813 in triode

RE: 813 in triode, posted on May 10, 2016 at 03:43:32
vinnie2 Audiophile Posts: 4481 Location: North Carolina Joined: September 28, 2013	I breadboarded one at lower B+ (500 or 600vdc I think) that had a really nice sound to it. May have to give that another try one of these days.

RE: 813 in triode, posted on May 10, 2016 at 05:23:47
glenz10183@aol.com Distributor or Rep Posts: 84 Location: New York Joined: September 27, 2003	Yes. Pete Millett

RH813, posted on May 10, 2016 at 06:14:30

RayP
Audiophile

Posts: 727
Location: Maryland
Joined: June 30, 2005

Link to another 813 possibility is in the link below to Alex Kitic's site. Be sure to read about the high frequency AC filament heating. I used it in my GK71 amp (20 volts) and it worked very well.

http://audioratbag.blogspot.com/2016/01/the-heart-attack-special-6s17k-v.html

ray

http://rh-amps.blogspot.com/2014/06/rh813-flagship-project.h

RE: 813 in triode, posted on May 10, 2016 at 08:30:35
sonicboom Audiophile Posts: 81 Joined: June 10, 2003	Be sure to use fixed bias - cathode bias isn't allowed here. Also, grid resistance must be bellow 30K which necessitates a robust, low plate resistance driver if RC coupled.

RE: 813 in triode, posted on May 10, 2016 at 08:48:29

Tubenstein
Audiophile

Posts: 251
Joined: August 5, 2011

I found this link, what do you guys think?? D3a IT coupled.

813 triode amp

RE: 813 in triode, posted on May 11, 2016 at 09:31:06
drlowmu Manufacturer Posts: 9730 Location: East of Kansas City Joined: January 10, 2005	Question : What is the efficiency of your speakers, that you are being drawn to big clunky obscure tubes ?? Such Finals often require extra stages and high current to drive. With your Moniker, if you are into tubes, run 100 dB sensitivity speakers and you can use simple. easy to drive, good sounding Finals tubes. Jeff Medwin

RE: 813 in triode, posted on May 11, 2016 at 16:28:58

PakProtector
Audiophile

Posts: 12363
Joined: May 14, 2002

The 813 is a very nice tube. However, if you can swing 7.5A of 5V, try the tantalum anode 4E27A. In the 5-125 form, it is comparable to the 813 in terms of plate dissipation, but is a true, 3-grid pentode. Very nice sounding too...:) IIRC it will do 35W with a 5k load on about 600V of B+( check the data sheet ). Stomps all over the driver sized tubes like the 45 and 2A3...:)
cheers,
Douglas

Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.

RE: 813 in triode, posted on May 16, 2016 at 01:24:18

Alex Kitic
Audiophile

Posts: 182
Location: Serbia
Joined: June 25, 2014

Let me just say that using ANY pentode/beam-tetrode in triode mode is a pity. It's like throwing away power - for the sake of sound?

With all due respect for everyone who will find hims/herself in the connotation that follows, I feel that the most important reason why pentodes are used in triode mode is lack of knowledge (on how to do it with good results). You can add marketing side effects meant to cover the above mentioned by popularizing triodes as the solution for the discerning taste.

This is in my view not only true with high powered tubes like the 813, but with 307A or EL84, to give a few examples. In my view, there's only power to loose - without gaining on sound (on the contrary, pentodes have very rich sound and might even sound dull in triode mode).

If you are into high power with triodes because you can't stand pentodes (?) go for the GM70.

******

http://rh-amps.blogspot.com/

RE: 813 in triode, posted on May 16, 2016 at 01:30:17
Alex Kitic Audiophile Posts: 182 Location: Serbia Joined: June 25, 2014	I haven't tried the tube you propose, but actually have a slight preference for beam tetrodes over pure pentodes. An example might be 1619 vs 307A (in pentode mode, obviously). It's easy to compare tubes when you can do it in the same amp ;) ****** http://rh-amps.blogspot.com/

RE: 813 in triode, posted on May 16, 2016 at 01:35:27
Alex Kitic Audiophile Posts: 182 Location: Serbia Joined: June 25, 2014	Not necessarily: the 813 is very easy to drive in pentode mode, easier than a 300B for that matter. The RH813 is almost too input sensitive for my taste: it would work perfectly fine with a selector and a pot as an integrated amp, or with a passive preamp if one prefers the versatility. ****** http://rh-amps.blogspot.com/

RE: 813 in triode, posted on May 16, 2016 at 05:56:29
Tubenstein Audiophile Posts: 251 Joined: August 5, 2011	Since the 813 is a pentode, it can be using AC for filament supply with AC balance adjustment instead of those "heavy duty" filtering for DHT, right?

RE: 813 in triode, posted on May 16, 2016 at 09:02:35
PakProtector Audiophile Posts: 12363 Joined: May 14, 2002	The 813 is an easier load than a 45....by nearly 50%, so don't worry about the 2A3, let alone the 300B. cheers, Douglas Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.

RE: 813 in triode, posted on May 16, 2016 at 10:03:13
Alex Kitic Audiophile Posts: 182 Location: Serbia Joined: June 25, 2014	Well not that easy a load as a 45 - in the RH813 you still need to swing some 60V peak (120V P-P) which is similar to a general 300B amp. Nevertheless, it's an easy load alright - just like all other pentode/beam-tetrode tubes. ****** http://rh-amps.blogspot.com/

RE: 813 in triode, posted on May 16, 2016 at 10:07:32

Alex Kitic
Audiophile

Posts: 182
Location: Serbia
Joined: June 25, 2014

Quote: "Since the 813 is a pentode, it can be using AC for filament supply with AC balance adjustment instead of those "heavy duty" filtering for DHT, right?"

I am not sure what you mean by "heavy duty filtering for DHT", but I use standard AC for all my direct heated tube amps - particularly for those where 2.5V or 5V are required (2A3, 300B).

The 813 needs 10V and a lot of current (5A) thus it hums quite loudly on standard AC (100Hz hum with the AC balance adjustment which BTW is not needed, 2 well matched resistors are just fine for balancing) -- which is why the HF AC solution (modified electronic transformer for halogen bulbs) comes into play.
******

http://rh-amps.blogspot.com/

RE: 813 in triode, posted on May 17, 2016 at 08:39:01
PakProtector Audiophile Posts: 12363 Joined: May 14, 2002	With a B+ suitable for an 813, driver output voltage should not be an issue. The 4E27 amps I built run the driver supply out 20% taps in the OPT's primary. cheers, Douglas Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.

Tube DIY Asylum

813 in triode

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