set el84 tube amp

[sarrisk]

Hi all ! I made this ( weak ) but really interesting amp few years ago (based on decware SE84) .
Its only 1.8 watt and now with my BL Horn Speakers i discover what a SET low power design can do !

just want to share it because it's simple construction.

An externally hosted image should be here but it was not working when we last tested it.

costas

 

[Bas Horneman]

Congratulations! How do you like it compared with your previous amplifiers?

 

[sarrisk]

Thanks !
This baby sounds really sweet (more sweet than my 807s, but lacks in dynamics) .
Its because of the el84 which is great tube ! . Obviously its 1,8 watt /channel its not a tremendous power but you can really enjoy solos , voices and ballads.

costas

 

[azazello]

Congratulations! Is EL84 in triod mode?

 

[Akita]

Nice wood chasis, I like that

 

[sarrisk]

Congratulations! Is EL84 in triod mode?

Nice wood chasis, I like that

Thanks !
El84 is in triod mode . Here is the schematic

costas

 

[Akita]

Interesting, What is the bias voltage of your 6n1p? Do it sound different by switch it to others bias point?

 

[sarrisk]

Interesting, What is the bias voltage of your 6n1p? Do it sound different by switch it to others bias point?

I never connected the 1,5k resistor in the bias circuit. If i remember well when checked once when first tested the amp sounds no difference. So 2 years before i modified the driving stage with this :

RK=430 ohm for Vp=250 volt

it matching better now.

regards
costas

 

[sarrisk]

personally i prefer 6922 instead of 6N1P . In my ears sounds more sweet .

costas

 

[Zmeika]

Hi ,
what kind of 6922 do you prefer?

regards Zmeika

 

[sarrisk]

Hi ,
what kind of 6922 do you prefer?

regards Zmeika

I prefer siemens and philips. Now I have a Chelmer valve ( CVC) - not very good - But i m searching to find Amperex that i heard sounds more better.

costas

 

[Akita]

How you ground your Amp when using wood chasis. I try to build one using wood chasis this week end, but It have humming when i turn it on. Any good advice?

 

[athos56]

I usually do is put the safety ground from the earth pin of the IEC socket near the plug. Run a bus ground from the first power supply cap connecting each stage in order and then ground near the input jacks. The sole ground connection (besides the safety ground) would be at the inputs, connected to the top metal plate. The safety ground is not connected to the other ground by anything other than the chassis.

On this topic I was thinking for an all wood chassis I would use a thick copper pipe as the ground running along the chassis. The same bus arrangement as above but with the safety and amp ground going to the pipe.

The other option I looked at was for a wood chassis with metal plates for the front and back, on which to mount the inputs/outputs and controls. Same bus arrangement but with the front and back plates tied together for a path to ground.

I think your first task would be to figure out if its a ground loop or some other problem. Is the hum low or high, loud or soft? Plus there's lots of info online about grounding. All of it different....

 

[Akita]

It is just a low and soft hum.

 

[sarrisk]

In my project there is an aluminum plate above and all parts are mounted on the aluminum plate. I have only one point (near the power supply capacitor ) as a central ground point. (star ground wired) This point connected to the ground pin of the AC socket.

You can also use an AC socket with RFI filter.

regards
costas

 

[Akita]

Yesterday, I assemble the right channel, It is just quiet. no hum at all. I try to switch the el84 tube. The hum remain the same at the left channel. I then replace the driver tube. It's same. I may need to check the solder join tonight.