A very different clone. The "HOPE" amp - diyAudio
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Old 14th March 2011, 02:44 AM   #1
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Default A very different clone. The "HOPE" amp

Hi folks, even though i have been a member for a while now i realised ihad not posted any pics of the 2 LM3875 amps i have built.

They re both essentially Peter Daniels excellent basic kits with a few tweaks here and there

First up we have the "HOPE" amp which got its name from the chassis, which i found in the scrap bin at the bike shop i live above! Its v.good quality stainless and an absolute mare to drill but worth the effort.
Hope Front.JPGhope back.jpg Ireally wanted to get amp going and after a false start it fired up and ran flawless but was messy. The pics you see are after a complete rewire, tidier layout total clean etc. I wanted the boards to look like they are flying almost like two battling space craft??hope side.JPGHope Top.jpghope undercarrige.jpg
The last pic was during the overhaul and just shows the bridge with ultra brite white led on left. This has the extra use of draining the caps on shut down which takes over a minute even with just 3000uf on each amp.

I know the heatsinks are too small but at low volumes on my front room system is fine, i usually point a small desk top fan at it. I just didnt want to spoil the idea in my head. This amp uses a star of stars aproarch to grounding with a through chassis auto bulkhead type clamp, all earth wire is the awesome Pirelli cable and power is good ol' Basec cable from Doncaster.

This amp is eerily quiet with no signal. virtually silent. Its clean and open sounding which became more pronounced after replacing the small fcs on rectifier with some same value Elnas i had.

I have owned many pieces of audio gear over the years and know what i like the sound of which of cause is subjective and this is my 3rd favourite sounding amp of all. (1st Sony STR recevier amp from 1972 just unbelivable... 2nd Grundig Valve radio 1952 full of Mullards). So all in all a resounding success i think youl agree.

Just as an after thought i put in a pic of my PSU. This is made from an old metal type consumer unit case which i adapted to house the 270va 20-0-20 EI traffo scavenged from a broken sansui ad22u. It has a bulkhead mains earth clamp on ac in and a 3amp fuse on live. 100nf MKP on swtch. 2 inline 1.25a slow blows on each side of traffo secondaries which with my abnormally high wall V gives around 23v insted of the rated 20. This Transformer seems perfect for the LM3875, almost made for it. After rec brdge my DC rails sit at an unfaultering 31v.THE psu.jpg

I have another build to hit you all with tomorrow. This one is made to look like a V-Twin engine using a disco light as a chassis!!!
Attached Images
File Type: jpg hope side.JPG (96.9 KB, 481 views)
File Type: jpg Hope Top.jpg (211.5 KB, 485 views)
File Type: jpg hope undercarrige.jpg (232.1 KB, 427 views)
File Type: jpg THE psu.jpg (239.8 KB, 405 views)
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Old 14th March 2011, 04:12 AM   #2
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Looks great!
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Old 14th March 2011, 04:17 AM   #3
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No it doesn't : the first thing that comes under my attention when looking at amplifiers is heatsink's size , this just don't fit !!
Therefore...

Last edited by picowallspeaker; 14th March 2011 at 04:20 AM.
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Old 14th March 2011, 07:52 AM   #4
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Default heatsink

Quote:
Originally Posted by picowallspeaker View Post
No it doesn't : the first thing that comes under my attention when looking at amplifiers is heatsink's size , this just don't fit !!
Therefore...
isnt that a bit like saying the first thing that comes under my attention when looking at cars is the spoiler. most of the time its for show and not really required. the thermal cutout hasnt tripped yet so im happy
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Old 14th March 2011, 08:33 AM   #5
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Yes ...DHT hybrid ICs looks nice !
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Old 14th March 2011, 08:44 AM   #6
Mooly is offline Mooly  United Kingdom
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Well they are certainly different

I thought you were going to say,
"2nd Grundig Valve radio 1952 full of Mallards"... and it sounded fowl
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Old 14th March 2011, 09:28 AM   #7
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Thanks, no Mullards. Mallards, thats just quackers.
wahay
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Old 15th March 2011, 12:09 AM   #8
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Quote:
Originally Posted by tom wesley View Post
isnt that a bit like saying the first thing that comes under my attention when looking at cars is the spoiler. most of the time its for show and not really required. the thermal cutout hasnt tripped yet so im happy
if you do not push your amp too hard or use low impedance speakers then the heat-sinks are fine. But what I would change is those tiny caps in the power supply..just put at least 10,000uf per channel.
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Old 15th March 2011, 04:54 AM   #9
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Depends on what he's driving...32Ohm 1Watter? We're good to go!
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Old 15th March 2011, 05:13 AM   #10
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Default RE

Quote:
Originally Posted by lanchile View Post
if you do not push your amp too hard or use low impedance speakers then the heat-sinks are fine. But what I would change is those tiny caps in the power supply..just put at least 10,000uf per channel.
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