• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Looking to build....

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Eli Duttman

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Joined 2004
If (as Tom indicated) the Klipsch RB-81s are 97 dB. efficient, Paul Joppa's 102 dB. rule tells us that (SIC) 4 WPC are enough. Deep Class "A" triode wired EL34s will affordably yield more than 4 WPC.

As a preamp (presumably with gain) will be available, the 12AT7 based "El Cheapo" splitter/driver is quite adequate. A 12AT7 and 2X EL34s comprise the signal tube complement of each channel (6 tubes total). Invest in decent O/P "iron". The Edcor model CXPP60-8-4.2K is the lowest grade item I'd entertain.
 
AuroraB

AuroraB

Member
Joined 2001
Hi...
If we're talking 30-60, I'm seriously interested,too!
Problem is, which of the many(?) alternatives out there are the "better" one?
( Whithout going to the very extremes, that is....)

EDIT:
Maybe I should add, - since I live and work in one of the "far away" corners of this world, I haven't heard any of the possible alternatives, and most probably won't either....
Only my brothers Cary's and a McIntosh....oh- and a Lumley....
 
E

Eli Duttman

Member
Joined 2004
AuroraB said:
Hi...
If we're talking 30-60, I'm seriously interested,too!
Problem is, which of the many(?) alternatives out there are the "better" one?
( Whithout going to the very extremes, that is....)

EDIT:
Maybe I should add, - since I live and work in one of the "far away" corners of this world, I haven't heard any of the possible alternatives, and most probably won't either....
Only my brothers Cary's and a McIntosh....oh- and a Lumley....
Click to expand...


Dude,

You're not the only Norwegian member here. The other nordic countries are also represented.

Ultra-linear mode PP AB1 EL34s are good for more than 30 WPC. Do you already own a preamp with gain? If so, the small signal circuitry I proposed to this thread's originator will work for you too. OTOH, if you are starting from the ground up, a Mullard style circuit employing 1/2 a 12AT7/ECC81, an ECC99, and 2X EL34s in each channel gives you the makings of a very nice "integrated" amp.

Sowter (England) winds nice O/P trafos. A merger of the characteristics of their model U065 and their model U082 is what the situation requires. You want the more massive "P" core and a 4 KOhm end to end primary impedance. Don't forget the UL taps.

Lundahl (Sweden) also winds good "iron". However, the 36% UL tap on their most suitable model does not sit well with me.
 
AuroraB

AuroraB

Member
Joined 2001
Eli Duttman said:

Dude,

You're not the only Norwegian member here. The other nordic countries are also represented.
Click to expand...

I'm very much aware of that fact......only thing is, - thre seems to be roughly 1000 miles between them and me.......;)

And-I'm quite familiar with Lundahl irons......I have spoken to the man himself on a couple of occations. European iron is not my problem, I think. There are several german makers, too.
My problem ( if considered a problem) is that I have little or no time to design or tinker too much..... I just want to build something reasonably good, and being the old geezer ( 55..?) I am, I do like to build it myself. That's most certainly a large part of the fun........
 
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Eli Duttman

Member
Joined 2004
AuroraB said:


I'm very much aware of that fact......only thing is, - thre seems to be roughly 1000 miles between them and me.......;)

And-I'm quite familiar with Lundahl irons......I have spoken to the man himself on a couple of occations. European iron is not my problem, I think. There are several german makers, too.
My problem ( if considered a problem) is that I have little or no time to design or tinker too much..... I just want to build something reasonably good, and being the old geezer ( 55..?) I am, I do like to build it myself. That's most certainly a large part of the fun........
Click to expand...

55, geezer? You're a "baby". :D I wish my carcass was that young.

Are you based up near Narvik or Hammerfest?

You spend the money to buy parts. There's plenty of help here on the design front. ;)
 
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Eli Duttman

Member
Joined 2004
audiowize said:
I think you are a stellar candidate for a 300B amp. For a more affordable project, triode strap a 6V6/EL84 instead. Eli's amp is also a good candidate, but with speakers that efficient, a single ended amp would be pleasant.
Click to expand...


Klipsch speakers are efficient. However, they seem to do poorly with the modest damping factors available with no NFB SET amps. I suggested Class "A" triode wired PP EL34s, as both sufficient power and adequate damping would be available. A LITTLE loop NFB provides the necessary voice coil control.
 
A

audiowize

Member
Joined 2005
Eli Duttman said:



Klipsch speakers are efficient. However, they seem to do poorly with the modest damping factors available with no NFB SET amps. I suggested Class "A" triode wired PP EL34s, as both sufficient power and adequate damping would be available. A LITTLE loop NFB provides the necessary voice coil control.
Click to expand...


I completely agree with you on that. I get a little spoiled with my Klipsch CF-4's. Their neo 12" woofs seem to sound best with a nice loose SET amp, but this is generally not the case. Of course, you could always implement the feedback on a single ended amp, but saying that might get me booted out of here!
 
AuroraB

AuroraB

Member
Joined 2001
Eli Duttman said:


Are you based up near Narvik or Hammerfest?
Click to expand...

What ? An american(?) with local Norgie knowledege??? :D

Quite right---I'm about 200 km straight line NW of Narvik - on the tip of an island in the Norse Sea ( 69.3 N-16.01 E)........and I quite like it here !
Lots of fresh air and natures own forces ( and trout ponds and lakes!)



As for the amp question... 300Bs and the likes are not for me , - not yet at least. My current speakers are around 89-90......
I play mostly classical, but the odd Cream or Zappa and the likes creeps up in between....;)
 
E

Eli Duttman

Member
Joined 2004
billbeau said:
Can anyone suggest a nice SE amp some NFB? Schematic with parts list.

50-60 watts. I would like to build a set of monoblocs. I am building a tube pre using two 12AX7s and one 12AU7.
Click to expand...


Dude,

You may not realize it, but you are JESTING. :cannotbe: SE amps must be Class "A". The max theoretical efficiency for Class "A" is 50%. In the real world, less than 50% is what you get. For example, 20% efficiency is common, when triodes are employed.

If you want "55" WPC, use UL mode PP KT88s. :att'n:
 
AuroraB

AuroraB

Member
Joined 2001
Richard Ellis

Richard Ellis

Member
Joined 2006
A little bit back on topic...Getting 50 Watts or so in SE can be done by using transmitter tubes of various types & there is a bit of a fringe group that likens to this genre.
My idea was to build an SE with 45 WPC using the 813 tube. Rather a big tube using very high voltages. I've put it all together on paper but found out an output transformer would run appx. $750 each...
That has slowed down my progress.
High power SE designs are doable but way out there in practicality.
______________________________________Rick..........
 

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AuroraB

AuroraB

Member
Joined 2001
40-50W SE will require some rather special and costly transformers, I think.. not what I want to do at this stage.

Even if the thread starter asked for 100Ws, I 'm still interested in what difference there are in different topologies.
I've asked this question before, but really didn't get any conclusive answers. I realize that this is apples and pears to some extent, but i was hoping for some pointers, at least....

These are the links I posted a couple of years ago:

http://www.vacuumstate.com/schematics/pp-1c_s.gif

http://www.pmillett.com/push-pull_k..._driver_pcb.htm

http://www.lundahl.se/claus_b.html

http://home.tele2.fr/boutailh-tan/ampli/ampli.htm

http://www.jogis-roehrenbude.de/Les...auanleitung.htm

Somehow I am leaning towards the last one ( which also have a appx 100w version). The output transformers seems to be of good quality, and are avaialble here:
http://www.roehrentechnik.de/html/gegentakt.html

Unfortunately, tha last ones are only available in german, but schematics are usually language independant,
( aren't they....? :cool: )
 
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