Emission Labs 274B

Hi,

I've run a Mullard GZ33 tube in my ST120 for quite some time. Great tube! I have only 1 of these and was thinking of buying a back up. The price on these is up over $100 and they are getting hard to find.

I saw some posts on the Emission Labs 274B tube that appears to be a GZ33. The Emission Labs 274B (The "B" has the pin out of a GZ33/GZ34) looks robust and the mesh plates of this tube I think would look unreal cool in the ST120.

Looking at the specs of this EML274 I think the tube would work-

http://www.emissionlabs.com/datasheets/EML274.htm

Spendy bugger!!! I don't know if I'll do it... AT this point wondering if this tube would work and looking for help on that topic.

Thanks,
Andy

PS - Not sure if any Radio Head people are on this forum. On my Comcast service on the Palladian channel is a live/studio session that is unreal good. Look for it.

How is it that a rectifier tube can make such an audible difference? I know the rectifier is a key component of the PSU but beyond not supplying enough current when demands high and the tube isn't able to provide said current, what other considerations are there?

Is a GZ33 not able to handle the current demands of the ST120 at the power outputs you need?

Nah, the GZ33 is excellent. I think perhpaps the best rec. tube for the ST120. The ST120 drives the rect. tube pretty hard and drives them to the max. If you get the cheap new production GZ34 they last about 4-5 months if you use the ST120 a lot and perhaps a shorter time if you play loud.

Emissions Labs really make a high quality tube. Toying with the idea of spending the $$...

Do the tec. specs work ya think?

Plexus-pick up a few different rectifier tubes and try them out for yourself. My NOS Mullard blows away my modern Sovtek and other NOS GZ34's I have each add their own "sound" to the final output. It really makes sense if you look at the schematic-dirty power means dirty sound.

heyraz wrote:Plexus-pick up a few different rectifier tubes and try them out for yourself. My NOS Mullard blows away my modern Sovtek and other NOS GZ34's I have each add their own "sound" to the final output. It really makes sense if you look at the schematic-dirty power means dirty sound.

how does a rectifier tube create "dirty power"?

They get noisy. Google it. Noisy power means noisy music. And a tube doesn't have to be old to be noisy, some are just born that way. Those are the ones that suck compared to the others. Those old Mullards are expensive for a reason, they can really bring out the best from an amp.
Diodes sound different too. Some are fast recovery and some switch on more smoothly than others. Diodes can be very noisy too.

Try this-put your amp on and tap the rectifier gently while you ears are close to the speaker and you'll hear something every time you tap. Noise on the power. Better yet, hook up a scope and look at the noise riding on the output.

If there's noise in the power, there will be noise in the signal.

I think that the 274A-274B would be a poor replacement for a GZ34 in a ST-120 because it has a maximum current rating of 160 mA instead of the GZ34's 250 ma. I would think that a GZ-34 is already working near its current limit in an ST-120. In addition, the 274 is rated for a maximum of 4 uF input capacitor, unlike the GZ-34's 60 uF. The internal resistance of the 274 is higher, so it will drop more voltage. In my view the major virtue of a tube rectifier is a slow warm-up to keep voltages from rising before the output tubes turn on. The 274 warms up much faster than the GZ-34.

All these disadvantages come with a price tag of $240 - ouch!

Best,
Dan

I have 2pr of MK3s here an have been playing with the 5U4...i have 8ea...old stock....thay sound great... much diff in sound than the GE ONS GZ34s i like
All the tone of the rectifier tube setup the Amps sound... it the frist tube...some say..but i have these 5U4s ...There is a littel B+V drop...just for fun... too see how diff in sound...Big sounds like a diff amp..
Thanks For the site Bob

5U4 was the stock rectifier in the Dynaco Mark II, which used EL34 outputs. Driver stage identical to the Mark III and transformers, too, except for lacking the 4Ω tap.