If the 3020A cannot have the tone control circuit bypassed and the diagram I am looking at shows only the phono section as using this circuit hence CB1,s comment- " the sound is really good on the AUX/Tuner" then a bypass switch/switches could be fitted internally so as not to show any external modifications .
"Loudness" also compensated for audio inefficiencies in cheaper loudspeakers of that era.
"Loudness" also compensated for audio inefficiencies in cheaper loudspeakers of that era.
Could you post the schematic you're using Duncan2 ?
Obviously, if CB1's unit has any added internal modifications, then none of us can realistically comment without the relevant details.
I always thought the 'loudness' circuit was used to 'correct' for audio insensitivities of the human ear, at low listening levels ?
Obviously, if CB1's unit has any added internal modifications, then none of us can realistically comment without the relevant details.
I always thought the 'loudness' circuit was used to 'correct' for audio insensitivities of the human ear, at low listening levels ?
Cheers Goldie, yes, this all sounds exactly right.
However, other 'faults' are:
- phono output is more bassy, and less sparkling midrange and treble clarity. (Aux and Tuner with CD/DAC are just sublime though!)
- that moving the MM/MC selector switch makes no effect.
Checked, the little pcb and switch with a DMM and it seems fine.. Any suggestions for where I might look next. Already, reflowed all the solder joints at the inputs.
I carefully recapped the whole amp a few weeks ago and Aux and Tuner output beautiful sound. (I’m just using the pre-amp of this Nad and it feeds into a freshly recapped Yamaha P2200.)
So, getting the phono section to work as beautifully as the 'aux' and 'tuner' is my goal, especially as the phono section has a good reputation. I’ve already disassembled and cleaned and tested the balance and tone pots. Selection switches are harder to access so have only had a good spray of Kontact 40 and multi presses of the switches.
However, other 'faults' are:
- phono output is more bassy, and less sparkling midrange and treble clarity. (Aux and Tuner with CD/DAC are just sublime though!)
- that moving the MM/MC selector switch makes no effect.
Checked, the little pcb and switch with a DMM and it seems fine.. Any suggestions for where I might look next. Already, reflowed all the solder joints at the inputs.
I carefully recapped the whole amp a few weeks ago and Aux and Tuner output beautiful sound. (I’m just using the pre-amp of this Nad and it feeds into a freshly recapped Yamaha P2200.)
So, getting the phono section to work as beautifully as the 'aux' and 'tuner' is my goal, especially as the phono section has a good reputation. I’ve already disassembled and cleaned and tested the balance and tone pots. Selection switches are harder to access so have only had a good spray of Kontact 40 and multi presses of the switches.
Correction - I think the 'A' version actually has a Mono switch instead of the earlier (3020) Mute switch.
If the AUX & Tuner inputs are both working perfectly, then the pre-amp section, including volume, tone, and balance controls must be working properly - that only leaves the phono section, and the input selection switches, everything else is common to all inputs as far as I recall. The MM/MC switch should have a noticeable effect, what are you using as phono source, and what did it sound like before recapping ?
Either way, it sounds like your best option is to identify which of the NAD 3020 service manuals best fits your phono section (most are on the hifiengine site), and work from there. Personally, I'd check the 3020B manual first, and see how it compares (I've never found a service manual specifically for the 3020A).
If the AUX & Tuner inputs are both working perfectly, then the pre-amp section, including volume, tone, and balance controls must be working properly - that only leaves the phono section, and the input selection switches, everything else is common to all inputs as far as I recall. The MM/MC switch should have a noticeable effect, what are you using as phono source, and what did it sound like before recapping ?
Either way, it sounds like your best option is to identify which of the NAD 3020 service manuals best fits your phono section (most are on the hifiengine site), and work from there. Personally, I'd check the 3020B manual first, and see how it compares (I've never found a service manual specifically for the 3020A).
Yes, Goldie, it's a mono rather than a mute switch on my 3020A.
This, from a previous thread courtesy Ian Finch, is helpful, "If you can't find a schematic, it's because the 3020A doesn't have one but electrically, it's almost the same as 3020 inside."
Prior to my restoration the phono section worked ok in the sense that the MM/MC switch operated. The phono section generally sounded fine, ..I'm aware of the potential irony at this point. I'll attach a couple of photos of the preamp section of the board, could anyone highlight or circle the components that comprise the only the 'phono' section path as I'm not very good with schematics yet.
This, from a previous thread courtesy Ian Finch, is helpful, "If you can't find a schematic, it's because the 3020A doesn't have one but electrically, it's almost the same as 3020 inside."
Prior to my restoration the phono section worked ok in the sense that the MM/MC switch operated. The phono section generally sounded fine, ..I'm aware of the potential irony at this point. I'll attach a couple of photos of the preamp section of the board, could anyone highlight or circle the components that comprise the only the 'phono' section path as I'm not very good with schematics yet.
Attachments
I agree, I've never found a NAD 3020A service manual or schematic either - but, in my case (2 - 3 examples), I found the phono stage to be closest to the NAD 3020B / 3120 phono stage, the original 3020 only had MM input, and no MM/MC switch. You can confirm simply by comparing your components to the schematic - this is the one I think you probably have, although one or two values may still differ (keep the original values in the amp).
There's no single 'path' thru' it as such, you'll need to double check everything you've done in that area. You didn't say what source you're using ?
There's no single 'path' thru' it as such, you'll need to double check everything you've done in that area. You didn't say what source you're using ?
Hi Goldie, apologies for my radio silence and appreciate your guidance on the most appropriate schematic.
So, looking at the attached photo I'm thinking of testing the transistors marked up with pink highlight.
If any test different to their 'twin' in the same location on the opposite channel I'll replace them.
Do you happen to know if there are replacements available for the following?
C2602 31G
BC559B PHP305
BC599B PHP310
My source is a Dunlop Systemdek II, Linn Akito Arm, Shure M55, stylus original Shure NE.
Does my plan sound ok?
Thanks again.
So, looking at the attached photo I'm thinking of testing the transistors marked up with pink highlight.
If any test different to their 'twin' in the same location on the opposite channel I'll replace them.
Do you happen to know if there are replacements available for the following?
C2602 31G
BC559B PHP305
BC599B PHP310
My source is a Dunlop Systemdek II, Linn Akito Arm, Shure M55, stylus original Shure NE.
Does my plan sound ok?
Thanks again.
Attachments
If the phono stage worked in both MM and MC modes before your activities and it works now only in one mode (MM probably?) then most probably you have a wire (to or from the switch) broken or desoldered. The switch is just altering the feedback network to change gain (according to Goldie99 schematics).
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'madis64' raises a good possibility for the MM/MC switch - the switch wiring is fairly 'delicate' where it joins the main pcb, and is often buried in glue - all of which I would clean off completely. Your cartridge obviously needs the MM position.
I assume at this point that you've already checked that the record deck / cartridge is working OK with another amp.
If both phono channels are affected it makes little sense comparing transistors between the two channels... that technique's more useful comparing a known good channel to a faulty channel.
If any non-phono sources have been connected to the phono inputs since it was working ok, it may well have damaged transistors in there, potentially in both channels. If not, then I'd be more inclined to look at the changes you've already made, especially those that are common to both channels. One that sticks out a little, is what looks like two polystyrene (PS) caps, they must be new, the 3020A had no PS caps. PS caps are easily heat damaged, even just by poor soldering technique. It's a 'shot in the dark', but in those locations (C415 & C416 ?) it would affect the sound if they'd been damaged. I don't quite understand some of the other changes you've made, particularly in light of your own comment "especially as the phono section has a good reputation".
Anyway - if you do end up needing to change any transistors - the 2SC2602 has been obsolete for years, something like KSC1845(FTA) should be fine, but ideally I'd leave them alone if possible: note - Q403 & Q407 are probably 'matched', Q404 & Q408 also. The BC559B's are still available, and don't need to be matched.
I assume at this point that you've already checked that the record deck / cartridge is working OK with another amp.
If both phono channels are affected it makes little sense comparing transistors between the two channels... that technique's more useful comparing a known good channel to a faulty channel.
If any non-phono sources have been connected to the phono inputs since it was working ok, it may well have damaged transistors in there, potentially in both channels. If not, then I'd be more inclined to look at the changes you've already made, especially those that are common to both channels. One that sticks out a little, is what looks like two polystyrene (PS) caps, they must be new, the 3020A had no PS caps. PS caps are easily heat damaged, even just by poor soldering technique. It's a 'shot in the dark', but in those locations (C415 & C416 ?) it would affect the sound if they'd been damaged. I don't quite understand some of the other changes you've made, particularly in light of your own comment "especially as the phono section has a good reputation".
Anyway - if you do end up needing to change any transistors - the 2SC2602 has been obsolete for years, something like KSC1845(FTA) should be fine, but ideally I'd leave them alone if possible: note - Q403 & Q407 are probably 'matched', Q404 & Q408 also. The BC559B's are still available, and don't need to be matched.
The "loudness" controls are thought and designed in accordance with the Fletcher Munson curves, so the bass and treble boost is not perceived at high volumes.
If they are well designed (I have a 3020 and it does it well), this is only perceived at low volumes, it is an acoustic phenomenon.
Just a thought, because a lot of people think it should work every time they hit the key.
Equal-loudness contour - Wikipedia
If they are well designed (I have a 3020 and it does it well), this is only perceived at low volumes, it is an acoustic phenomenon.
Just a thought, because a lot of people think it should work every time they hit the key.
Equal-loudness contour - Wikipedia