 2 JAN Phillips.  I can't tell a brand that is better. It's just that some individual tubes sound better than others to me.

With respect, Tubenit

Let me rephrase.  I really like the transparent sustain in your clips.  Very similar to studio quality compression.  Does the lower gain of the tube lend itself more to that liquid tone as opposed to a distorted tone you get when pushing EF86 or does the gain better complement the 12AY7?

[tubenit]

Ed, 

Excellent question regarding the 5879 "liquid tone" vs EF86 "distorted" tone.

I am honestly not familiar enough with the EF86 to give a really valid answer. My best guess is that the 5879 "softer" gain and tone may play a positive factor in sort of a smooth or liquid tone which I prefer.

With respect, Tubenit

[moonbird]

Tubenit --

I have the same unused chassis as you mention and suitable PT/OTs for this build. I had considered building both of these but if I can just build ONE ... I'm in!!! However I really doubt I can keep up with you  , but I am game to try. I would like to also add the "second" boost pentode option for the 5879 side (like Geezers).

Could you possibly publish your chassis punching plan?

That would help me alot. Are you building a combo amp or a head? I think I would rather do a head (ala marshall where the chassis sits on the bottom of the cab). Even if you are doing a combo - a pattern for the knobs/tubes would help me out. I am dog slow with that kinda stuff. Do you think the 17x8x2 is big enough for a head?

Is there room for your famous 1 tube reverb you think? Thanks for doing this for all of us.

[Ed_Chambley]

Ed, 

Excellent question regarding the 5879 "liquid tone" vs EF86 "distorted" tone.

I am honestly not familiar enough with the EF86 to give a really valid answer. My best guess is that the 5879 "softer" gain and tone may play a positive factor in sort of a smooth or liquid tone which I prefer.

With respect, Tubenit

Thanks for the honest answer.  I ordered a few 5879's this morning to play with.  Sometimes the only way to know is melt some solder.

[tubenit]

Could you possibly publish your chassis punching plan?

Don't have a drawn plan really.  BUT,  I will post a couple of chassis photos on Thurs July 4th prior to noon with some comments about spacing etc.

Gonna try and get the layout board done this wkend and the pots, sockets and trannies installed.

Initially, I am thinking it will be just a head.  However, I punched it out and laid it out so I can flip it upside down into a combo if I want.

I think you could scratch the active FX and do the one tube reverb real easily and a PPIMV instead.

With respect, Tubenit

[moonbird]

I will post a couple of chassis photos on Thurs July 4th prior to noon with some comments about spacing etc.

Much appreciated I will start rounding up a list of waht I need to order. thx!

[tubenit]

OK, here is a D'MoSo56 with one tube reverb and PPIMV.  The power rail is on the SCH version.

The reason for the PPIMV is that the active FX acted like a master volume, so the PPIMV is my other favorite master volume for this type of amp.

I did the 56T which had reverb and was Geezer's HoSo56 with one tube reverb.  It was a nice amp and the reverb worked just fine, IMO.

With respect, Tubenit

[Glennjeff]

Just built and debugged the 5879 front end.

Highly likely I'm wrong but we may be short 1 triode.

Mine sounds pretty similar with channels running at same volume. Very useful  DRIVE N BOOST with a relay I should imagine.

Maybe the HoSo is getting it's overdrive from the pentode saturating the following triode stage.

Maybe include HoSo's V1b after the pentode,  change this V1b back to D'Mars spec and follow the first triode with it, as per D'Mars, mix them into a triode, either a cathode follower or a gain stage with a MOSFET follower. OR could the 2 V1b's be mixed into a MOSFET follower directly, leaving us with a spare triode. OR have both V1b's followed by their own MOSFET followers (2 MOSFETS) and then mix.

OR somehow use relay switching to change the gain after the MOSFET with passive R divider. When using triode clean there is no attenuation after the MOSFET but when using pentode driving V1b harder for overdrive, reduce the gain after the MOSFET to get a more balanced volume setup.

I don't know, I'm a NEWBIE.

This amp, D'Mars EL84, has had a funny little intermittent fizzy bug since I fired it up and have not been able to find it until now, a weird brand new 1 Meg pot of all things.

[Glennjeff]

Results of valve swapping for D'HoSo front end in D'Mars EL84

12AY7 sounds much more open or transparent than 5751's or 12AX7's, fuller bottom and more scooped in low mids.
Got a HiFi sort of vibe to it. (NICE IMHO)

Using 12AY7 V1(a&b) the 5759 won't really go to lots of overdrive (pre gain max, master vol down).Guess that depends on your definition.

There is a nice contrast in tone between 5879 and 12AY7. Not much difference in sound between 5879 and 5751/12AX7 with D'Mars biasing on V1b.

If I really want to get loads of overdrive with 5879 then need to plug a 12AX7 in the first slot. So if using separate 2nd stage triode for 12AY7/5879 first stage I'd want a 12AX7 backing up the pentode and a 12AY7 backing up the 12AY7.
Got any use for a spare side to a 12AX7 - reverb ?

Maybe!
12AY7 is nice foundation for front end, just won't go the whole way with OD.

(12AT7 not enough GO, and lacking the tonal twinkly bits of the  12AY7, 12AU7 is plain dull to my ears)

Just thinking out loud folks.

[tubenit]

Mine sounds pretty similar with channels running at same volume

Yikes!  That is NOT good news!  If that is truly the case using 6V6's, then it sort of defeats the original idea behind the amp design.

Just to make sure that I am understanding you.  Your saying that at the same volume ............. the 12AY7 triode sounds like the 5879 pentode?  *See schematic comparison below.

Given the significant gain difference between the 12AY7 and the 5879,  I was anticipating a significant difference in tone at the same volume?

My thinking is that you'd have the "clean" clean of the D'Mars  vs.  the  "FAT chimey" slightly overdriven/clean of the HoSo56??  

I wasn't expecting a giant difference but at least a clearly significant difference in tone.

So now I am wondering IF maybe your EL84's are being so easily overdriven that the overdriven tone from the power section (meaning EL84's)  is coloring the tone so much that it masks a difference between the 12AY7 triode vs. 5879 pentode?
   

Glenn, can you PLEASE confirm that I am understanding you correctly & that essentially the 12AY7 triode and the 5879 pentode sound pretty similar in your amp?   Thanks!

With respect, Tubenit

[tubenit]

There is a nice contrast in tone between 5879 and 12AY7. Not much difference in sound between 5879 and 5751/12AX7 with D'Mars biasing on V1b

OK,  that helps explain it.   Thank you!  That is what I was anticipating. 

I am understanding that there is indeed a nice contrast between the 5879 and the 12AY7. 

However, using a 5751 or 12AX7 (which have higher gain than 12AY7) lessens the contrast in the tone between the 5879 and the 5751?

Am I now understanding this correctly?   

and THANK YOU for the information, it is a great help!  It's this very kind of trading observations and tweaks that makes this forum a really fun and innovative place to be 

With respect, Tubenit

[Glennjeff]

Don't take my word for anything special, I'm a bit thick when it comes to subtleties.

There is a difference between the 5879 and the 12AY7, not there if using 12AX7/5751.

The 5879 is a little brighter in the upper mids / lower treble and has less low bass.

I'm not driving the output tubes hard, master volume way down, like 5 watts.

Once again, just giving you my perception, I think you folks have much more experienced ears when it comes to the subtleties of guitar sounds, plus I'm running through speakers designed for a completely different application( I'll have my Loarantz Greenback clone in a few days).

[tubenit]

OK,  thanks for the clarity!   Definitely helpful and useful info.   And thanks for ruling out that it was EL84's being overdriven.

One change in the design that may help with even more contrast is to use a 2.2uf instead of 4.7uf on the V1-3 cathode and have the V1-3b
cathode cap be simulataneously switched.  * schematic below

I'll plunge on into the fog and report back after I get the amp built.  

Guys, maybe you want to proceed with caution and a back up plan in mind in case this doesn't work out like I am hoping?

I'm not shooting for a clean to OD change where you would not need or use an OD pedal.  Just attempting to go from clean clean to FAT chimey  overdriven/clean.   AND then use a pedal for additional OD when needed.

With respect, Tubenit  

[Glennjeff]

Also,

The 5879 and 12AY7 could be tweaked by changing the value of volume pots and coupling caps to "select" the character that one likes in the valves.

I have both tubes loaded with 250K pots running off .01uF caps INTENTIONALLY so I can hear the difference in the tubes. Your original schem has the 12AY7 running into 1Meg and the pentode running into 500K so that will make the pentode a bit brighter methinks, and its got the extra gain, so it could all even out nicely.

[Glennjeff]

I have had an ultra-fun day tweaking with these two valves.

Did not sleep last night, lying in bed thinking about what sort of ideas could be tried with this setup.

I am mixing the two channels together now, not switching them.

With selection of bypass and coupling components into the valve bias and feedback networks I have got a really interesting input section.

Using the strength of the 12AX7, Nice clean fat bottom and bright transparent tops, I scooped out the frequency response between about 200Hz and 800Hz, big mid cut sound.

Using the strengths of the 5879, punchy low mid to high treble, I rolled off the bass and bright /presence part of the frequency response.

Now the two input gain controls can be adjusted to give a really wide range of tonal effects. Gain and tone stack in one two knob unit.

I'll get a sound clip up to demonstrate this within the next couple of hours.

Next I'm going to extend this idea with a 3 pos rotary switch on each channel switching bias and bypass reactances. Maybe I could get rid of pots altogether and just have lots of rotary switches on my amp.

[tubenit]

Very cool!!  Nice idea with blend pot approach.

With respect, Tubenit

[Glennjeff]

Here is the soundclip.

Anderson Hollow Drop Top with Neck and Centre single coil in parallel. Vol dimed, Tone dimed.

I touched nothing except the two gain controls for input valves, V1a (12AY7) and V2 (5879).

http://soundcloud.com/glennjeff/testing-the-scoopers

[tubenit]

Wow!  That is quite a variation of tone!  Cool tone.   Thanks for sharing it.

Amp sounds like it is reasonably touch sensitive and articulates well.

With respect, Tubenit

[tubenit]

Moonbird,

Here are some photos and dimensions for punching out a chassis.

And for doing a layout board which is 12" in length.

With respect, Tubenit

[overtone]

Here is the soundclip.

Anderson Hollow Drop Top with Neck and Centre single coil in parallel. Vol dimed, Tone dimed.

I touched nothing except the two gain controls for input valves, V1a (12AY7) and V2 (5879).

http://soundcloud.com/glennjeff/testing-the-scoopers

I just listened on computer speakers and 0:56 sounds really very nice, I can imagine that would work well in a song / band context.
tony

[tubenit]

Keeping in mind, that I presume this amp will need some tweaking (since I've never not tweaked one) .......... I tried to lay this out using turrets in a way that would be the easiest to remove a part and replace it with something else.

Note the direction of the Orange Drop caps installation.  A couple of these may seem headed the wrong direction, but if you study the layout 7 schematic, I think you'll see that they are correct.

Since I am trying to make this an inexpensive amp,  many of the parts are "used" meaning were perhaps in another build for some months and then removed. About 66% of the caps are used and I even had to use two used 1M resistors (ugh).

As I populated this board, I realized that adding a couple more turrets between rows of outer turrets made sense. And I will update the schematic and layout after I do some initially tweaking to reflect that.  

I narrowed the board from 3" to 2.5" to make sure that there will be plenty of room to install relays for footswitching the clean/5879 & midboost. I cut one of Doug's boards down using a hacksaw. It took about 20-30 seconds to cut the 12" strip. And I kept the strip to install turrets on for mounting other components.

IF all goes well,  I may finish this up next wkend!

With respect, Tubenit

[moonbird]

Tubenit --

Thanks most kindly for posting the punch info. Should really help me!!!   

GJ --

What an interesting preamp layout. It would be a perfect match for an idea I have had for some time. I have been collecting old organ swell pedals for a while now. Some of the Lowrey pedals are really cool in that they have 3 pots connected to one pedal. My idea was to use these pedals as part of an amp. If they were applied to your amp, you could have fulltime access to these tone changes. This got me thinking about organs -- the rotary switches you are considering would almost be like the pull "stops" giving you a different "base" tone if you will.

I think your *all nighter* really produced something new and interesting.  Thanks for sharing!!

[Glennjeff]

moonbird,

PLEASE, don't get me started, I need sleep. Had that foot pedal, multi-pot thing floating round in the dark recesses of consciousness for a few days, thinking it may be a bit susceptible to noise however.

At some point I will need to reconcile Utility with Complexity. Not all guitarists have engineering degrees and astronaut licences.

Dr Frankenstein's monster and it's actually very noise / hum free ???

All the best.

[moonbird]

Tubenit -

Messy? Messy?!? Weren't exactly the thoughts that went though my mind. 

On the contrary - thanks much for the look at the master's work. Looking forward to the final gut shot. I am very intersted in how you will route the power across the board. This is VERY helpful for me. Thanks MOST kindly for posting this!! 

[Glennjeff]

That looks great. Can see a few ways to do things better just from looking at your pictures.

Looking forward to hearing it.

[Tone Junkie]

Looks good Jeff , cant wait to hear it.
Thanks Bill                                                 

[tubenit]

OK, I got it wired up.  Not sure about the layout design?  

Wiring is sort of odd color coded, but it's actually very easy to follow what goes where.  

Since I am expecting to be tweaking this, I wanted it reasonably easy to follow and access parts.

Hopefully, I will get to fire it up Sat am and see how it sounds.  IF the layout is not problematic, then I think it will be a very nice sounding amp and friendly to pedals also.

With respect, Tubenit

[Geezer]

Looks great....I like the layout

[Willabe]

Yep, looks great Jeff!


              Brad