What new production power tubes do I want to try next in my VTA 70?

Wanting to try something new. looking for recommendations of new production. Cant really afford NOS at the moment.
Running new production svetlana EL 34 at the moment. They have been the only power tubes ive ran since ive built the 70, not including the stock ones.
Wanting to go in the direction of tubey, warm, liquid sound. Prefer the sound of triode mode.

Remove your present rectifier and Install a 5U4GB rectifier and re-bias.

Midwestside wrote:Wanting to try something new. looking for recommendations of new production. Cant really afford NOS at the moment.
Running new production svetlana EL 34 at the moment. They have been the only power tubes ive ran since ive built the 70, not including the stock ones.
Wanting to go in the direction of tubey, warm, liquid sound. Prefer the sound of triode mode.

Whatever you get, make sure they are matched. A matched quad is better
as all tubes may be moved around.

I use JJ EL34 with good experience. Eurotubes.com does a proper matching.

yel17 wrote:Remove your present rectifier and Install a 5U4GB rectifier and re-bias.

What characteristics change should I expect from this?

That warm, tubey sound. It might also help to go with JJ fat boys 6CA7’s but make sure you buy them from a reputable seller and be sure they have been burned in at least 24 hours because that helps weed out the bad ones.

Midwestside wrote:

yel17 wrote:Remove your present rectifier and Install a 5U4GB rectifier and re-bias.

What characteristics change should I expect from this?

Would a 5u4G without the B be an ok choice or are you specifically recommending the GB?

The GB is what I used. It made a real difference when paired with the JJ 6CA7 fat boys. You could try a 5U4G, but stay away from the cheap Chinese 5U4G. The 5U4G should sound even more tubey than the GB.

The way I understand it is that you'll just get a little less power by switching to a 5U4GB (from a 5AR4).
The up side of the 5U4 is that they are very common and very inexpensive (NOS).
The VTA ST 70 calls for the 5AR4, though.

One thing I learned the hard way when I first got my VTA ST70 and wanted to try different power tubes:
Make sure you clean the sockets and re-tension when swapping in a new set.
(Just a heads up...sorry, if you already know this.)

Also, After trying different set of power tubes, I decided that (except for my NOS Mullards) the Valve Arts that came with the amp were actually the best sounding (and most inexpensive).

One, the 5U4GB draws 3 amps of 5 volt heater current, the 5AR4 draws 1.9 amps. If you are using an original Dynaco "low stack" power transformer you are adding significant transformer overload. A Triode Electronic or perhaps another "replacement" power transformer with a heavier 5 V output rating alleviates this problem.

Second, a 5U4GB heats up much faster than a 5AR4, bringing on high voltage before the tubes have heated up. I would recommend a CL-80 NTC varistor as a minimum on the 120 volt side of the transformer or better: (2) CL-90s in parallel to both slow down the inrush and somewhat delay the high voltage. Better still, consider a high voltage delay timer on your power supply (as well as the CL-80).

Just a couple of thoughts...

Yes, your voltage, and therefore your output power will be very slightly lower with the 5U4XX series rectifiers.

Hi I actually have a Dan Steele ST70 from the 90 that being said tube sound should be similar to my experiences. The Power Tubes I've run vintage Sylvania 6CA7's, Electro Harmonix EL34EH now running Electro Harmonix 6CA7 (4x) = $108 from Tube Depot matching not burned but that is an option for a couple bucks. I have a thing for the big bottle design, liking them very much and would agree with this review -
“Designed to the exacting specifications of the Phillips 6CA7, this classic tetrode returns to life in a big bottle design. The 6CA7EH is built to withstand today’s high-gain amps while still retaining the detailed tone and component integrity of the original. A direct replacement, with military reliability, for any EL34”. - Tube Depot I'm running them through 1974 Allison Ones which are more "wall of sound" than super detailed big sound stage, so I would consider them already warm. Cheers