• 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.

20 Watt SE. I had found it.

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Jump to Latest
H

Hojvaelde

Member
Joined 2005
Hello

As You all know am I looking for a 25 Watts SE amplifier.

After help from You here at the forum, I had decided to build 4 pcs clones of Goliath from Triode Dick. 2 to my friend and 2 to me.

I can also see the new Hammond 1638SEA OPT fit to the 211 tube.

Does any had build a Goliath clone? Sound?

I have a few problems and the first is where can I buy D3a tubes? :confused:

Regards

Benny
 
Miniwatt

Miniwatt

Member
Joined 2004
Hey, that's great!! I'm going to build them too -once my turntable and pre-amplifier are ready:rolleyes: )

Do you understand Dutch? If not, there's a firm in Holland that quite closely cooperates with Triode Dick, they have complete transformer sets for this amp: www.ae-europe.com. They also have silver output transformers for this project (€€€€€€€€). Without them, power xformers and chokes are about € 300 I recall..

I'm not so worried about finding those d3A's, I'm more concerned with those EY500A rectifiers..

Keep us posted about your project, I'm very curious about your experiences!

Good luck!

P.S. 211's are great!!:cool:
 
S

schiller

Member
Joined 2005
I don't want to discourage you, but this amp cannot produce more than 12 watt (with 1000v at the plate). The only way to get such power from a 211 at plate voltages around this, is driving the grid in the positive region, supplying grid current.

The circuit you pointed uses a coupling capacitor, which will rectify your signal and create horrible distortion. You need a direct coupled cathode follower or an interstage transormer to provide the needed current.

By the way: One 5687 cathode follower with 8mA cannot drive the 211 in the positive region, despite the "ongaku" shematics that you can find in the net.
You need at least 15mA anode current for the driver (e.g 2 sections 5687 in parallel). I don't believe that the original ongaku has such a big mistake, this simpy cdoesn't work.

Greetings
Konstantinos
 
S

schiller

Member
Joined 2005
This is the well known shematic with the 5687 cathode follower, which, i repeat, doesn't work properly, unless you parallel 2 systems of the tube. Bei +20v at the grid the 211 draws 8mA current, which is the idle current of the 5687 follower. You need at least twice that value, otherwise the distortion near full power (in this case above 15w) will be severe.

I firmly believe that the original ongaku does use 2 sections 5687 in parallel cathode follower as driver.

According to the datasheet, you can get about 20w from an 211 in A1, biasing it at 100% plate dissipation (1200v/ 60mA). I wouldn't do it, it shortens tube life unnecesarily.

I think you are doing well, asking in the forum, not all shematics on the web are correct. A lot better is, by such elementary things (tube operatin in class A), if you can judge for yourself.

Good luck with your project
Konstantinos
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Top Bottom