"Pseudo" channel switching implemented

[Geezer]

Here's something I've wanted to try for a long time & finally found the time......"pseudo" channel switching.

This will work on any similar circuit (with more than one voltage divider/pot controlled gain stage), either for overdrive tones, or just for gain boost or different settings for solos & such.

All I did was add an extra set gain & trim (pre-PI Master) pots, then use a footswitched DPDT relay to select between the original set of pots (channel 1) & the "new" set (2nd "channel").
I used another relay to switch in a bypass cap & mid-boost (raw) since I wanted it to be for overdrive tones. Those values can be tailored to taste, or not used at all depending on what you are trying to accomplish.

I absolutely LOVE it! Works perfectly & you'd never know it wasn't a "true" channel switching amp.

Here are several drawings...the circuit by itself, and integrated into the HoSo56 (now the HoSo56 II)

Geezer

edit: tweaked/changed the value of the V2a bypass cap (lowered from 4.7u to 0.68u) and the mid-boost resistor (lowered from 68k to 33k)

[topbrent]

Great implementation Geezer!

A friend of mine did a similar thing to his JCM800 2204 clone last year and it works brilliantly.  Dual switchable gain/volume relay setup. 
I played the amp at a big amp show we have here in Utah once a year.  That amp was the most fun of all the amps I plugged into.  Although there were Boutiques aplenty, and tons of awesome vintage amps everywhere, this homebuilt ceriatone sourced dual volume/gain jcm800 was the real treat for me!

[Geezer]

Thanks Brent.....yeah, this can be done to just about any amp, but it's especially cool on amps that get a good overdrive when the gain is cranked up.

Oh, forgot to say that I put a 68p bright cap on the #2 trim pot, as it stays in the lower 1/2 of the range & loses some sparkle & the cap really helps.......

G

[The_Gaz]

This looks really cool and useful, but wouldn't the gain controls be interactive, where one setting affects the other? Have you experienced that at all?

[Geezer]

wouldn't the gain controls be interactive, where one setting affects the other? Have you experienced that at all?

No, not at all.

Look closely @ the circuit (trace it thru @ the gain pots) & you'll see that the un-used pot simply "hangs" like a 1meg resistor to ground. It has no (noticable) effect on the gain, & has absolutely no effect on the signal when adjusted (if you turn the pot when "off").

G

[The_Gaz]

That's was a great explanation! Come to think of it, I think the SLO dual master volume is set up the same way. That's really cool -- thanks for posting.

[tubenit]

Super cool idea!  THANKS!

With respect, Tubenit

[jojokeo]

+1
I like the idea Geezer. Instant gain, mids, and a slight brithness w/ the kick of a single switch. I can see your mind working..."Tweak amp one way, I like. Tweak amp a second time, I like. Now to simply go from one to the other...piece of cake!" An infamous quote from Vince the ShamWow guy, "are ya following me camera guy?" 

[Geezer]

If there's a long distance between the pots you want to switch (or if you just have an unused relay you want to employ) here's a 2x relay version.

G

[Fresh_Start]

Don't know if this makes any sense, but if "channel 2" is supposed to be higher gain it might be helpful to put a resistor "under" Gain 2 to give it a minimum signal level higher than Gain 1.

Just a thought.

Chip

[pullshocks]

Cool idea Geezer.  In the Hoso schematic are relays 1 and 2 meant to be switched together?  Or is relay 2 a separate thing?

[Geezer]

Cool idea Geezer.  In the Hoso schematic are relays 1 and 2 meant to be switched together?  Or is relay 2 a separate thing?

I have mine switched @ the same time, but you could do them separate, switch in the 2nd channel with one footswitch, then use the other relay for the mid-boost on a separate footswitch.

I used the amp @ practice last nite & it is fantastically useful....does exactly what I wanted.

I'm going to build a larger version with full tonestack switching, schem attached.

G

[Geezer]

OK, made a few small (but important) changes in the HoSo56 II & it's the best yet.
I played it this morning w/ the band & it was the most natural sounding, fun to play & easily cuttin' thru the mix amp I've built.

The changes?
After reading Merlin's info about using grid stoppers to sculpt overdrive sections ( http://www.freewebs.com/valvewizard/gridstopper.html ), and using some of the experience I've gained from the Dumble-style builds, I added some strategic stoppers to the OD "channel" only.

Schematic attached

It really smoothed out the OD, giving it a pleasing tone & removing any hint of blocking distortion. It also gets the "vowel"-like tone when you dig into the strings....very touch sensitive to that.
I was also able to increase the V2a Rk cap from 0.68u to 4.7u & remove the 68p bright cap (although, as always, these should be tailored to your own taste if you build this amp).

Wow!
This amp is more "Dumble" sounding than any of the "real" D-style amps I've built, plus it's a very simple circuit.

Geezer

[tubenit]

It really smoothed out the OD, giving it a pleasing tone & removing any hint of blocking distortion. It also gets the "vowel"-like tone when you dig into the strings....very touch sensitive to that.
I was also able to increase the V2a Rk cap from 0.68u to 4.7u & remove the 68p bright cap (although, as always, these should be tailored to your own taste if you build this amp).

Wow!
This amp is more "Dumble" sounding than any of the "real" D-style amps I've built, plus it's a very simple circuit.

Double wow!! That's incredible!

For real??  This sounds more Dumble than the TOS and/or TBM?   That's really cool!

THANKS for sharing it!  With respect, Tubenit

[Geezer]

Well, I'm not even sure I know what a Dumble is supposed to sound like (  ) but this is what I would want my Dumble to sound like! 

There's just something really "special" about this amp (to my ears). It's just very "comfortable" to play thru.

I'll try to get a sound clip up, just not sure when I can.....may be several weeks.

G

[kagliostro]

Hi Geezer

Many thanks for sharing your experience

Kagliostro

[tubenit]

Well, I'm not even sure I know what a Dumble is supposed to sound like (   ) but this is what I would want my Dumble to sound like!  There's just something really "special" about this amp (to my ears). It's just very "comfortable" to play thru.

That's an exceptionally cool description! Definitely got my attention.  Your other amps sounded totally remarkable and stellar to me, so if you like this amp ......... it's got to be an incredibly great amp.

This is an EL84 poweramp like it used to be?  Is there a nice contrast between the clean and OD "channels"?

I'll look forward to some more great guitar playing and amp tones in the soundbits!  As always, thanks for sharing. I think you've really come up with some phenomenol tone and innovation in your amps.

With respect, Tubenit

[Geezer]

This is an EL84 poweramp like it used to be?

Yes, exact same HoSo56 PA...in fact, exact same HoSo56 with the addition of the switchable gain/trim pots.

I'm working up a 36w version with separate CF's & tonestacks, using 16GK6's (EL84 specs w/16v heaters, I have 8x really nice NOS GE tubes) that will go into the larger head cab (the one with the new faceplate......you know the one   ). I had several extra chassis made to fit that cabinet.

36w version attached

Is there a nice contrast between the clean and OD "channels"?

Actually, that's what I like about it....there's NOT a big "contrast". It's like the same basic tone, but with a mid-boost, lots more gain/sustain available & the great vowel-like touch sensitivity.
*Channel 1 is the great HoSo tone, the "clean but not-too-clean" sound.
*Channel 2 gives you control over> more gain, more volume, more mids/cuttin thru, all at the step of a footswitch.

I've always liked the HoSo tone. This is "more" of all the good stuff!

[Tone Junkie]

Geezer I really like the look of that I cant wait to hear clips, thank you for continuing to share these great amplifiers with us.
Bill

[pullshocks]

Geezer, how have you got the additional controls laid out on the panel?  Where do you position the relays?

[topbrent]

Hey Geezer, in a somewhat similar manner that dual tonestack thing is what mesa is doing with their Lonestar amps, albeit with a fender ab763 flavor.

[Geezer]

Geezer, how have you got the additional controls laid out on the panel?  Where do you position the relays?

Front panel layout attached

For the relays, I will probably place them along the front edge/corner, right under the pots, as near center as possible (somewhere near the channel select switch) & try to position them for the shortest signal wire runs possible to the pots.

G

[Geezer]

Another option for a smaller faceplate would be to stack the channels on top of each other.

[Tone Junkie]

Geezer with your double hoso56 you parallel a 5654 with 5879 does that give it a big jump in volume that sure would be nice to figure how to use that as a solo boost, I guess before I think out loud I should ask you what your thoughts are with the sound of it paralleled like that. Thanks Bill

[tubenit]

I did the same thing with 5654 (or 6AU6) and 5879 paralleled using 5881's. The 5879 Carolina Blues Rocket.  "to get a fat/thick harmonically rich sweet tone."

http://www.el34world.com/Forum/index.php?topic=6368.0

No, not a big jump in volume but a thicker fatter overdrive from what I remember?  It was kind of cool because you could unplug one or the other and compare. In other words, not a big jump in volume but a change in tone, harmonics and touch sensitivity. Probably not the best choice for a "boost" , IMO.

with respect, Tubenit

[pullshocks]

Would the HOSO56 II preamp work OK with a single ended PA?  I seem to remember someone saying that preamps ending with a cathode follower and tone stack don't work well with a single ended power amp.  I was planning on 6V6 but could go 6BQ5 if that would be better

[DummyLoad]

I've tried making a Hoffman style layout for Geezer's latest HoSo56 revisions.

Can someone PLEASE look over it and post that it looks correct?  I'd like another pair of eyes on it.

with respect, Tubenit

OK i think it's closer... a couple of errors. please review. 

respectfully, a suggestion... use a third relay for switching TR1 & TR2 - to me it seems like a potential source of oscillation b/c of output signal of the PIs proximity to the output signal of the first stage.

[tubenit]

ISOtone,

THANKS for the review of the layout! I have corrected it and the SCH layout is in the SCH library with Geezer's post.

http://www.el34world.com/Forum/index.php?topic=10999.msg100944#msg100944

I will let Geezer make the call on the 3rd relay since it's his amp and I don't have one. As I understand it, the two relays are working for him without issues currently.

with respect, Tubenit

[tubenit]

OK,  I also added a DRAFT Bill of Materials for this amp.

The revised schematic and layout etc........... are all here:

http://www.el34world.com/Forum/index.php?topic=10999.new#new

With respect, Tubenit

[Tone Junkie]

Thick/fat harmonically rich sweet tone sounds good to me Tubnit.
Thanks Bill   

[Geezer]

Change of pace.......found a bunch of NOS/JAN 6005W/6AQ5A tubes I had forgot about having.
I'm going to run a quad of these in the new amp instead of the 16GK6's.....I'll save the 16's (along with their separate 16v filament transformer) for another project.

G

[Tone Junkie]

Please keep us posted i got at least 10 6aq5 tubes myself.
Thank Bill

[Tone Junkie]

So I take it Geezer this was what you were working on i always like the look of those peralleled pentodes. Keep us posted . Thanks Bill