Good choices for a first tube amp?

[pekka]

Hello!

I have some experience in building my own electronic stuff (and theoretical background as I'm an EE by training). In recent years I've been contemplating building my first tube amp. Finally I'm getting closer to realizing this plan: I'm actually thinking of buying some parts

Next week I'll be on a business trip in Japan, and I've planned to visit some of the shops in Akihabara (Tokyo). I'll try to find the output transformers for my project there. Specifically I've been eyeing James OPTs, which are sold by Hino Audio.

My only "problem" at this stage is to decide what type of amp to build. The choices I've had in my mind are:
- SE 2A3 amplifier
- PP 2A3 (6B4G) amplifier
- PP EL84

A few watts should be enough, as I will eventually use the amplifier in a biamped system with fairly sensitive mid/high units. I've found some promising schematics for all the mentioned types of amps.

I'm interested in building a good amplifier which whould serve as a worthy introduction into "tube magic". I believe that there can be significant differences between the amplifiers mentioned and therefore I'd appreciate your comments on the choices. Please a feel free to suggest other tubes / amplifiers as well! I'm also interested in some experiences from fellow travellers. Any good schematics you could recommend?

Best regards,
Pekka U.

 

[dhaen]

Hi,

I believe James transformers are not Japanese, but Malaysian or Taiwanese.
This might mean that the price in Japan is not the best deal on these.

These people stock them:
http://www.octave-electronics.com/Parts/james.shtml

Cheers,

 

[pekka]

James transformers for the project?

I believe James transformers are not Japanese, but Malaysian or Taiwanese.
This might mean that the price in Japan is not the best deal on these.

These people stock them:
http://www.octave-electronics.com/Parts/james.shtml

Thanks for the comment. I agree, James transformers are Taiwanese AFAIK. I might be able to get a good price from Octave Electronics. However, I suspect that delivery costs to Europe could become quite high. Customs would take their share as well... If I buy the transformers in Japan, I can carry them myself and save the post and packing, customs duty & VAT.

Hino Audio prices I've seen last year for some of the transformers were not too bad: roughly 80 EUR for a SE 2.5k primary 20 W OPT. I just hope they have the transformers in stock...

Regards,
Pekka U.

 

[Joel]

A non-feedback EL84 SE, or some variant, is really the best way to go for the true beginner. It's a simple topology, with very few parts, and very few connections to muck up.
As others have noted before, it will not be cheaper than a PP amp with equal performance though.

 

[Ken Chuang]

Hi Pekka,

I have no EE background. Managed to Clone the Decware SE84CS after studying it for a while.

This is a SV83/EL84 amp in Triode SE mode. I kind of like the sound. It's a fast sounding amp, I have configured it to wide band type suitable for most sorts of music. It's not the laid back sound with thick mid range types. Some liked this, those who are familiar with typical 300B/2A3 sound find it too fast.

Good about this design is the outstanding presentation of plucking guitar sound. This is usually missing from the more laid back configurations.

We are talking about the clone version. I personally have not heard of the original Decware piece.

Photos are in my photo album.

http://photos.yahoo.com/ken_chuang/

 

[SHiFTY]

My opinion is that both PP and SE can be great sounding.

PP has the advantage of more power, but you need twice as many valves, and a well designed phase inverter and bias scheme. Also a little inverse feedback is necessary. A lot more to tweak and it can get really complicated. You can get really good PP transformers cheaply which is a plus.

SE is incredibly simple, only a few components necessary; and usually sounds really nice straight off. The russian 2A3s are very hardy, you can run them at 25W or so with no problems (about 5W audio power)

If I were you I would go SET 2A3! You can always build it into a PP later on... Just leave space on your chassis and get an oversize power transformer...

 

[pekka]

Thanks, guys!

Thanks for all comments. I think I'll probably try to find a SE transformers with both 5k and 2.5k primaries. James has one in their product range. I could try EL84 first and maybe use the same transformers for 2A3 later - if I ever get the urge.

Now it's time to go to the airport...

Pekka U.

 

[Positron]

Distortion?

Hope you don't run into a distortion problem. Try to use very high efficiency speakers if you can.