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What about a switch on the first capacitor?

141.239.172.61

Posted on August 19, 2016 at 09:46:34

DAK
Audiophile

Posts: 2712
Location: PACIFIC
Joined: August 8, 2010

of a CLCLC ps as an alternative to switching the B+ line?
In my amp which is a PP Class A amp the power supply is LCLC and is on a separate chassis. I would also like to use this ps for other amps such as single ended amps and would like to make the voltage range wider. Currently the Av is 350 with tube rectifiers. I was trying to get it to 400vdc to see what sonic difference that would make. THe amp has a LCLC filter supply and I could install another C in the C1 position. I have a 5uf x 600vdc cap for C1 and that should bring the B+ up past 400vdc. Would putting an appropriate switch on either the + or - leg of that cap be an issue? The switching would only occur when the amp was off. cheers, Dak

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RE: What about a switch on the first capacitor?

TomWh

11:29:48 08/20/16

RE: What about a switch on the first capacitor?

Triode_Kingdom

10:15:53 08/19/16

RE: What about a switch on the first capacitor?

drlowmu

10:00:00 08/19/16

...

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RE: What about a switch on the first capacitor?

TomWh

11:29:48 08/20/16

RE: What about a switch on the first capacitor?

Triode_Kingdom

10:15:53 08/19/16

RE: What about a switch on the first capacitor?

drlowmu

10:00:00 08/19/16

RE: The PS is already built

DAK

11:06:19 08/19/16

RE: The PS is already built

drlowmu

08:11:44 08/20/16

RE: The PS is already built

DAK

09:29:34 08/20/16

RE: The PS is already built

drlowmu

10:34:11 08/20/16

DAK

12:57:22 08/20/16

drlowmu

13:22:14 08/20/16

RE: The PS is already built

FenderLover

17:58:59 08/19/16

RE: Yes that is true. nt

DAK

18:13:39 08/19/16

RE: Yes that is true. nt

FenderLover

18:36:38 08/19/16

RE: What about a switch on the first capacitor?, posted on August 19, 2016 at 10:00:00
drlowmu Manufacturer Posts: 9730 Location: East of Kansas City Joined: January 10, 2005	DAK, You want to avoid C input filters. You have it right, use an L as the first thing the tube rectifier sees. Can you post a schematic of your supply, with VACs and VDCs, and estimated load?? We can then PSUD2 the unit and offer suggestions. Fun to do. Jeff Medwin

RE: What about a switch on the first capacitor?, posted on August 19, 2016 at 10:15:53
Triode_Kingdom Audiophile Posts: 10049 Location: Central Texas Joined: September 24, 2006	"The switching would only occur when the amp was off." The concept of adding an input cap is fine. Install the switch in the ground lead of the cap, and be sure the outer frame of the switch is securely grounded. That way, you won't get a shock if the switch shorts to the frame internally.

RE: The PS is already built, posted on August 19, 2016 at 11:06:19
DAK Audiophile Posts: 2712 Location: PACIFIC Joined: August 8, 2010	If i make C1 switchable in the circuit, i can go to LCLC for my lower voltage SE amps and switch in C1 for the PP amp. Here is a photo of the ps. The PT is on the left, L1 is the big can in the back right, L2 is the smaller trans on the right. The caps in the middle are ASC 100uf x 370vac oil caps. I would add the 5uf oil cap under the chassis. regards, Dak

RE: The PS is already built, posted on August 19, 2016 at 17:58:59
FenderLover	You are running two 5AR4 rectifiers and only getting 350VDC B+? Is this correct? Thanks!

RE: Yes that is true. nt, posted on August 19, 2016 at 18:13:39
DAK Audiophile Posts: 2712 Location: PACIFIC Joined: August 8, 2010	.

RE: Yes that is true. nt, posted on August 19, 2016 at 18:36:38
FenderLover	Looks like you will need to go to solid-state rectification, to get 400VDC with your unit. Or some fancy voltage doubling.

RE: The PS is already built, posted on August 20, 2016 at 08:11:44

drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005

Yes, I realize that the supply was built already.

Dak, its impossible to offer a design suggestion from the picture you have posted.

It may be very easy to get your desired voltages with a switchable FILTER SYSTEM, L1/ C1/ L2/C2 under the chassis, employing two small, high current, less-than-critical inductance chokes, which will also likely be lower in DCR than what you have there, and thus give FAR better dynamics to your Push Pull, higher voltage amp.

So please tell us this:

(1) With a certain Line voltage ( eg 120, 124 ?? )

(1A) what is the VAC at the HV secondary, and
(1B) is it a center tapped secondary.

(2) What is the value in HY , and DCR of L1 and L2.

(3) What is the measured VDC ( B+ ) at C2, and what is the measured VAC at C2, under load.

(3A) What IS the total amp load normally, and
(3B) what is the anticipated mA. load of the P-P amp expected to be.

With the above, we will stop guessing and SEE if we can come up with a great alternative for you, we all would be using PSUD2 and our imaginations.

Fun to do !! Cheers and have fun.

Jeff Medwin

RE: The PS is already built, posted on August 20, 2016 at 09:29:34

DAK
Audiophile

Posts: 2712
Location: PACIFIC
Joined: August 8, 2010

Hi Jeff to answer your questions
(1) With a certain Line voltage . My wall volts is 120

(1A) what is the VAC at the HV secondary Pt secondary is 450-0-450

(2) What is the value in HY , and DCR of L1 is 5H 38 ohm .4A
L2 is 10H 100 ohm .2A

(3) What is the measured VDC ( B+ ) at C2, B+ is 370
VAC at C2, under load. I dunno what you mean by "under load" but i measured it with all the tubes in after 1 hour I am guessing because i did not note that number. My memory is less than .1 ma

(3A) What IS the total amp load normally, Amp is running 4 6550 @ 82ma in UL + 2 x 6sl7 @ .8ma
3B. it is running where i more or less expected to be, other than i wanted b+ to be around 400vdc.
Thanks for the help, Dak

RE: The PS is already built, posted on August 20, 2016 at 10:34:11

drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005

DAK,

So if I read you right, you have a total current draw in the P-P amp of 82 mA. times four, and 0.8 mA. times two, or, 329.6 mA.

The first thing we must realize is your L2 choke is rated at 0.2 A. so it is not usable at 0.392 A., is it ?

To better input PSUD2, I would like to have two other DCR measurements. made with amp OFF.

(1) DCR of power trannie primary ( one to three ohms )

(2) DCR of power trannie secondary, either " end-to-end " red to red, OR, " either end - to ground ", tell us which it is. The first, red-to-red is double the second.

These two will allow me to fine tune the simulation's input, as I can't figure out why we got 331 VDC and you are talking 370 VDC. GIGO.

So DAK, I DID TRY to PSUD your Supply, with 329.6 mA. as the laod, and it came up around 331 VDC, 40 VDC away from this 370 VDC you have discussed. What gives??

In the second PSUD2 simulation, I also switched the 38 Ohm 5 HY choke - to L2 position, and added a Hammond 600 mHY 8 ohm choke as L1, just to see what a lower value ( non critical inductance ) choke would do to the B+, with the same 392.6 mA. current.

Besides a much higher B+. we got about 40 mVAC of ripple at C2. This leads to a second DESIGN consideration.

You state that the supply has 0.1 mVAC of ripple as configured at 370 VDC.

Anything, ripple-wise, 1 or 2 mVAC is FINE for the front end stages. Anything 800 mVAC or less is OK for the SET finals stage.

ARE you running the front end stages, AND the finals stages off of the very SAME B+ tap, without decoupling the two??

That is usually a poor way to execute a supply design, because you have " over filtered" the Finals, and lost most of the amp's get up and go, and FUN factor to hear. The two parts of the amp ( front end and finals ) have different design requirements, and " one size does not fit all ".

Take a look at the two PSUD shots, and feel free to continue with the other two DCR questions. BTW, if we used 5U4GBs for the second PSUD shot, it would be closer to 400 VDC I would guess, easy to simulate .

Lets refine, and discuss decoupling DAK. No rush.

Have fun.

Jeff

RE: What about a switch on the first capacitor?, posted on August 20, 2016 at 11:29:48

TomWh
Audiophile

Posts: 764
Location: Tucson Az
Joined: August 7, 2003

Sound like you have a good plan. I run separate power supplies for every tube. I play around with small caps all the time to fine tune the B+. There are plenty of smart minds who have argued benefits of a small 1st cap. I only used my ears. Now the sound difference if you throw sand in the mix I seem to hear a difference every time not for the better. As a side bar the largest one I have used is 2.5 uf.

Enjoy the ride
Tom

RE: , posted on August 20, 2016 at 12:57:22

DAK
Audiophile

Posts: 2712
Location: PACIFIC
Joined: August 8, 2010

Hey, Jeff, i am not sure what the residual AC ripple is at the C2 as i dont usually measure that. I am going by memory so don't hold me to that number. I will have to remeasure to be sure.
As far as the DCR of the pt primary, i measured it before i installed it and the value was in that 1 to 2 ohm range. Re measuring the dcr of the secondary i dont think i can get a true measurement of that with my power supply hooked up and i am not going to fuss with that. I am familiar with your preferences in power supplies and that is ok.
And the differences between your PSUD simu and my actual ps i dont see any issues with your numbers and mine. I might be off by a few volts and your numbers are not that far off.
About my front end supply it is further decoupled by 100k resistor and 20uf x 500v caps.
I am not overly concerned about the numbers your sim has shown. This amp is a prototype and I am really mostly concerned with the amp's performance. And to that i feel that it is exceptional with better bass and excellent dynamics. The soundstage is the most precise of any amp i have heard. All the recorded information is portrayed realistically. In all of the cds that i use to monitor an amp's performance, this amp has revealed more information than any of my other amps while still retaining a "single ended sound quality" of smoothness, realism and a lack of audio artifacts. It is this resolution of small signal information with single ended sensibility that i was seeking in building this amp. Since that was my goal, i consider the amp to be a success. cheers, Dak

Pins 4 or 6, posted on August 20, 2016 at 13:22:14

drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005

Amp OFF. Pull rectifier. Ohms scale. One probe on Pin 4 or 6, other probe to chassis ground.

Choke in second simulation is a Hammond 159Y, rated 0.6 HY at 11 ohms ( not 8 ) and 0.75 A. current, $28.94, 102 mm by 57 mm by 67 mm, goes below deck.

I can't really comment on what you have heard previously, or are hearing.

Have fun. Hope I helped you... tried to.

Jeff

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