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Suggestions on seperate amps and where to find.


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26 replies to this topic

#21 of 27 KenA

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Posted July 13 2000 - 09:06 AM

Thanks, Andrew. Since, I'm building a sonotube, I'd prefer a rack-mount amp, so the Jr doesn't fit the bill. I'd also like a little more power than 100w. Preferably in the 200w range. I'm been looking at some of the other suggestions in this thread, but I was hoping to hover around $1/watt.

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#22 of 27 Andrew Pratt

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Posted July 13 2000 - 09:20 AM

check out your local pawn shops or dealers that take in trades. I managed to find my hafler sitting there collecting dust so got it for a decent deal (in the $1/1 watt area) There's a couple on mono blocks in the For Sale area that look like they'd be perfect for a sub if you can swing that much.

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#23 of 27 Vince Maskeeper

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Posted July 21 2000 - 10:54 PM

Sorry guys, this thread dropped off my radar for a few days, so I didn't notice the addition questions...

Quote:
Now the brand I don't hear much is Carvin. I really want to hear more about the DCM-2000. I know they are a direct mail order company, but based on their amp design it looks very good and well constructed. So what is your take on this amp and company?

Chris- I get asked about this stuff all the time actually. Carvin (not to be confused with Carver) is a mail order only company out of California that makes budget products, specifically targeted at "Working Musicians", similar to the approach of companies like Peavey or Mackie.

I have had very very little hands on experience with Carvin amplifiers. However, I once worked a summer at a campground that had a Carvin mixing board, and it was one of the biggest pieces of dog poopie I have ever used. Unreliable, noisy, all sorts of strange anomolies- it was less than a year old but 3 channels (of 24) didn't work! I dislike Mackie products, but in this case I would have given anything if I could have replaced the Carvin with a Mackie...

Although Carvin amps may be decent, I have trouble trusting a company that doesn't allow their gear to be carried in a store when I can see it/touch it/play with it. What are they hiding? In addition, the Carvin products I have seen (mixer mentioned above, as well as their speaker boxes) have not at all impressed me. I also wonder about repair issues: I think Carvin can only be repaired by Carvin, so that is another pain in the behind!

Finally, you have companies like Mackie and Peavey who have essentially the same products as Carvin, designed with the same mindset (budget products that work) at essentially the same price point, so why bother messing with carvin? With Mackie/Peavey you can buy locally, demo before you buy, repair locally, and there are tons of Mackie/Peavey owners out there who's opinion you can solicit. These other products are also much more widely available on the used market, if you want to go that route. It just has always seemed to me that dealing with Carvin was a waste of time.

Again, they might make good amps, but all the crap surrounding them makes them not that appealing!

Oh, hey Jim, If you end up with your 2 JBL 18's driven by a Macrotech 3600/K2 (or similar)- You have to invite me over! I'm dying to see this running in someone's livingroom Posted Image

Anyone else with amp questions: feel free to post here (I'm getting a lot of emails about amps and would rather discuss it here for the benefit of everyone rather than via private email!!)

-Vince

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#24 of 27 Seungsoo Hwang

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Posted July 23 2000 - 03:29 PM

Ok a lot of suggestions have been made on WHAT to get, but the second part of the question is not being answered by many people, if anyone. WHERE to buy one of these suggested amps? There are the obvious like Ebay, and it is easy to find realiable places to buy them new. But where can one go to realiably buy used amps? I am either looking for a used Mackie m1400 or a Ashly FTX2001. I would like to get one of these for $450 or under shipped? Any suggestions? The only place I know is ugbm.com, but they dont have these often and they are not that cheap for a Used gear dealer.
thanks

#25 of 27 Greg Monfort

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Posted August 12 2000 - 05:10 PM

Quote:
WHERE to buy one of these suggested amps? There are the obvious like Ebay, and it is easy to find realiable places to buy them new. But where can one go to realiably buy used amps?

Any suggestions? The only place I know is ugbm.com.....

Pro:
http://www.jamminjersey.com/
http://www.soundbroker.com/

Quality:
http://www.audiogon.com/

Also, do you have a Miller's Music, Rhythm City, or similar pro shop somewhere in the state? They usually have some used gear.

Used amps such as Adcom, Hafler, etc., are sometimes available if there's a used HiFi store.

Quote:
In the case of HT application, with clean, undistored, high noise ratio signal is used, they recommend to use amp power of twice the speaker IEC wattage, giving enough headroom thus, as so well stated by Vince.
But this is for cinema application....... in our case, I think the idea is to estimate the SPL level seeked, then calculate how much amp power is needed to go above this level by 3 or 6db, as protective headroom.
In my case: let's say 113db SPL total at listening position (2 subs,99db 1w 1m sensitivity, 20hz high pass, 80hz THX crossover) for instance requires: 512w per sub, 2 subs.
512watts=125db @1meter - 18db for 6meters distance (listening position from sub, rule is -6db for each double distance so 6meters=18db loss, 2meters being -6db, 4meters -12db, 6meters -18db) + 6db from second sub (as per JBL file)= clean,cool 113db SPL with 2x512w from the amp (2x700max). Could be wrong in this calculation (missing data: room size, absorption factor, cable losses, equalization effect etc).

Cinema sub requirements are normally based on how many acoustic watts are needed for a given volume/110dB SPL, then the appropriate speaker amp combo, and quantity of each, is selected based on this value. The power requirements are normally based on the driver's peak rating.

A 6dB drop/doubling distance only occurs in a very large room. The average HT drops ~3dB in the LF above where room gain kicks in, so for 6m: 10*log(6/1) = 7.78dB. If you decide to use -6dB as a 'headroom' buffer, then: 20*log(6/1) = 15.56dB.

The calcs are off a bit, and the 99dB/W/m sens seems to be too high for a single driver at <80Hz (even factoring in a corner), but worst case using your numbers: 113dB + 15.56dB -6dB = 122.56dB/m

2^[(122.56-99)/3.01] = 227.11W total for both subs to hit 113dB/listening position sans any EQ/room gain.

Quote:
bottom line: headroom, damping factor, current output and multiplication of the subs is the right safe way to go. (positioning is important as to not nulify the effect of multiple subs). Stacking them is often used in theaters.

One more time Posted Image, damping factor isn't a 'factor' with SS amps. The resistance of the VC, especially after it warms up, nullifies it.

If very low distortion is desired, then calculate the peak SPL (factoring in any EQ) requirements based on 1/4 - 1/3 the driver's rated power, to keep VC heating to a minimum, and use as many drivers as necessary. Allow ~ +2dB headroom to stay off the limiter (if any). Select wire size for a 1/2V max drop. Unless you use expensive drivers, this is often less costly and better sounding than driving one or two drivers to their limits with high power.

Normally in cinemas, subs set on the stage floor, arrayed around the center channel, and up against the baffles (or set in their own baffles) for max boundary gain.

GM




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#26 of 27 brentl

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Posted August 13 2000 - 11:21 AM

Hey Vince ...anything good to say about the PV500 from Peavey? I saw it yesterday and and was wondering

Brent L

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#27 of 27 brentl

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Posted August 13 2000 - 11:25 AM

Nevermind Vince...I was just on the Peavey site and noticed that it puts out 130 watts a 8ohms. The same as my THX Kenwood.
If I am going to move up it will be at least 250watts at 8ohms

BrentL


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