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Old 29th June 2005, 04:43 PM   #1
TDWesty is offline TDWesty  Canada
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Default GC compared with NAD int. amp

I have read much of the gainclone discussion with interest, including many of the sites with details on various designs. I am hearing some very good things about the sound quality, etc. My problem is that I have one of the few NAD int. amps which does not have a Pre-out section (NAD 3125), so I will need to invest in another int. amp, or a preamp, in order to use a GC. (building a pre-amp is a bit ambitious for me right now.)

I have always been very happy with the sound of NAD gear, including the 7020, 3125, and 7155 I have used over the years.
It appears that to build a GC properly with toroid supply, the cost will be $100-200 US, which is in the ballpark of what a used NAD amp will cost. Can I really expect a significant improvement in sound quality with the GC? How does the 40-50 watts output compare with a typical 30W NAD with 3+ dB of headroom? My speakers are PSB 70Rs, which sound decent with the NAD, but could benefit from more power. (part of the reason I am considering an upgrade - they are now in a much larger room with high ceilings, and the NAD is pushed a bit harder to fill the room).

I know these are mostly very subjective questions, but I'd appreciate feedback from others who may have been in similar situations, or are familiar with the gear I use.

Thanks.
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NAD 3125 & 3020 amps, 4125 tuner / Rotel RCD-965BX CD / B&O 2400 / Nakamichi BX-125 / PSB 70R speakers / BrianGT chipamp in progress...
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Old 29th June 2005, 05:23 PM   #2
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Hi,

I have had several Nad amp, most recently a second hand 3020 in superb nick bought from a car boot sale for 25 and a C350 bought new for a heavily discounted 180. Both are great amps for the money IMHO however i now have a set of BrianGT/CarlosFM powered Lm3886 Chipamps (yep not Gainclones Carlos!!).

I found straight off plugging then into the preout of my Nad that the difference was considerable. Even my girlfriend commented and that is saying something.

I have in the last few days finished a Nuuk Buffered Preamp to go with the gainclone, this makes a significant difference as well.

All in at this stage I think that my setup with blow pretty much any Nad into the dust and a lot of other more exotic stuff too i wouldnt be suprised. There is still work to do on it, but easily the best amps setup i have ever had.

fil
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Old 29th June 2005, 08:16 PM   #3
TDWesty is offline TDWesty  Canada
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Thanks for the feedback! I will pursue this a bit further then. The integrated passive preamp + GC amp approach sounds perfect for me. Has anyone tried building an amp with a non-toroid power transformer? I was thinking I could try using something I have on hand before deciding on which toroid I should use. What is the minimum voltage I can use?
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Old 30th June 2005, 12:34 AM   #4
TDWesty is offline TDWesty  Canada
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I have a Hammond 165L50 transformer, 50V output, 100VA, center tap. Would this work for testing a GC circuit? I'm assuming I can get 25V+- from it right?
Sorry if this is a dumb question... it's been many years since I've fiddled with this stuff.
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Old 30th June 2005, 08:05 PM   #5
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Check around this forum, a lot of folks are using inexpensive batter power for their chip amps with great success. I don't know if the detail, but it has been recommended to me in the past.

Good luck!
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Old 1st July 2005, 06:01 PM   #6
Stabist is offline Stabist  Slovenia
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Quote:
Originally posted by TDWesty
I have a Hammond 165L50 transformer, 50V output, 100VA, center tap. Would this work for testing a GC circuit? I'm assuming I can get 25V+- from it right?
Sorry if this is a dumb question... it's been many years since I've fiddled with this stuff.
Nope - from 1x50V secondaries you can not get 2x25V! You will get around 70V.

You need around 18V secondaries to get 25V DC.

Toroidal trannie is not a must, offcourse - you can use whatever type you like/have/is cheapper/.... Personnaly - I think a good EI trannie is better choice than toroidal trannie ...
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Old 1st July 2005, 09:01 PM   #7
DC Dave is offline DC Dave  United States
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Quote:
Originally posted by Stabist


Nope - from 1x50V secondaries you can not get 2x25V! You will get around 70V.

You need around 18V secondaries to get 25V DC.

Toroidal trannie is not a must, offcourse - you can use whatever type you like/have/is cheapper/.... Personnaly - I think a good EI trannie is better choice than toroidal trannie ...

If the tranny's secondary is 25 - 0 - 25 (50v) then this would work for testing. It will give you about +-35v DC after rectification which is fine for the LM3875 LM3886 LM4780. Only 100VA, is small for more than 1 channel, but test away.
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Old 1st July 2005, 11:06 PM   #8
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Quote:
Has anyone tried building an amp with a non-toroid power transformer? I
Yep..the gainclone I built for my son uses a EI transformer.
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Old 1st July 2005, 11:18 PM   #9
mb is offline mb
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I've built a TDA9274 chipamp, applying many of the tips so generously suggested. The amp has been brought to setups with NAD amps (eg. C370 power amp), and the owner almost immeidiately indicated a preference, in terms of tonal balance, speed and clarity. There was no concern that on paper, the C370 had 3x or greater power.

I own(ed) a NAD 7125 receiver. Nice, but getting old, and not really comparable, IMO.

Caveat: IME, different chipamp "recipes" will produce drastically different results. Mine can probably be described as non-inverting, non-regulated, large cap snubberized. I've listened to two Sugden A21as in different setups, and my chipamp probably sounds closer to the A21a than to other commercial amps (NAD, Rotel, some class-D amps, Ampzilla, MF,..).
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Old 2nd July 2005, 04:20 PM   #10
Hugh M is offline Hugh M  Canada
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TDWesty

I ran nad 3140's 3240pe's, 3150s, a rotel rb870, heath ap 1800/aa-1600, and soundcraftsmen a-5000 and a couple of others. All into Klipsh Lascala speakers.
The Chip amp system I am running now with buffered 3875's dual E-core power supplies, and active opa627/buf634 pre, lays waste to all of them IMO.

In defence of the older nad equipment I'm sure they could have sounded much better had they been recaped with new electrolitics all the way through. (quite a job in the 3140 as there are quite a few of them)

My 2 cents
Hugh
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