Norge 1000 GOLD Stereo Integrated Amplifier (Technical Review)
It has been quite long since I last wrote a review. The last one was of my beloved Logitech Z-2300 which still remains with me & performs with full gusto. But as I travelled through the different posts of many audio forums, it became quite crystal clear to me that a separate stereo integrated amplifier with a pair of bookshelves/floor-standers are the best way to listen to music.
Now from an Indian perspective & considering my mere budget of INR 12K max, I was left with two choices when it came down to amp selection, i.e. either Norge or Sonodyne + plus some local made bookshelves. God knows how they would have sounded.
My PC Audio Setup
Anyway, I luckily met a person who wanted to sell his 6 year old Sony SS-GN88D bookshelves at a very nominal price of INR 1.5K. This was one of a kind offer, so I bought them immediately.
Before buying these, I googled a lot about these bookshelves and became quite impressed with their spec sheet. Sony have excellent brand value in India. They are often recognized by masses as a supreme quality product manufacturer(which they are not) & if anyone wants a quality product, he/she have to pay more & buy a Sony.
I never blindly believed in this motto, and when I luckily came in the contact with these wonderful people who are known as “audio enthusiast” or better still true blue “audiophile” is when I came to know about brands like Krell, NAD, Marantz, Warfedale, Dali, Boston Acoustics, Cambridge Audio, Yamaha etc. I don’t know how the Sony fanboys are going to react after hearing the audio nirvana from one of these above products, but surely they will refer 'Sony' as 'Bony' from then on-wards.
Getting back to the groove, I contacted one of the Sony dealers here, came to know that that these are no more available & they used to sell them at INR 10K a pair nearly 5 years before. Mine is 6 years old and in pristine condition.
I then googled for the past ten year history of Sony Mini-HiFi in India and became pleasantly surprised to know that these are the best set of bookshelves that every came with their Mini-HiFi systems in India. If I am not wrong there were only two Sony bookshelves with 8 inch bass drivers which came with their Mini-HiFi, and this is one of them and the better one still, since this model came with two additional mid range drivers that the other one is missing. It is also the heaviest of all the Sony’s bookshelves at nearly 9 kilos per speaker & 18 kilos in total, meaning that the drivers have big magnets(can handle more power) & the MDF is thick enough to withstand heavy bass waves generated by this 8 inch bass drivers. Though I admit they are nowhere near to audiophile grade speakers.
Sony SS-GN88D Speaker specification:
Speaker System: 3-way, 4-units, bass-reflex type (magnetically shielded)
Subwoofer : 8 inch X 1
Mid woofer : 3 inch X 2
Tweeter : 2 inch X 1
Rated Power : 150W per speaker
Nominal Impedance : 6 ohms
Dimension: 265 X 415 X 320 mm
Mass: 8.7 kg approx per speaker
Tweeters (2 inch)
Midrange Drivers (3 inch)
Bass driver (8 inch)
It is extremely rare nowadays to find an eight incher in general consumer audio as they are mainly dominated my flashy looks with big LCD screens & ten tiny speakers units of different colors, while none of the drivers being over 5 inch in diameter. So one always end up with 80Hz~20kHz in the sonic range.
But these bookshelves are a different beast altogether, with an 8 inch bass driver, two 3 inch mid ranges & a 2 inch tweeter. So, we are looking at a pair which is capable to travel 35Hz~20kHz in the sonic range. This are extremely favorable for bass heads like me.
Now with a set of good bookshelves in my bag, I went for amp hunting. Within INR 12K, it boiled down to Sonodyne or Norge. Fortunately, in the classifieds I found a person who wants to sell his one month old Norge 1000 + Norge Millennium speakers at INR 20K because he wants to upgrade. I contacted him & he was kind enough to sell his Norge 1000 GOLD amp to me at INR 10K. GOLD DEAL!!!:yahoo:
Anatomy of Norge 1000 GOLD
Looks : If looks is anything to go by then this amp is surely a disappointment. The Sonodyne amps are much better looking, have better fit 'n finish & also posses a lot more features. For Norge amps looks can be deceptive, since you have no idea of what performance lies inside. This amp is kind of retro styled with plain Jane looks. My amp came with black facia(which I like over the brushed aluminum one). The front facia are dominated by four control knobs namely volume, bass, treble, balance, a power switch with built in LED, three push button input option selector(AUX, DVD,TAPE), a tone defeat button and a phone jack.
At the back you have RCA inputs for AUX,DVD,TAPE, one RCA line out. A pair of banana connectors for the speakers are provided. This amp has a minimalistic look from the outside and truly speaking at INR 10K you do not expect much. Two things that struck me when I bought this amp was the weight, which generally means that the amp has a potent power supply and secondly the size of the heat sink at the back, since for 250 watts of power @ 4 ohms this is just too small, but I thought maybe I am viewing half of it and the rest half is lurking under the hood.
Specifications as per manufacturer:
Power Output(RMS) : 125W X 2 @ 4 ohms
Frequency Response : 10Hz - 80Hz + 0.5db
THD : < 0.04%
Input Sensitivity : 500mv
Input : AUX / DVD / Tuner
Gross Weight : 8.75 Kg
Under The Hood
Before I continue, I want to state that the views that I am going to provide regarding the Norge 1000 are my personal ones, though some of them were verified by Mr. Shyam Bajaj himself. I had a three week long conversation with him in mail before I wrote this review. I will be much obliged if someone can cast more light on them and rectify me if I am wrong.
Norge 1000 Amplifier Innards
The first thing you notice after opening the cabinet is it looks like a home-made amp. These circuits are not done in computer controlled 1,000 bakes per minute machine, rather they are handcrafted for painstakingly long hours by just 3 persons in the 15’ by 20’ room of Norge Audio workshop. It has a neat and uncluttered look from inside, attention to detail can be found everywhere, like closely tied wires to the chassis so that they do not wobble around, and hand soldering of different electronic components to the PCB are just spot on. These are very neatly designed handmade amplifiers with a certain level of exclusivity & provide a quality feel that says they are build to last. No wonder why Mr. Bajaj gives a 3 year warranty. Also I found there are ample safety measures taken so that minimum damage is done to the circuitry.
Power Supply Unit
To me the most important component of any amp is it power supply unit. It also houses the heaviest & most costly component i.e. the transformer. It is this unit which is going to provide all the unadulterated juice (read as power in watts) to the power-amplifier & pre-amplifier modules so that they can fulfill your desire. Looking at the power supply of the Norge 1000, I must admit I am thoroughly impressed. The amp innards is mainly dominated by this one big toroidal transformer shown below and I will not at all be amazed to find if it costs nearly 50% of the Norge 1000 price i.e. INR 5K.
The primary fuse used is a T3AL250V.EI type. The power amp module uses same fuses for each of the four power transistors. More of it latter.
Common terms used:
V : Volts, VAC : Volts AC, VDC : Volts DC, A: Ampere, Watts : V X A
Toroidal Transformer Details [Confirmed by Mr. Bajaj]
VA Rating: 310.50 VA
Primary Input: AC 230V/50Hz
Secondary Output :
i) 30VAC x 2, 5A (Goes to the power amplifier)
ii) 15VAC X 2, .35A (Goes to the pre amplifier)
Height: 60 mm
A toroidal transformer uses a doughnut shaped core & is much slimmer than a conventional (EI) transformer. It has numerous advantages over EI type such as low weight, low hum, low noise and also being smaller in size than an equivalent EI type. On the downside they are much more expensive than a conventional EI transformer. But it is worth the pay since you get better performance.
So, Mr. Bajaj has got the first step right. Also this is a potent transformer which is capable to deliver:
60V X 5A = 300.00 VAC [goes to Power amps]
30V X 0.35A = 10.50 VAC [goes to Pre amps]
Total = 310.50 VAC = 310.50 watts ~ 311 watts
Since all the electronic components of the amp run in DC, the power supply has to convert the AC secondary output of the transformer to DC in-order that other circuit components can work with it. Below is the picture of the PCB that houses the rectifiers & the ripple filter capacitors used for both the power amp & pre amp modules. It also houses voltage regulators for pre-amp. In the picture below, you will find the upper part of the PCB is used for power amp while the lower part is for pre amp.
Rectifier + Ripple filters + Voltage Regulators (AC to DC PCB)
The rectifiers(tiny black ones) are used for AC to DC conversion, while the ripple filter capacitors are used to smoothen this DC output. A pair of beefy Samwha 4700uf, 50V capacitors are used per channel for power amps module. Adding four of them for the two channels you end up with 18,800 uF of idle power lurking there to assist the transformer when big demands of power are required. The transformer's +/- 30 VAC secondary for the power amp module after passing through the rectifier & power capacitors will be +/- 42 VDC, the current being 5A.
For pre-amps module a pair of Samwha 1000 uf, 25V caps is used per channel which makes 4000uF in total. Since the volts supplied by our home wall AC inputs are not exactly 'clean' having all sorts of spikes and dips, the voltage from the secondary output of the transformer must be regulated. Pre amps are quite sensitive to voltage fluctuations which can cause a significant dent on the the sound quality. This is why voltage regulators are recommended. Norge 1000 uses a pair of Fairchild 7815/7915 voltage regulators.
Fairchild 7815/7915 voltage regulators in between the caps
These voltage regulators reduces the voltage by 10 volts approximately and the op-amps operate under this regulated voltage. The transformer's +/- 15 VAC secondary for the pre amp module after passing through the rectifier & power capacitors will be +/- 20 VDC. Now, the voltage regulator cuts down the voltage by further 10 volts, so that the DC voltage supply to the pre amp module be a 'clean' +/- 15 VDC, the current being 0.35A
Almost all the capacitors used in the amplifier are of the Korean manufacturer Samwaha. It is quite a reputed brand in Korea and supplies capacitors to electronic giants like Samsung & LG to name a few. But they are not Nichicons for sure and also you do expect them in an INR 10K amplifier. There are very few Rubycon caps at places where it is absolutely necessary, for performance reasons, since they are more costly caps than Samwha. Personally, I am highly satisfied with the power supply unit.
The PCB of the pre amplifier module looks like one of the Rod Elliott designs. This pre amp PCB uses PCB mount pots, and provides a complete stereo preamp with bass, treble, balance and volume controls. It has an innovative tone defeat function that rather than completely disabling the tone controls massively de-sensitises it.
The design looks fairly conventional, with the main advantage being that there are almost no wires to run. Source switching is done by three separate push button switches (Tape/DVD/Aux) found in the front panel of the amp. The volume pot is actually spaced a little further apart than the others to allow a larger knob, since this is the most commonly used control in any preamp. The use of 16mm pots makes for a small and neat layout, and makes it very easy to include this pre amp module with a power amp module, making a complete stereo integrated amplifier system.
Texas Instruments TL072CP
This pre amp module houses three Texas Instruments TL072CP operational amplifiers. This JFET-input TL072CP operational amplifiers has very low input bias and offset currents and fast slew rate. The low harmonic distortion and low noise make the TL072CP ideally suited for high-fidelity and audio pre amplifier applications. Each amplifier features JFET inputs (for high input impedance) coupled with bipolar output stages integrated on a single monolithic chip. TL072CP being a dual op-amp have two op-amps inside to handle stereo channels.
The Power Amplifiers
The Norge 1000 GOLD is a solid state/discrete amplifier, i.e. it uses a pair of power transistors per channel to produce the desired output rather than using chip power amps. Discrete amps are generally regarded superior that Chip amps (Please flame no war).
Solid State vs Chip Amps
On a chip amp IC the transistors are formed on a single silicon wafer and it is very difficult if not impossible to optimize all the transistors for where they are used in the circuit. Input stage, output stage, etc, all have different requirements. With a discrete amp one can chose a design topology which will be easier to make and much more stable. With discrete design, one can pick transistors suitable for the design. Since resistors and capacitors within the IC are formed on silicon, they pose another challenge for an IC designer. The properties of resistors and capacitors are difficult to control on IC chips, while it's just a design consideration/choice in discrete design amplifier. Here and there all these factors accumulate, there is no question why a well designed discrete amplifier could be better than the best IC amplifier.
Norge 1000 uses a pair of Taiwanese CKT branded A1943/C5200, BJT type transistors per channel.
CKT branded A1943/C5200
A bipolar (junction) transistor (BJT) is a three-terminal electronic device constructed of doped semiconductor material and may be used in amplifying applications. The A1943 is a slicon based PNP triple diffuser type transistor while the C5200 is a slicon based NPN triple diffuser type transistor.
These pair of BJT transistors are complementary with each other and operate in push-pull mode, which means that while A1943 produces one half of the audio signal sine, the C5200 produces the other half of the audio signal sine. The transistors are CFP configured i.e. power goes directly to the emitter of the power transistors. They can produce 150 watts of peak dissipation, but the safe operating area(SOA) is roughly 80-100 watts regardless of load.
Power Amplifier Module
Here also the PCB of the power amplifier looks like one of the Rod Elliott designs. The basis for this power amplifier is almost 30 years old, as an amplifier it remains "state of the art" - this is an extremely good amplifier. It seems simple to build and uses commonly available parts and is stable and reliable. This amplifier, although very simple, is capable of superb performance. This is not an amp to be under estimated, as the sonics are very good indeed, and this is due (in part, at least) to the inherent simplicity of the design. The amp is exceptionally quiet, and is reasonably tolerant of difficult loads. The design has had the benefit of many, many years of consistent use, and this version is the best of all - the refinements ensure minimum "switch on" or "switch off" noise (though it is quite significant for Norge 1000), and the availability of really good output devices has improved on a known and very stable design. With a pair of A1943/C5200 power transistors, 100 watts @ 8 ohms per channel is easily obtainable at +/- 42 VDC.
Norge 1000 GOLD amplifier’s continuous power output capability
In order to produce a 250W of continuous power, an amplifier of Class-AB type will require a transformer that is capable to deliver at around two times the claimed wattage. Since watt is volts multiplied by ampere, 250W of continuous power output requires a 500 watts or 500 VAC transformer.
Since, 300 VAC is channeled to the power amplifier module, the Norge 1000 will produce a maximum of 160 watts of continuous power at around 55~60% efficiency regardless of load.
This means Norge 1000 is always capable to provide 160 watts i.e. 80 watts of continuous power per channel to the speakers regardless of the impedance(1 ohm, 2 ohm, 4 ohm, 6 ohms, 8 ohms, 16 ohms, ....) of the speaker. But, for safety reasons one should not use speakers below 4 ohms impedance with this amp. Personally, I believe 8 ohms rated speakers are best suited for this amp.
Discrepancies about Power Output Figures
One has to remember that most audio amplifiers do not have power supplies capable of driving their rated power continuously. This holds absolutely true for all general multimedia speakers systems, consumer home audio products & even low to mid level audiophile grade systems. Only true blue top end audiophile grade HiFi systems costing a lot of green have power supplies that are able to match the continuous power rating of the amplifiers.
This is because music is not like a continuous sine wave. It has peaks of intensity, then relatively quiet periods. If music has a 20dB dynamic range then if the peaks are 200W, the average power is probably around 5W.
A transformer can sometimes go well beyond its rated power output for small amount of time to handle these peaks of intensity. For example the 300VAC transformer of Norge 1000 can go up to 360VAC to handle the peaks & produce 190W for that particular moment.
If even further power is required to handle this peaks of intensity, say 250W, then the additional 60W is supplied by the four large power supply ripple filter capacitors for this short period of time. The filter capacitors can charge back up during the relatively quiet periods.
The 311 VAC transformer of Norge 1000 is perfectly capable to deliver 160W of continuous power & can easily handle peaks reaching 250W @ 4 ohms i.e. the dynamic power of the amp is 250W @ 4 ohms. While listening music, dynamic power is more important than the continuous power.
Continuous Power Output of Norge 1000 :
4,6,8 ohms load : 80W X 2 = 160W
Dynamic Power Output of Norge 1000:
i) 4 ohms load : 125W X 2 = 250W
ii) 6 ohms load : 100W X 2 = 200W
iii) 8 ohms load : 80W X 2 = 160W
Where Goes The Heat?
Now comes this very important question. When I bought the amplifier I was skeptical about the tiny 3.5 inch height of the heat sink, since this is too small for a 250 watt amplifier. A heat-sink of this size can handle a max of 70 watts of heat dissipation.
Heat Sink Fins
Considering the case that Norge 1000 in Class-AB mode will deliver 160W with 55~60% efficiency, it will be dumping something around 140 watts of heat to this tiny heat sink. One should use this heat sink for each pair of A1943/C5200 per channel but instead all the four transistors are tied in this single heat sink.
To give you a rough idea, my Logitech Z-2300, 2.1 speaker set uses Class-AB chip amps and have a transformer of 150VAC. As usual 70 watts is dissipated as heat through heat sink and the rest 80 watts are available to speakers. Now for these 70 watts of heat dissipation, Logitech uses a heat sink of 9 inch in height, 4 inches wide and 1.5 inch deep containing 9 fins. Just think.
Logitech Z-2300 heat sink
Here is a picture of what a real 100 watts per channel amp heat-sink should look like:
My doubt became even more clear when I played ultra bass heavy tracks like "Handle this" by Basstronics at half PC volume & amp volume at 40%. This song will simply suck any amp dry & immediately the heat sink became very hot in 5 minutes time. Listening to this type of songs at this volume levels for sustained periods can lead to permanent damage to the power transistors & I was advised my many supremely knowledgeable people who are in this business for years to never use speakers less than 8 ohms & never to go past 50% volume with this amp.
This is not because the amp is an under performing amp but because the heat sink does not have the ability to dissipate 140 watts of heat when the transistors are in full load which results to heat buildup & thermal breakdown.
One has to remember that I am listening to these songs with a pair of bookshelves that are capable to handle 300 watts of power at 6 ohms having a total of two 8 inchers + four 3 inchers + two 2 inchers. They are pulling massive amounts of power from the amp, and the Norge 1000 GOLD is just as happy to oblige, but then the underperforming heat sink just cannot dissipate this heat. Heat builds up fast and you start to fear about the amp getting overheated and finally going bust. Even Rod Elliott commented that the heat-sinks are tiny and are not build for 4 ohm loads.
I Want A Solution!!!
I was provided with two solutions by these people, either add another heat sink for optimum heat dissipation or use cooling fans to cool down the heat sink. The second option looked better for me as the amp does not give any scope to add another heat sink to it.
Also, cooling fans are very efficient and can increase the heat dissipation rate by two folds or even more. I measured the fins of the heat sink to be a ~80mm & square sized. This was a coupe for me since 80mm PC cooling fans are widely available in the market. I bought a pair of CoolerMaster 80mm silent fans and used very small amount instant glue(drops of) to stick the fans at the back of the heat sink fins.
CoolerMaster 80mm fans
I had an old PSU lying around of late, so used it to power these fans. 4 pin Molex to Fan input adaptors were used.
Now my Norge 1000 runs super cool. When I play the same song at the same volume levels, I find the heat sink is running super cool. I also tested with this type of bass heavy songs at 50% volume for over half an hour and the amp simply refuses to heat up. FAN SURELY MAKE WONDERS WITH HEAT.!!!! hyeah:
From now on I can enjoy long hours of music listening at high volume levels without ever being bothered about heat buildup & the amp going bust.
Headphone Output: I found an amazing concept in Norge 1000. The audio source for the headphone jack is taken directly from the amplified speaker output terminals (banana connectors), and Mr. Bajaj have used resistors to decrease the power and provide it to the headphones.
Using resistors to decrease the power and provide it to the headphones
Generally, when someone plugs in the headphones the external speakers should go mute. But in the case of Norge 1000, both speakers and headphones play at the same time. Amazing & weird concept.
The only reason I can fathom is, he desired the best quality undistorted audio signal to reach the speakers, and if this had to go through headphone socket in order to cut the power when headphones are plugged in, some distortion in audio signal must have crept in.
RCA Line Out: Well I tried everything, connecting to a headphone, my Logitech z-2300, but there is no audio signal coming out from this line.
The truth is at INR 10K, you cannot expect a better stereo integrated amplifier in India than Norge 1000 GOLD, though I would have loved if Mr. Bajaj could have shoved in another heat sink, and rise the price by even 1K. The amp would have been rock solid then. But anyway the qualities of components used are of high standards & are build to last.
You will never be able to push this amp if you are using a pair of bookshelves that are rated at 8 ohms having a 5 inch midwoofer and a tweeter, and it will always remain cool. These 5 inch mid woofers cannot produce anything below 80Hz so the amp will never go under a situation of strain. The heat buildup also depends on the kind of songs you are listening, bass heavy songs producing sound waves between (10Hz~200Hz) at moderately high volumes on 4 or 6 ohms speakers are going to ask a lot from this amp. This is when the heat builds up on the heat-sink.
Regarding the sound quality of this amp, I don't think I have to say much, this amp is going to return every penny of your hard earned money in terms of sound quality. Fascinating & truly musical are the terms to describe. And it has performance in heaps with 160 watts of raw continuous power output capability it can virtually drive any speakers from any make be it floor standers or bookshelves.
The best aspect of this amp is its neutrality, it does not possess any sound signature, and it sounds just as good while playing hip-hop as it sounds while playing ghazals.
You will find hundred of threads in audio forums singing the praise on the Norge 1000 GOLD & also of Mr Shyam Bajaj. Look for them.
As of now I am a very happy man with my 27 kilo PC audio system.hyeah:
Comments will be appreciated.