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Informative questions before starting β24 build

beta24

Re: Informative questions before starting β24 build

Postby Pieterh » May 27th, 2017, 11:48 pm

amb wrote:The big screw terminal caps are indeed rated for higher current and long life time, but the Nichicon LGU or LGY series is more than sufficient for the job. The Elnas I used are 35x70mm (diam/height). The aforementioned Nichicons are 35x40mm. Since they are so compact, you may want to "upgrade" to 15000µF in the same series, which are 35x50mm. Or, go with Nichicon LLS1H153MELC which is 18000µF in 35x50mm, and higher ripple current rating too.


Ok, so we can use between 2x10.000 up to 2x18.000uf per channel? can we use larger capacitance than 10.000uf without any side-effects like the need for a soft-start circuit?

I found that Nichicon also has a series of audio-grade capacitors, the LKG series. LKG1H103MESCBK is the 50V 10.000uf version (35 x 50mm). Ripple current is 5.05A. Lifetime is 'only' 1000 hrs at 85C but this shouldn't be a constraint, right? What do you think, could this LKG-type bring any advantage over the LGU/LGY or LLS 'standard' series?

I understand now that screw type capacitors have their safety vent on the same side as the screw terminals and therefore have to be mounted upright (or horizontally). This isn't practical/aesthetic in the B24. That is why you advise snap-in types, right? What about Lug terminal types, any thoughts?
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Re: Informative questions before starting β24 build

Postby amb » May 28th, 2017, 5:19 pm

Pieterh wrote:Ok, so we can use between 2x10.000 up to 2x18.000uf per channel? can we use larger capacitance than 10.000uf without any side-effects like the need for a soft-start circuit?

Higher capacitances will increase the power-up current surge. If you're using a conventional switch or a electromagnetic relay as a power switch, then it might affect the contacts' longevity, so you might want to consider a soft-start circuit. No such problem when using a suitably-rated solid state relay though.

I found that Nichicon also has a series of audio-grade capacitors, the LKG series. LKG1H103MESCBK is the 50V 10.000uf version (35 x 50mm). Ripple current is 5.05A. Lifetime is 'only' 1000 hrs at 85C but this shouldn't be a constraint, right? What do you think, could this LKG-type bring any advantage over the LGU/LGY or LLS 'standard' series?

For power supply purposes there is no need for "audio grade" capacitors. I would stay with the longer life units.

I understand now that screw type capacitors have their safety vent on the same side as the screw terminals and therefore have to be mounted upright (or horizontally). This isn't practical/aesthetic in the B24. That is why you advise snap-in types, right? What about Lug terminal types, any thoughts?

Which specific capacitor are you referring to?
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Re: Informative questions before starting β24 build

Postby Pieterh » May 29th, 2017, 7:35 am

Thanks for your feed back! I will be using the Crydom D2440 solid state relay 240V/40A.

When looking for 50V / 10.000uf / dimensions close to your Elna's, I came across this lug type Nichicon LKG1H103MKN which is 35x80mm. I wondered why these lug types have larger dimensions than snap-in for similar voltage/capacitance?
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Informative questions before starting β24 build

Postby amb » May 29th, 2017, 1:57 pm

Since the LKG series is offered in both snap-in and lug styles, and the lug style tends to be taller, perhaps it has something to do with the internal construction of the lug posts requiring the added height? Just guessing.
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Re: Informative questions before starting β24 build

Postby Pieterh » July 1st, 2017, 4:05 am

I had some interaction with the Polish Toroidy about their Supreme Audio grade V2 toroidal transformers. Their loaded/unloaded voltages are 30V/30.5V (500VA, unreg.) and 35V/35,3V (30VA, reg.). Idle current 500VA transformer is about 50mA. They use a multifilar winding methods, sectioning of secondaries is not an option. A softstart is not needed with 530VA they say.

Now I am thinking about having separate transformers toroids for unregulated/regulated parts, one 500VA (170 mm diam. by 80mm height) and one 30VA (105mm diam. by 50mm height). Toroidy says that this could be beneficial. What is your opinion on one or two transformers here? We know that they can also make one transformer with all 30 and 35V secondaries in 170mm by 80mm.

If I have two transformers, these are a little bit larger than the reference build by Ti (166 mm and 83mm), I have been playing with the FPE drawing tool to see whether I can fit the two larger transformers (blue) and other components on the bottom plate and cap bracket (see figure). I think that potential problem areas are with the bulgin push button in the front plate which needs about 20mm space between front plate and transformer. Ti, you have 24mm between front plate and the Plytron. We can bent the solder tabs of the bulgin button a little to gain 5mm space there?

Another potential problem area is with the components on the back plate like the IEC inlet, the small (17mm height) 1,6VA transformer and the E24. But I think with some relocation, I can manage that.

In this design, the two relais are mounted on the top of the cap bracket. As a result, the two bleeder resistors have to be mounted on the underside of the cap bracket with tapped drill holes. I think I'll take the smaller Nichicon 35x50mm 15.000uf caps.

Do you have any other thoughts about this design?

Bottom cap plates V2.JPG
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Re: Informative questions before starting β24 build

Postby amb » July 1st, 2017, 2:14 pm

If there is any theoretical advantage of separate transformers, it probably won't materialize in the β24 due to the good regulation of the σ22s. I chose two transformers because it was easier to get.

As for front and rear clearance, it is a very tight fit. You're correct about the Bulgin switch needing space, as well as the rear panel components. Keep in mind that I used another 10mm "front panel" for my rear, and mounted all the rear panel components on a subpanel that bolts onto the main panel, so that gave me an additional 10mm of room that I actually needed.
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Re: Informative questions before starting β24 build

Postby SonusBonum » July 18th, 2017, 11:58 am

Hoi Pieter,

Why don't you come over and listen...? :-)
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Re: Informative questions before starting β24 build

Postby lugili » July 19th, 2017, 5:58 am

Pieterh,

not sure why you are thinking of buying separate transformers from toroidy for the regulated and unregulated parts of the amp.
I have their version with all secondaries on one primary and so does sonusbonum, as far as I understand. I have built the class AB version, he has several class A versions of the beta 24.
I sold my Pass, he sold his Burmesters ...
Why make your life complicated ?
;-)
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Re: Informative questions before starting β24 build

Postby SonusBonum » July 19th, 2017, 9:03 am

Hoi Pieter,

I think I understand what you're going thru: it's the pre-fun part of a complex project. Having said that and knowing I went thru the same process (Ti and others know) I can now guarantee you that what ever you build, it will be beyond your imagination. See lugili's post to confirm. With all due respect I think you have to determine first:

Class A or A/B:
Can't say anything about this. Following my gut feeling I always went for class A. It's just the most logical choice.

One cabinet or two:
Two cabinets gives you shorter cables to your speakers. That's what you want with respect to damping factor.

As far as those Toroidy transformers are concerned: They are the most silent I have ever had. Like I said before, my very expensive (...!) four Burmesters were louder than a hairdryer with respect to both high efficiency speaker noise as well as magnetic hum. And those Burmesters were class A/B in idle mode, to keep the electricity bill down. The Toroidy's I use now are constantly on (24x7) supplying 2 times 1,4 amps of current per channel...! And you can hold your ear against it, you will not hear it. And all that for a rediculous price.

One tip before I go sit in my listening chair to meditate: The wires coming out of those Toroidy's need more (bending) space than you think. Keep that in mind.

Still open for a listening/demo session and there to help...!

Ronald
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Re: Informative questions before starting β24 build

Postby Pieterh » July 30th, 2017, 7:56 am

Hi guys! Thanks for your responses! I really appreciate! Due to circumstances i am a bit late with my response. I like to know more about some of the components that we use and why some of those have been chosen by others. E.g. why do we use certain caps for the non-regulated part. Or, I try to understand more about the quality indicators of the toroids versus El trafo's. e.g. how do idle currents compare (they are about the same (50-65ma) for the 500va plitron and the toroidy one). I talked to Pavel on this forum who gave insightful info on his trafo's. It is that type of info that is nice to examine and then think what i should do. Then consult Ti and you guys about those ideas and reconsider.
Or why do highend amp manufacturers use plitron or noratel toroids? About that I have spoken to a dutch toroid manufacturer who told me some about menno van veen, a dutch engineer, who cooperated with plitron and together they developed the plitron low noise and low inrush toroid for audio. He explained e.g. why those plitrons are twice as heavy as the toroidy transfomers. That kind of stuff is very interesting to know, besides currently i have more time to think while commuting than to solder at home. Busy work and family. Times will change....

Then the plitron is so expensive to import to the EU. The noratel (norway, but made in far east factory) is also very expensive as they focus on large number orders and not single piece. The dutch company I contacted has a perfect audiophile trafo (all voltages in one black pot) but much more expensive than the toroidy. About the 2 trafo's. The arguments pro are the (theoretical) chance for improvement over a single one, and two trafo's may show off better ( i think). Arguments against are the limited space inside the hifi2000A4300 and easier build. And i want to stick to that size chassis. So I think I'll go with one polish transformer but I have the summer to think it through. Responses welcome!
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