5AR4 to 65U4GB

the 5U4 draws 3A of heater current while the 5AR4 only draws 1.9A. So you should make sure that your PT is rated to supply the extra current or you may have problems.

Also, the voltage drop is much higher with the 5U4 so your B+ and other voltages will be lower which means your operating points will change.

And . . . the 5AR4 is indirectly heated, which results in a slow start to the B+ and the 5U4 is directly heated so your B+ voltage will hit the tubes much faster

B+ voltage will hit the tubes much faster, posted on January 2, 2021 at 06:22:22

PakProtector
Audiophile

Posts: 12364
Joined: May 14, 2002

With a cap input supply this matters less( or it should) from a parts ratings view. With an LC filter, The difference between normal operation and flash peak is about 50%. With DH power tubes, this matters less 'cause they're heating up and conducting just as fast.

Just a couple more possible different effects. There are bound to be more, consult a licensed consultant, from the department of redundancy department consulting.
cheers,
Douglas

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

RE: 5AR4 to 65U4GB, posted on January 2, 2021 at 08:11:42

Eli Duttman
Audiophile

Posts: 10455
Location: Monroe Township, NJ
Joined: March 31, 2000

The short answer is no.

The 5U4 draws 3 A. of filament current, while the 5AR4 draws 2 A. of heater current. The max. allowable 1st filter cap. size is greater for the 5AR4 than the 5U4. Forward drop is greater in a 5U4 than in a 5AR4.

The 5AR4 is "half indirectly" heated, while the 5U4 is directly heated. B+ must be taken from pin 8 of a 5AR4, as that is where its cathode sleeve is connected. The best residual hum performance when a 5U4 is employed is obtained by taking the B+ from a CT on the 5 VAC filament winding.

Eli D.

RE: B+ voltage will hit the tubes much faster, posted on January 2, 2021 at 09:07:13
Salectric Audiophile Posts: 1358 Location: East Coast Joined: February 23, 2003	A hefty bleeder resistor across the first cap in a LC filter will dampen the DC voltage until the tubes warm up.

"5AR4 is "half indirectly" heated", posted on January 2, 2021 at 10:07:22
Story Audiophile Posts: 10453 Location: NJ Joined: December 11, 2000	I'd like to know more about this, gotta link?

RE: "5AR4 is "half indirectly" heated", posted on January 2, 2021 at 10:42:43
Eli Duttman Audiophile Posts: 10455 Location: Monroe Township, NJ Joined: March 31, 2000	Half indirectly heated means the cathode sleeve is tied to 1 end of the heater. An advantage of that construction style is the elimination of heater to cathode potential limit worries. A disadvantage is that a half indirectly heated type can't share a filament winding with signal tubes, like the 6X4 or 6CA4 can. Eli D.

Make all power supplies ( 70 ohms, ... Thorsten Loesch got it right~nT, posted on January 2, 2021 at 10:45:12
Cleantimestream Audiophile Posts: 7551 Location: Kentucky Joined: June 30, 2005	~! The Mind has No Firewall~ U.S. Army War College.

RE: "5AR4 is "half indirectly" heated", posted on January 2, 2021 at 23:40:44
Triode_Kingdom Audiophile Posts: 10047 Location: Central Texas Joined: September 24, 2006	This...

RE: "5AR4 is "half indirectly" heated", posted on January 3, 2021 at 04:23:26
Story Audiophile Posts: 10453 Location: NJ Joined: December 11, 2000	yes, I knew all about this except for the term 'half indirectly'. It was never used in any of my books, as simple as I am for studying my old tomes.

RE: "5AR4 is "half indirectly" heated", posted on January 3, 2021 at 05:19:59
Eli Duttman Audiophile Posts: 10455 Location: Monroe Township, NJ Joined: March 31, 2000	The terminology is NOT original to me, but I don't immediately recall where I came across it. Eli D.

RE: "5AR4 is "half indirectly" heated", posted on January 3, 2021 at 12:28:43
Triode_Kingdom Audiophile Posts: 10047 Location: Central Texas Joined: September 24, 2006	Don't care for that term myself. My understanding is that only the cathode - not the filament - is emitting electrons into the stream. Being electrically connected removes the need for HV insulation between the two elements, but it has no other substantial effect. The cathode is still "fully" indirectly heated.

He did..., posted on January 4, 2021 at 02:46:58

91derlust
Audiophile

Posts: 1101
Joined: December 25, 2014

well, at least that is my way of thinking right now.

I tend to design PSUs according to his design objectives in the "Thoughts about single-ended amplifiers" paper, re impedance and DCR. Modern SiC diodes make his goals more attainable without some of the downsides.

I miss having TL (KYW) here sometimes.

"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein

What is the Pin-1 connection on the 5AR4? NT, posted on January 4, 2021 at 06:37:03
Alpha Al Industry Professional Posts: 2958 Location: N. Carolina Joined: February 16, 2004 Contributor Since: December 3, 2015	Never seen that.

According to the 5AR4 data sheet..., posted on January 4, 2021 at 08:03:51
1973shovel Audiophile Posts: 10117 Location: Greenville SC Joined: February 25, 2007

RE: According to the 5AR4 data sheet..., posted on January 4, 2021 at 10:22:40
Eli Duttman Audiophile Posts: 10455 Location: Monroe Township, NJ Joined: March 31, 2000	Pin 1 is the connection for a metal ring on the base, when such a ring is present. That's nicely illustrated here. Eli D.

RE: He did..., posted on January 4, 2021 at 15:07:29

Tre'
Industry Professional

Posts: 17302
Location: So. Cal.
Joined: February 9, 2002

I like that paper but I don't understand this,

"For ideal conditions we have about 560uF as final Filter/Reservoir Capacitor. This is an Elna Cerafine Capacitor (or Film or whatever you like and what keeps distortion low).40mS / 560uF = DCR in kOhm = 0.071kOhm
This suggests a DCR of no more than 71 Ohm for the entire PSU "

The output impedance of the supply is determined by the reactance of the last cap. Why is he bring up the DCR of the supply? What does that have to do with the output impedance?

Tre'

Have Fun and Enjoy the Music
"Still Working the Problem"

Let me try... but I'm no EE., posted on January 4, 2021 at 22:09:27

91derlust
Audiophile

Posts: 1101
Joined: December 25, 2014

I think in that part of the paper, Thorsten was combining two goals: low output impedance and fast enough capacitor charging/ PS recovery.

He had calculated an ideal last PSU cap size to give low impedance down to 4Hz. As I understand it, he then calculated the required PS DCR for a 40mS capacitor charge time. FWIW, he then relaxed the 4Hz requirement to 16Hz for 150uF and greater acceptable DCR (266 Ohm).

The need to factor in capacitor recharge times in SE amps is contentious. Thorsten gives his reasons in "3) timing and dynamic considerations", suggesting it applies to SE amps that could be run close to clipping on peaks.

Whether fast recovery is needed or not I can't say because I don't have sufficient data: it is an unknown for me. Because I accept it's feasible, the additional cost is not great, I run low-power SET amps full-range, and the amp where I have used this approach sounds better in bass than a similar amp that does not (i.e. that is not evidence though), I include it as a design goal. One day I may research it further.

Cheers.

"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein

Thanks, I remember now but...., posted on January 5, 2021 at 07:26:50
Tre' Industry Professional Posts: 17302 Location: So. Cal. Joined: February 9, 2002	I don't use SET for bass. To me there are other reasons not to. Tre' Have Fun and Enjoy the Music "Still Working the Problem"

change to air Core Inductors @ 8 gauge and THEN have a listen~nT, posted on January 5, 2021 at 11:48:48
Cleantimestream Audiophile Posts: 7551 Location: Kentucky Joined: June 30, 2005	! The Mind has No Firewall~ U.S. Army War College.

RE: Thanks, I remember now but...., posted on January 5, 2021 at 11:50:26
91derlust Audiophile Posts: 1101 Joined: December 25, 2014	For sure. The recovery design goal will not apply to every situation. "Confusion of goals and perfection of means seems to characterise our age." Albert Einstein

RE: change to air Core Inductors @ 8 gauge and THEN have a listen~nT, posted on January 5, 2021 at 11:52:56
91derlust Audiophile Posts: 1101 Joined: December 25, 2014	It is interesting you mention that. I have just those types of inductors wound to replace the iron core inductors on the bass. They have been sitting on the shelf for years - never got around to using them. One day. "Confusion of goals and perfection of means seems to characterise our age." Albert Einstein

I assume you are talking about speaker level crossover inductors?, posted on January 5, 2021 at 13:22:38
Tre' Industry Professional Posts: 17302 Location: So. Cal. Joined: February 9, 2002	. Have Fun and Enjoy the Music "Still Working the Problem"

RE: I assume you are talking about speaker level crossover inductors?, posted on January 5, 2021 at 14:46:55

Cleantimestream
Audiophile

Posts: 7551
Location: Kentucky
Joined: June 30, 2005

of course, Tre. 8 gauge for the woofer, 12 ga for midrange and tweeter.

First tried it out with Klipsch Forte speakers and was er... astonished, because the result did not square with my thinking. I have always had a habit of overkill and love to experiment. The room trumps any other factor in music, then the speakers... and then {dare I say it?} the preamplifier {only then the amplifier}; this all assumes no expense {in quality not necessarily money} has been spared for the source... whether TT or digital.

Is becoming apparent that active crossovers may trump passive, making all this twaddle am saying null and void. 2 watt 45 still runs out of steam for rock and roll and full tilt symphony, but everything else is more than loud enough for me in THIS room.

The Mind has No Firewall~ U.S. Army War College.

RE: I assume you are talking about speaker level crossover inductors?, posted on January 5, 2021 at 17:50:26

Tre'
Industry Professional

Posts: 17302
Location: So. Cal.
Joined: February 9, 2002

A high damping factor is critical for bass speakers. Using 8ga wire will improve that for sure.

This issue is, a SET amplifier has a very low damping factor to start with and even with no DCR added by a crossover inductor, the amplifier's low damping factor will harm bass performance.

I use JBL 2231 woofers and they need both a high damping factor amplifier and some power. I use SS amps for bass with an active low pass filter. Nothing but speaker wire between the amp and the JBLs.

There are many ways to skin a cat.

Tre'

Have Fun and Enjoy the Music
"Still Working the Problem"

RE: He did..., posted on January 8, 2021 at 06:58:02
FlaCharlie Audiophile Posts: 940 Location: Gville, FL Joined: June 1, 2003	If there is a link to the paper you're referring to could you please post it? Thanks

RE: He did..., posted on January 8, 2021 at 11:38:59

elblanco
Audiophile

Posts: 3486
Joined: August 20, 2004

I think

this is it

RE: I assume you are talking about speaker level crossover inductors?, posted on January 17, 2021 at 05:49:43
Cleantimestream Audiophile Posts: 7551 Location: Kentucky Joined: June 30, 2005	What SS amps, Tre? For bass, the finest I have ever heard was a Krell KSA-50 and A Bedini 100/100 Class A {rather rare one not usually seen for sale... I had one I gave to a friend and have only seen two in 20 years. Am sure there are others of this caliber and I was curious what you deemed excellent. The Mind has No Firewall~ U.S. Army War College.

Tube DIY Asylum

5AR4 to 65U4GB

202.40.157.165