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Old 19th May 2017, 02:18 PM   #3311
Eric is offline Eric  United States
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Quote:
Originally Posted by Dennis Hui View Post
Am I understanding correctly that with the IRFP044 you are getting rising gain as the frequency increases, until it oscillates at 130K?

The freq response in the article with IRFP240 seems very well behaved
Hmm... I never went back to compare to the plots from the original article. Yes, I am getting what appears to be rising response with frequency with the 044 part. I'll have to run my signal generator directly into my scope to make sure it's not an artifact of an out-of-spec generator.

I never thought much of it, just attributed it to what people described as bright on top .
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Old 19th May 2017, 05:40 PM   #3312
ZacharyP is offline ZacharyP  United States
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Originally Posted by nycavsr2000 View Post
Ask yourself what components make up the signal path?

Best,
Anand.
I'm still learning and I've re-read the ACA article multiple times, but my uneducated guess would be the gate stopper resistors (R5, R6), C1 at the output, but the rest I'm not sure about..


Am I on the right track?
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Old 19th May 2017, 07:13 PM   #3313
nycavsr2000 is offline nycavsr2000  United States
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Quote:
Originally Posted by ZacharyP View Post
I'm still learning and I've re-read the ACA article multiple times, but my uneducated guess would be the gate stopper resistors (R5, R6), C1 at the output, but the rest I'm not sure about..


Am I on the right track?

Zachary,

You are getting close. Refer to the AMP CAMP 1B schematic.

Ask yourself this. What are the amplifying components in the signal path in this circuit? What is the function of the 2SK170? What is a buffer? What is the function of Q1? How is Q1 biased? What is the different between the modes of operation (common gain, common source and common gate)? Although this article is his explanation on how opamps work, he does it by explaining discrete components first so check it out: https://www.passdiy.com/project/amplifiers/diy-op-amps

How does the function of Q2 differ from Q1? What is a current source? What are the components of the current source in this mu follower type circuit? Why use a current source in the 1st place?

What is the feedback path of this circuit?

The answer to your queries: The main amplifying component in this circuit is Q1. The signal goes in the gate which is where R6 is, and out the drain which is where R1, R2, R3, R4 are connected and finally through C1 to eliminate DC, so that the "AC music signal" is sent to your speakers. From the input side, the AC signal goes through R11, C3, then the 2SK170 JFET buffer and onto R6.

Q2, and several other components surrounding it, are all part of the current source.

If I were upgrading parts for this circuit (and I am not recommending that you should, since that can be a rabbit hole from a $$$ standpoint!), they would be R11, R12, C3, R6, R9, R1-R4 and finally C1. R13 and the LED are useless to me, and I personally would not even install them.

Best,
Anand.
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Old 19th May 2017, 11:03 PM   #3314
ZacharyP is offline ZacharyP  United States
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Quote:
Originally Posted by nycavsr2000 View Post
Zachary,

You are getting close. Refer to the AMP CAMP 1B schematic.

Ask yourself this. What are the amplifying components in the signal path in this circuit? What is the function of the 2SK170? What is a buffer? What is the function of Q1? How is Q1 biased? What is the different between the modes of operation (common gain, common source and common gate)? Although this article is his explanation on how opamps work, he does it by explaining discrete components first so check it out: https://www.passdiy.com/project/amplifiers/diy-op-amps

How does the function of Q2 differ from Q1? What is a current source? What are the components of the current source in this mu follower type circuit? Why use a current source in the 1st place?

What is the feedback path of this circuit?

The answer to your queries: The main amplifying component in this circuit is Q1. The signal goes in the gate which is where R6 is, and out the drain which is where R1, R2, R3, R4 are connected and finally through C1 to eliminate DC, so that the "AC music signal" is sent to your speakers. From the input side, the AC signal goes through R11, C3, then the 2SK170 JFET buffer and onto R6.

Q2, and several other components surrounding it, are all part of the current source.

If I were upgrading parts for this circuit (and I am not recommending that you should, since that can be a rabbit hole from a $$$ standpoint!), they would be R11, R12, C3, R6, R9, R1-R4 and finally C1. R13 and the LED are useless to me, and I personally would not even install them.

Best,
Anand.
Thank you, this is exactly what I'm looking for. I'll have some spare cash soon and figured why not upgrade a few ACA components, and try out a linear power supply.

Thanks again Anand
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Old 27th May 2017, 01:42 AM   #3315
3GGG is offline 3GGG  Australia
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I am looking to build a ACA in one of these chassis Express Delivery Aluminum power amplifier enclosure chassis case w/ heatsink | eBay the kit is o/s in the Diyaudio store.

I understand each channel requires a heatsink with a rating of around 1degree C per watt, as the eBay vendor is unable to provide this detail can anyone estimate the capacity of the chassis?

Apologies of the noob question.
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Old 27th May 2017, 02:45 AM   #3316
aspringv is offline aspringv  Australia
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I reckonbyou could use that case if you didn't do the higher current mod. I've an aca using heatsinks of that kinda fin depth and about 85mm by 180mm, and that's kinda borderline.
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Old 27th May 2017, 05:49 AM   #3317
romanescu is offline romanescu  Romania
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It will work but i think you will need a fan to have good temps...
That case without accesories is cheaper here http://m.ebay.com/itm/2107-Full-Alum...%257Ciid%253A1

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Old 29th May 2017, 02:19 PM   #3318
Enochrome is offline Enochrome  United States
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Quote:
Originally Posted by Variac View Post
Actually 24v has been used by many people and there seem to be no problems, in fact they prefer it, so 22-24v would be an upgrade with no downside...

19v PSUs are so popular for laptops that they cost about half what 24v PSU's so that's the main reason Nelson spec'ced them.
I am new to building an amp and electronics. How do you learn about power supplies, in regards to changing the power source for the ACA from 19v to 24v?
Also, I know there are secondaries on power supplies that can provide power to another component, but not sure how to do read or do this. My questions stem from that idea of powering the aca and the aikido lv off the same transformer(s).
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Old 29th May 2017, 03:59 PM   #3319
nycavsr2000 is offline nycavsr2000  United States
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Quote:
Originally Posted by Enochrome View Post
I am new to building an amp and electronics. How do you learn about power supplies, in regards to changing the power source for the ACA from 19v to 24v?
Also, I know there are secondaries on power supplies that can provide power to another component, but not sure how to do read or do this. My questions stem from that idea of powering the aca and the aikido lv off the same transformer(s).
Enochrome,

I was wrong about the overall gain of the 6GM8 version of the Aikido LV line stage, by just a few dB (see our discussion on pages 326-327 of this thread for a refresher). The overall gain is about 15dB, I had thought that it was 17dB. To calculate the gain of any Aikido circuit it is always equal to 1/2*mu. The mu of the 6GM8 is 14. 1/2*14 = 7. A mu of 7 is equal to a gain of 16.9 dB, by using this equation: dB= 20* log (amplification ratio or gain ratio). Here it is 20*log(7) = 16.9dB. In real life though it is a little lower as shown in the link below. So the actual value is about 15dB.

The overall gain of the ACA is about 14 dB.

Total is about 14+15 = 29 dB. That would be close to the overall gain of the amplifier.

You can most likely use the same switcher supply that is supplying the ACA, since the Aikido LV draws such little current or you can design a separate linear supply for just the Aikido LV and run the ACA off the switcher. Your choice and free for experimentation.

Details on the actual gain of the 6GM8 Aikido LV, and examples of linear supplies for that design is right here.

Best,
Anand.
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Old 15th July 2017, 10:33 AM   #3320
2 picoDumbs is offline 2 picoDumbs  Australia
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Thinking of doing a not-quite-turbo version with 24V rails.
Probably going to get a pair of these 24 Volt Roland Keyboard supplies.
https://www.rolandcorp.com.au/products/psb-14u/
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