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Amp Camp Amp - ACA
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Old 16th May 2018, 10:09 PM   #4351
MEPER is offline MEPER  Denmark
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Here a 20 kHz square (5v / div with 8.2 ohm load).
Does this look acceptable?

If other ACA can do the same it is a good starting point for a listening test?

I first need to finish the big 24V linear PSU's.
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Old 16th May 2018, 10:47 PM   #4352
MEPER is offline MEPER  Denmark
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20 kHz sine looks like this.....Ok I think.
When I turn signal down to zero I have approx. 1.4A bias. When I turn up to 1.9V in (5.3 V RMS out) bias drops to approx. 1.27 A.

Amp seems to behave well.........

I see no problems so far.......
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Old 16th May 2018, 11:28 PM   #4353
tjw59 is offline tjw59  United States
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Default Looks as good as it sounds!

so far.......[/QUOTE]

A collective NICE! For all of your pics.

We spent a couple of hours the first night I had mine running putting rubber pads behind pictures because of the bass response is phenomenal. Good to see it, too. I was too lazy to drag all of that stuff out and measure it. Was too busy listening.. : )
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Old 16th May 2018, 11:36 PM   #4354
tjw59 is offline tjw59  United States
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Quote:
Originally Posted by MEPER View Post
Maybe I will need an active preamp........instead of the passive I use in the moment.
The Emotiva Stealth DC-1 DAC gets along very well with these amps. It has both balanced and unbalanced outputs (Level controlled for both).
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Old 17th May 2018, 01:19 AM   #4355
RafaPolit is offline RafaPolit  Ecuador
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Hello again friends!

So, I went one more time hunting for heat sinks. The original design description by Mr. Pass (Amp Camp Amp #1) reads:
Quote:
It is designed to mount on the flat surface of a heat sink with the output devices. Each channel of the amplifier has its own switching power supply and draws about 1 amp of current DC. The supply should be capable of delivering more than 2 amps of current short term. At 19 volts, the dissipation of the amplifier is about 20 watts, and the heat sink it is mounted on should not be allowed to get more than about 25 degrees Centigrade above the ambient temperature. This means that the rating of the sink should be around 1 deg C per watt.
I can get my hands on this:
http://disti-assets.s3.amazonaws.com...eets/23768.pdf

Which is rated at 1.4C/W, which is about 50% less efficient than what is required in the literature. I was thinking I could put two of them in-line per channel, but they only have 3 in stock.

Is it really not enough or is there a chance that 1.4 may just work? They are sensibly smaller than those pictured in the kit cases, that is for certain.

Thanks for any feedback, best regards,
Rafa.
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Old 17th May 2018, 04:11 AM   #4356
kpsthakur is offline kpsthakur  India
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How much are they for? Did you try the diyaudiostore site? You can buy same or better sized ones there

40mm Heatsinks – diyAudio Store
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Old 17th May 2018, 04:14 AM   #4357
Extreme_Boky is offline Extreme_Boky
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Quote:
Originally Posted by MEPER View Post
20 kHz sine looks like this.....Ok I think.
When I turn signal down to zero I have approx. 1.4A bias. When I turn up to 1.9V in (5.3 V RMS out) bias drops to approx. 1.27 A.

Amp seems to behave well.........

I see no problems so far.......
Both photos look good. The amp behaves admirably bearing in mind the simplicity, which is its main virtue.

Did you do the measurements with 19V DC or 24V DC?

Can you repeat the measurements with 4 ohms resistor loading?

Thanks,
Nick
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Old 17th May 2018, 04:25 AM   #4358
RafaPolit is offline RafaPolit  Ecuador
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Quote:
Originally Posted by kpsthakur View Post
How much are they for? Did you try the diyaudiostore site? You can buy same or better sized ones there

40mm Heatsinks diyAudio Store
Thanks. The ones I have access to are $16 each.

The ones from DIY store are magnificent and oh, so beautiful and perfect. But I live where shipping two of those costs $40 on heat sinks and $46 on shipment.

So 6L6, Jason and people here have been incredibly kind and helpful in counseling me on locally available options.

Perhaps I can somehow make enough area touch the entire chasis so that it can help also with the dissipation?

Thanks once more,
Rafa.
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Old 17th May 2018, 05:44 AM   #4359
myaleks is offline myaleks  Germany
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@RafaPolit
If you have problem with shipping to Ecuador may be is good to look for this DIY kit from ebay Hood 1969 Class A Power Amplifier Kit with 1083 Regulator Toshiba 5200 Output | eBay
I tried it and it sounds really great. Not so expensive (only 16,66$ per channel) with free shipping. :-)
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Old 17th May 2018, 05:54 AM   #4360
MEPER is offline MEPER  Denmark
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Quote:
Originally Posted by tjw59 View Post
The Emotiva Stealth DC-1 DAC gets along very well with these amps. It has both balanced and unbalanced outputs (Level controlled for both).

I use a Cambridge DAC Magic Plus which also has fixed or adjustable ouput (pre-amp). But I don't know if DAC can output more voltage that I get out in fixed mode. In pre-amp mode it adjusts output in the DSP by multiplying the digital input by a factor (usually < 1). I get better sound by using fixed output and passive pre-amp after DAC. Also when I put my ear close to the tweeter it is 99.99% silent but with DAC as active preamp the tweeter is "only" 97% silent or so......(the "sshhhyyyy" sound).


But I am looking for a DAC upgrade......but DAC Magic Plus was good sound for the money. Maybe a DIY Pass DAC?
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