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NAD 3020 amp upgrades?
NAD 3020 amp upgrades?
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Old 10th January 2007, 06:43 PM   #11
planet10 is offline planet10  Canada
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NAD 3020 amp upgrades?
Shawn,

You being in Victoria, there is a good chance i sold that 3020 when it was new....

While you do need to heed what has been said about extra power amp rail capacitance, i modded one with and extra 80,000 uF/rail and that amp was in daily use until just recently. And did it ever give that amp some kick.

You can certainly tweak a 3020 to be quite a bit better, but it will never be a cost effective project.

I tried to remove tone controls once, i ended up using that one as parts, so not a mod to take lightly -- does get a lot of stuff out of the signal path thou.

The biggest changes come about by changing caps. I worked with one guy in MN who replaced every cap and many Rs (while keeping the unit cosmetically stock). It became a real sleeper. In a lot of cases you can't use poly caps so black gates are called for. He also upped the size of some of the caps, but you have to be really careful mucking with the reg board (which is for everything but the output stage) as it is carefully tuned and eay to throw off.

That said a 7020 is actually a better candidate for modding as there is more room and it is much easier to rplace the flakey connecters.

dave
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Old 11th January 2007, 03:53 AM   #12
TDWesty is offline TDWesty  Canada
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Dave,

Actually, I bought this one off ebay... but I did spend lots of time in Sound Hounds in the 80s... :-)

I just pulled the bottom off tonight, and see what you mean about pcb and build quality... pretty awful looking, even compared to my 3125 which is only 4-5 years newer.

By reg board, do you mean the smaller ps board mounted on the back panel? It has two 470uF 35V caps so I'm guessing this is for the pre-amp power section. It sounds like you're suggesting just replacing with like-sized caps would be wise for this section, especially for a novice?

I'm still trying to get a handle on the layout and studying the schematics to place everything and try to understand how it all works...

thanks
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Old 12th January 2007, 04:12 AM   #13
sletol is offline sletol  Norway
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The simplest and perhaps most obvious upgrade -and it is free- is to remove the nasty break-off contacts (in the headphone connector) from the output signal path. Best do this by shortening the the path, by taking the signal directly to the speaker terminals. (But through the zobel thing, needlesss to say). Also remove thermo-mechanical protection units (in small black plastic housing), these are meant as a protection agains lasting, heavy abuse ("party fuse"). If I remember right, they are about 0,2 ohm, but the ohms are not as important as are the contacts. (I am a contact freak). Remember, 90% of the problems in this world are contact problems! Remember also that we are dealing with huge amounts of current, relative to the low impedances in question. The contact issue is probably 100 times more important than the silly cable issue!
If you believe that the 0,2 ohm resistance plays a part in design, you can always use an ordinary resistor instead of the thermo thing, instead of just shortening its terminals.


WHen I was a money-lacking student I experimented a lot with the 3020, using the power sections in multi-amp setups. I still have 5 or 6 of them laying about unused, both old and new versions. One I actually use for my PC speakers, which are the Rogers LS3/5a. The 3020 traditionally sounds too weak with these demanding speakers, but with help of the loudness button and some bass knob adjustment it can be brought to sound surprisingly good. (The amount of loudness added can be regulated by using the PC volume knob).

The newer version, 3020i, was not so well build as the old one, and there was always annoying mechanical noise from the cheap transformer. If the original version sounded a little warmer, the sound signature however was pretty much the same in both, in my opinion: Pleasantly airy with a relatively full bass, but all-over a tad soft. It does not change much to add to the capacitor battery, I found. Well may be a tad, and I always -routinely- doubled it. As an experiment at one point I used a ten-fold increase (with outboard capacitors), but essentially the amp sounded the same. Another tad (of improvement) came from using only one channel of each amp, I you understand what I mean. I have little experience with the pre-amp section.

A curious experience was to try modern output transistors with the 3020. I used MJ something in TO3 housing. According to the specs it should be better than the 2955/3055 in all regards. The amp worked percectly well in the technical sense, but it became subjectively extremely dull and sterile sounding, like an average japanese inexpensive amp from the eighties, somewhat. Unusable for music, I would say. As an experiment I improved the cooling and turned up the q current (many times the original level), also put in new, matched driver transistors: Nothing helped!

Another experience: All four of the old verson of 3020 I have owned were very nice sounding, with the mentioned tad of warmth to the sound. Two were made in England and two were early Taiwan made (must not be confused with cheap Chinese successors). What strikes me is the superiority of the imaging of ONE of the Taiwanese units, when used as a stereo (power) amp.

I recently used this "best" unit as a stand-in when repairing my main amp, an original Electrocompaniet 25 watt amplifier, and was again struck by the imaging capability. with greath depth and precision of this particular nad unit! (The lack of muscular power is also striking, compared to the EC, which, on the other hand, has this great -unique among all I have heard- ability to sound powerfull also at low levels).
But how big are in general the variations among individual amps, due perhaps to good or bad matching of components between channels, one may ask.
Anyway.. Good luck with the project!
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Old 12th January 2007, 04:40 AM   #14
planet10 is offline planet10  Canada
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NAD 3020 amp upgrades?
Quote:
Originally posted by sletol
The simplest and perhaps most obvious upgrade -and it is free- is to remove the nasty break-off contacts (in the headphone connector) from the output signal path.
Another is to toss the ugly big solid metal pre-power amp jumper loops


Quote:
A curious experience was to try modern output transistors with the 3020.
Somewhere i have an upgrade transistor pair noted that a fellow in Quebec did a bunch of research to search out. I've the flu so i'm not searching it out right now... that might be in this document which covers a very extensive set of mods....

dave
Attached Files
File Type: txt nad7020_saga2.txt (37.3 KB, 598 views)
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Old 12th January 2007, 08:21 AM   #15
lineup is offline lineup  Sweden
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In the context
of NAD 3020, NAD 7020 etc
we may add one of the later amplifiers of NAD.
Quote:
Description

The C320BEE is a descendent
of NAD's first low-cost, high-performance integrated amplifier, the 3020,
which thrived in the late 1970s and early '80s.

Audio legend and current NAD engineer Bjorn Erik Edvardsen
designed the 3020,
and his initials on the updated C320BEE honor his continuing contributions
Quote is from a review by Jeff Stockton
when C320BEE got the award: Hi Fi Product of the Year 2002
Click the image to open in full size. Click the image to open in full size.


Product page at http://nadelectronics.com/
NAD C320BEE - details

I will probably buy one NAD C320BEE
before it's too late ......
An externally hosted image should be here but it no longer works. Please upload images instead of linking to them to prevent this.


Regards
lineup
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Old 12th January 2007, 10:17 PM   #16
Piercarlo is offline Piercarlo  Italy
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Default Re: NAD 3020 amp upgrades?

Quote:
Originally posted by TDWesty


My thinking so far is this:

1. replace the main PS caps (4x 2200uF 35V -seems awfully small to me, less than 1/2 that found in my 3125 amp). At what point is extra capacitance wasted?
Seem that replacing PSU capacitors is a widespread sport activity... with heavily misunderstanding of the reason which drive designers to keep them "low".

Is not only a question of avoiding stressing on rectifiers; there is an "hidden" more serious reason for keeping low power supply reservoirs: power dissipation and SOAR related problems with output stages.

If you see the internal construction of NAD 3020 (and of many others commercial amplifiers) you note first of hall that heatsinks are not exactly "generous". They are dimensioned for just a 10-15 Watt of continuous output power with speakers of nominal impedance, not for full continous power which, with these heatsinks, will drive output stages to a plain meltdown (risk increased, in NAD 3020, by fhe absence of emitter ballasting resistors).
To avoid this the designers usually "strangle" power supplies using none but essential capacitor values. In normal listening condition (usually keep well down 10 Watt of continous power), power supplies give it's nominal voltage.

Instead when amplifier is continously stressed above this "domestic power", ripple cut out a quote of supply voltage in order to mantain *average* dissipation limited at values
that amplifier can safely sunstain. If, indifferent to distortion, the user "push" power amplifier to continous max power output, then average recharging current of capacitors became high enough to "warm" the main fuse (usually of retarded type) and drive it to blow (hopefully!) before and not after output stages have reached their thermal limits.

"Low" capacitors values and cleverly selected retarded fuses are just a way to do a compromise with phisical constraints of amplifier (which, as usually build, *can't* soustain maximum output power continously as - some! - professional power amps do) and "commercial/marketing/cosmetics" exigences which usually push for a quadrature of circle with "high power with near the costs of a pocket radio".
Arranging fuses and capacitor values is, until now, the best and cheap way to obtain this "miracle" without calling Heaven Lords for doing something about this question.... is not perfect but the limited resources of convent and friars - i.e engineers! - can't pass anything more!

In conclusion: be cautious in rearranging power supplies. If not carefully thought, some "improvements" may turn itself in plain disasters.

Hi
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Old 18th January 2007, 08:35 AM   #17
lineup is offline lineup  Sweden
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Default Re: Re: NAD 3020 amp upgrades?

Quote:
Originally posted by Piercarlo

Instead when amplifier is continously stressed above this "domestic power", ripple cut out a quote of supply voltage in order to mantain *average* dissipation limited at values
that amplifier can safely sunstain. If, indifferent to distortion, the user "push" power amplifier to continous max power output, then average recharging current of capacitors became high enough to "warm" the main fuse (usually of retarded type) and drive it to blow (hopefully!) before and not after output stages have reached their thermal limits.

"Low" capacitors values and cleverly selected retarded fuses are just a way to do a compromise with phisical constraints of amplifier (which, as usually build, *can't* soustain maximum output power continously as - some! - professional power amps do) and "commercial/marketing/cosmetics" exigences which usually push for a quadrature of circle with "high power with near the costs of a pocket radio".
Arranging fuses and capacitor values is, until now

Anybody used/using NAD PreAmplifiers?

NAD does not only make good Power Amplifier for your money.
Like the interesting Award winning NAD C320BEE I mention above
BEE = Bjorn Erik Edvardsen = NAD 3020 designer


lineup
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Old 18th January 2007, 10:22 AM   #18
h_a is offline h_a  Europe
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If you're ad it, you could replace the volume pot. It's cheap and fails after some years.

Cheers, Hannes
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Old 23rd January 2007, 04:46 AM   #19
TDWesty is offline TDWesty  Canada
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Quote:
Originally posted by h_a
If you're ad it, you could replace the volume pot. It's cheap and fails after some years.

Cheers, Hannes
Thanks, I will check that out. It seems ok after a dose of contact cleaner, but we'll see how it lasts.

I'm planning to replace all the EL caps, and figured I would just make a list and order them all now, since many are common sizes, and quite cheap. I noticed a few differences between my amp and the schematic/parts listing I have though:

The smaller regulator board has a C915,C916 which are 10uF 35V, but are duplicate numbers with the C915,C916 used in the main supply section (2200uF 35V). The ones on the reg board don't appear anywhere in the service manual I have, so must be a later revison. They appear across Q903/Q904.

I also have a lone cap, C427, which doesn't appear anywhere, and doesn't have a pair.

One final oddity is that several caps which are said to be Tantalum in the parts listing appear to be EL - they are 1uF and 0.68uF 16V and sure look like EL cans to me... Two of them are in the Bass circuit, so shouldn't matter, but the others are in the Normal IN filter circuit, so definitely in the signal path if I use Normal (which I don't usually).

I was going to order the parts tonight, but it looks like I should study this a bit more and grab my 11x17" schematics at work and figure out which caps are in the signal path.

I was planning to do things in this order, with some listening between each:

main PS caps
reg board caps
any smaller caps in the signal path (using lab in)

Does this make sense?
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Old 23rd January 2007, 05:21 AM   #20
unclejed613 is offline unclejed613  United States
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replacing reg board caps is a good idea..... fresh caps actually make regulators run cooler in many cases......
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