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Old 15th July 2005, 06:35 AM   #701
Coulomb is offline Coulomb  England
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I am going to be buying some 400VA 15-0-15VAC R-Core transformers for my Mini A and Aelph 30. They will be $65 US plus shipping to me (to be shared equally) and then shipped to individuals. Shipping would be about $10 each to ship from Hong Kong to Toronto, Canada and $10 Each to ship from Toronto to anywhere in North America via ground.

Here is a Photo of the product. The dimensions are as follows:

Click the image to open in full size.

165mm X 135mm X 75mm
3.8KG

Approximately $85 US each all told for a high quality R-Core transfomer, not bad all in all. I need to order 15 to make the minimum qty for the custom configuration. I have orders for 8 already. Please email me ASAP if you are serious about participating.

Regards

Anthony
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Old 15th July 2005, 06:39 AM   #702
jleaman is offline jleaman  Belgium
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Quote:
Originally posted by Coulomb
I am going to be buying some 400VA 15-0-15VAC R-Core transformers for my Mini A and Aelph 30. They will be $65 US plus shipping to me (to be shared equally) and then shipped to individuals. Shipping would be about $10 each to ship from Hong Kong to Toronto, Canada and $10 Each to ship from Toronto to anywhere in North America via ground.

Here is a Photo of the product. The dimensions are as follows:

Click the image to open in full size.

165mm X 135mm X 75mm
3.8KG

Approximately $85 US eache all told for a high quality R-Core transfomer, not bad all in all. I need to order 15 to make the minimum qty for the custom configuration. I have orders for 8 already. Please email me ASAP if you are serious about participating.

Regards

Anthony
weird the photo didnt work for me.. and what is eache ?
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Old 15th July 2005, 06:41 AM   #703
jleaman is offline jleaman  Belgium
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It';s working now..but actually here is a better pic.. Pic stolen from krell group buy..
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File Type: jpg r-core01m.jpg (66.2 KB, 1016 views)
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Old 15th July 2005, 06:46 AM   #704
Coulomb is offline Coulomb  England
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Quote:
Originally posted by jleaman
It';s working now..but actually here is a better pic.. Pic stolen from krell group buy..
This transformer is of poorer quality as it has no screen and a cheaper metal stamping.

Regards

Anthony
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Old 18th July 2005, 12:01 AM   #705
chrisb is offline chrisb  Canada
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Default bias setting for 4 or 16ohms

Thanks to Jason & Dave, I'll be embarking on assembly of mini-A shortly.

My main question is that since it's almost certain the amp will driving only bipoles (either CSS WR/FR125 or Fostex FE127E)

Is there a consensus whether the 10watt version of this unit sounds better in either 4 or 16ohms. If not, my preference in the past with tube gear has generally been with series (16ohm) wiring.

In either case, can anyone advise, or point a link to instructions on the recommended bias resistor values for 4 or 16ohms.

thanks all y'all
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Old 18th July 2005, 12:12 AM   #706
jleaman is offline jleaman  Belgium
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Chris that's 15 Watts with 20- + V rail's.
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Old 18th July 2005, 04:41 PM   #707
chrisb is offline chrisb  Canada
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Default thanks, J

Quote:
Originally posted by jleaman
Chris that's 15 Watts with 20- + V rail's.

for the correction

my original question stands to the builders group - any preference for sonic merits in 4 vs 16 ohm loads? and if so, how does a math challenged old fart determine any necessary revision to bias setting resistors?

I've tried a quick search on the subject, and results were either none, or every thread ever referencing the mini-A.
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Old 18th July 2005, 04:46 PM   #708
jleaman is offline jleaman  Belgium
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Default Re: thanks, J

Quote:
Originally posted by chrisb



for the correction

my original question stands to the builders group - any preference for sonic merits in 4 vs 16 ohm loads? and if so, how does a math challenged old fart determine any necessary revision to bias setting resistors?

I've tried a quick search on the subject, and results were either none, or every thread ever referencing the mini-A.

I found this...

Keep in mind that you can jack up the bias by increasing R11. The stock value for the Mini-A is 47k. That gives you about an amp of bias. Just for fun, I tossed in a 220k resistor, and ramped up the bias to something like 1.6A.


Here ....The Mini-A

Post # 16

Sorry this is R13 NOT R11

Resistor 13 is the one you want to change.
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Old 24th July 2005, 03:18 AM   #709
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Default some experience to share..

In my quest to get this thing going I found it nice that others have shared thier Aleph experience as it helped tremendously! Here are a couple of my experiences...
__________________________________________________ _______
Just as a reference as to what you may see or expect regarding bias bias on the mini-a. Mine works nicely and measures as follows:

I am using .5R source resistors and rails are +-~17v. My output resistors are 4x1R in parallel.

-With r13 at 47k I get .55v across the resistor (1.1a).

-With r13 lifted I get .68v across the resistor (1.36).
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I had 1 noisy channel.. tons of distortion. It was a bad protection zener. This has happened to me before on an A30! I pulled all my protection zeners because I seem to have NO luck with them.

__________________________________________________ ________

I had seemingly irreconcilable hum. I am using dual supplies but This may help on single supply too. The hum was there with or without inputs..inputs shorted...not shorted..whatever.Nothing seemed to work. The solution ended up to be doing a 'serial' board ground. In other words..I took a wire from the star ground into board 1, then wired the ground of board 2 directly to the board 1 ground (at board 1). Board 2's ground does NOT go to star. Hum gone

LOL. I was left with a faint buzz and spent HOURS troubleshooting to no avail. The other night I decided to let the amp 'burn in' all night in the garage by just leaving it powered. As I left the garage I turned off the florescent lights.. guess what..buzz gone. DOH!

Marc
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Old 25th July 2005, 10:10 PM   #710
steenoe is offline steenoe  Denmark
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Quote:
Please find attached Aleph 5 part designations for brian's pcb,s if somebody else wishes to check for errors please feel free to report your findings.
Just found this XLS file in post #615 Did you guys consider R8 in the original Aleph 5 schematic? The input resistor for singleended is only 1K. (R8) It is connected after the 10K resistor for Balanced input! Any thoughts on that?

Steen
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