Stereo tube poweramp preliminary question

[joesatch]

These things have gotten ridiculously expensive so i may build one. I have seen the one posted here but i will build a 6L6 version. so 4 6L6 total. .  Does the PT need to be different than one used on a standard single channel amp?  I know it needs 2 OT. 

[sluckey]

Does the PT need to be different than one used on a standard single channel amp?

yes

[shooter]

any tranny spec'd for a Marshall 100 should work just fine


or,


go by weight, >10lbs for OT, >8lbs for PT, >8lbs for choke 

[joesatch]

so i would go with a PT that normally would power (4) 6L6?  Like a Twin PT along with 2 Vibrolux OT's?

[shooter]

the PA section is typically wired as 2 sets of parallel tubes in PP configuration, so 1 BIG OT


to early to hunt up the OT I used, it was spec'd for a 4 tube Marshall, I used it with 2 EL34's.


knowing your target VDC, current, n impedance for the PA are good starting points for OT web browsing.

[joesatch]

the PA section is typically wired as 2 sets of parallel tubes in PP configuration, so 1 BIG OT


to early to hunt up the OT I used, it was spec'd for a 4 tube Marshall, I used it with 2 EL34's.


knowing your target VDC, current, n impedance for the PA are good starting points for OT web browsing.

how do you get a stereo signal with one OT?

[Williamblake]

It is called mono-block and welcome to hifi-world. I ditched the idea on building a tube amplifier for now although it seemed tempting. More chances to reinvent the wheel badly than in guitar amplifiers. Are you sure, you really need 6L6s in push pull? Take a look at this http://www.tube-classics.de/TC/GermanTubeHifi/Integamps/RIM%20Maestro/RIM-Maestro.htm

[SILVERGUN]

Here's another something to look at. I don't think anyone would argue that the Mesa power amps aren't some of the best.
When you look at this schematic keep in mind that the power supply page is singular but the power amp page is for one individual channel, so you would be building two for stereo.
Boogie_290.pdf (el34world.com)

[shooter]

 
I missed stereo in the title!


as noted by others, mono blocks are kinda handy


I did my 1st AND ONLY stereo tube amp, weighed 56lbs, lots of annoying bugs, hums n hisses
after that it's been mono blocks, or even better, cloths pin the nose n build SS amps from handy kits

[joesatch]

i'm going to get a twin PT and a couple OT's  from a 40W deluxe.  We'll see how it goes. (4) 6L6 and 40 watts per side @ 8 ohms.

[66Strat]

Here's a link that may interest you. The Quad II caught my eye.
https://keith-snook.info/

Here's a link to DIY Audio. There are lots of projects there that may interest you.
https://www.diyaudio.com/community/forums/-/list

Here's a link to the Mullard 5-10 schematic. Not 6L6, but an interesting amp none the less.
http://www.r-type.org/articles/art003bca.jpg

Here's a link to an old Acrosound transformer catalog that contains several hifi circuits.
https://worldradiohistory.com/BOOKSHELF-ARH/Technology-General/Acrosound-Output-Transformers-1955.pdf

[joesatch]

i should preface this by saying this amp is for my rack guitar rig. not for a hi-fi audio system. I cannot see myself dropping $1k + for a poweramp when i can build one for $300 in parts

[thetragichero]

i suppose it depends on how much you value your time at: https://reverb.com/item/51009660-peavey-classic-60-60-stereo-power-amp-classic-60-60
i had the 120w mono version in my bass rig for the better part of a decade

[joesatch]

that thing's on it's last leg

[SILVERGUN]

Here's another something to look at. I don't think anyone would argue that the Mesa power amps aren't some of the best.
When you look at this schematic keep in mind that the power supply page is singular but the power amp page is for one individual channel, so you would be building two for stereo.
Boogie_290.pdf (el34world.com)

oops, I went a little overboard on the power.
Yours would be more like this: (same principal on the schematic)
Boogie_5050.pdf (el34world.com)

[joesatch]

Here's another something to look at. I don't think anyone would argue that the Mesa power amps aren't some of the best.
When you look at this schematic keep in mind that the power supply page is singular but the power amp page is for one individual channel, so you would be building two for stereo.
Boogie_290.pdf (el34world.com)

oops, I went a little overboard on the power.
Yours would be more like this: (same principal on the schematic)
Boogie_5050.pdf (el34world.com)

that looks promising. i'd love to get my hands on a clearer schematic

[shooter]

here's the only stereo guitar amp I've ever repaired, little underpowered for your spec's but it's fun hurting the brain following the circuit 
If you want more mental abuse, look at the original Ampeg schematic 


Ampeg_echotwin.gif (1024×480) (el34world.com)

[thetragichero]

that thing's on it's last leg

you lookin to play geetar through it or put it up in a museum? (also note: it's a peavey so that thing will outlive you, me, and any progeny we may have)
there are others for not much more, or local pickup for 300 if you happen to be in California (although that one is listed as "classic 60/60 preamp" for some unknown reason)

not saying don't build a power amp for funsies but if you're just looking for a stereo tube power amp there are options (and the mosvalve stuff may be solid state but sounds FANTASTIC)

[DummyLoad]

The Peavey 60/60 seems to be the simplest of the lot presented. You'd probably want to ignore the Balanced Input circuitry and build the Twin's power supply. I'd build with 2 bias power supplies, one for each channel.
Another decent stereo 50WPC amp is the Carvin TS100, it's a dual 50W amp bridgeable for mono use like the Peavey 60/60, Peavey 120/120 and Mesa 290. The Carvin and Mesa have a switch selectable Bias supply that allow you to use either EL34 or 6L6GC output tubes.

Carvin TS100 schema attached - Link below to the Peavey 60/60 as the file is >1024KB.

https://www.dropbox.com/s/oy1mqqj9etblqs9/Classic%2060-60.pdf?dl=0

--Pete

[joesatch]

Thanks my friend. I would much rather build this thing myself than buy a 20 year old unit and not be able to sleep at night. I have a good deal of parts on hand as well. Thanks for the schematic

[joesatch]

After some investigation,  you don't need (2) PT . This Rivera uses one big PT and double everything else.

[SILVERGUN]

This is what my MESA Simul 395 looks like with the lid off. This thing weighs too much. I don't know why I'm still hanging on to it.

[shooter]

This thing weighs too much. I don't know why I'm still hanging on to it.

well set it down then 

[SILVERGUN]

This thing weighs too much. I don't know why I'm still hanging on to it.

well set it down then 

Hey, THANKS shoo....I never thought of that 


And, just for the record:
I spent a lot of time in my bar/club band career with less than optimum TONE because I was never able to get this thing off of 2-3 on the volume control. I couldn't understand how I had spent ALL of this money but all the Marshall 50W guys sounded better than me.
Some of the magic comes from being able to drive the output tubes. But, if I had driven these 8 output tubes in the clubs I was playing I would never play there again. There were places where soundmen wanted to punch me in the face, and I know the overall sound of the band suffered because I was a dumb kid.
The moral of the story is that you only need the amount of output tubes that you can safely drive within the constraints of where you are playing. Otherwise, your TONE will suffer as you decrease the grid signal.
The greatest sound I ever got was an OUTDOOR show where the PA was able to keep up with me. I got those volume controls up to 6 and ran 2 - 4x12 cabs.
Now, I've got one KT88 and 1x12 and I'm always pushin it

[shaun]

I've built two stereo amplifiers using single PTs - I did the math on current draw and heater draw and bought the appropriate PTs. But even when supposedly within spec, the PTs got very hot, so the next stereo build I am about to do, I'm still using a single PT, but it is way overspec'd, like, by about 40%. Hopefully, it will run cooler.

[joesatch]

I've decided to use two PT. This is what i have so far.  Will be 40w per side. (4) 6L6 with each channel having a volume, depth, and presence. Is there a way to accomplish this with 1 preamp tube per channel or do i need 2 (one for Pre and one for PI) ?

[SILVERGUN]

I've decided to use two PT. This is what i have so far.  Will be 40w per side. (4) 6L6 with each channel having a volume, depth, and presence. Is there a way to accomplish this with 1 preamp tube per channel or do i need 2 (one for Pre and one for PI) ?

When in doubt I always just defer to the experts.
Do it like Mesa did it. There's a reason they are Mesa.

[acheld]

You're going to need a an engine hoist to truck that thing around.

But, yeah, you need a tube for the PI. 

[shooter]

or do i need 2

If this was an audio build you could get by with 1, since it's guitar with TS you'll need 2
IF you don't use a TS, AND you use a Cathodyne PI, AND the guitars had hot pickups, you might squeak by with 1


don't have my notes handy, but to drive 6L6 you need a pretty good-sized signal feeding them