life is good, again

millwood0 · 发表于 2013-8-25 04:34:45

My trusty Harman Kardon AVR630 went out yesterday. Bought 10+ years ago and it had been a trusty workhorse. Great sound and built like a tank: it must weigh like 40+ lb. The amp kept going into protection so had to turn the speaker-out off. Fortunately, it has pre-out so I just needed an amp.

Went into the attic, and picked up my Parasound 855A (another 30lb+ beast, designed by John Curl). Pop'd in my Eagles: Hell Freezes Over DVD (dts or pcm stereo). Hotel California filled my garage in no time. Last time I listened to it was like 10 years ago. Curl is god.

since then, I have rewatched Ice Age and City of Angels (Cage + Ryan). Beautiful sound, and the Parasound is just slightly warm.

My set-up:

1) AVR630 as preamp (70+w / ch).
2) Parasound 855A as power amp (80+ watts / ch, 5 chs driven). It will blow any Japanese junk out of the water;
3) PS2;
4) some no name DVD player (I picked it up for $10 years ago). No DD or DTS.
5) PSB Alpha x 4 + 1 Radioshack Optimus center. no subwoofer. The Alphas sound better today than when I got them home 15 years ago.
6) Toshiba Cinema Series 36" CRT TV: over 200lb heavy and no slot to any of today's flat screen TVs.

life is good, again.

millwood0 · 发表于 2013-8-25 05:02:50

Not having the manual anymore, I decided to google the parasound: http://www.parasound.com/vintage/hca855a.php

With 85 watts per channel this amplifier is able to reproduce explosive transients, and deliver clear, intelligible dialog from a movie's soundtrack. All the goodness of a bigger Parasound amp, with far better sound than you could get from a receiver.
FEATURES
Direct coupled - no capacitors or inductors in signal path
DC Servo and relay protection circuits
High bias Class A/AB operation
1 kVa Toroid power transformer with independent secondary windings for each channel, 68,000 µF power supply filter capacitance
Independent power supplies for each channel
Input stages use hand matched complementary JFETs
20 matched 15 amp, 50 MHz bipolar output transistors
AC present, standby/normal, current overload indicators
Rear mounted gain controls and rear handles
12 volt DC automatic turn-on circuitry Gold-plated metal structure RCA input jacks
Gold-plated 5 way speaker binding posts
Custom designed removable IEC AC cord
Three rack space height front panel
Rack mounting adapter available (RMK-3)
SPECIFICATIONS
Continuous Power Output:
85 watts RMS x 5, 20 Hz-20 kHz, 8 Ω
125 watts RMS x 5, 20 Hz-20 kHz, 4 Ω
Current Capacity:
30 amps peak per channel
Slew Rate:
> 130 V/microsecond
Power Bandwidth:
5 Hz-100 kHz, +0/-3 dB at 1 watt
Total Harmonic Distortion:
<0.03 % at full power; < 0.01 % typical levels
IM Distortion:
<0.03 %
TIM:
Unmeasureable
Dynamic Headroom:
> 1.5 dB
Interchannel Crosstalk:
> 80 dB at 1 kHz
> 60 dB at 20 kHz
Input Impedance:
33 k Ω
Input Sensitivity:
1 V for 28.28 V 1.2 V for full output
S/N Ratio:
> 115 dB, full power, IHF A-weighted
Damping Factor:
> 800 at 20 Hz
Dimensions:
17" wide x 5 1/4" high x 16" deep (6" high with feet)
Power Requirements:
110 Vac-120 Vac 750 Watts
Net Weight:
41 lb

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Wow! 1kva tranny, 2 pairs / ch output devices, 130v/us slew rate, 41lb and 750w power consumption.

The output devices are a little bit skinny - my other power amp is a Signature 2.1, with 3 pairs of output devices and is only rated at 75w/ch, all channels driven.

Not sure how much I paid for the Parasound then but I would say something like that would go for $1 - $1.5k new now, and I think I paid less than $1k then -> good amps retain their value well.

ddqq · 发表于 2013-8-25 07:35:01

高手，跨界音响的电子高手

mowin · 发表于 2013-8-25 07:53:57

拜读了，羡慕不已

dhbighead · 发表于 2013-8-25 10:00:45

膜拜搞音响的

millwood0 · 发表于 2013-8-26 05:19:20

I was asked if I could give some suggestions to build a high-quality home audio / video system.

I think you should first set out a budget. then, divide it up between software and hardware. I would say be prepared to spend 2/3 on software (CDs, DVDs, etc.) and 1/3 on hardware (electronics). Of the hardware budget, spend 2/3 of it on speakers, then 20% on power amps / avrs and then the rest on (digital) sources. going analog will be considerably more expensive.

Speakers have the most impact on sound quality and you want to spend most of your money on. The good thing is that most value-line speakers today are manufactured in China so you have access to much lower prices there. British speakers are very good, expensive as well. On the other spectrum are Japanese speakers - they are crap and should be avoided at all cost. Canadian speakers are good value for your money.

If you are really into sound quality, be prepared to invest in a quality power amp + a good set of pre/pro. Most home hifi power amps are fairly expensive - a low-end Pass for example goes for $40K/2ch. I have had some great success with using commercial power amps (Crown or QSC makes good and inexpensive commercial power amps). for $2-300, for example, you can get XLS1000: 200wx2ch. They will blow your socks off in terms of how good they are. However, they generally are ugly as hell and many of them are actively cooled -> noisy. You will need to put them in a rack somewhere and use a 12v trigger to turn them on / off remotely.

A pre/pro's job is to switch video / audio sources. This is where things get a little bit more complicated. For pure switching, it is easy, especially for (analog) audio. However, you may have different video sources (composite, s-video, component, hdmi, interlaced vs. non-interlaced, etc.). High-end pre/pros will perform conversion of the various audio sources so that you have one set of wires to your display. Most of othe conversions are from a lower qualityy format (like composite) to a higher quality format (like component). This is called up-conversion or upscaling (from a lower resolution format to a higher resolution format). There are also down-conversions (typically among the analog formats). There is where most of the money on pre/pros is spent.

The good news is that if your display / source is recent, it is typically hdmi and hdmi switching is fairly common even among low-end pre/pros.

Another alternative is to get a cheap avr with pre-out and use that as a pre/pro.

millwood0 · 发表于 2013-8-26 05:50:31

Now, onto the audio video receivers (avrs).

An avr is essentially a pre/pro + power amp. As such, it is typically highly compromised and generally don't deliver as good quality sound as a component system (pre/pro + power amp) would. But it is considerably cheaper.

What to look for in a good avr?
1) high quality power amps: you want those power amps to be deliver loads of current into your speakers at the same time. If possible, get a sense as to how many output devices they use per channel. 2 pairs (TO247s) in my view are the bare minimum for a 40-50w / ch amp.
2) video conversion capabilities: you need to figure out what display you have and what video sources you have and how they would work together. If you have all digital sources, you are in luck. If you still have a vhs or a s-video somewhere, be prepared to pay through your nose for that - because you will need some very sophisticated conversion here. Look for Marvel's QDEO or DCDi from Faroudja. The latter is the older and more expensive technology.
3) pre-out: to maintain future upgradability, you want your avr to have pre-amp outputs so you can hook up a few amps to it. They are typically in 7.2 format and all analog.

What NOT to look for in a good avr:
1) power ratings: pay no attention to them, particularly among low-end brands (like Sony, Pioneer, or Denon / Onkyo). those figures are usually rated single channel or two channels driven and at high THD levels. High-end units typically rate their units all channels driven.
2) sound dsp: those are basically useless. you need to do stereo, and native DD or DTS. Some have found Logic 7 (Harman Kardon) or Neo to be quite good, or DPLIIx. I generally view them as gimic.

For the less informed, how do you buy an avr?
1) buy on weight. All the stuff in the power amps are heavy - transformers, heatsinks, etc. 30lb is the minimum for avrs with analog amps. 25lb if digital amps are used.
2) buy on brands: I would write off most of the Japanese. I may consider Yamaha or Pioneer Elite. A good brand was HK but they have moved away to focus on in-car entertainment systems. Marantz is a good brand, as is McIntosh: both are fairly expensive.

What about DIY? diying an avr is not worth it and out of the capabilities of most people. DIY'ng a power amp is totally doable but still expensive: transformers, case, output devices, and protection circuitry are all fairly expensive to acquire. a 5.1 system, 50w x 5 + active subwoofer (optional) would deliver very good performance in most homes / apartments.

mowin · 发表于 2013-8-26 12:11:23

难得大师讲课，学习中……

dudududu · 发表于 2013-9-3 17:24:05

我表示，有道翻译有压力，于是................

wangxuedong · 发表于 2013-9-3 17:38:07

电赛很紧张啊

life is good, again

阿莫论坛20周年了！感谢大家的支持与爱护！！