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SE Pentodes?

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Posted on February 27, 2016 at 17:10:16
rws
Audiophile

Posts: 303
Location: Minnesota
Joined: September 7, 2004
Hello
Please excuse if this is in the wrong forum, but the question is;

What are the pros and cons of SE Pentodes as compared to SE Triodes?
My first guess would be they are less expensive.
Is either more or less dependent on speaker match?
In general do SET's have a smaller power output than SEP's?

Thanks Bob




"Sometime I will have to give account of myself. How would the Father in heaven judge me if I followed others and not Him", Anton Bruckner

 

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RE: SE Pentodes?, posted on February 27, 2016 at 17:48:20
hifipaul
Audiophile

Posts: 735
Location: NY
Joined: December 22, 2008

SE pentodes and tetrodes can sound very good but usually not as good as DHTs. The biggest benefit that I've found is a single uncomplicated filament supply. The biggest drawback is the need for negative feedback, even when triode wired.

The price of the tubes is generally less, and if you are willing to use some oddball types, they are dirt cheap. 6CB5s,6KN6s,6BG6Gs,807s,6GE5s,6Y6s can be had for $10ea. There are others as well.

 

RE: SE Pentodes?, posted on February 27, 2016 at 19:17:06
Paul Joppa
Industry Professional

Posts: 7294
Location: Seattle, WA
Joined: April 23, 2001
To expand a little on hifipaul's contribution, triode-wired pentodes (and beam tubes) are almost always less linear that the older triodes. That can add some warmth to the sound at low levels, at the price of some congestion at higher levels. A modest amount of feedback can help but it's always a two-edged sword.

In pentode mode, they are usually more efficient but the output impedance is very high, requiring much more feedback to match speakers.

As hifipaul indicated, there are many pentodes and beam tubes to choose from, while the traditional triodes are few, dominated by the 45, 2A3, 300B, 211, and 845.

 

What he said!, posted on February 28, 2016 at 13:10:37
Triode_Kingdom
Audiophile

Posts: 10012
Location: Central Texas
Joined: September 24, 2006
"The biggest drawback is the need for negative feedback, even when triode wired."

Triodes allow one to experiment with NFB, starting with none. The inherent distortion level of pentodes doesn't permit that luxury.

 

RE: What he said!, posted on February 28, 2016 at 14:35:08
rws
Audiophile

Posts: 303
Location: Minnesota
Joined: September 7, 2004
I had kind of figured a true SET was better. So, what manufacturers do you recommend (I don't know of many) or would I need to build my own, which I am not sure if I could pull that off

Bob




"Sometime I will have to give account of myself. How would the Father in heaven judge me if I followed others and not Him", Anton Bruckner

 

RE: What he said!, posted on February 28, 2016 at 16:26:00
hifipaul
Audiophile

Posts: 735
Location: NY
Joined: December 22, 2008

Since you are new to this you are likely to be best off with a 300b amp. If you want to build something, go with a kit: Bottlehead is a good place to look first. As for manufacturers; you'd be best to read a bunch of reviews and learn about this whole SET thing. Even having a great amp is no guarantee of great sound. Speaker matching, tube swapping, and component matching are important issues with SETs. When you get it all "right" It's really nice to listen to.

 

RE: What he said!, posted on February 28, 2016 at 17:51:04
charles1dad
Audiophile

Posts: 157
Location: michigan
Joined: January 2, 2009
Hello rws,
You have gotten some very good and wise replies. At this stage you're in, educate yourself via reading articles and reviews of SET amplifiers. Be patient and you'll steadily develop a fund of basic knowledge. The biggest factor for success with SETs is selecting the proper speaker match. Wrong speaker and you'll just experience failure and frustration.

With the right speaker match the listening experience and long term happiness can be superb. IMO any of the true DHT tubes can sound wonderful. This will depend on the builder/designer talent, part quality(particularly output transformer) and of course implementation. Take your time and read. Despite the relatively small genre of SET amplifiers, there are many good choices available, patience is an asset.
Charles,

 

What to Buy..., posted on February 29, 2016 at 12:27:10
Triode_Kingdom
Audiophile

Posts: 10012
Location: Central Texas
Joined: September 24, 2006
"So, what manufacturers do you recommend"

The heart of a SET amplifier - tubes aside - resides in the quality of the output transformers and power supply. The former are very expensive if done right, and because they're key to overall sound quality, it's important to know who made them. For this reason, I wouldn't recommend any amplifier manufactured by a company that doesn't use a brand of known, high-quality transformer. This eliminates all Asian manufacturers as far as I know, with the exception of a few in Japan. It may also eliminate a few Western companies that don't publish the source or specs of their transformers. If I was in the market for a new amplifier, I'd probably start by contacting transformer manufacturers like Magnequest, Lundahl, Sowter, etc. to ask for a referral.

 

RE: What he said!, posted on February 29, 2016 at 13:24:39
krankkall
Audiophile

Posts: 296
Location: New Mexico
Joined: April 5, 2014
I can run a pair of home built 89db/1 watt speakers, with my home built 8wpc EL34 SEUL amplifier.
It can certainly get loud....but....not 'blow out the windows' loud.

Steve

 

RE: What to Buy..., posted on February 29, 2016 at 15:15:41
rws
Audiophile

Posts: 303
Location: Minnesota
Joined: September 7, 2004
Thanks to everyone for all the input. I will most likely buy American made maybe from a smaller manufacturer, or possibly British. Also good point about checking on sources for parts.
I used to have a push-pull made by George Wright but sold it and I really want to try single ended

Bob




"Sometime I will have to give account of myself. How would the Father in heaven judge me if I followed others and not Him", Anton Bruckner

 

Not only distortion, posted on March 2, 2016 at 09:09:07
JJ Triode
Audiophile

Posts: 716
Location: Northwest
Joined: December 2, 2004
Also very importantly, SEP amplifiers need NFB to lower the output impedance (raise the damping factor) to levels permitting adequate woofer control. The bass frequency extension may also be inadequate without feedback.

 

what about the Carey 300SEI, posted on March 2, 2016 at 17:26:30
rws
Audiophile

Posts: 303
Location: Minnesota
Joined: September 7, 2004
seems like alot of power for 300b's, didn't also make a 2A3 version?




"Sometime I will have to give account of myself. How would the Father in heaven judge me if I followed others and not Him", Anton Bruckner

 

RE: SE Pentodes?, posted on March 3, 2016 at 04:17:34
morricab
Distributor or Rep

Posts: 9160
Location: switzerland
Joined: April 1, 2005
What about the 813? This is a DHP(direct heated pentode) that is extremely linear when wired as a triode. Aries Cerat uses this tube almost exclusively in their amps for this reason.

 

Yes, good point! nt, posted on March 3, 2016 at 17:52:56
Triode_Kingdom
Audiophile

Posts: 10012
Location: Central Texas
Joined: September 24, 2006
nada aqui

 

RE: what about the Carey 300SEI, posted on March 3, 2016 at 17:57:13
Triode_Kingdom
Audiophile

Posts: 10012
Location: Central Texas
Joined: September 24, 2006
Sorry, I don't know how Cary qualifies their transformers or the operating conditions for specifying output power. Those are good questions to ask them. :)





 

Whatever the pros and cons the RH84 sounds lovely nt, posted on March 4, 2016 at 01:37:18
Bas Horneman
Audiophile

Posts: 4081
Joined: March 28, 2001
.

 

RE: SE Pentodes?, posted on March 4, 2016 at 14:48:57
SETdude
Audiophile

Posts: 3944
Joined: January 20, 2000
The link is to an interesting and affordable Japanese 300B.

Can you guys decipher the circuit?

I have had their Model 3 CD transport for years and it has been a bullet proof solid performer.

 

RE: SE Pentodes?, posted on March 14, 2016 at 14:35:42
gavinhaley
Audiophile

Posts: 29
Location: St Louis
Joined: January 31, 2016



I don't know about all of the feedback and so forth but I built this amp a few years back and it sounded really good.

 

RE: SE Pentodes?, posted on April 7, 2016 at 17:40:07
coffee-phil
Audiophile

Posts: 1444
Location: Shingle Springs CA
Joined: January 7, 2010
Hi Gavinhaley,

An EL34 is certainly a pentode but in that circuit it is "triode connected" so you have in essence a SET amp.

Phil

 

RE: SE Pentodes?, posted on April 7, 2016 at 23:56:54
aknaydenov
Audiophile

Posts: 106
Location: Sofia, Bulgaria
Joined: September 13, 2015
The tubes are only one of the keys to a good sound. I've seen many flawed designs on the internet that are DHT and just don't deserve it. Mediocre power supplies, coupling elements, poor driver stage, poor hook-up wires,

If you want a good DH tube amplifier, you have to make sure all other components in the amplifier deserve it. Otherwise, it's just a waste of good tube IMHO.

Every component affects the sound quality in the SET: power supply - chokes, capacitors, resistors, rectifier, power transformer ; output transformer, bias elements - cathode capacitor/resistor, coupling capacitor/interstage transformer, grid resistors, the hook up-wire and also the grounding and overall wiring scheme.

 

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