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Capacitance Filter Question


SemperFiAg08

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I've been a member on here for a few years and have thoroughly enjoyed my Klipsch speakers. I recently picked up a set of La Scala Industrials that my father in law  (CECAA850) rebuilt the crossovers and helped me source parts to get them in pristine operating condition. They are hands down my favorite set of speakers I've listened to and I'm looking to build an amp to drive them (200W Max/Ch). 

 

I've been reading in this section of the forum and there's been a ton of very useful information. While I wait for my TPA3255 (backordered until roughly Christmas), I'm trying to do research for all of the other necessary pieces. I know there's a ton of knowledge from others who have built amps and I'm hoping someone in this forum could help me out. I'm looking to do a linear PS, and I'm trying to right-size the transformer and filter cap/rectifier. My big questions are:

 

1) Can I overdo thing on the cap filter and what effect would that have? I've read it can alter the sound and I'm aiming to make this as clean and crips as possible.

 

2) On the website it mentions that the output of the rectifier board will be 1.414 times the input. Is that correct? If so, I should shoot for a 35V transformer to hit approximately 50V (max is 53.3V for the board), right?

 

3) For a board that's rated at 600W (4 Ohm) and roughly 370W (8 Ohm), is a 800VA going to be overkill? Would a 625VA transformer work well enough, and what would be the tradeoff?

 

Right now I'm looking at the Sure rectifier filter board and an Antek toroidal transformer. I'm open to recommendations on parts and manufacturers without spending a fortune.

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ROM estimate for FW rectifier/120Hz/100W/8 Ohm the current required is 3.5A so for given reservoir cap size the Vp-p ripple voltage is then:

 

15,000uF / 1.93Vp-p

30,000uF / 0.97Vp-p

60,000uF / 0.48Vp-p

120,000uF / 0.24Vp-p 

 

The 30,000uF recommendation is reasonable.  If you plan on amplifying electronic music or your building a sub amp then 60,000uF.  

Use a grounding wand.

 

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3 hours ago, wdecho said:

A lot of your questions can be answered by reading this thread starting at September 17th.

 

https://community.klipsch.com/index.php?/topic/172028-class-d/&page=2

 

1. Some say you can but 30K uf is plenty enough and even 15K uf is probably plenty. 

2.  I used AN4434 with my build, 400VA 34V. Be careful not to exceed the 53V rating of the board because many D boards will shut down with too much voltage. Using that toroid I think I remember having around 51V with my wall AC. With our speakers 400VA is plenty enough. Those toroids get big and heavy with more VA. Cantilope on our forum is driving 3 of the TI boards with a 800VA. 

3. See 2.

Very easy to hook up capacitors using a bridge rectifier using better caps and rectifier without paying for Sure board. I believe you said you can solder. Caps hook up positive to positive, negative to negative. 

 

 

 

Thanks wdecho. I've read that entire thread twice already (that's where I got the most information on this board and had all my other questions answered).

 

I wanted to get as close to 53V as possible without going over, because I've read the instructions that TI put out that says it has overload protections. I definitely won't mind going with a smaller transformer, but eventually, I want to build a rig like Cantilope's if I like the sound.

 

I'll look into building it myself. I know it's not difficult, and I can solder, I just don't want to spend a ton of time (meaning my wife doesn't want me to spend a lot of time) assembling this.

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1 hour ago, SemperFiAg08 said:

Thanks wdecho. I've read that entire thread twice already (that's where I got the most information on this board and had all my other questions answered).

 

I wanted to get as close to 53V as possible without going over, because I've read the instructions that TI put out that says it has overload protections. I definitely won't mind going with a smaller transformer, but eventually, I want to build a rig like Cantilope's if I like the sound.

 

I'll look into building it myself. I know it's not difficult, and I can solder, I just don't want to spend a ton of time (meaning my wife doesn't want me to spend a lot of time) assembling this.

 

 

 

Sorry if you already understand this, but just in case...

 

The Antek transformers are designed for 115 /230 volts.  If your voltage is higher, the output will be higher as well.  Last summer, our voltage spiked to 133 volts for quite a while until the power company finally fixed it.  

 

Is Sure power supply you referenced designed for + / - DC outputs?.  If you used the same  an4434 transformer wdecho used and wired it for 115v (inputs parallel, outputs series), you'll get both a + 48 volt dc output and a - 48 volt output.  You would only use 1 of the outputs.  I guess if you wired the inputs in series (which I assume wdecho did???), then you would get +24 and - 24.  You would then hook up your amp ground to -24 and positive to +24, which is the same as 0  and +48.

 

I hope I got that right.

 

Mike  

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I asked William the same exact questions when I received my Antek transformer, which is the same model as his.

 

I'm just guessing, but if each primary is parallel connected, you'll get more current/power. If connected in series, you'll get less current and maybe a bit more voltage...same with the secondary leads. Sumthin' like that...

 

The supply I built for my 3255 is a exact copy of William's, the only difference is I used a 15,000uF 80V Chemi-Con capacitors.

I checked the supply voltage yesterday while the amplifier was powered up with music playing, and I measured 49.5 volts from a wall voltage that is pretty constant at 119-121 volts AC.

 

I wouldn't sweat much over getting an exact 53 volts on the supply used for the 3255, the manual for the evaluation board states 51 volts as being optimum. I'm guessing as long as it's 48-51 volts, a couple few volts probably isn't going to matter much with regard to audio output. Now maybe 10 volts or 15 volts lower might make a difference...

 

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19 hours ago, mike stehr said:

I checked the supply voltage yesterday while the amplifier was powered up with music playing, and I measured 49.5 volts from a wall voltage that is pretty constant at 119-121 volts AC.

 

The RMS voltage isn't the issue, it's the ripple at full power under load measured with a load simulating complex speaker impedance and able to dissipate full amplifier power without catching on fire.

 

Ripple current, if excessive, causes a big, big, BANG!

 

 

 

 

 

 

 

 

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On 11/11/2017 at 11:38 AM, mboxler said:

Sorry if you already understand this, but just in case...

 

The Antek transformers are designed for 115 /230 volts.  If your voltage is higher, the output will be higher as well.  Last summer, our voltage spiked to 133 volts for quite a while until the power company finally fixed it.  

 

Is Sure power supply you referenced designed for + / - DC outputs?.  If you used the same  an4434 transformer wdecho used and wired it for 115v (inputs parallel, outputs series), you'll get both a + 48 volt dc output and a - 48 volt output.  You would only use 1 of the outputs.  I guess if you wired the inputs in series (which I assume wdecho did???), then you would get +24 and - 24.  You would then hook up your amp ground to -24 and positive to +24, which is the same as 0  and +48.

 

I hope I got that right.

 

Mike  

 

 

I understand the input voltage changing the output, but now I'm going to have to look into how to wire up the board (or the caps/rectifier that I build) to make sure I do it correctly. I looked on the site for any sort of instructions, and it's got a positive, negative, and a ground for the outputs, and two AC inputs (at least that's what it looks like).

 

22 hours ago, mike stehr said:

I asked William the same exact questions when I received my Antek transformer, which is the same model as his.

 

I'm just guessing, but if each primary is parallel connected, you'll get more current/power. If connected in series, you'll get less current and maybe a bit more voltage...same with the secondary leads. Sumthin' like that...

 

The supply I built for my 3255 is a exact copy of William's, the only difference is I used a 15,000uF 80V Chemi-Con capacitors.

I checked the supply voltage yesterday while the amplifier was powered up with music playing, and I measured 49.5 volts from a wall voltage that is pretty constant at 119-121 volts AC.

 

I wouldn't sweat much over getting an exact 53 volts on the supply used for the 3255, the manual for the evaluation board states 51 volts as being optimum. I'm guessing as long as it's 48-51 volts, a couple few volts probably isn't going to matter much with regard to audio output. Now maybe 10 volts or 15 volts lower might make a difference...

 

Do you have any pictures of your build (with the caps)? I've looked around for anything I can find on the TPA325X and there's a lot of information, but not many pictures. Just the responses on here have made me consider building the rectifier and using better caps.

 

That's what I'm expecting the voltage to be--around 50v. I'm not trying to hit 53v, just want to get close to get as much power out of it as I can.

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  • 3 weeks later...

Regarding the transformer...

 

Yes, Peak voltage from the transformer will be the output voltage times 2^0.5 (i.e. 1.414...)

 

You will want to take into account that the AC mains is +/- 10% and the transformer will usually be rated at 115VAC or 120VAC, so do the calulations based on 132VAC = 187V peak, or the output winding voltage rating times 1.414 times 1.1 to see what peak voltage you will get.

 

Also, the voltage rating is at full transformer load, so with no load the voltage will be a little higher, so fudge on the low side. You may want to ask the manufacturer what the "no load" output voltage is, or find it in the spec sheet.  The bigger the core vs output power, the less this number is affected.

 

If the part you are using has an ABSOLUTE MAX rating of 53VDC, then is probably based on a 60V process (semiconductor speak), and the transformer voltage will need to be sized based on "high line" (AC voltage +10%) and "no load" conditions.

 

10% less than 50V is 45V.  Shoot for that (about a 32V secondary winding), and if the transformer core is small, go lower.

 

Also, since you are close to 50VDC, step up to 63VDC rated capacitors.

 

 

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