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Old 27th October 2004, 04:33 PM   #1
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Question Amps, are there differences?

Hi All,

I'm new to car audio amps, at least from the repair perspective, and I've read a lot about the differences in power delivery, build quality etc, between amps. Over the last couple of weeks I've repaired 9 older (1998ish) ordinary 2 channel car amps, with a few more on the way, just to get an idea about construction, ruggedness, common practices, and generally discover the differences between the good the bad and of course the ugly. To my surprise, there was little or no difference between the random selection I bought, with a few conspicuous exceptions. No class D amps here, just your regular AB models...

For your reading pleasure here's the list of what I've repaired:

Soundstream SA80
Rockford Fosgate punch 250a2
Boss audio US250
Kenwood KAC728s
Hifonics Falcon
Pioneer GMX-362
US Acoustics USX2080
Pioneer GMX952
Earthquake Power 400xO

Some of these are so similar internally I'd guess there is only one actual design house for them, the odd ones being the soundstream, pioneers and kenwood amp. The soundstream, pioneer and kenwood models have heavier aluminum extrusions, and are generally more overbuilt than the others, bigger transistors relative to power output etc. None of them were underbuilt in any obvious way except for heatsinking...

They all have mosfet DC to DC converters, about 1/3 are regulated, but only half have mosfet power amps.

They all met their power ratings, just...however, not many of them would survive very long doing so, the heatsinking provided by the extrusions is simply not adequate, the hifonics amp being the smallest and hottest by far, for comparison the SA80 is the same size with less than half the power rating, so it does much better in the heating test...

I don't really know which of these is considered 'cheap' or 'good', but if I was choosing which to use, it would probably be the soundstream, then perhaps the big pioneer or kenwood, though they are much larger...the hifonics amp provides very big bang for it's size, but it also gets very hot very fast...of course the listening test will provide the final answer, but based on my looking at the amp schematics, I don't expect any big differences here...

I'll be doing some actual listening tests later, let me know what you guys think of these amps...not sure what I'm gonna do with them once I've finished testing, but I will want to use a couple...

Stuart
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Old 27th October 2004, 06:50 PM   #2
sdoom is offline sdoom  Germany
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Well, all guys are cooking with water

The reason for beeing similar is that most amps are made in Korea or China. Nowadays this got even "worse" . I think 70% of the amps sold in Germany are made in Korea by KIA , one of the major manuf. for this stuff. No matter what brand you get, they all use the same parts and curcuits, difference in power is achieved by putting more output stages "in parallel" , or in the DC-converters most of the times there are just mor MOSFET used.

But there are still big differences in assembling quality.



The amps you got should have some differences in the DC-converters , e.g. Kenwood DC converrtes are a biz oversized, in my repair time I never had a kenwood with a DC-converter failure.

the hifonics amps usually run hotter, especially the blue "8" Series amps due to "small" heatsinks compared to the available output power.

Differences can also be found in part-quality. While nowadays the standard-transistors in the amp-section are KTD778 and KTB998 Hifonics used to install TIP35 /36C , that can handle more power . Also capacitors influence the "sound" of an Amplifier. While in "cheaper " amps regular caps are used, better amps have Low-ESR caps with higher tempoerature ratings installed. Sometimes itīs just smaller things...... that matter
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Old 27th October 2004, 08:41 PM   #3
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Question Perhaps mine are not 'current' amps...

Hi,

According to the markings on the amps they were made in the USA, some clearly marked on the board as being assembled by a company call Zed audio, perhaps they also did the design, explaining the similarities.

All of these amps use irfz44 or buz11 fets in the smps, most use the tl494 control chip, some have an additional chip to provide make muting and regulation, error control etc work.

The mosfet amps all use irf parts in the output, while the bipolar amps either use tip35/36 or sanken transistors of very similar ratings, package etc.

Some of the failures were as follows:

GMX952: 1 output transistor not tight on heatsink cooked itself, shorted out.

KAC728s: power previously connected with reverse polarity, protection diode fried and shorted out.

Hifonics: dry solder joints making intermittent shutdown

SA80: Someone tried driving a dead short and destroyed one channels output and one of the smps fets.

250a2: cooked smps fet

400xO: input opamps killed, presumably by high level signal on low level input.

GMX362: capacitor exploded internally, ultimately shorted and shut smps down

BA US250: loose input RCA

So since they are all working again, which do you think are the 'best'?

Stuart
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Old 27th October 2004, 09:29 PM   #4
sdoom is offline sdoom  Germany
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Hi

Probably the Hifonics and the SS are "ZED" amps, , maybe Stephen Mantz had his fingers involved here. he is one of the pioneers in Audio- Amplifiers . Probably the TED-amps are "the best" , but how would you want to consider " best" and how to compare.

regulated DC-converters usually make more power possible , but there are a few old Korea-Amps around that have fixed Dc-converters and still deliver enourmous power and stability.

Personaly I like American made amplifiers the most. Most American amps deliver unsophisticated sound and power, manuf. quality is very good in most cases compared to todays Asia-amps. Again personally I dont "demand" to much on car amplifiers but I like when the amp is capable of producing clean sound at higher levels, and standard amps like the kenwood or the pioneer are good for general purpose.

but I think all amplifiers you have got some or their quality , you should see amplifiers around here, itīs a big market in germany and everyone wants to make big money. Iīve seen so much trash "wrapped" inside nice heatsinks . But I also have seen very good products from socalled "cheap producers" .

As always, mans own opinion decide wheather its a good or a bad Amp.
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Old 27th October 2004, 11:36 PM   #5
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Default best, what does it mean?

Doom, thanks for your input, I tried finding Zed audio on the web, there are a few mentions of the company, but they don't seem to have any website of their own. I have managed to get schematics for most of these amps, and in most cases I didnt need them, but when things need adjusting it's nice to know approx. settings and voltages.

With respect to best, in this case, for me, it means the sound quality. Since these guys are all supposed to be able to drive 2ohms, they are all going to get a bit of a workout, I have a pair of Apogee Duetta's Signatures, by repute a tough load for any amp, let the best/surviving amp win...I have a transformer from a heavy duty battery charger, rated about 35-40 amps continuous, I plan on using it in parallel with a couple of 12v/7ah UPS batteries, and 0.25F, made from parallel caps, a real 0.25F cap...

Should be good for a few sparks if nothing else...

When I'm done I think I'll offer the survivors in the trading post, basically at cost, there are probably people here who'd like them.

Stuart
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Old 28th October 2004, 12:00 AM   #6
sdoom is offline sdoom  Germany
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Hi


sorry, my English is not any good.....anymore. I was lucky and spent 1 year in Oregon and went to Highschool there. Fun time !

)Also I didnīt mean Ted, I meant Zed )

Here is some information on Stephen Mantz , he designed some of the toughest and "best" amplifiers on the market, including the Series8 of Hifonics, still one of my favorites amplifier series.


Stephen mantz / ZED Audio


I think alll your mentioned amps can be used and they all can deliver good results if they are used for what theyīve been made for, meaning you dont have any trash there.

These are pictures of an amplifier I fixed last week...... stated 1600W of power...... I was really surprised that nowadays things like that are beeing sold. I think this is fraud.

Click the image to open in full size.

Click the image to open in full size.

There is no SMPS. They used 2 power IC from Toshiba, capable of delivering 4x20W RMS into 4 Ohms at max. power supply (16VDC). Thats real garbage ! Those Toshiba IC are sometimes used in cheap Car stereos (I mean the headunitīs installed amplifiers) ....... But the dealers make tons of money with the amplifier shown in the pics. Usually it goes for 60 to70 US Dollars in ebay.


Hope anybody can understand what Iīm trying to tell
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Old 28th October 2004, 12:31 AM   #7
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Default oh my god...

Doom,

Your english is fine, and infinitely better than my german...

I have never seen anything like it, I was assumed I'd got the worst the car audio industry could offer through buying only dead units, but boy did I luck out. You should publish your pictures in a new thread so people have a better understanding of just how bad these things can get...does that unit have a brand name I might recognise?

Really I bet most people buying these things don't understand how badly they are being ripped off.

Stuart
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Old 28th October 2004, 03:16 AM   #8
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Zed hasn`t had anything to do with hifonics since the 7 or 8 series,and most of ones they did were name after greek gods(their slogan was power of the gods) so the Falcon is most likely designed by someone else.there were and still big corporate buy out,it`s sad.
As doom said they were small heatsinks on most of the ones that they had done.As for the others I`m not real sure.
I think that the days of good stuff is about gone.I`ve been buy some of the `80`s and early 90`s stuff just because I think that it is much better in many ways.I`ve got a PPI that brought almost 20 years ago and use it daily and knock on wood it`s never missed a beat.And the new PPi stuff you want get that.
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Old 28th October 2004, 03:50 AM   #9
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When I've shopped for cheap used or new car amps, I disregarded the stated specs and judged power by the fuse size and power in wire or terminal. You can't expect and amp to put out more than 60% of the fuse rating x 13V
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Old 28th October 2004, 08:22 AM   #10
sdoom is offline sdoom  Germany
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Hi , sometimes I also think that there are no useable amps around anymore, but there are

Ever heard of Audison ? Not sure if they are sold in USA , itīs an Italian company, they do most of their amplifier design in Italy and also the assembly is (at least parts of it) in Italy .


ebay picture

They can be called " recommendable" for better speaker systems (ok, the one on ebay is totally burned ) Also Signat has some very good products.

The last "big" amplifier I got for driving to 15" was the Hifonics zeus GenX , probably already a Korea-amp . But still very high output, low distortion and good assembly. the latest Hifonics models are real Korea-amps, and I guess thatīs the reason for them beeing way cheaper than the series8 amps had been . And There are many damaged /broken GenXI amplifiers on ebay over here...... the new stuff (US-distribution by Maxxsonics, in Europe itīs Audiodesign ) is just not bulletproof anymore.

I was talking to a guy from Audiodesign homepage and he told me that all the models are made in korea now, incl. even some of the speakers, def. all amps are designed and made in Asia. He admitted that quality has changed by far and the "stuff" needed to get much cheaper for them to survive, although the bigger models are supposed to be better......... i think a lot of customers donīt care about the used technique rather than a funky amplifier outfit or woofers with neon-lights


BTW: The cheap Amp above using two Toshiba IC are called TZS - First Austria , the same amplifier is sold with the name "Rockwood - 4x400W)"
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