Which Tube amplifier should I build first?

[lng]

Hi all, I am thinking to build a tube amplifier. I am comfortable in the electronic works, but not in the tube world. I also dont want to spend to much money for the first tube amplifier. Could you suggest some schematics which you would recommend for me. What I am looking for, nice sound, cheap tubes and transformers.

Thanks!

 

[ballpencil]

Hybrid or full tube?
Low or high voltage? I'd say below 100v is considered low voltage.
What is the power required --> speaker sensitivity, room size? Desktop amp?

These are the questions you need to answer first before we can suggest you anything.

 

[lng]

Hi, High voltage would not be a problem. Speaker sensitivty about 88-90 dB, room size about 20 sqm. I would build a full tube amp.

Thanks!

 

[ballpencil]

With such low speaker sensitivity, a typical single-ended amplifier can be crossed off the list, unless you're comfortable working with over 700v and build a single ended transmitter tube such as 813.

I would suggest a push-pull amp with something above 15W. Those that come to mind are:
- Pete Millet's Engineer's amplifier
- Baby Huey EL84
You can do a google search for these amps.

Others will surely have other suggestions.

 

[artosalo]

I guess you can easily find soviet tubes from Hungary.
Therefore I recommend a simple SE-amplifier with one 6N9S (6SL7) as voltage amplifier and two TV sweep tubes 6P41S or 6P31S. These two work identically in the below circuits.
The output transformer can be Indel TGL 20/001 or TGL 5/001.
You will get some 4...5 watts with the UL-connected version, which is absolutely sufficient power for normal home listening.
The triode connected version gives some 3 watts.

TGL 20/001 INDEL - Transformer: speaker | TME - Electronic components

TGL 5/001 INDEL - Transformer: speaker | TME - Electronic components

 

[lng]

Baby Huey EL84 looks interesting, the only thing what i dont like is the transistors in the bias line, and the diodes in the power supply. I wanna build a full tube amplifier. And I also dont know how much would cost the transformers.

 

[ballpencil]

So.. totally sand free then? Check out Mullard 5-10 or 5-20.

 

[lng]

Yeah, maybe in the power supply ok, but in the amplifier not.

What do you think about this one?

Dynaco Dynakit Stereo 35 (ST35) Tube Amplifier Schematic and Manual

Who is the best quality/price transfomer manufacturer in th EU. I checked the Hammond trafos but they are quite expensive (100€/pc).

Thanks

 

[ballpencil]

Yes Dynaco ST35 is also a good amp. You can see it is not too different from Mullard 5-10.

Can't recommend any transformer maker in EU. Edcor is cheap and good.. or maybe search Ebay for James Audio Output Transformer. Many are satisfied by Edcor or James Audio.

 

[rayma]

What do you think about this one?
Dynaco Dynakit Stereo 35 (ST35) Tube Amplifier Schematic and Manual

This is very good for mid/high end frequencies. You can buy all the parts to duplicate the original, including pcbs if you want.
ST-35 KIT (120 VAC)

 

[hooman]

hi
807 se amp is one of best hifi amp in diy project.

 

[Eli Duttman]

I disagree with the assessment that a few watts will do. Paul Joppa has provided us with a useful rule of thumb, which states an amp/speaker combo should be capable of 102 dB. SPL peaks at a 1 M. distance in an "average" sized listening space. Applying Joppa's Rule to that 88 dB. figure suggests that upwards of 30 WPC is appropriate.

Before the OP spends a considerable amount of money only to be disappointed, he should provide additional info. about the speakers. There are several reasons for derating speakers that are to be mated with tubed power amplification. What is the nominal impedance of the speakers? What is the exact sensitivity specification of the speakers? Do the speakers have significant dips in the impedance curve?

BTW, high PIV Schottky diodes are every bit as quiet as vacuum rectifiers. Therefore, I see no good reason for employing vacuum rectification in a new power amp build.

 

[artosalo]

Joppa's rule is one sort of opinion.
That's my opinion.

 

[famousmockingbird]

Single ended is probably out of the question due to the sensitivity of your speakers, you can get powerful single ended amplifiers but the iron is really expensive.

I recommend the Mullard 5-20, no silicon in the amp and it's easy to build with good performance. Don't let the 20 watt rating fool you, it puts out more power than that, the 20 watt rating is just so they can boast a low THD% spec.

 

[sargon]

Transcendent Audio

 

[lng]

Thanks,

I think that I will go for a EL34 PP version it is about 15 W and it is more than enough for me, the tubes are quite cheap, and easy to find in the EU, and maybe I can find some cheaper trafos.