Which Circuit?

[stanbp64]

Ok, I'm itching to build another SE amp. I am trying to decide between another SE magnavox (modified circuit) amp or the Rh84. Has anyone done side by side comparisons of the se maggies and the Rh84. Which sounds better? Thanks. Stan

 

[PabloL]

I would

Make the Rh84, it gets good reviews

 

[jaymanaa]

Are you starting with an old amp, or from scratch? Are you locked solid with any certain output tube? Do you already have the OPTs?:scratch2:

 

[Kegger]

Yah what Jay said!!

 

[stanbp64]

Are you starting with an old amp, or from scratch? Are you locked solid with any certain output tube? Do you already have the OPTs?:scratch2:

Will be starting from scratch. Probably have to stick with either el84's. 6gk6 ( i think these do sound alittle better than 84's), or 6v6. Can't afford the high priced triodes and such. I've got some edcor se opts, some Magnavox opt's i believe came from a 8600, and some other used opt's i can't remember offhand where they came from. Looking for something with a low parts count that will sound very good. Thinking about solid state rectification for economic and current requirement reasons. ( the pt's i have have lowish current ratings) May even go with monoblock config. as i have two pt's that would work well for that. (not enough juice to use them in a stereo amp)

 

[Kegger]

My first thought from what you have and what I would build is using the Edcor outputs
and run 6V6 in SE UL, with maybe say a 12AT7 or 6BK7 as a driver and 300v supply, if
your power tranny's have the heater current an whatnot there is a lot of output tubes
that could plop in where the 6V6 is, way to many to list that have the same pinout.

----------------

EDIT: found an older post of mine..
(amp circuit here) (6SL7 would take a different operating point)
Here is a link to a post I had where the OP built the amp, same thing as above but it's
using a cheap 6BK7, 6BQ7, 6BZ7 for the driver, the above or any of these would work.
http://www.audiokarma.org/forums/showpost.php?p=2608400&postcount=25

 

[jaymanaa]

My first thought from what you have and what I would build is using the Edcor outputs
and run 6V6 in SE UL, with maybe say a 12AT7 or 6BK7 as a driver and 300v supply, if
your power tranny's have the heater current an whatnot there is a lot of output tubes
that could plop in where the 6V6 is, way to many to list that have the same pinout.

----------------

EDIT: found an older post of mine..
(amp circuit here) (6SL7 would take a different operating point)
Here is a link to a post I had where the OP built the amp, same thing as above but it's
using a cheap 6BK7, 6BQ7, 6BZ7 for the driver, the above or any of these would work.
http://www.audiokarma.org/forums/showpost.php?p=2608400&postcount=25

You are the UL man Keg.:yes: What OPTs are those for the 6V6UL SET?

 

[Kegger]

Yes I have to admit I'm fond of a good UL setup..

The Edcor 5K 8ohm(or whatever speaker impedance you run) have the UL taps and I've
run quite a few very simple scheems like this with very satisfying results, it is the same
basic circuit as the 6LU8 amp, you also heard the electrocution device at the fest with
those EL500, 6GB5 tubes..
(If you need/want more drive, replace the drivers cathode resistor with an LED)

 

[PabloL]

Edcor

Yes I have to admit I'm fond of a good UL setup..

The Edcor 5K 8ohm(or whatever speaker impedance you run) have the UL taps and I've
run quite a few very simple scheems like this with very satisfying results, it is the same
basic circuit as the 6LU8 amp, you also heard the electrocution device at the fest with
those EL500, 6GB5 tubes..
(If you need/want more drive, replace the drivers cathode resistor with an LED)

I'm gathering parts for both a 6v6 PP and 6v6 Se, the great thing about edcor is that 2 each of the 5k GXSE and 8k GXPP run about 120-130 bucks, or aprox $30 each. Cheap enough to get your feet wet. If you cross over to a SUB and don't mind losing the earbleeding 18 to 20khz (I can't even hear that high), then these ops are great for the money. With these opts and tubes you can try any number of circuits.

 

[bricktop]

I did this with dirt cheap tubes and Edcor output iron. The power supply doesn't really need to be that complicated, but regulation certainly adds a bit of a cool factor and improves performance a bit.

 

[stanbp64]

Thanks for the replies! The power trannies that I have on hand are a 300-0-300 90ma ( was thinking that with sand rectification i could squeeze a stereo amp outta this), (2) 250-0-250 pt's -- don't know current capacity on these but I think it is not much as they got very hot on a Maggie SE amp i built-- I was thinking monoblocks for these, and a 350-0-350 pt which came off a pp mono amp. I want to use these before I spend more for power trannies.....the wife has been fussing about the money i spend on this hobby!

 

[jvdk01]

My first thought from what you have and what I would build is using the Edcor outputs
and run 6V6 in SE UL, with maybe say a 12AT7 or 6BK7 as a driver and 300v supply, if
your power tranny's have the heater current an whatnot there is a lot of output tubes
that could plop in where the 6V6 is, way to many to list that have the same pinout.

----------------

EDIT: found an older post of mine..
(amp circuit here) (6SL7 would take a different operating point)
Here is a link to a post I had where the OP built the amp, same thing as above but it's
using a cheap 6BK7, 6BQ7, 6BZ7 for the driver, the above or any of these would work.
http://www.audiokarma.org/forums/showpost.php?p=2608400&postcount=25

I am the OP Kegger is referring to. I couldn't be happier with it. I use it with my computer and some unknown drivers that fit the holes in a pair of Baby Advent cabinets I had. I think it sounds very good and can play at volumes beyond what I'm comfortable listening to with what I imagine are fairly inefficient speakers. Here is a link to the original thread if you're interestred.
http://www.audiokarma.org/forums/showthread.php?t=218792

John

 

[GordonW]

My first thought from what you have and what I would build is using the Edcor outputs
and run 6V6 in SE UL, with maybe say a 12AT7 or 6BK7 as a driver and 300v supply, if
your power tranny's have the heater current an whatnot there is a lot of output tubes
that could plop in where the 6V6 is, way to many to list that have the same pinout.

This sounds like a good idea... especially with 12AT7 driver. As some here and at diyaudio.com have found, the 12AT7 is a very "complementary" tube for 6V6s, 6L6s and such... it tends to "cancel out" some of the nonlinearities of these outputs, resulting in lower total distortion than is usually achievable with either of these tubes (the 12AT7 or 6V6) by themselves.

EDIT: After reading over Kegger's schematic there... I have to say, the 6BZ7 doesn't suck either. It's got similar plate curves to the 12AT7, in a lot of ways. The advantage of the 12AT7 would be higher gain... which would allow you to add feedback, if desired...

Regards,
Gordon.

 

[stanbp64]

I am the OP Kegger is referring to. I couldn't be happier with it. I use it with my computer and some unknown drivers that fit the holes in a pair of Baby Advent cabinets I had. I think it sounds very good and can play at volumes beyond what I'm comfortable listening to with what I imagine are fairly inefficient speakers. Here is a link to the original thread if you're interestred.
http://www.audiokarma.org/forums/showthread.php?t=218792

John

That's a great looking amp.

 

[Kegger]

Thanks for the replies! The power trannies that I have on hand are a 300-0-300 90ma ( was thinking that with sand rectification i could squeeze a stereo amp outta this), (2) 250-0-250 pt's -- don't know current capacity on these but I think it is not much as they got very hot on a Maggie SE amp i built-- I was thinking monoblocks for these, and a 350-0-350 pt which came off a pp mono amp. I want to use these before I spend more for power trannies.....the wife has been fussing about the money i spend on this hobby!

I'm with yu on the using what you have part, inspire most of my designs that way..

If you think you have something in mind, shoot it out here and we'll go from there with it.

 

[stanbp64]

I think I have decided on the SE 6v6 you posted earlier---should be able to use one of these pt's I have. I have a couple more that I pulled from something(s) but i need to test them to see what kinda voltage they produce. Is there any way to find out the current capacity on a power tranny? the 300-0-300 90ma might be stressed on that amp, I guess? Do you think it might make it with solid state rect. ? I have never used SS rect. though....


update: The 600 v pt is 150ma so i should be good to go with that. What about using 6922's in the front end? I have a few of these on hand. Any/what changes would be required to use these?

 

[stanbp64]

OK, I guess a 6922 is the same as a 6dj8 ?? and I see in a post that it can be dropped in with no changes. Gotta gather some parts now....

 

[Kegger]

Sorry Stan I've been away and a bit busy here lately..

But I don't know of a way to find current ratings on power tranny's that are not spec'd.
(I will usually go by the physical size compaired to others of known/stated ratings)
(then after building checking for eccessive heat from the tranny)

(For heaters usually measuring that voltage will tell you a lot)
(low your taxing it, high there loafing)

90ma for the stereo amp is a "bit" on the low side, a pair of say 60ma or higher for monos
would be good here, or at least say 110-120ma for a stereo amp, as close to 300v u can.

 

[Kegger]

And yep a 6DJ8 or 6922 would drop in the same spot on this 6V6 amp using the
same 6BK7 type pinout, no circuit mods needed.

(the 6922 is a beefier version of the 6DJ8, not all are marked correctly though)

But in this circuit either one is just fine..

 

[stanbp64]

Thanks Kegger, I am going to order some parts this evening for the 6V6 amp. I will probably try some monoblocks out of the smaller pt's i have later. Hope you had a great 4th!