[Folsom]

I've been meaning to try James Transformer OA core. They have the most sound principles.; including a shield I've chatted briefly with them, and they can offer exactly what I want. 150/200va is enough juice, 120v primary, 16v secondary.

But I haven't done a direct ear comparison yet. The shield should give benefits like the dual bobbin does, but I want to confirm that.

[lacro]

I've been meaning to try James Transformer OA core. They have the most sound principles.; including a shield I've chatted briefly with them, and they can offer exactly what I want. 150/200va is enough juice, 120v primary, 16v secondary.

But I haven't done a direct ear comparison yet. The shield should give benefits like the dual bobbin does, but I want to confirm that.

What's the max secondary voltage of the transformer that should be used? I would like to be able to use the Antipole PS with the TDA 7297, and some class D amps (TPA3116/3118) amps. 

[Folsom]

The Antipole rectified voltage should not exceed 45v, which is about 30v AC from transformer.

[shadowlight]

I like to thank Larry (Lacro) for building my amp for me.  I have not had a chance to listen to it yet (life getting in the way ).  Here are some pictures of the build.

















I currently have a Astron and a Dell laptop power brick.  Need to order power connector for Astron and transformer/case for the Antipole.  Until then can I use a power strip with the laptop brick (19.5v @ 6A) with out impacting the amp?

[Odal3]

 

[Folsom]

As long as the laptop power brick can maintain 19.5v it'll work. So power it up and play some music loud and watch the voltage with a volt meter, if it stays above 19v easily, it's ok. With linear power supplies you can watch the voltage drop, so they need a much larger buffer over 19v. The recommend transformer lands it around 24v and does a great job of not going too low during big loads.

[Odal3]

I'm using an Astron with my amp, and it works really well in my set-up. I rarely play very loud so the lower voltage still works fine in my system, plus it sounded better than a laptop power brick.

[lacro]

As long as the laptop power brick can maintain 19.5v it'll work. So power it up and play some music loud and watch the voltage with a volt meter, if it stays above 19v easily, it's ok. With linear power supplies you can watch the voltage drop, so they need a much larger buffer over 19v. The recommend transformer lands it around 24v and does a great job of not going too low during big loads.

Jeremy, thanks for that description...
So to clarify in my mind: The Transformers secondary delivers 16V AC; it's rectified to 24V DC by the Antipole PS, and is regulated to 17.8-18V on the amp board. Is that correct? So what is happening when the DC voltage delivered to the amp is lower than 19.5V continuous such as when someone is using the 13.8V Astron linear PS? Does that take the regulator and 12 Oscon capacitor bank out of the circuit, and power the chip with the 13.8V?

[Folsom]

When it's lower the amp sees very significantly reduced power. The KMR only turns on as an "infinite capacitor" once it hits sufficient voltage. When I tried it, the bass wasn't that great at all volumes.

[shadowlight]

I rarely play loud and the speakers that I have are the Zu Druid V @ 101db efficient so I think I will be good for the couple of weeks that it will take me to get the antipole up and running.  I already have the transformer, just need to find the case for it and build it out.

[mlundy57]

This may be a dumb question but I'll ask it anyway. If the Antipole, or other PS, supplies 24VDC to the amp board, can you connect a 24V battery directly to the amp board without using the Antipole?

If so, what are the pros and cons of connecting the battery direct to the amp vs going through the Antipole?

OK so that was two questions...

Mike

[S Clark]

Yes you can.  That's the way I've been running mine all summer, and so far, I'm happy with the results. 

[Odal3]

S Clark - what battery are you using?

[S Clark]

Twin 12V 18AH connected in series.  They are about $35 each from Amazon w free shipping. 

[Odal3]

Thanks for the info. How long does the charge last for?

[Captainhemo]

Twin 12V 18AH connected in series.  They are about $35 each from Amazon w free shipping.

Scott, did you get a charger  for your batteries yet, seem to recall yo uwere using your bike  "charger"
I've already got the 75ah  single 12v batter  and my C-TEK but it won't charge  2 of them  wired in  series, I don't want to have to re wire in parallel every time I want to cahrge

Been thinking of a setup that I could run my Dodd pre  at 12v, the folsom at 24v, and have a simple charging solutioin , a fw ideas but not sure any would actually work 

jay

[S Clark]

No, I'm still using a motorcycle tender with everything put together with alligator patch cords.  It only takes me a couple of seconds to redo the wiring to charge, or to put it back again to play.  It's a little bit of a pain, but not bad.  When the Texas heat breaks, the Folsom amp will go back in the closet and the Dodd tubes come out. 
When I do finally get around to it, I've got a 24v charger for a DAC that Gary D built for me years ago... and it hasn't worked in a while.  I need to adapt it to the Folsom amp batteries.

[S Clark]

Thanks for the info. How long does the charge last for?

I don't know... it's never run down to the point of any noticeable degradation. I'd say you are probably good for at least a long day of listening- 12 hours???

[Folsom]

Radioshack sells alligator test leads. I use them for a lot of things but I got mine somewhere I forget a bit cheaper.

[KR500]

my amp project is at a standstill due to  not finding an affordable case .
I did look at the C+C one from Surplus Sales but it didn't seem tall enough to accommodate the height of the transformer .
Since other builders appear to be using that case I was curious how they are dealing with that issue ?
I've scoured the area and online for a case my budget can handle but nothing so far.