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Old 25th March 2004, 05:48 AM   #21
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Quote:
Yes, it is indeed a battery powered - thirty-something 12 volt batteries in series
Any proof to support this statement? Or were all the reviewers too dumb to notice the batteries?
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Old 25th March 2004, 05:59 AM   #22
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Quote:
Originally posted by rwagter
Just a nice pic of the inside (be patient):

http://www.lothx.com/mj4.jpg

Interesting that they would take a photo of the very rectifiers providing the DC. Hmm, where's the customer feedback line, the backside of my hand is feeling uppiddy..

Tim
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Old 25th March 2004, 06:04 AM   #23
imix500 is offline imix500  United States
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Yup, sure looks like a switcher to me.
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Old 25th March 2004, 06:08 AM   #24
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That look as if they either use a full blown SMPS or transistors as sysnchronous rectifiers. If doing the latter, maybe they even use a trick to minimise switching noise or stabilise the DC voltage or both.

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Charles
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Old 25th March 2004, 06:35 AM   #25
stormy is offline stormy  United Kingdom
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Quote:
Originally posted by jlsem


Yes, it is indeed a battery powered - thirty-something 12 volt batteries in series. It's made in Korea and it costs more to ship the power supply from there than the batteries cost. Beautifully made stuff although it's only a simple WE91-type circuit.

John

Hi,
I just had a look at 1 of the revues on the same page and thay talk about a mains cable when mentioning the layout, also i cut
this out for you to read.

"As is part and parcel of the single-ended triode community's approach to reality, there is an element of mystery to the circuitry of the Ji300. According to its designer, who allegedly worked on high-tech military power supplies, the circuit is unlike any other SE, especially the 'rectifier-less' power supply and the output transformers; power supply impedance is fifty-times lower than conventional rectifier/filter components and is supposed to replicate DC power via an innovative new circuit; but as the importer said, 'Don't ask me - we couldn't get into the amp!' The output transformers are toroidals and have foil windings as well as round section copper wire and they are said to be the world's first semi-silver-foil output transformers. The theory is that foil suffers 24-times less skin effect than wire in this application."


Looks verry like a switcher.


Regards stormy.
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Old 25th March 2004, 02:55 PM   #26
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Quote:
Originally posted by LaZarus
Walt Jung writes about a full wave ac-dc converter without a rectifier. I haven't read that part, but it could be interesting.

Follow this link and look on page 150.

Cheers

LaZarus,

Are you referring to the PDF page 150, which is 141 in the document, or 150 in the document. In either case, there is a diode there somewhere. In the case of the circuit on page 141 (PDF 150), the diode is Q1. Whenever you connect the collector and base together you form a... diode! The diode connects from the negative input to ground, and causes the amp (A1-A) to conduct only half wave. I guess the other half goes directly to the Q6, Q7 combo. I wonder there the +/- 15 volts is coming from ? Hmmmmmmm. Unless it is powred by the AC coming in being... (Ahem. Cough, cough)... rectified?

BTW, where the heck is Q2???!!

At any rate, page 150 in the document shows clearly right in the middle a bridge rectifier.

So... I guess a switched supply, even though it rectifies to DC before the switcher circuit, still uses diodes (AKA Rectifiers) somewhere.

Gabe
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Old 25th March 2004, 05:59 PM   #27
stormy is offline stormy  United Kingdom
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Its got to be a sales pitch, this amp cannot claim to be
rectifireless for the fact that the input is ac.
wheather it uses diodes to do this or not is of no consiquence

the fact that ac is converted to dc means its rectified,
unless the mains lead thay mention in the revue is a dc input,
I think not or thay would have mentioned that.




regards stormy
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Old 25th March 2004, 11:01 PM   #28
jlsem is offline jlsem  United States
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Quote:
Any proof to support this statement? Or were all the reviewers too dumb to notice the batteries?
The iteration I saw had a lead-acid battery power supply in a separate box. This one is obviously Mark II. No need to get your panties twisted.

John
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Old 26th March 2004, 11:52 AM   #29
igormak is offline igormak  Russian Federation
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Hi, guys.

Quote:
Originally posted by jlsem


The iteration I saw had a lead-acid battery power supply in a separate box. This one is obviously Mark II. No need to get your panties twisted.

John

It could be that Mark II a battery supplyed. Question under discussion here - is it possible or not what they said: rectifierless
power supply. Looking at pic http://www.lothx.com/mj4.jpg I see
electronic switcher. Seems to be they need say Power Transformer Less amp, imho. It is possible, of cause.

Igor.
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Old 26th March 2004, 04:48 PM   #30
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No, it has a high frequency transformer.

Tim
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