Hi vubkevin,
No, just if you need to add any caps. Don't use ceramic. Eliminating all other ceramic caps in the amplifier stages will improve the sound quality. It is subtle but worthwhile. Use mica, teflon or polystyrene if you can.
-Chris
Possibly. They are a little faster than the original devices. These should have lower distortion.
u=you?
No, just if you need to add any caps. Don't use ceramic. Eliminating all other ceramic caps in the amplifier stages will improve the sound quality. It is subtle but worthwhile. Use mica, teflon or polystyrene if you can.
-Chris
Hello,
I found this forum searching the internet for replacing tranisistors in my Nad 3020a. these transistors you are talking about (MJ21193 / MJ21194)...what improvements will they give to the perfomance of my nad. Im really looking for more power and weight to the performance. My Friend has a Pioneer SA-8500 amp and he replaced his transistors with the best of the same sort that were all ready in the amp, and when we heard the new transistors it was awesome, so much more bass n control. Anyway any help will b appriciated, bearing in mind im 17 and can't rework circuits, but i think replacing the transistors will be simple as they seemed to just be blted down..
Thanks
I found this forum searching the internet for replacing tranisistors in my Nad 3020a. these transistors you are talking about (MJ21193 / MJ21194)...what improvements will they give to the perfomance of my nad. Im really looking for more power and weight to the performance. My Friend has a Pioneer SA-8500 amp and he replaced his transistors with the best of the same sort that were all ready in the amp, and when we heard the new transistors it was awesome, so much more bass n control. Anyway any help will b appriciated, bearing in mind im 17 and can't rework circuits, but i think replacing the transistors will be simple as they seemed to just be blted down..
Thanks
Hi John,
Replacing transistors will not give you more power. Sorry.
Replacing transistors will not give you much improved sound. Unless the originals were broken.
After all this, the bias current must be set (properly). Then you have to make sure it's not oscillating. So you need an oscilloscope and a good DVM - minimum.
People should do some research before they dive into these things. Unless your friend is a properly trained technician, he just rolled the dice.
-Chris
Replacing transistors will not give you more power. Sorry.
Replacing transistors will not give you much improved sound. Unless the originals were broken.
Not even close! Those transistors have thermal compound applied on both sides of a fragile mica insulator. You must clean everything completely without cracking the insulator. You also need to apply fresh (=new) thermal compound and the mounting hardware must be torqued down to the correct pressure. It's not much. Too much grease and you may crack the die inside the transistors, not enough and it bakes.
After all this, the bias current must be set (properly). Then you have to make sure it's not oscillating. So you need an oscilloscope and a good DVM - minimum.
People should do some research before they dive into these things. Unless your friend is a properly trained technician, he just rolled the dice.
-Chris
Hi John,
You really can't. A new amp needs to be designed from scratch. It may be possible to gain a couple watts, or improve the sound of the existing amp. It's not worth the effort.
What is required is a larger power supply in both voltage and current with a matching redesign of the amplifier itself. Heatsinks will also need to be enlarged to handle the extra heat. In other words, a completely new amplifier. Doubling the power will only gain you 3 dB. You may possibly notice this - just.
-Chris
You really can't. A new amp needs to be designed from scratch. It may be possible to gain a couple watts, or improve the sound of the existing amp. It's not worth the effort.
What is required is a larger power supply in both voltage and current with a matching redesign of the amplifier itself. Heatsinks will also need to be enlarged to handle the extra heat. In other words, a completely new amplifier. Doubling the power will only gain you 3 dB. You may possibly notice this - just.
-Chris
anatech said:
The tech who did the search thot it was worthwhiel. I just offer it as more subs. Here is his note:
But one with more real world capability than some "bigger" amps -- the 1st gen carver cube for instance.
No arguement from me on that,,, hmmm,,, i have an NAD 2040 that could use a power amp stage replacement. I already pur a chip amp into a Technics power amp. Time for something different?
dave
Hi Dave,
Changing the original parts could cause oscillation easily enough, or oscillation bursts on certain waveforms possibly. If it was stable, the more linear Japanese parts would perform better and have lower distortion. The problem is that you would be hearing the design and not the parts. Replacing some ceramic caps out for mica or polystyrene would have a greater effect.
I'm sorry about the comments I made about your tech, but they don't hold water. There is much I have kept to myself here. Did he install the 2SD733 and 2SB557 in your amp? If so, they are not even complimentary pairs. 2SB557 and 2SD427 were popular output pairs and performed well. These were very good, but not the parts with the highest ratings. I often used 2SB554 and 2SD424 unless I needed parts with higher ratings.
-Chris
ECG book by chance? The 2SD733 is a 140V 12A 100W device, the compliment is 2SB697 (not 2SB557 which goes with a 2SD427). It's normally pretty simple to come up with a good sub. I also doubt strongly that a 30 A part would come close to the speed of these early Japanese devices. It was normal to see 2N3055 in NAD, which all Japanese parts would kill in a speed contest.
Changing the original parts could cause oscillation easily enough, or oscillation bursts on certain waveforms possibly. If it was stable, the more linear Japanese parts would perform better and have lower distortion. The problem is that you would be hearing the design and not the parts. Replacing some ceramic caps out for mica or polystyrene would have a greater effect.
Wow. What a comment! This reflects more on the load than anything else. The ability for the driver stage to run the outputs into saturation would have more to do with output transistor beta than the current capacity of the outputs. The only difference there is whether the output transistors turn into wire or not.
Possibly if you were comparing them to a Toshiba or some other lightly built unit. The Carver cube kills a NAD for power and design complexity, but not for sound quality. The Cube was a design in a very embryonic state. Bob Carver did prove to the world what the promise was though. I don't think you could compare the two though. The design goals were completely different.
I'd say. The SymAsym and the NAD are similar in the intent of the design. They would be compared more evenly. The SymAsym should walk all over the NAD without breaking a sweat.
I'm sorry about the comments I made about your tech, but they don't hold water. There is much I have kept to myself here. Did he install the 2SD733 and 2SB557 in your amp? If so, they are not even complimentary pairs. 2SB557 and 2SD427 were popular output pairs and performed well. These were very good, but not the parts with the highest ratings. I often used 2SB554 and 2SD424 unless I needed parts with higher ratings.
-Chris
anatech said:
We did this actual test. NAD vrs NAD pre driving Carver Cube (1st gen) driving a very benign close to resistive load (Magnepan MMG). The Carver went into audible distress at significantly lower volume levels than the NAD. ie the NAD had more effective real world power than the Cube. The differences were more dramatic with tougher loads.
Not really my tech. A fellow i met on a mail list. I bought his modded 7020 off him and it did sound better.
dave
Hi Dave,
Yes, the first cube had supply issues. Uneven firing of the triac. Therefore the power supply was ailing. I'm not surprised about your test. They even had to upgrade the triac as well as redo the control circuit on them.
Not that I like cubes (I don't really), but they have way more raw power when they are running properly. The later models got real output transistors too. The originals were junk. The fact that they ran as the first model was amazing when you consider all the new technology and iffy parts.
It's also not hard to make an NAD 3020 sound better either. It also suffered from poor quality parts. The circuit isn't that great either. Another example of what you can get away with at low power (and low supply voltages). Don't worry, I'm not only picking on NAD here. Many other brands in the same boat. Many English brands were / are terrible. There are at least two notable exceptions to that.
-Chris
Yes, the first cube had supply issues. Uneven firing of the triac. Therefore the power supply was ailing. I'm not surprised about your test. They even had to upgrade the triac as well as redo the control circuit on them.
Not that I like cubes (I don't really), but they have way more raw power when they are running properly. The later models got real output transistors too. The originals were junk. The fact that they ran as the first model was amazing when you consider all the new technology and iffy parts.
It's also not hard to make an NAD 3020 sound better either. It also suffered from poor quality parts. The circuit isn't that great either. Another example of what you can get away with at low power (and low supply voltages). Don't worry, I'm not only picking on NAD here. Many other brands in the same boat. Many English brands were / are terrible. There are at least two notable exceptions to that.
-Chris
anatech said:
The one we had could have easily been amoungst the 1st 100 made.
Not hard at all. And they certainly were a piece of art in the sense of managing circuit & parts to get the best sound for the least amount of money. It would chew up & spit out the typical Japanese competition, but now, some 30 years later the attrition rate is much much higher vrs that Japanese kit (i think i have 2 or 3 dead ones downstairs)
dave
Hi Dave,
Now, one of those would make an excellent chassis for a new, small design. Dead is cool!
If you feel up to it, I'll suggest some component changes that should improve the sound quality. Good output transistors would be a good start.
Let me know if you are interested. Personally, it's an interesting project. Otherwise, it would be perfect for a new circuit transplant. I am looking for a preamp chassis to experiment on. Low to no features. Balance, volume and input selection. Tone controls would be okay. This is for the WAF when I want to try out a new idea upstairs. Hacked stuff with wire hanging out makes for a bad first impression.
I must admit that seeing an ailing NAD was very common in my old shop in Mississauga. We didn't even do warranty on that line. There were other brands along that line. Remember Vector Research?
-Chris
Now, one of those would make an excellent chassis for a new, small design. Dead is cool!
If you feel up to it, I'll suggest some component changes that should improve the sound quality. Good output transistors would be a good start.
Let me know if you are interested. Personally, it's an interesting project. Otherwise, it would be perfect for a new circuit transplant. I am looking for a preamp chassis to experiment on. Low to no features. Balance, volume and input selection. Tone controls would be okay. This is for the WAF when I want to try out a new idea upstairs. Hacked stuff with wire hanging out makes for a bad first impression.
I must admit that seeing an ailing NAD was very common in my old shop in Mississauga. We didn't even do warranty on that line. There were other brands along that line. Remember Vector Research?
-Chris
Hi timbert,
Believe me when I say, you do not want to wash my feet!
Thank you, but understand that everyone starts out somewhere. There are many people who do have more or different understanding than I do. Always remember to at least consider what everyone has to say. Even if they are incorrect, they may have a really good idea in there somewhere.
All we can ask is this. Learn. Do. Help other people out. It goes without saying that you should always do a neat and proper job on anything you work on.
E-gads! I'm a fossil!
-Chris
Believe me when I say, you do not want to wash my feet!
Thank you, but understand that everyone starts out somewhere. There are many people who do have more or different understanding than I do. Always remember to at least consider what everyone has to say. Even if they are incorrect, they may have a really good idea in there somewhere.
All we can ask is this. Learn. Do. Help other people out. It goes without saying that you should always do a neat and proper job on anything you work on.
E-gads! I'm a fossil!
-Chris
Nad 3020
IMHO the NAD 3020 is designed very nicely as it is. If it's busted I recommend taking it to a shop familiar with that style and age of componentry or very carefully replace with OEM spec components.
NADs are what they are by virtue of their design - nice equipment that does - out of the box - what it was capable of.
I own piles of vintage NADs and wouldn't change anything about 'em! Fabulous sound.
[edit] Like Planet10 I have some deaders too (among them a big "C" series that I think is one of the nicest amps I've ever owned)! Just too attached to them to chuck 'em. Like I'll actually get to them some day...
Regards,
Tom
IMHO the NAD 3020 is designed very nicely as it is. If it's busted I recommend taking it to a shop familiar with that style and age of componentry or very carefully replace with OEM spec components.
NADs are what they are by virtue of their design - nice equipment that does - out of the box - what it was capable of.
I own piles of vintage NADs and wouldn't change anything about 'em! Fabulous sound.
[edit] Like Planet10 I have some deaders too (among them a big "C" series that I think is one of the nicest amps I've ever owned)! Just too attached to them to chuck 'em. Like I'll actually get to them some day...
Regards,
Tom
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