[JoshK]

The best tubes to start with if you're a DIY'er will be the 811, 572B or 813 pentode. I highly recommend the 813 to start with.

Umm...I don't think those are good first projects!  That is seriously lethal voltages we are talking about.  Not a great place to learn the rougher points of building amps IMNSHO.

[Ericus Rex]

Maybe he meant 'if you're new to RF tubes', not new to tubes or DIY in general...

[Niteshade]

You're right. That is what I meant.

Big RF amps that are commercially made typically have a capacitor discharge circuit and have a safety switch that immediately shorts out the B+ if the lid is opened. For audio, at least a good discharge circuit is necessary.

Maybe he meant 'if you're new to RF tubes', not new to tubes or DIY in general...

[Steve]

For those new, one of the problems that must be addressed with very high power tubes is the higher order distortions at the output. This is the result of higher distortion figures of the driver or predriver high gain stages attempting to produce the high driving signal/power necessary for the output tube's input.

Even though the HD products may be low order; when combined with the lower order harmonics of the output tube can produce higher orders. So careful design is necessary.

Another tube worth consideration is the EL156 tube. I found it does a fine job in both triode and ultra-linear applications.

Cheers.

[Niteshade]

Steve,

Do you have a good source for the EL156? It's a very interesting tube.

[baldrick]

Well NOS Telefunken EL156 tubes go for $275 each!   
I don't have any familiarity with the sonic characteristics of the EL156 but for that kind of money it would be more economical to use parallel EL34s or KT88s in Push Pull configuration.
Shuguang makes a new production version and by many accounts it is very robust, but I don't know of any dealers that sell them.
If you're into rare output tubes why not try the 8417 output tube?

[PLMONROE]

Here's impressive....the Amber Wave Audio 304TL amplifier...



And....they do sound good...

Are they ever! The last time I saw them I think the price was around $250K. They said they only had built six pair -- and as of that time (2years ago) had not yet sold even one. But they sure were impressive!


Paul

[Steve]

Steve,

Do you have a good source for the EL156? It's a very interesting tube.

I use the Chinese brand and it sounds very very good.

Steve

[Lord Soth]

Wanted to share my recent experience with the so called "best" EL34 tubes.

The bottom line is that metal base Philips holland EL34s are worth the $$$$.

I finally splurged on a NOS pair from EBay for about US$500, which is a very good price nowadays.

Before that I was happily living with a pair of Mullard Blackburn XF2s.

There is simply no contest between the Metal Base tubes and other variants such as Mullard XF2s or Amperex Brown Base Holland DD getters.

I am now getting a wider soundstage with massive 3D effect from stereo speakers.
The dynamics are also phenomenal with the faintest whispers from vocals.

1. Glorious Mids
2. Involving music
3. Bass tight and with tone
4. Improved transparency
5. Presence of "live" venues
6. Euphonic mids and highs
7. Air from classical music
.......

[mgsboedmisodpc2]

If you were to build a 304TL amplifier you could coax 700 watts RMS of audio power from a single push-pull pair of 304TL tubes.  However you'd need to run plate voltages of 1000VDC - 1500VDC.
There are transformer and inductor sets available if you wanted to build one, but the transformers alone cost $28,000  see here

"THIS AMPLIFIER IS NOT A CONSUMER PRODUCT. It is offered only to organizations or individuals having experience with high voltage equipment. THE VOLTAGE WITHIN THIS AMPLIFIER IS LETHAL"

[tommymats]

My favorite EL34 family of tubes is the E34L tubes. The ones from JJ are relatively inexpensive.