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Old 4th June 2003, 09:47 PM   #1
Prof is offline Prof  United Kingdom
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Question Which Gainclone ? Which PSU ?

Hi folks, I`ve been browsing this forum for the last few weeks, trying to decide on which LM3875 based circuit to build as my first Gainclone. I know there will be no definitive answer to this question, but I`d like a little help in choosing which circuit to go for.

I currently have a (heavily modified !) NAD C521 CD player, Mission M73i speakers. I listen mainly to rock music.

I have the LM3875s, connectors, 1000ufs a few resistors etc. I just need to order the transformer(s).


1. Do I build an Inverting or Non-Inverting circuit ?

2. Do I use 1 big (300VA) or 2 small (160VA) transformers and are 18v secondaries "the best bet" ?



Any general advice would be most welcome, I`m good at soldering, but bad at making decisions !
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Old 5th June 2003, 06:59 AM   #2
Taco is offline Taco  Netherlands
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1) Non-Inverting is very populair and sounds very good.

2) I think 300VA is sufficient, secundair voltage depends on the power-output you want.
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Old 5th June 2003, 08:32 AM   #3
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Default Re: Which Gainclone ? Which PSU ?

Quote:
Originally posted by Prof
1. Do I build an Inverting or Non-Inverting circuit ?
Go for inverting

Quote:
Originally posted by Prof
2. Do I use 1 big (300VA) or 2 small (160VA) transformers and are 18v secondaries "the best bet" ?
I'm using dual 160VA transformers - personally think that this is the way to go. Dual PSU's makes it easier to avoid earth loops and hum problems.

Some people have expressed a preference for 18V transformers, and if your speakers are efficient, then perhaps this would be the safest bet. But as my speakers 83dB/W, I went for 25V. My initial experiments were with a single 18V 120VA transformer - I didn't notice any bad effects when I upgraded to the 25V models.

If you haven't already done so, check my WWW and also Nuuk's. As well as the GainClone info, both these pages have lots of links to other GainClone site on the web.

Hope this helps,

Mark
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Old 5th June 2003, 08:02 PM   #4
Prof is offline Prof  United Kingdom
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Default Looks like it will be dual transformers

Thanks for the advice.

Today, I ordered 1 x 160VA 18+18V toroid. I`ll prototype and test 1st, then I`ll invest in another transformer. My speakers are quite efficient, so I think 18v will be the right choice.

The "tweaker" in me will mean that I`ll end up trying both inverting and non-inverting modes, and I`ll probably end up "fiddling" with the circuitry until I get it right. I can`t wait to hear what all the fuss is about, I just hope I`m not dissapointed !

I`ll post the results in the next few days.
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Old 8th June 2003, 08:24 AM   #5
Prof is offline Prof  United Kingdom
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Default Not dissapointed !

If these Gainclones "burn in" then I`m in for a treat in the next few days. If improving the quality of caps/bridge recs/resistors gives better sound, then I`ve got a Nad amplifier for sale !
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Old 8th June 2003, 05:13 PM   #6
gregorx is offline gregorx  United States
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Thumbs up What components did you end up using

Congratulations. I am in the same boat trying to decide which way to go. Looking at the forums it seems the way to go changes daily. Could you post a link to the schematic that you used?
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Old 8th June 2003, 07:04 PM   #7
Prof is offline Prof  United Kingdom
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Default The route I took was :

www.diyaudio.com/forums/attachment.php?s=&postid=163274

I had to add a 0.1uf 100v between pins 1 & 4 (on some circuits this is a 1uf electrolytic) This cured a slight distortion problem. I didn`t use the 4.7uf Black Gate N as my CD player has no DC on it`s output. The input pot I`m using is a 100k LIN. The resistors are 1/8watt carbon, but I will try metal film, just to see if this makes any difference. The 1000ufs are reasonable quality rubycons (35v, 105 degree). I am using an 18 + 18v 160VA transformer, now I know this gainclone is good, I`m going to build another power supply to run each channel separately.

Results ? I`m very impressed, I`m no HI-FI expert, but it sounds quite a lot better than my NAD C350, which is supposed to be a decent quality amp (cost £300). The sound is clearer and more lively than the NAD. I will build my Gainclone into a case and replace the NAD with it !
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Old 8th June 2003, 07:33 PM   #8
gregorx is offline gregorx  United States
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Default NAD NOT

Thanks. I also have an NAD (2400) power amp and I have always liked it. From your experience It sounds like after I finish my gainclones the NAD might have to move to the center channel

What is the sensitivity of the speakers that you used with your gainclone? I was just trying to decide between 18v and 22v toroids as this is the most expensive part (my B&W CDM7 SE are 90db.)

Its nice to know another NAD user liked the gain clone.
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Old 8th June 2003, 10:46 PM   #9
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Prof..its hard to beleive that it sounds better than your NAD amp...no disrespect intended....but I`ve had a PE2120 and it is very spacial with just a small pair of 2 way Klipchs on it.....I`m building a chip amp based on the LM3886 chip...hope I get the same results

Cheers!!The DIRT®
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Old 8th June 2003, 11:05 PM   #10
Prof is offline Prof  United Kingdom
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Default Better than NAD ?

Hello Joe,

Well, I`ve only been running my new Gainclone for a day or two, but from memory, it is producing better noises than my "proper" amplifier. I will connect the NAD back up in the next day or so, that will be an interesting test. I think the NAD will sound very "flat" after the Gainclone. My gainclone just sounds so clear and detailed, I`m sure you`ll get the similar results. Let me know how it goes.
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