adcom 5400

bolelet1

Will adcom 5400 (125 wpc) be able to drive my RTI10 or do I really have to get a higher wpc power amp, like 5500. Thanks for any info.

marker

The GFA-5400 will be enough to make them scream!

danger boy

the GFA-5400 will be enough power for your RTi10's. i use one from my fronts. and it's enough power for most any speakers. does your 5400 get pretty warm? mine does. and i hear it's normal.

bolelet1

yes, it does warm up a bit and I'm a little bit worried that it might break down. I saw a parasound HCA1000 (110 wpc) on ebay. will this warm up the same way as my 5400. or does all power amplifier, regardless of wattage, warm up when used for a long time?

danger boy

ummmm. i can't say for the other brands of amp.. someone else on here with more experience can answer that. i just know that my 5400 heats up alot. even just on but not powering any speakers. bad design maybe. not sure.

marker

Mosfet amp design. That's why. They typically run hotter.

Has anyone compared the 5400 to the 545, and if so, how did they stack up? I have no experience much with the newer series except for my cousin has some. I don't even know the model numbers. He runs an Adcom amp and pre-amp on some JBL S38 speakers, and it sounds killer.

unc2701

I liked the bipolar ones better, but I think its a matter of personal preference. They definitely give you more bang for the buck & I'd take a pair of 565's over any of their current 2 channel amps.

marker

^ +1! I have an old 535 that still works fine and sounds great!

I found out that the model my cousin has for his JBLs is the GFA-5400, but I've already forgot the pre-amp model number, GTP-650 maybe?

He has a surround set with JBL Studio Series speakers with S38 mains driven by a Yamaha DSP-A1 processor/multi channel integrated amp, and then the 2 channel rig in another room with the S38 and Adcoms.

aaharvel

danger boy wrote:

the GFA-5400 will be enough power for your RTi10's. i use one from my fronts. and it's enough power for most any speakers. does your 5400 get pretty warm? mine does. and i hear it's normal.

hey Danger my Adcom 5300 gets really warm too- maybe alittle bit more so on the right side than the left side- bEing a Mosfet design- maybe it IS normal. my 7300 (non-mosfet) is a bipolar design amp powering my center, sides, and back surrounds. That thing NEVER gets hot. Probably just in the design. That being said I think the 5300 sounds better when it's warmed up. The differences I heard from the older and newer adcoms were with the 535 vs. the 5300. IMO the 5300 sounded more musical, warmer, and less in your face. While both sounded great and the 535 particularly impressed me due to it's size and age- I like the 5300 better for it's musicality- again prob. attributed to the MOSFET design but different strokes for different folks.

marker

I think Ron P has the the old 535 and just picked up the newer model that replaced it, 5200 or 5300 maybe? Maybe he'll see this thread and weigh in since he's probably in the best position of anyone to compare the old model to the one that directly replaced it in the new line.

nellis8166

I have the GFA 7400. It barely even gets warm, even at extended periods of loud volume.

aaharvel

nellis8166 wrote:

I have the GFA 7400. It barely even gets warm, even at extended periods of loud volume.

Hey Nellis. Your 7400- like my 7300 are BIPOLAR designs. It's normal for them to hardly get warm at all- regardless of the output. The 5400's and 5300 (which I have) are MOS-FET designs- designed for 2channel and thus provide a more musical sound but the downside to that is they do tend to run very warm- almost hot. The 7xxx's are more for home theater/multi-channel applications; so this temperature issue is perfectly normal. When I bought both of my amps I e-mailed Adcom and they verified this; hence why I have my stereo pair connected to the Adcom 5300- and my center, and 4bipolar surrounds connected to the 7300. BTW Adcom's customer service is fantastic; almost as good as Polk's.

I'M THE KING OF DIRK!

bolelet1

before this 5400, I was using onkyo 282 (100 wpc) and it never gets warm although I must acknowledge that the sound reproduction is totally different. Then, going back to my original question, will other power amp, like parasound HCA 1000, warm up the same way as the 5400?

bolelet1

what does bipolar mean?

marker

Dirk Diggler, are you saying that IYO the newer series is definitely better for music?

BrentMcGhee

bolelet1 wrote:

what does bipolar mean?

It means you should be in a clinic

aaharvel

marker wrote:

Dirk Diggler, are you saying that IYO the newer series is definitely better for music?

hey Marker. that's what i'm saying; 'IMO'
thanks for correcting me.

marker

DD, actually I wasn't correcting you. I just wanted to make sure that's what you were saying. This exactly what I've been wondering, for someone who has both series comparable models to, well, compare them to each other. Thanks!

aaharvel

marker wrote:

DD, actually I wasn't correcting you. I just wanted to make sure that's what you were saying. This exactly what I've been wondering, for someone who has both series comparable models to, well, compare them to each other. Thanks!

yes, I believe that the newer 5xxx (as opposed to the 5xx) have a more laidback, relaxed sound that is IMO more suitable for 2channel music that's not hard rock or anything of that nature. The 5xxx's are MOSFET designs and the 5xx's are BIPOLAR designs.

They kept the BIPOLAR designs for their multichannel amps (7xxx) b/c i guess it's easier for these kind of amps to drive multiple speakers without heating up too much- i'm not sure. But both types go great with each other. Driving my stereo pair with the 5300 and the center and 4surrounds with the 7300- everything mixes and matches just fine.

VR3

THE* ultimate Adcom stack!

The old series is better than the new ones. Why? Because the old one cost a whole lot less and thats a fact jack. Money talks.

aaharvel

Vr3MxStyler2k3 wrote:

THE* ultimate Adcom stack!

The old series is better than the new ones. Why? Because the old one cost a whole lot less and thats a fact jack. Money talks.

from that viewpoint you're right on. I would never buy an Adcom brand new.

(edit) how are those poor things breathing?

VR3

They ran pretty hot. But the only time I've had an adcom that wasnt overly hot was when it was outside on its own.

But they did breathe pretty well...

I sold them all though - no regrets really. I just miss having the abilities to mess around with 10 channels of power...

I did some crazy stuff - stacking, biamping, dual centers... blah blah blah

heiney9

The main reason the Mosfet series of amps run hotter is 1) heavily biased towards Class A operation. Class A simply put, means the output tranny's are "on" more than they are "off", up to a point it reduces switching distortion that is found in a bi-polar design. 2) They have a higher idle current running thru the output tranny's also when (you guessed it) idiling. 3) I think I read somewhere Mosfets "come into" their sound with a higher temp. Don't know if that is fact or fiction. This is completely normal and as long as there is proper ventilation this SHOULD NOT affect lifespan.

I have a Nakamichi receiver that runs very hot simply because the idle current runs so high for the Stasis circuitry. If I touch the bottom of the chasis where the output tranny's are it's very hot to the touch. This unit is 19 years old and still running.

The newer multi-channel Adcom are Bi-polar in design. My best guess is effeciency for multiple channels and cost reduction. As to which is better...Mosfet or Bi-polar...let your ears decide. I prefer the Bi-polar, but I haven't spent a lot of time w/ the Mosfet design.

H9

P.s. see next post for info on the 3 designs

heiney9

Here is a quick rundown of the diff. (Valves=tubes;Transitor=Bi-Polar; Mosfet=Mosfet) Copied from Elliott Sound Products website.

The problems that befall valves are many, and include

* Fragile - The glass envelopes are very thin, and are easily broken.
* Limited Life - Even if a valve is operated well within its ratings, it still has a finite life. The main causes of valve failure are cathode emission degradation (happening all the time), and gas, when small amounts of air "break" the full vacuum.
* Microphonics - All valves tend to be slightly microphonic, which is to say that they act as a microphone. This can cause additional colouration to the signal if the sound from speakers vibrates the amplifier.
* High Voltage - Having to ensure that the 600V DC typical of a high power amp does not "flash over" valve bases is a constant headache, and ensuring that these voltages are kept well away from small fingers is mandatory. High voltage capacitors are also more expensive than lower voltage ones.
* Heaters - Valve cathodes must be operated at the correct temperature so they emit electrons properly, and "boil off" contaminants. If the heater voltage is too low, the cathode will become poisoned, and the valve is useless. The heater power used is all wasted, in that none of it is turned into sound.
* Output Transformers - The output transformer for a valve amp is expensive, bulky and heavy. It introduces its own distortion components, which are difficult (or impossible) to eliminate completely.
* Heat - All valve amps run hot. The valve will not work unless it is hot, and the heat causes problems for other components, shortening their life. The heat is all wasted energy.
* Damping - Valve amplifiers nearly all have a low damping factor, caused by a relatively high output impedance. Speakers must be very well damped indeed to work well with any valve amp, or the bass will become poorly defined, and crossover networks (which rely on a very low amp impedance) may not work as well as intended.

On the positive side, valve amplifiers have a "warm" sound, partly because of the low order harmonic distortion introduced. A good valve amp will also have a very wide bandwidth, and will have an easy job driving loads that cause solid-state equipment to have severe heartburn (or just blow up on the spot).

At low levels, valve equipment has vanishingly small distortion levels, and when all is said and done, there is something nice about little glass tubes, with little lights inside, making your music.

---

Transistors - A Summary

Just as with valve amplifiers, I have only scratched the surface. Entire books are written on the subject, and range from basic texts used in technical schools, to very advanced tomes intended for university students. Since transistors are easy to work with (and safe), there is much to be gained by experimentation, and you will have the satisfaction of having designed and built a functioning amplifier.

Transistors also have their fair share of problems, and there are some things that they are just not very good at. Some of the major failings include:

* Low Impedance - Bipolar transistors are inherently low impedance, and additional circuitry is needed to make them work satisfactorily in high impedance circuitry. Noise is also a problem when high impedance sources are used.
* Heat - Transistors dislike heat, and if it is not removed, they will destroy themselves. Most transistors can operate with junction temperatures up to about 125 degrees C, but at that temperature, can do no work at all. The life of a transistor is severely shortened by operating at high temperatures.
* Thermal Stability - Transistors are subject to some major changes in operation, depending on their temperature. This can make the design of high quality amplifiers difficult, because the transistor has a tendency towards "thermal runaway". This means that as the device gets hotter, it will draw more current, which makes it get hotter still. This continues until the maximum operating temperature is exceeded, and the transistor(s) fail.
* Second Breakdown - This is a version of thermal runaway, but at a molecular level. Parts of the internal structure become hotter than others, causing the hottest part to do the most work. This makes it hotter still until the transistor fails. Second breakdown is the most common cause of output transistor failure in power amps. It also happens very fast, and without warning - transistors can fail from second breakdown even when at ambient temperature.
* Short-term Overload - Largely due to second breakdown effects, transistors do not tolerate short term overloads, and in many cases even a momentary short circuit will cause instantaneous failure. Compared to valves, transistor circuits are much less capable with difficult loads, and usually must be over-engineered to sometimes extreme levels to prevent failures.
* Hard Overload - when a transistor amp goes into overload, it does so with startling clarity. The harmonics produced are such that tweeters can be destroyed very easily, and the sound is altogether unpleasant

Again, there are many advantages as well. Transistor amplifiers are very reliable, and can be counted on to give many years of life without requiring even a basic service ( most of the time anyway).

They are also very quiet (generally much quieter than valve amps) and do not suffer from microphony, so room vibrations are not re-introduced into the music. Efficiency is much higher, with lower voltages and no heaters (its a pity they don't look really nice, though).

Output impedances of 0.01 Ohm are achievable, so loudspeaker damping can be very high. Because transistor amps are very mechanically rugged, they can be installed in speaker boxes, so speaker lead lengths can be very short.

Typical transistor amplifiers have much wider bandwidth than valve amps, because there is no transformer, this is especially noticeable at the lowest frequencies - a transistor amp can reproduce 5Hz as easily as 500Hz.

---

FETs - A Summary

Junction FETs
The surface is again, only barely scratched. The junction FET (A.K.A. JFET) is ideally suited to circuits where high impedances are expected, and will give the lowest noise. They are an invaluable electronic building block when used where they excel - providing extremely high input impedance.

Like all devices so far, JFETs have their limitations ...

* Gain - JFETs do not have the high gain of bipolar transistors
* High Frequency Response - Generally, JFETs have a high frequency performance that is not as good as bipolar transistors
* Linearity - The linearity of JFETs is not as good as bipolar transistors (so distortion is greater), but can be improved by using current source loading or feedback.

There is generally an ideal (or close to ideal) amplifying device for every application, and when used properly, the JFET is extremely versatile and at its best when high impedances are needed. If you have a need to send an amplifier into space, then JFETs are preferred due to their greater "radiation hardness".

JFETs (in fact all FETs) are more sensible than bipolar transistors when heated, and problems of thermal runaway are not encountered with these devices.

MOSFETs
The MOSFET is one of the most powerful of all the current range of amplifying device, with extraordinary current capability. Ideally suited to very high power amplifiers, where extremes of operating conditions are regularly encountered, the MOSFET has no equal.

... And, as always, there are limitations ...

* Gain - Like JFETs, MOSFETs have a lower gain than bipolar transistors, which usually means that additional gain must be applied to the driving circuit to ensure that the global feedback is sufficient to maintain low distortion at low levels.
* Gate Capacitance - The capacitance of the gate to source can be as high as 2nF (although more typically around 1.2nF). This is not a lot at low frequencies, but makes the drive circuit work very hard at high frequencies.
* Static Damage - Until installed in a circuit with full protection, the MOSFET is susceptible to damage from static discharge. The voltage and current needed to destroy the device are generally below the threshold of feeling for humans. Some devices have (limited) protection built in.
* Linearity - Most MOSFETs are not very linear at low currents, so for low distortion higher quiescent is needed to ensure that crossover distortion is minimised.

To some extent, all the above can be forgiven when you really need the capabilities of a MOSFET. The complete freedom from second breakdown and the massive current capabilities of MOSFETs are unmatched by any other active device. With a properly designed drive circuit, MOSFETs are also very fast, capable of performance that is generally superior to that of bipolar transistors. This is not very helpful in audio, but is essential for switching circuits.

Coupled with a positive temperature coefficient that completely stops thermal runaway in a linear circuit, the MOSFET is almost indestructible, provided that precautions are taken to ensure the gate voltage is kept below the breakdown voltage.

The positive temperature coefficient is a great help in audio circuits, although it can be a problem in switching power supplies, since the "on" resistance also increases with temperature, and in a switch-mode power supply this can cause thermal runaway (exactly the reverse of bipolar transistors in this application).

http://sound.westhost.com/amp-basics.htm

Take it FWIW....Learning is so much FUN

H9

heiney9

Keep in mind the above explanations are very GENERAL and each manufacturer has it's own way of dealing with inherent short comings depending on their end goal. Don't read the above and then start thinking your particuliar design is BAD because of this and that.....Those are just some general disadvantages and in many cases can be addressed by a particular design to minmize/offset said short comings.

FWIW

H9

danger boy

H9 thanks for the info. I would imagine a MOSFET designed 5 or 7 channel amp would heat up an entire room with it's heat output. :eek: so that makes sense that most of todays multichannel amps would be a bipolar design.

I know that when I used to turn off my amp. it would take a good 30 minutes before it would sound good. otherwise it was somewhat flat in the highs. Now that i leave it on.. it sounds the same 24/7 even on holidays.

louthewiz

I have 2 audio source amps and one onkyo M-282 amp and to tell you the truth they never even get warm during heavy music or movie listening , now I know for sure that some carver and adcom are famous fo heating up because of dipolar design. another interesting thing I have discovered is that multiple amps sound better than multichannel amps for some reason.

heiney9

louthewiz wrote:

I have 2 audio source amps and one onkyo M-282 amp and to tell you the truth they never even get warm during heavy music or movie listening , now I know for sure that some carver and adcom are famous fo heating up because of dipolar design. another interesting thing I have discovered is that multiple amps sound better than multichannel amps for some reason.

Actually the term is Bi-polar meaning they are "two polarity" devices. Actually Bi-polar tranny's are very temperature sensitive therefore it's advisable to keep temps constant as thermal stability affects performance. Typically bi-polar tranny's are biased for a small amount of class A operation because if they were 1/2 on all the time it would cause thermal runaway and burn up. Remember in instances like these Heat=Inefficiency. The power is being dissipated as heat.

In Mosfet designs (again general speaking) Heat is not an issue as far as the semi-conductor is concerned .So typically the Mosfet design is heavily biased towards class A operation, this causes them to be "on" more than off. The reason for this is Mosfet's are not very linear at low currents (more distortion is present) so the idle current has to be high enough to overcome this phenomenon. Hence they run hotter, remember heat=inefficiency.

Mosfet are rugged; and have extraordinary current capability. Not sure why one is better suited than the other as there are other stages of an amp which depending on design may benefit the use of one over the other. The result is a superbly smooth, spectacular sounding output section, with practically unlimited voltage and current capability.

My best guess....is Mosfet allows the 5xxx series of amps to run a much higher Class A bias which to some may sound better.....also Mosfet's have a "softer" sound to them, The high input impedance of Mosfets allow for the use of an extremely simple gain path, and their negative thermal characteristics give high thermal stability, allowing high output stage bias, low offset voltages, and very high output current and voltage with reliable operation.

If I have any of this wrong...please feel free comment, this is my best understanding w/o going into much more detail as there are many other variables.

FWIW

H9

EDIT: Adcom does state in their literature that their design is Pure Mosfet used in all stages, so I stand corrected about Adcom 5xxx units having Bi-polar input/gain stages.