Planning a stereo tube guitar amp

[Toxophilite]

I've been wanting to build a stereo tube guitar amp for a while
I want it too be powerful enough to produce cleans in small venues with a drummer
the second channel would be for the wet signal of my RE-150 tape echo
I would also have he dry signal from the 1st channel split into the 2nd channel as well. likely with a volume control
They don't need to be identical
I was contemplating 7189s or Russian equivilants in the 1st(dry) channel and either the same in the second or maybe ECL83s in the second to save a tube spot.


These channels can share a power supply but even if they were both running the same power tubes they would need separate bias supplies. right? or could I have one circuit feed them both bias?

If I had a bias vary tremelo. could I have it control both amps??

[PRR]

One bias supply, two pots.

It needs to be a "solid" supply, not the kind that drops -400V down to ~~20V depending on pot load.

[SILVERGUN]

Posting this for reference because it's the first amp I thought of after reading your post.
See: shared power supply and shared bias supply.
This is a super cool amp that came up a while back, when Willabe posted a demo of the reissue.

Obviously, if you tried to use output tube bias modulated tremolo it would affect both channels simultaneously.
For simplicity, I'd love to see someone do stereo SE, cathode biased, and just wiggle a preamp cathode to get vibrato.
IMHO, a stereo single ended setup IS loud enough to get over a drummer (ask me how I know  .... but I also use some pretty efficient speakers)

http://el34world.com/charts/Schematics/files/magnatone/magnatone_280a.pdf

[Toxophilite]

Hmmm I don't know if single ended amps will give me enough perfectly clean headroom. I'm not looking for any distortion


That magnatone looks cool though and sounds good too,,but the modern smaller version is $3500 for an amp!! crazy!


That modern 4 El84 version looks mostly to be  stereo for the vibrato

[sluckey]

That Magnatone 280A is not a stereo amplifier. It has a "stereo FM vibrato" circuit and two power amps that are simply connected parallel. It has a very good sounding vibrato, but the amp ain't stereo.

Gibson has several true stereo amps, GA-78 and GA-79 are a couple. The GA-79RVT is a true stereo amp built for true stereo guitars like the Gibson 335 Stereo (requires special instrument cable). The two channels are truly discrete from inputs to speakers. Reverb (easily removed) and bias vary tremolo are applied to only one channel. Output tubes are common 6BQ5 (EL84s) which are close to the expensive/hard to find 7189s you say you want.This should be a good candidate for consideration. The GA-79 is the same amp without reverb and tremolo in case you don't want reverb and/or tremolo. Take a look...
   
     http://el34world.com/charts/Schematics/files/gibson/Gibson_ga79.pdf
     http://el34world.com/charts/Schematics/files/gibson/Gibson_rvt791.pdf

Gibson has a few other stereo models and the schematics are in Doug's schematic library.

PS... If you have a source for 7189s please share. I need a pair for my Magnatone 10A.
 

[shooter]

Ampeg's super echo twin comes to mind also, PITA to work on, but very nice chimey when working

[silverfox]

What are you thinking in terms of the preamp? Stereo preamps? Pedals for preamps? Or is this just a stereo poweramp build?

silverfox.

[jjasilli]

I want it too be powerful enough to produce cleans in small venues with a drummer
I submit that this is the most recurrent topic on the Forum.  IMHO, as a patron, a Deluxe Reverb (2X 6V6) is too loud for the average bar with a small drum kit & bass amp to match.  However, with a large drum kit (hence louder bass guitar), it's too weak to stay clean.   What's a small venue: 50 people or 2000?  Is power amp overdrive a requirement?  If mic'ing or DI > a house PA amp is available or desirable, you could use a Champ-like amp (SE). 


I further submit that the fact that the amp is stereo has not much effect on volume output.  It will only add an extra 3dB of perceived volume, which is barely noticeable.  Maybe that's just enough to keep a stereo PP 6V6 amp clean; but maybe not, depending on the circumstances.

[DummyLoad]

build a couple of bassman amps (leave off the bass channel) side by side. add your effects loops between the LTPI and preamp. use a twin reverb PT and supply.


maybe one bass channel; the other the normal channel, each with their own respective LTPI  and output stages.




--pete

[DummyLoad]

stereo aa_864 bassman - see attached.

EDIT: should fit in a 100W JCM800 enclosure. you'd need to punch holes for the 2 additional preamp bottles - there's plenty of room. the second OT should fit next to the existing.

--pete


EDIT of the EDIT: use a 5A slo-blo fuse.

[Toxophilite]

Hey thanks for all the input
I currently have:
- super reverb (great sounding but too bog for most places and HEAVY!)
-Two homemade deluxes designed as a little stereo rig (one a single channel deluxe reverb the other a 2 channel deluxe no effects)
-Another homemade 2x 10 deluxe reverb, this one done a little better (no ground loop and orientated on the AO-43 chassis like a tweed amp (tubes on one edge controls on the other)
- A homemade vibrolux reverb


I often use a combination of any of the reverb amps and the 2 channel deluxe as a live rig.
With my quieter band the deluxes seem to do the job
2 amps together do make for an increase in volume,,,..of volume (meaning size as much as actual loudness)


BUt just for fun I wanted to see if I could design and build something relatively compact (maybe 2 10s or a12" and a 10"


-two separate preamps and power amps
shared power supply
Maybe slightly angled front baffle to gain a little spread out front but not as much as the Gibson amps
i will make a flowchart/picture of the arrangement I use to give an idea


Here's a picture of a studio rig for now ,,,ignore the leslie (though I like to use it to)
This is also the setuo i use live
amp 1 on left is dry sound(but with reverb and tremelo when I want) (line out of this amp to amp 2)
space echo in between dry sound to amp 1
echo to amp 2 on right
Am 2 also has dry sound from amp 1 to retain a 'stereo' sound when echo is off


leslie is run off of a external speaker jack on amp 2

[jjasilli]

OK!  Seems like you have a great concept for a 2-amp rig in one box.   

[Toxophilite]

oh and S. Luckey
I have a few 7189s myself
I thought there was a Russian equivilent that used to be cheap like borsch...
Apparently they've escalated in price in the last few years
https://www.ebay.com/itm/4-x-6p14p-EV-Gold-7189-6BQ5-el84m-EL84/142602101230?hash=item2133bf61ee:g:SZAAAOSwehZaDHri

[Toxophilite]

For a  stereo amp is it besteasiest to keep the two power amps identical ?(Same tubes)
My 'echo amp' doesn't need to be quite as loud


Can the two power amps be powered off the same B+ stage or should there be a dropping resistor or filter cap between them


If I use different power tubes (say 7189s or 6V6s first amp, ECL86 second amp) I would just have dropping resistor and filter cap for the second amps power amp to accomodate teh lower voltage needed.
Does that seem like the way to go?

[sluckey]

For a  stereo amp is it besteasiest to keep the two power amps identical ?(Same tubes)
My 'echo amp' doesn't need to be quite as loud

Yes, keep them the same for simplicity.

Can the two power amps be powered off the same B+ stage or should there be a dropping resistor or filter cap between them

If they are the same then use the same B+ nodes.

If I use different power tubes (say 7189s or 6V6s first amp, ECL86 second amp) I would just have dropping resistor and filter cap for the second amps power amp to accomodate teh lower voltage needed.
Does that seem like the way to go?

No. You want the power amp to get the full juice from the rectifier so don't use dropping resistors for the smaller amp. If you must build different power amps, use a common PT but use separate rectifier/B+ rails.

Take a look at this Hammond AO-63. It has a big main amp and a smaller reverb amp. It uses a common PT but separate tube rectifiers/B+ filters. The more I think about it, this just may be a perfect donor amp for your project. I have one and really like it. It's a clean, loud amp. I call it a Hampeg GemiVibe. Any how, study the original schematic in this link and see what you think. You may want to pivk up one of these for a donor...

     http://sluckeyamps.com/hammond_2/AO-63.pdf

[Toxophilite]

Thanks
That clears a bunch of stuff up
The idea of using the ECL86s was to save a tube spot as they have the triodes too (built in phase inverter!)


However I would be using a solid state rectifier for this amp, should I have 2 then if I used the ACL86s


I can make the power amps the same I guess having the extra PI isn't a big deal because I need the same amount of room inside the amp for 2 2nd phase inverter circuit anyway


It might be nice to go for a double 6G9 power amp and use those Russian 7189 subs. people report good results with them for hifi amps that required 7189s (it is internet opinion of course)


The Ao-63 is a cool amp, and I had one (my friend has a chassis kicking around too, though now gutted).
However I don't need quite that much power for my clean amp.
Also I'd like to keep the weight down and the AO-63 is a bit of a beast!
18-22 watts for each amp would probably be adequate I think with efficient speakers


I guess I'd have 4 power tubes (El84s/7189/6V6)and with reverb and tremelo , probably 7 preamp tubes


If I'm using a 325-0-325 Pt then the calculator here:
http://thesubjectmatter.com/calcptcurrent.html

Says I'd be drawing about 148.89ma at 16521r calculated load


mind you I might not be using it right for an amp that has two separate power amps and OTs


Seems like an Hammond organ A0-29 PT could cut it


The vibrolux PT from Hammond mfg does 325-0-325 and 207ma


it's also pretty well the exact size of the AO-43 PT..not that that really means something


i also have a largish standup HIFI PT that seems to measure 395-0-395
I have no idea of it's current capcity and I stupidly didn't label it.

[Toxophilite]

Another couple confusing questions

For these questions I'll refer to the two amps as left and right (left being the dry channel and right being the wet channel)

- power supply to left and right preamps
Can they be run off the same power rail like a 2 channel fender amp?


Option 1-(blue line)-I want to take the signal from the left channel and send it into the right amps phase inverter
Can I do this using 220 blocking resistors between this offshoot, the original left channel signal and the right channel?
-Also if I wanted to be able to adjust the mix could I put a Potentiometer here


Option 2 -(red line)-alternatively if I want it to be a little different, perhaps a little quieter and have no reverb can I run the line from the left amp to the right amp from before the reverb circuit and send it to the right channel

Option 3 - (green line) - a line from the left power amp line out(see schematic, via a mixing potentiometer into the PI of the right channel PI) This would include the tremelo and the reverb o the 'dry' signal going to the right amp but leave the signal from the right preamp unaffected by the tremelo and reverb.


-Lastly , regarding tube and board layout. is it best to lay it all out in a line, left preamp, right preamp, reverb, tremelo, left PI right PI left power amp, right power amp
or should I group the PIs and power amps together?


As it's going to be a long narrow chassis I'll probably be keeping power at one end and preamps at the other


Any suggestions?


I'm including a rough unfinished schematic, please ignore voltages, any mistakes in the power supply, bias voltages, tube number labelling and speaker impedances

[jjasilli]

I'm having trouble seeing if there's a signal phase issue in the preamps, if their signals are to be combined.  This could be a bug or a "feature" depending o your preference for out of phase tone.  If the amps are kept separate AND are out of phase, this easily can be corrected by reversing the speaker wires for one amp. 

The phase issue also applies to an "internal" line-out circuit.  Personally, I would keep the preamps as separate as possible.  I.e, if the line-outs are to be mixed, they the can be tapped off each speaker jack, tested for polarity and mixed "externally".  Alternatively, there may be little benefit in mixing the lines-out at the amp at all.  Ea. line-out could be run to a mixer or stereo pedal.  The question is: where do you want your complexity -- inboard or outboard?


Also your current line-up features amps that probably use 6V6's or 6L6's.  El84's can present a glassy, brittle tone which can be difficult to deal with.  If you're looking to save space the 6GW8 is similar in size & function to the El84; lacks the brittle, glassy issue; and contains a triode, saving the space of a PI tube.

[shooter]

if there's a signal phase issue in the preamps

A quick pre-coffee look says they are phased ok

[92Volts]

The left channel seems to have an extra gainstage compared to right or vibrato, which will invert phase... it also appears output from the extra stage (reverb recovery?) is fed back to its own input, which seems wrong...

I may be confused what the red, purple, and blue colors mean. If those wires are switched to either use or bypass that extra stage (and/or reverb itself), that would make sense. With that said, you'd want to do more to cut out that stage than just jumper around it by switching those wires.

The cathode bypass cap between the two cathodes is interesting, but it needs to be nonpolar while many bypass caps are cheap electrolytics. It would increase part count but may decrease cost to have two separate ones. I'm curious what the effect of jumpering the two like that would be, it may have more effect than just being a shortcut to jumper the cathodes, if there's something I'm missing there it might be worth keeping.

[Toxophilite]

I'm having trouble seeing if there's a signal phase issue in the preamps, if their signals are to be combined.  This could be a bug or a "feature" depending o your preference for out of phase tone.  If the amps are kept separate AND are out of phase, this easily can be corrected by reversing the speaker wires for one amp. 

The phase issue also applies to an "internal" line-out circuit.  Personally, I would keep the preamps as separate as possible.  I.e, if the line-outs are to be mixed, they the can be tapped off each speaker jack, tested for polarity and mixed "externally".  Alternatively, there may be little benefit in mixing the lines-out at the amp at all.  Ea. line-out could be run to a mixer or stereo pedal.  The question is: where do you want your complexity -- inboard or outboard?

I'm wondering about phase in amps. Is it all resolved in the power amp? As I've been using a homemade deluxe reverb and 2 channel homemade deluxe live for the past couple years. I even run a signal from the line out of the deluxe reverb(from which these power amps were derived(quick cut and paste) into channel 2 of the deluxe , no problem, with echo in channel one
And why is the phase flipped every time the signal goes through a gain stage?

Also your current line-up features amps that probably use 6V6's or 6L6's.  El84's can present a glassy, brittle tone which can be difficult to deal with.  If you're looking to save space the 6GW8 is similar in size & function to the El84; lacks the brittle, glassy issue; and contains a triode, saving the space of a PI tube.

Personally I believe in the sound of different circuits in an amp, not so much in the sound of tubes or individual components. I've had hifi and guitar amps with El84 and 7189 output tubes and none has sounded brittle or glassy. This is coming from someone who has used a super reverb live etc for the past 25 years.
i think the brittle and glassy and or 'British sound derives from the vox circuit which is quite bright and I think lacking in negative feedback. The fender 6G9 uses El84s and supposedly has a very fender sound with little of the brittle and glassy attributes people commonly attach to the EL84.

[Toxophilite]

The left channel seems to have an extra gainstage compared to right or vibrato, which will invert phase... it also appears output from the extra stage (reverb recovery?) is fed back to its own input, which seems wrong...

I may be confused what the red, purple, and blue colors mean. If those wires are switched to either use or bypass that extra stage (and/or reverb itself), that would make sense. With that said, you'd want to do more to cut out that stage than just jumper around it by switching those wires.

The cathode bypass cap between the two cathodes is interesting, but it needs to be nonpolar while many bypass caps are cheap electrolytics. It would increase part count but may decrease cost to have two separate ones. I'm curious what the effect of jumpering the two like that would be, it may have more effect than just being a shortcut to jumper the cathodes, if there's something I'm missing there it might be worth keeping.

Hi If you read my post I think I explain what the different colours in the circuits mean, they are each single  options for the final build, not switches.


Also as my post explains, this is a rough unfinished schematic mainly to help illustrate the overall layout of the amp and help depict the questions asked.It was a quick cut and paste job from a vibrolux build I did a year or so back. If you are referring to the cap on the power tube cathodes , ignore it because that's not relevant to the question. Thanks


Was my post too confusing? I was trying to take a bit of extra time to organize the questions etc. They mainly revolved around the mixing the left amp preamp into the right and with the right am preamp. that is NOT a finished schematic, just a rough cut and paste. I want to have everything happen in the amp, not at a board or through any outboard mixing devices. I know it can be done.


I'm building this for a specific purpose. to reproduce in one stereo guitar amp what i usually do with 2 mono guitar amps. here is a flow chart of my usual setup live. i want to build a stereo guitar amp to accomplish this.

[shooter]

why is the phase flipped every time the signal goes through a gain stage?

same logic as this transistor explination

https://electronics.stackexchange.com/questions/174838/why-signal-is-inverted-in-common-emitter-amplifier

after WAY to much coffee, I looked at V4b as a CF, as a gain stage, it is outta phase. you can "fix" it at the speaker.

[92Volts]

Sorry I missed the other parts of your post, I got distracted by the discussion of phase and focused on that part of the schematic.

I'm wondering about phase in amps. Is it all resolved in the power amp? As I've been using a homemade deluxe reverb and 2 channel homemade deluxe live for the past couple years. I even run a signal from the line out of the deluxe reverb(from which these power amps were derived(quick cut and paste) into channel 2 of the deluxe , no problem, with echo in channel one
And why is the phase flipped every time the signal goes through a gain stage?

The phase is flipped every time it goes through a gain stage because an increasing voltage at the grid causes the tube to draw more current. This decreases the voltage between the tube's plate to cathode, or increases the voltage lost across the plate resistor, to look at it another way. Therefore, an increasing voltage at the input of the stage results in a decreasing voltage at the output.

Phase is not "automatically" resolved by the power amp, though it's easily fixed at the output by switching the connection at the speaker... if you have 2 speakers that are out of phase. If you have two signals in the amp which are out of phase, you can't mix them like that because they'll cancel out and you'll get zero signal (ideally-- in reality, it will be a weak signal with strange frequency response).

Out-of-phase speakers aren't such a big problem because they aren't producing sound at the exact same location, so they don't perfectly cancel each other out. There are all sorts of weird interactions between multiple speakers based on frequency and distance between them, and the position of the listener, whether they're in or out of phase. It's not a big concern because of this, plus it's easy to fix. Mixing signals inside the amp is where you really would worry.

[Toxophilite]

Okay, so if I take the dry sound from prior to the gain stage after the reverb circuit (red line option) then I shouldn't have phase issues with mixing that into my right channel?


Do deluxe reverbs and (non reverb) deluxe amps have opposite speaker polarity?




ON another note I was thinking it would be cool to have 2 10s in front for the main LEFT amp and maybe a pair of 6x9 elliptical speakers, on on either side slightly angled towards the front for the right/echo amp, like an old tone cabinet.

[jjasilli]

I thought there was a signal phase issue.  Thanks, guys for the confirmation. 


A gains stage flips phase, because the wobbling AC signal voltage on G1 impresses a mirror image of itself upon the electron flow inside the tube (the actual flow is from cathode to plate).  This is not a problem, unless and until 2 separate signal paths are combined. 

If speakers are out of phase, the real world result might be sound cancellation, or reinforcement, in whole or in part, depending upon their placement with regard to one another AND within the dimensions of the room they are in. 

For sound & recording guys, out of phase signals from different sources can cancel each other in the mixing board.  This is why the phase of your lines-out matters.

[92Volts]

Okay, so if I take the dry sound from prior to the gain stage after the reverb circuit (red line option) then I shouldn't have phase issues with mixing that into my right channel?

Yes, that should be fine

Do deluxe reverbs and (non reverb) deluxe amps have opposite speaker polarity?

Those amps should have the same phase behavior because reverb is mixed in "parallel" with the circuit-- the main signal does not pass through an additional gain stage because of the addition of reverb.

Anyways, there is no clear "right" or "wrong" speaker phase if they're not in the same physical cab... if sound travels 1000 feet per second, 100hz sound becomes opposite or "out of phase" after traveling 5 feet (half its wavelength). If one cab is 5 feet further from the listener, 100Hz sound is "out of phase", even though the speakers produced it "in phase"! But only for that frequency and that location of the cab/listener... there's just too much chaos from the room/cab/listener to worry about phase when you're actually producing physical sound.

Only inside the amp will 2 signals really cancel each other out and cause a make-or-break difference in performance because of a phase mismatch.

ON another note I was thinking it would be cool to have 2 10s in front for the main LEFT amp and maybe a pair of 6x9 elliptical speakers, on on either side slightly angled towards the front for the right/echo amp, like an old tone cabinet.

Could be cool! Keep in mind their efficiency will be lower than purpose-built guitar speakers and the frequency response will be different, but it might be totally fine for reverb/effects signal only.

[jjasilli]

 

[Toxophilite]

Okay, so if I take the dry sound from prior to the gain stage after the reverb circuit (red line option) then I shouldn't have phase issues with mixing that into my right channel?

Yes, that should be fine

Do deluxe reverbs and (non reverb) deluxe amps have opposite speaker polarity?

Those amps should have the same phase behavior because reverb is mixed in "parallel" with the circuit-- the main signal does not pass through an additional gain stage because of the addition of reverb.

Anyways, there is no clear "right" or "wrong" speaker phase if they're not in the same physical cab... if sound travels 1000 feet per second, 100hz sound becomes opposite or "out of phase" after traveling 5 feet (half its wavelength). If one cab is 5 feet further from the listener, 100Hz sound is "out of phase", even though the speakers produced it "in phase"! But only for that frequency and that location of the cab/listener... there's just too much chaos from the room/cab/listener to worry about phase when you're actually producing physical sound.

Only inside the amp will 2 signals really cancel each other out and cause a make-or-break difference in performance because of a phase mismatch.

ON another note I was thinking it would be cool to have 2 10s in front for the main LEFT amp and maybe a pair of 6x9 elliptical speakers, on on either side slightly angled towards the front for the right/echo amp, like an old tone cabinet.

Could be cool! Keep in mind their efficiency will be lower than purpose-built guitar speakers and the frequency response will be different, but it might be totally fine for reverb/effects signal only.

Thanks for straightening me out on the phase thing. I should know that but I haven't tried it in practice, within an amp.
As far as the 6x9 speakers go, they're actually out of different old organs. So full range musical drivers and not car stereo speakers.
From what I understand about speakers (particularly older ones) and I could be very wrong, is that most of the pressed basket speakers were pretty generic. The common Jensens used in guitar amps could also be found in organs and many other uses. Sometimes as woofers in a hifi setup.
One of my leslies pulled from an organ uses a 6x9 speaker, I run it as an extension cab from one of my amps (not in the diagram )It sounds great.
My little deluxes are using JBL D123s a 12" full range hifi speaker.


I don't need the amp to be stereo in the conventional way Ie; Two exactly matching channels. I just need it to have two channels that are roughly similar in power, The 'echo' channel  can actually be a little quieter and usually is set that way in my normal two separate amp setup.
It's also okay if they sound a little different too. I usually find that to be complimentary

[jjasilli]

You're messing with a number of variables at the same time.  R&D is a bitch.  I would not build this project on mere assumptions about tone & performance.  E.g., the 2X oval speaker idea is appealing in theory; but will it work for you in practice?  I suggest you build a test speaker box for them.   Or, make them a baffle board you can swap into an existing combo box; then hook them up to an amp with appropriate wet signal & see if you like their performance in the real world.  If yes, then you know with confidence that the ovals can be built into the stereo box. 

Once you finalize an amp schematic, I suggest you breadboard the build first.  I 'm sure Dummyload would agree. 

[Toxophilite]

Yes, thanks, I know, and I'm not terribly worried
It's actually not that ground breaking a concept and I've made several amps from scratch now.all quite successful.
Usually using recylced parts and completely gutted and reconfigured Hammond organ amp chassis , transformers etc. I never use kits or bought parts (except caps, resistors, pots, switches, jacks, the odd choke etc) my tube cup runneth over too.
So every amp I build is R&D and requires a bunch of pre build headscratching and then some adaptation and troubleshooting along the way
I find it fun and that's also why I'm here asking dumb-assed questions!


I do appreciate your concern though.
It is after all only a guitar amp, not a space shuttle..whew!


Valco, Supro and Magnatone all used 6x9 speakers with success
I have used one in my leslie cab ext, speaker for years


I was planning to put two in separate bafflles and sit them on either side of my vibrolux wired as extension speakers.(it has a multitap OT) and i could also use one of my other amps to power them and try it with echo. It would be very simple to check out
It would a neat solution to speaker layout to keep a stereo amp compact


This amp will be essentially two, simple, small AB763 amps in one chassis. I might go with a 6G9 style. both are tried and tested designs
I'm not afraid to make mistakes as long as I don't die or let the magic smoke out in the process...


Though in the big scheme of thing I am a beginner I do have some experience.


I did have some questions about tube and board layout that got lost in the phase inverter speaker discussion
Here they are again, thanks!


-Lastly , regarding tube and board layout. is it best to lay it all out in a line,
 left preamp, right preamp, reverb, tremelo, left PI right PI left power amp, right power amp


or should I group the PIs and power amps together?
left pre, right pre, reverb, tremelo, left PI ,eft PA, right PI, right PA


As it's going to be a long narrow chassis I'll probably be keeping power at one end and preamps at the otherAny suggestions?

[jjasilli]

I suggest you checkout the chassis layout of slukey's Hammond amp suggestion, and other stereo tube amps such as Fisher,  Stromberg Carlson, etc.


Usual layout rules apply.   PS on one end with the power tubes & PI.  4 power tubes can be in-line or form a square.  Preamp tubes should be in a line or cluster for ea preamp.


If chassis space is a problem, the combo box will be big enough to house  multiple chassis.   E.h., the power amp can have it's own chassis at the bottom of the cab.  See slukey's home page.  Each preamp could be in its own chassis.  Reverb, tremolo circuits can be on supplemental chassis.

[kagliostro]

This is what Lectrolab did on 1961 building the Capitol Amp

Preamp on the Top, PS and Power Amp on the bottom







Franco

[Toxophilite]

Thanks I was doing that last night
Checked out Luker amps, They have a stereo deluxe reverb all in one chassis that looks quite interesting
Made me wonder if I needed reverb in my amp. But then I'd have to buy a pedal
Thought about how Gibson used to put their power amps in the bottom of the amp, (that would require running a reverb tank up the side of the amp)
Fender was doing that recently with their excelsior amp. They used electrical conduit to tie them together.
I was looking at stereo hifi amps as well.
I have had a couple of AO-63 Chassis like S. Luckey was suggesting. They have the ultimate boat anchor PT and main OT. Good iron but overkill for what I want to do
As well as various stereo hifi amps at one point or another. Dynaco, Eico, Sherwood, etc.


That looks cool kagliostro. I think I could go that route if I decided on no reverb and/or side mounted speakers

[kagliostro]

........ (that would require running a reverb tank up the side of the amp)

not mandatory, VOX used a double bottom





Franco

[Toxophilite]

That's cool
I was hoping to build a combo but that could be used in that setting
I was thinking about speakers too and that cool Capital amp
And though one could have 2 10's in front and have a 6x9 on either side
and have each amp power on 10 and one 6x9 which would give you an up front stage mix but also a lot of space and dimension to the stereo effect
just tossing ideas around in my head
I've thought of a head and two cabs attached together but that would be 3 things, I already carry 2  and tie them altogether with patchchords.
 I really want to accomplish this in one unit!

[kagliostro]

If I've correctly understand you mean something like in this amp (1978 Fender Deluxe Reverb ?)



I think that also this Gibson arrangement will be a good alternative to increase the stereo effect with less speakers

Note the position of the reverb tank





Franco

[jjasilli]

kagliostro:  you're right on the money with these examples!   

[shooter]

I think Franco has an un-healthy amount of amp porn

[Toxophilite]

Good stuff though!
I'm familiar with the Gibson setup
No forward facing speaker though
That first one is NOT a 78 deluxe reverb though


Neat to see that it looks like Gibson lines up all their preamp tubes
but has the power tubes and the PIs grouped together
They also put the OTs on the upper chassiss


Thanks

[kagliostro]

I think Franco has an un-healthy amount of amp porn

 

Less than that you can think 

---

I've find the photo of the first amp labeled that way

but now I think it can be a 1959 Tweed Gibson GA83s

https://youtu.be/06XPF5tmEcI

Franco

[Toxophilite]

I like the way they're using 8" speakers
I once found gibson amp (just the amp now cabinet) I think it was a GA 90? Anyway the original cabinet was 8  8" speakers

[Toxophilite]

Just found this. What a funky design. Don't know if it's what I'd use but pretty interesting nonetheless
http://www.amplifiers.com.au/goldentone_6_10.html


The guild 200s looks cool too

[Toxophilite]

So
I've kind of figured out what i want to do with this amp-wise


I have one stupid question
Is there any reason (besides B+ voltage which I can tweak)
That I can't use El84s/7189s with the standard AB763 circuit?
I know fender used them in the 6G9 but it seems to be a little different and I know they used voltages that were hard on the El84s


Is it mostly the b+ I need to change (maybe not so much for 7189s) ?

[SILVERGUN]

So
I've kind of figured out what i want to do with this amp-wise


I have one stupid question
Is there any reason (besides B+ voltage which I can tweak)
That I can't use El84s/7189s with the standard AB763 circuit?
I know fender used them in the 6G9 but it seems to be a little different and I know they used voltages that were hard on the El84s


Is it mostly the b+ I need to change (maybe not so much for 7189s) ?

When I think of a ZERO distortion power section for clean tones, EL84 is not the tube that comes to mind, primarily due to it's low grid drive requirement.
Also, the B+ voltage will be lower throughout the rail (as compared to using a bigger/better suited output bottle) and you won't get the type of headroom that I'd be looking for if I was designing for pristine cleans to get over a drummer.

[Ed_Chambley]

So
I've kind of figured out what i want to do with this amp-wise


I have one stupid question
Is there any reason (besides B+ voltage which I can tweak)
That I can't use El84s/7189s with the standard AB763 circuit?
I know fender used them in the 6G9 but it seems to be a little different and I know they used voltages that were hard on the El84s


Is it mostly the b+ I need to change (maybe not so much for 7189s) ?

When I think of a ZERO distortion power section for clean tones, EL84 is not the tube that comes to mind, primarily due to it's low grid drive requirement.
Also, the B+ voltage will be lower throughout the rail (as compared to using a bigger/better suited output bottle) and you won't get the type of headroom that I'd be looking for if I was designing for pristine cleans to get over a drummer.

Could if you used 16 EL84's, 8 each in push pull and use the Output Trans from a Twin.


Need 2 OT's, but could save a little on the power supply.  Chassis punching would suck and oyu may lack some bottom end, but you can do it.  You can also put windshield wipers on a Jackrabbit if you try hard enough.  Why would you, hell I don't know but it is DIY and as PRR says a lot in DIY we sometimes waste a little time and money.  What the hell, right.

[Toxophilite]

Good Grief!
Thanks for that useful response Ed!
You obviously gave it much thought and care
I appreciate your help even though you were trying to disguise it as mockery
I understand that you are unable to express your loving and generous nature any other way.
It's okay. Keep trying!I believe in you!


All the amps I've built have worked and I've used them live successfully. They've all cost less than $2-300 including quality speakers..EVERYTHING! I've built every part of them that it was possible for me to build.
I don't believe there are TOO many rules, just past successes to build upon and or try altering.
For Fun. Not 'DIY' or whatever happens to be the current catch phrase with the young people.

I've experimented in design for fun and it's mostly worked and most importantly I've always learned something and enjoyed the process.
Which would seem to be the point
I've made my own chassis, found good quality vintage transformers for cheap and haven't wasted alot of $$ on anything , quite the contrary
I've been using a 2 amps stereo setup live for the past 25 years as a pro musician. It's not new to me, sounds beautiful and people tell me this regularly.
My one band is lighter jazzy/latin and my drummer plays with dynamics isn't a pounder (though I have another band with one of those.)
I'm having fun designing something for myself

With 7189s you can get 10 watts a pop out of them
Together in pushpulll you can achieve 20 watts hmmm
Pretty close to 6V6s and as soon as you have 2 amplifiers doing the same thing you get a bigger fuller and somewhat louder sound
Which is what my setup would be doing if the schematic above was perused.
Also speaker configurations can make big differences in size and quantity of sound

Anyway my question wasn't:

Would I want to do this?
Or
'Am I an idiot who is wasting money for trying for no &^%&^ idea?'
Or 'can I put windshield wipers on a Jack Rabbit?'...yuk yuk yuk

my question was "Is this possible"
Obviously it is so thanks!

[jjasilli]

Ed & Silvergun are making valid points. The benchmark standard for endless clean tone is the BF Twin.  A Super is right there with it.  A UL Super is for a smaller niche of aficionado's, but is right up there for endless clean tone.


A small bottle power amp will simply not have endless clean tone (unless it has a lot of bottles, as Ed says).  It might have enough clean tone in the right situations. 


Yes you can substitute EL84's for 6V6's.  Operationally, they're close.  But small bottle power tube substitutions get you nowhere in terms of clean headroom.

[shooter]

"Is this possible" Obviously it is

My best HiFi build was an SE, Quad of EL84's, even my audio buddies begrudgingly said I did "ok"!
could it overcome a loud drummer, no clue, clean, absolutely, but even with a Quad, she still only came it around 20ish watts.  84's can do clean, but when I do it again, it'll be with 1 KT88 running hot into really big iron.

[Ed_Chambley]

Good Grief!
Thanks for that useful response Ed!
You obviously gave it much thought and care
I appreciate your help even though you were trying to disguise it as mockery
I understand that you are unable to express your loving and generous nature any other way.
It's okay. Keep trying!I believe in you!

I was certainly serious and EL84's running at lower voltages will last a long time.  Really, this time I was not being a wise.


You mention of El84's generally turns ones mind to 2 in push pull.  You know, the 18 watters and AC15 sort of Blues Junior Martchless lightining thing.  If you compare the life of 4, 6L6GC running hard in a twin, I can attest new production tubes will start breaking down in about a year.  Twins around me are cheap, don't know about where you are.  For instance, a 2, EV loaded Twin, 1976 Silverface can be had at a local shop in Atlanta for $600 and the EV's would bring more than that so after a week of ebay or Reverb, you have a twin chassis and iron plus cash.


The reason I mentioned so many tubes is if these are run at lower voltages, say very close to 300vdc, they will last.  For instance, I have a small HiFi using 4 I made fro an old Zenith.  It was from 1961.  I just recapped it and used the same tubes and they worked great and still are.  It is a bookshelf stereo.  If you want a UL and clean amp, you can certainly use these tubes and they will provide a character you may not have.


My thoughts is a stereo amp is basically just 2 amps.  There is a real cool thing ad AC30 does which is similar to the way a KT88's do.  The sensitivity of the screen will make them overdrive, but you may be surprised with the actual tone.  It is more of a sustain than distortion, and it is pushing 4 pretty hard.  I saw Brian May using 11 AC30 and unless he has effects, he could be loud and clean.


So I have wondered ever since I buit my AC15 and how great it sounds with the shimmering clean tone coming from the EF86 and El84's, even with a Les Paul.  But thinking of your preference of tone, you may prefer more headroom than an AC30.  I am almost certain since you really like your UL amp.  I have 2 UL guitar amps myself and really like them.


So the next step in my mind was to double the tubes to 4 per side which is 16 in stereo.  I know it may sound extreme, but compared to a Tube Organ, this is nothing.  They are basically the same size as a 12AX7 and Fender used 3.5 of these for a Tremolo.  The only issue is the Output Trans from a 1976 would not be UL.  From 77 to 82 the sliverface did come with a 135 Watt UL Transformer.  The Transformer is a 013691 and is 2K load to 8 ohm.  The hammond replacement is the 1750WR.  Should be a good match and have plenty of available frequency response being a 135 watt OT.


I'll bet since there is not a lot of love for Fender UL amps, you could get one cheaper.


Right now I have an Top Boost AC30 I just finished recapping and tubes.  I have never really played one a lot since I prefer the older ef86 version, but I must say it is a tad light on bass and the Celestion Blues are not bass firm either, but I did try it with a pair of Altec 417 and made a huge diffference.  Only observation is even the AC30 can be pushed into distortion, but the Altec speakers made this not as obivous.  Actually it seemed like I had added a nice DBX Compressor, so I was gettin clean sustain which I really love.