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Old 10th October 2009, 02:05 AM   #5131
labjr is offline labjr  United States
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Quote:
Originally Posted by fishski13 View Post
my Naim amps did this quite frequently.

i placed an order for a 18+18 500VA TX from SumR. the other TX i have from Richard is dead quiet. not terribly expensive at $98 either. the PS will be in a separate chassis a la Naim for possible future Pass recipes. i've opted not to go down the bridged amp route for now - it's time i started playing around with FR drivers.

heatsinks arrived today too!
Did that price include potting?
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Old 10th October 2009, 02:53 AM   #5132
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Originally Posted by labjr View Post
Did that price include potting?
no. $130 total for an encapsulated/shielded, plus shipping is $26 to MN. i had Richard pot my other TX for a B22 headphone amp/preamp that some builders have had noise problems with. although the non-potted version does have a "banded shielded core" to help absorb some EMI. lead time is 1 wk or so.
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Old 10th October 2009, 03:09 AM   #5133
labjr is offline labjr  United States
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Originally Posted by fishski13 View Post
no. $130 total for an encapsulated/shielded, plus shipping is $26 to MN. i had Richard pot my other TX for a B22 headphone amp/preamp that some builders have had noise problems with. although the non-potted version does have a "banded shielded core" to help absorb some EMI. lead time is 1 wk or so.

I'm still debating with myself about getting another 300VA Plitron to make mono blocks or getting 500-600VA transformer for a stereo amp. I noticed the SUMR transformers don't regulate quite the same as Plitron. Not sure if this would affect anything. Just want to be sure to get proper secondary voltages so everything is running in the sweet spot.
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Old 10th October 2009, 04:57 AM   #5134
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Quote:
Originally Posted by labjr View Post
I'm still debating with myself about getting another 300VA Plitron to make mono blocks or getting 500-600VA transformer for a stereo amp. I noticed the SUMR transformers don't regulate quite the same as Plitron. Not sure if this would affect anything. Just want to be sure to get proper secondary voltages so everything is running in the sweet spot.
to put your mind at ease: http://ecmweb.com/mag/electric_basic...mer_voltage_2/
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Old 10th October 2009, 08:53 AM   #5135
AndrewT is offline AndrewT  Scotland
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Originally Posted by labjr View Post
I'm still debating with myself about getting another 300VA Plitron to make mono blocks or getting 500-600VA transformer for a stereo amp.
build two completely separate monoblock power amplifiers.
Locate each immediately behind the speaker terminals with very short speaker cable.
__________________
regards Andrew T.
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Old 10th October 2009, 11:37 PM   #5136
alazira is offline alazira  United States
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Default P1/r3

Quote:
Originally Posted by Nelson Pass View Post
If you have a scope and/or distortion analyzer, then you
can play with this. Try different values, starting with values
close to the stock values and see what you get.


Thanks for the reply.
One other thing that I have been wondering about is the P1/R3 portion of the circuit (the 2.2K paralleled with the 5K trim pot). Why not just use a 1.5K trim pot and save the resistor?

Garrett
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Old 11th October 2009, 06:18 PM   #5137
CBRworm is offline CBRworm  United States
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Originally Posted by alazira View Post
Thanks for the reply.
One other thing that I have been wondering about is the P1/R3 portion of the circuit (the 2.2K paralleled with the 5K trim pot). Why not just use a 1.5K trim pot and save the resistor?

Garrett

I don't know for sure, but one benefit might be to prevent mass destruction if the pot goes open for some reason.
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Old 11th October 2009, 06:44 PM   #5138
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Originally Posted by CBRworm View Post
I don't know for sure, but one benefit might be to prevent mass destruction if the pot goes open for some reason.

Yes, but also it allows you to fine tune it so you can adjust by tiny amounts to get your DC offfset to almost zero


Fran
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Old 13th October 2009, 02:18 AM   #5139
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Has anyone tried using switchmode power supplies but incorporating crc or clc at the output to remove any of the noise switch modes are renowned for?
This is something I would like to investigate but I am not sure where I can pick up a 500 Watt switchmode with the appropriate votages
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Old 13th October 2009, 02:29 AM   #5140
jleaman is offline jleaman  Belgium
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Originally Posted by thanh1973 View Post
Has anyone tried using switchmode power supplies but incorporating crc or clc at the output to remove any of the noise switch modes are renowned for?
This is something I would like to investigate but I am not sure where I can pick up a 500 Watt switchmode with the appropriate votages
switchmod on a class a ? are you crazy ? way to much work way to much noise. Not worth it at all. Toroidial transformer caps etc etc
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