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Old 30th December 2011, 11:46 PM   #1
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Default Which to choose?

So, if you had the following choices of power amp clones to build, which would you choose:
A Naim 140:
50W amplifier PCB Naim 140 !! | eBay
Krell KSA100:
High Power Pure Class A amplifier PCB KSA100 ! | eBay
Quad 405:
Class A dynamic biasing 80W amplifier PCB Quad 405 2pcs | eBay
JLH 2003:
Pure Class A OCL SEPP amplifier bare PCB JLH 2003 | eBay
Krell KSA50:
High Power Pure Class A amplifier PCB KSA50 ! | eBay
Musical Fidelity A1000:
Pure Class A 50W amplifier PCB MF A1000 1pc ! | eBay

Any one of these has more than enough power for my needs. I am not very experienced building solid state power amps but I've built plenty of other things in the past.
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Old 31st December 2011, 01:03 AM   #2
Bigun is offline Bigun  Canada
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In terms of comparing these amps - I've not heard them, but their reputation is such that I expect they all sound really good.

But in terms of building them there are quite a few differences I imagine. For example, the Class A amps will tend to operate at lower output power and/or require significant heatsinks to get rid of the excess heat - they'll want some beefy power supplies too. These things are usually more expensive, bulkier and heavier and the Krell amp originally had a fan to cool the heatsink further.

I'm not familiar with this supplier - don't know how good their pcb's are. As a suggestion, if you want a Class A amp I'd choose one from the Pass labs forum because you will be able to go there for support and you know for sure they all work really nicely.

F5 power amplifier

I don't know which pcb's are officially sanctioned - if you Google for Pass F5 you should find a few options for buying pcb's.
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Old 31st December 2011, 02:53 AM   #3
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by dirkwright View Post
Any one of these has more than enough power for my needs. I am not very experienced building solid state power amps but I've built plenty of other things in the past.
#1. JLH 2003 (15W-25W?)
This is a classic. Problem is the low wattage may not suit certain speaker and room. Many supports can be found from a dedicated JLH thread in DIYAudio or from The Class-A Amplifier Site.

#2. MF A1000 (50W)
This is easy to modify, and because of the topology is very common, I like the possibility to use PCB intended for other amps. Problem is in matching of the components, especially the output devices. That's if the high quality sound is wanted.

#3. Krell KSA-50 (50W)
I don't know about the difficulty you will have to build this amp. Original one is using special small heatsinks with a fan. You can use a different but a much bigger heatsink.

#4. Krell KSA-100 (100W)
The only good thing about it is its power (compared to KSA50 for example). It is this power and the associated difficulty in building which also puts this amp below the Musical Fidelity.

#5. Quad 405 (80W)
I'm not sure about this amp. Have heard only once in a used audio shop. But I have built a better current dumping amp and a Quad 303 that is more favored by a few so I think I can grossly "rate" its quality. Not really a class-A so not difficult to build.

#6. Naim 140 (45W)
While easy to build, this is not high end, cannot be compared with class-A amps.
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Old 31st December 2011, 03:56 AM   #4
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The best point about Ebay kit product is that they are a single, low cost purchase for just the amplifier PCB parts.

It's also worth staying with popular kits which have plenty of help and comment here.
Just don't forget that the kit purchase is only a part of your amplifier so go for a class AB
and 50 watts or less in a discrete design without op-amps or chipamps so there is something there to learn from.
That should narrow things a bit
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Old 31st December 2011, 12:12 PM   #5
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Quote:
Originally Posted by Ian Finch View Post
The best point about Ebay kit product is that they are a single, low cost purchase for just the amplifier PCB parts.

It's also worth staying with popular kits which have plenty of help and comment here.
Just don't forget that the kit purchase is only a part of your amplifier so go for a class AB
and 50 watts or less in a discrete design without op-amps or chipamps so there is something there to learn from.
That should narrow things a bit
Thanks. Can you suggest some of the latter amplifiers please? I'm perfectly happy with just a circuit board and a schematic.
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Old 31st December 2011, 12:15 PM   #6
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Quote:
Originally Posted by Bigun View Post
In terms of comparing these amps - I've not heard them, but their reputation is such that I expect they all sound really good.

But in terms of building them there are quite a few differences I imagine. For example, the Class A amps will tend to operate at lower output power and/or require significant heatsinks to get rid of the excess heat - they'll want some beefy power supplies too. These things are usually more expensive, bulkier and heavier and the Krell amp originally had a fan to cool the heatsink further.

I'm not familiar with this supplier - don't know how good their pcb's are. As a suggestion, if you want a Class A amp I'd choose one from the Pass labs forum because you will be able to go there for support and you know for sure they all work really nicely.

F5 power amplifier

I don't know which pcb's are officially sanctioned - if you Google for Pass F5 you should find a few options for buying pcb's.
I did a brief read of that thread and Google'd the Pass F5 but didn't find a circuit board. I didn't spend much time looking though. Can you suggest a source? Thanks for your help!

I have purchased from this supplier and was very happy. The board appeared to be high quality with gold plating on the through holes in the board. They were very helpful with the questions I asked. It doesn't make sense to me to buy a complete kit from Hong Kong when I have reliable suppliers here, so just getting the boards and a schematic and BOM is fine with me.
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Old 31st December 2011, 12:18 PM   #7
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Quote:
Originally Posted by Jay View Post
#1. JLH 2003 (15W-25W?)
This is a classic. Problem is the low wattage may not suit certain speaker and room. Many supports can be found from a dedicated JLH thread in DIYAudio or from The Class-A Amplifier Site.

#2. MF A1000 (50W)
This is easy to modify, and because of the topology is very common, I like the possibility to use PCB intended for other amps. Problem is in matching of the components, especially the output devices. That's if the high quality sound is wanted.

#3. Krell KSA-50 (50W)
I don't know about the difficulty you will have to build this amp. Original one is using special small heatsinks with a fan. You can use a different but a much bigger heatsink.

#4. Krell KSA-100 (100W)
The only good thing about it is its power (compared to KSA50 for example). It is this power and the associated difficulty in building which also puts this amp below the Musical Fidelity.

#5. Quad 405 (80W)
I'm not sure about this amp. Have heard only once in a used audio shop. But I have built a better current dumping amp and a Quad 303 that is more favored by a few so I think I can grossly "rate" its quality. Not really a class-A so not difficult to build.

#6. Naim 140 (45W)
While easy to build, this is not high end, cannot be compared with class-A amps.
Hi Jay! thanks for your reply and analysis. I'm leaning towards the KSA50 or the A1000. Thanks for the warning about the Naim. The Quad seems to be really old, from 1975 or so. The JLH doesn't have enough power for my needs. I didn't extensively research these before posting them.

I've also looked at a few products from Ampslabs.
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Old 31st December 2011, 12:25 PM   #8
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Have a look at the Pass threads too. They are simple to build and sound stunning.
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Old 31st December 2011, 12:49 PM   #9
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Quote:
Originally Posted by dirkwright View Post
I did a brief read of that thread and Google'd the Pass F5 but didn't find a circuit board. I didn't spend much time looking though. Can you suggest a source? Thanks for your help!

.
the pass f5 boards are available right here in the diyaudio store . just clik the store tab at the top of this page

cheers Woody
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Old 31st December 2011, 01:15 PM   #10
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High Dirkwright
On your list, most are class A. I would not buy kits of those but go with Pass DIY stuff later, when you know your way around and what sort of sound you prefer
.
The last two are the Quad which is not straightforward and I agree with other comments but the NAP 140 is the only option of class AB and a long thread here wanders along as newbs try their luck with it. Some don't like the classic British NAIM sound and it doesn't just happen. These simple kits of unmatched parts won't add up to great sound without thoughtful, selected tweaks of matching key parts, buying some quality bits - building a good, quiet power supply and preamp to go with it, wiring it carefully and much more like checking the websites dealing with the original as well.

Last, avoid kits featuring expensive or unobtanium parts. Fakes abound and no EBAY store is perfect. Iv'e bought kits where the output transistors alone were as expensive in China as the whole kit.
Google around a bit - check the threads here using the search button by posts. Here is the big one for the NAP 140 if you missed it - NAP-140 Clone Amp Kit on Ebay

Edit: Tubeshunter has a paur of PCBs for the 140 for $20 - It accepts metal can or plastic outputs. Not great value with freight but the boards are fine.
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Last edited by Ian Finch; 31st December 2011 at 01:33 PM.
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