NAD 3020 amp upgrades?

[TDWesty]

After many years of NAD amps, I picked up an original 3020 for cheap, which works fairly well given its age. I was able to put my 3125 back into service with the help of Tim Schwarz, so now I'm free to fiddle with the 3020 in my den.

I've read lots about the 3020, and recall when it came out (my Dad still has a 7020 receiver he bought new), but I haven't seen much detailed mention of mods/upgrades here. google turns up some sites on mods, but many are lacking in details for someone ummm... new to this.

Is the lack of discussion here because most of you have moved on to newer/better things and the 3020 is old news now? Or is it not really worth spending a lot of time on?

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?
2. there appears to be a separate PS section for the preamp on a separate board (or maybe this is for the phono pre-amp only?). I rarely use vinyl anymore, so won't bother if this is phono only, otherwise upgrade caps as above.
3. Beyond that, I was planning to strip out the tone controls, loudness and muting switches, and possibly the balance. I never touch them, so would rather get rid of them.
4. After that, I was considering using it as a pre-amp for a chipamp project.

Advice welcomed... :-)

[unclejed613]

extra capacitance can shorten the life of the rectifier bridge, because you increase the repetitive charging current spikes. increasing capacitance can increase dynamic headroom a bit, but you will need a higher current bridge to handle the charging current.

as far as the controls go, just leave them flat...... unless you have inquisitive children around.....

as far as the reg board goes, i think that is for the whole preamp, and one page i saw with 3020 mods, recommended recapping the board with low esr caps

[lineup]

Originally posted by TDWesty

Is the lack of discussion here because most of you have moved on to newer/better things and the 3020 is old news now? Or is it not really worth spending a lot of time on?

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?
2. there appears to be a separate PS section for the preamp on a separate board (or maybe this is for the phono pre-amp only?). I rarely use vinyl anymore, so won't bother if this is phono only, otherwise upgrade caps as above.
3. Beyond that, I was planning to strip out the tone controls, loudness and muting switches, and possibly the balance. I never touch them, so would rather get rid of them.
4. After that, I was considering using it as a pre-amp for a chipamp project.

Every now and then, has been topics about NAD 3020.
It is really one Classic and good Amplifier.

We should know that there were several versions of NAD 3020.
With some modifications in components.

Here at The Class-A Amplifier Site
is a schematic of such classics.
I guess the version is the original NAD 3020.
http://www.tcaas.btinternet.co.uk/index-4.htm
Schematic:
See my attachment.


Regards and New Year 2007
lineup

[unclejed613]

see my post above..........
any "vintage" equipment is worth getting running/improving/etc.....

[es44]

I agree with unclejed613. And from what i've read, the 3020 is certainly worth keepin' alive.
I haven't been able to pick up one myself yet, unfortunately, but i'd love to try it.
If it could be of any help for you, i have two different service manuals for it, and i'll be happy to upload it some place if you want it.

Best regards
Ebbe

Edit: Put the first one here: Nad 3020 11Mb
Second one: Nad 3020 1.2Mb

[TDWesty]

Thanks for the replies, and the manuals. I had one of those already, but not the other.

What about the PS capacitance? Is there a rule of thumb for choosing how far to upgrade? Do other component upgrades become necessary if main PS caps are upgraded? The stock 3020 has 4x2200uF @35V. They are quite narrow, only 12.5x25mm or so. I was thinking I can maybe fit 16mm wide caps by using radial leads and mounting them above the board a bit. This should allow me to go to 3300uF, maybe even 4700uF.

I have also read that replacing resistors in the signal path with metal film versions might be worth doing - any thoughts?

The volume pot was quite scratchy, but a dose of contact cleaner seems to have cured it nicely. I still would like to bypass the tone controls though...

[chrisb]

No doubt the 3020 /7020 are among the all time classic bang for buck giant killer products of that era ( along with the original Advent loudspeaker).

But, as creative as some of the circuitry was, the early NAD products were not over-engineered, or built to Krell standards.
Before you start pulling parts off any of the PCBs, be aware that the quality of the board substrate (particularly the early production with phenolic boards), foil traces and wave soldering was simply put, poor.

Even with careful use of solderwick or other vacuum desoldering devices, it's not uncommon for foil traces or solder pads to delaminate from the boards or fracture, necessitating tedious repairs.

Some of the most common failures with these units was actually in the mechanical switches, solder connection on the rear terminals, and noisy controls.

As for PS capacitance, I wouldn't recommend huge increase in values (too much C for the operating current draw of the amp, could well bog down the dynamics) and don't forget that sonic quality of electrolytics has improved hugely in the past 30yrs. It might not hurt to upgrade the rectifiers with Fast Recovery or similar.

[TDWesty]

Thanks for the warnings - I will be careful with boards, and use reasonable sized caps, maybe 3300uF as the next size up.

I looked at Recotron's website on the Fast Recovery stuff, but they list no Canadian distributor. I was hoping to use digi-key for parts, since they have a cdn location, but they're not listed. Any ideas?

[N-Channel]

Originally posted by unclejed613
extra capacitance can shorten the life of the rectifier bridge, because you increase the repetitive charging current spikes. increasing capacitance can increase dynamic headroom a bit, but you will need a higher current bridge to handle the charging current.

as far as the controls go, just leave them flat...... unless you have inquisitive children around.....

as far as the reg board goes, i think that is for the whole preamp, and one page i saw with 3020 mods, recommended recapping the board with low esr caps

Originally posted by TDWesty
Thanks for the warnings - I will be careful with boards, and use reasonable sized caps, maybe 3300uF as the next size up.

I looked at Recotron's website on the Fast Recovery stuff, but they list no Canadian distributor. I was hoping to use digi-key for parts, since they have a cdn location, but they're not listed. Any ideas?

It's too bad that the low voltage rails can't be actively PFC'ed like the HV Section of an audio-grade SMSP. Then, the issue of capacitor charging current spikes thru the main rectifiers would be moot.

Steve

[vinylkid58]

Originally posted by TDWesty I looked at Recotron's website on the Fast Recovery stuff, but they list no Canadian distributor. I was hoping to use digi-key for parts, since they have a cdn location, but they're not listed. Any ideas?

Take a look at these: http://www.partsconnexion.com/catalo...onductors.html

Jeff