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SE 6c41c/6s41s amp

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Finally completed my tri-channel amp...suitably called frontrow..rugby fans will now what I mean..if not still a meaningfull name puts you on the frontrow of a cinema/concert ;-)

Have listened for 2 evenings now and it ....well... it makes me a proud and happy man..

For details


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Thanks Shifty!

With a name like frontrow..it had to be a Kiwi to reply first! :)

I'm originally a South African, now living in Holland, hence my love of rugby...

Back to business.

Here are a couple of links..


and you can get them from KWTUBES on eBay or directly from
http://kwtubes.s5.com/ in Lithuania..From Gintaras Sakenas..great to do business with.. Great contact and speedy handling of order..only drawback (IMHO) is bidpay since there is no paypal in Lithuania yet.

But since you are a Kiwi and first to reply, I'll send you a pair if you mail me your adres...
looks pretty neat :)

the woodwork is great.

sound good??
I had a russian DHT coming a while back, but it broke in the mail :(
( a couple 807's made it though, ill have to give them a shot.. probably for guitar though).

I've got some 6159's (25v heater version of the 6146 transmitting tube). I think I will try them in AB, if I ever get the iron for it..

nice work!
Thanks Colt45

Thanks for the compliments...

What DHT did you get? that broke...I have a couple of russian GU 13 that I want to use in a future ..future project... a guitar amp is also a project that I want to do..just for fun...i don't play guitar ...but what the hell

The woodwork is pretty plain..2 boxes with a top...that has a profile routed in...but it turned out quite nice if I may say so myself..

It sounds very good...tremendous detail..nice mid's and high..bass is not super..but can be improved if I bypass the cathode..even then it is not super but that is also limited by my speakers ofcourse (mission761) but i find that that muddles up the mids a little.(cathode bypass that is) .so i've actually left it unbypassed..

...it's the best amp i've ever had/made....I still can't believe I actually built it..and it works? Hum is only audible if I put my ear to within 1meter of a speaker..It worked right "out of the box" so to speak and I had to do no debugging to get it this quiet.. it's choke input and I did not know that choke input could be so quiet..i always thought that it would be noisier...

Good luck with the 6146 project...
Hi Frank,

Thanks for the compliment on the website and amp...

What Hum????? ;-)

Last night put up in a 15uF Audyn cap as bypass..so if I understand correctly I'll have everything above around 20Hz fed back..but the treble sounded horrible that way...so I added a 0,056 russian teflon cap...voila...a lot better. Sounds pretty good and I will keep it like this for a while before I start tuning it..

diyAudio Senior Member
Joined 2002
Hi Bas,

.Hum is only audible if I put my ear to within 1meter of a speaker..It worked right "out of the box" so to speak and I had to do no debugging to get it this quiet.. it's choke input and I did not know that choke input could be so quiet..i always thought that it would be noisier...

That is what I meant .
Since I have no idea about the efficiency of the Mission 761 I was just wondering if it could still be improved upon.
If it doesn't bother you the better.

See you,:)
diyAudio Senior Member
Joined 2002

Hey Bas,

Me, I am using my Croft OTL MKIII powerhouses.
These are two monoblock designs using 10 6080 for the output,
they can take the more powerful 6336A's as well but they sound too sweet to my taste then (probably a tad too much Miller effect.
Everything is hardwired with silver solid core and all coupling caps are MIT polystyrene and tin foil.
Critical resistors are replaced with Holco H2 and a Vishay bulkfoil in the feedback loop.
A pair of 12BH7A White CF's are driving those.
Phase splitting is done with an ECF802 and the input is a trioded EF86.
All HT rails are regulated with valves (shunt reg.) but not the output stage.
They date from 1987 but still beat a lot of the competion hands down.
Very fast and the go up to 250 KHz without any problem.

Another one I use is a parallel 2A3 SE Intergrated amp I occasionally use on another set of smaller speakers for DVD and such.

diyAudio Senior Member
Joined 2002


These amps were actually part of my company's (now defunct) demo material.
At that time I wasn't all that knowledgeable so I had to learn it the hard way.
I can honnestly say those where the greatest days of my life.;)
Later the company concentrated on distributing electron tubes worldwide (98% export) and consulting.
The only hard part in designing an OTL amp is the phase splitter since the output stage is inherently unbalanced.
All the stuff I designed was always for other companies so I never got around to building much for myself.
I did design quite a few OTL amps for some private customers,all of them still use them today.
That's very gratifying I think.:)


P.S.Getting good quality parts wasn't really that hard,just ordered them by fax.What was harder to do was sourcing the parts.
Hi Frank,

It is indeed copper foil..I read an interesting article on the site of Aiken amps saying that the outer foil of a capacitor should be connected to the lower potential (earth)...providing EMI protection.

Because nobody could tell me where the outer foil was on the Audyn caps...I wrapped copper foil around it and connected that to earth.

The copper foil is by 3m and provides shielding effectiveness (far field) is in the range of 60dB to 80dB (30 MHz to 1 GHz).

Funny thing is....i don't know how much is really helps in my application...but I just did it anyway...

It is also used as electrostatic shielding between transformer windings.
diyAudio Senior Member
Joined 2002

Hello Bas,

A quote from that article:

"Proper orientation of the capacitors will make the amplifier much less susceptible to outside noise, including hum, interference from fluorescent lighting, and tendency towards oscillations or frequency-response peaks and dips due to unwanted feedback from nearby signals within the amplifier."

Assuming the Audyn caps are constucted the same way as most other axial filmcaps the earthing point should be constistently at the input,i.e. the A of Audyn.
I stress that that is where it should be,field tests will show that not all manufacturers bother.
If you would peel away the plastic foil with brandname and specs
you may have found that band.
Sometimes you can actually feel it without peeling away anything.

If you have the necessary test equipment to run the test as described by Aiken it would surely tell the tale.
Building as they describe will provide a bit of extra immunity to RF
and EMI induced garbage.
Especially true in case of your design since it's in virtual "cabrio" mode.
That copper tape is relatively expensive too,isn't it?

Give it a try if you like.

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