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Old 1st October 2014, 01:04 AM   #21
chrisb is offline chrisb
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Join Date: Aug 2002
Location: victoria BC
Quote:
Originally Posted by Variac View Post
Only Nelson Pass Amp Kit Available is the Amp Camp Amp (ACA)

ACA illustrated build guide

Out of stock at the store ATM but should be back in about 3 months:
Amp Camp Amp Complete Kit - Parts, Chassis, 2xPower Supplies - Amp Camp Kit - Kits
Worth every penny, AFAIC, and I was lucky enough to order early enough that inventory was not depleted.
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Old 1st October 2014, 10:55 AM   #22
Trismos is offline Trismos  Canada
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Quote:
Originally Posted by Variac View Post
Only Nelson Pass Amp Kit Available is the Amp Camp Amp (ACA)

ACA illustrated build guide

Out of stock at the store ATM but should be back in about 3 months:
Amp Camp Amp Complete Kit - Parts, Chassis, 2xPower Supplies - Amp Camp Kit - Kits
Thanks Variac I've seen this, and while I didn't think it wasn't a great deal, I've already built an amp and when I was going to do another, it was going to be an attempt at something 'right up there'. So this amp didn't seem to fit the bill - but it got me to thinking about 'watts' vs speaker efficiency'.

This is only a 5 watt amp. It might spec out pretty good, but if I'm having trouble getting decent volume out of my 85+ watt Virtue M-901 using my 91db speakers, how much of a problem will it be with 5 watts?

But now I'm finishing off a set of 96db open baffle speakers. I have a few other amps including a Elekit TU-879S 6L6GC rated at 8.5 watts that I'm hoping to get better performance out of verses the older speakers.

So the wonder i'm wondering is how does speaker efficiency fit into the amp output curve? How is 5 watts vs 100 watts into 90 db compare to 5 watts vs 100 watts into a speaker even 1 db more efficient?

Dave
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Old 2nd October 2014, 10:03 AM   #23
AndrewT is offline AndrewT  Scotland
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Working in dB makes the estimation very easy.

1W = 0dBW. This is our reference.
2W = ~+3dBW
4W = ~+6dBW
8W = ~+9dBW
10W = +10dBW
16W = ~+12dBW
20W = ~+13dBW
32W = ~+15dBW
40W = ~+16dBW
64W = ~+18dBW
100W = +20dBW

Note that 1W, 10W and 100W are exact.
Whereas the doubled values are approximate. This is due to double not being exactly 3dB. Double Power is actually ~+3.0103dB

Using speaker sensitivity, add on the dBW of the amplifier and you end up with the SPL output, provided neither the amplifier nor the speaker are overloaded. One also has to make a correction for power compression.

eg
88dB/W @ 1m speaker with a 64W amplifier gives 88 + 18 = 106dB @ 1m

99dB/W @ 1m speaker with a 5W amplifier gives 99 + ~7 = ~106dB @ 1m
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Last edited by AndrewT; 2nd October 2014 at 10:05 AM.
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Old 2nd October 2014, 11:55 AM   #24
Trismos is offline Trismos  Canada
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AndrewT

Thanks very much for that!

Dave
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Old 13th November 2014, 09:50 AM   #25
chrapladm is offline chrapladm  Australia
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Is there a guide to which amp puts out said amount of power?

Curious which amp I am wanting to do based on that. PLUS after that I would like to make something crazy if possible.
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Old 13th November 2014, 11:19 AM   #26
AndrewT is offline AndrewT  Scotland
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The maximum output depends on the supply rail voltage and the load impedance that the amp can drive.

You have to work it out. Then adopt your first guess values or change to suit your target.
It is easy !
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Old 13th November 2014, 09:51 PM   #27
chrapladm is offline chrapladm  Australia
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Thanks Andrew, So most of the designs are different but none of them have any set values that cant be adjusted for more gain?

I was curious because looking at building something like a 30watt amp and then jumping up to something more extreme I wondered if it could be the same basic design or not. Obviously different values for each.

Secondly what is the biggest amp that anyone has created from one of these Pass designs, gain wise?

Hoping that if I were to build a very large output amplifier that perhaps someone already has done this before. If not then I will have to do a LOT more reading.
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Old 13th November 2014, 09:54 PM   #28
6L6 is offline 6L6  United States
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The diyAudio build guides
Gain and power are not the same thing... Can you be more specific as to what your goals are? Speakers you will be driving? More information will be very helpful.
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Old 13th November 2014, 10:15 PM   #29
chrapladm is offline chrapladm  Australia
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I will be building all new speakers for my front HT channels. The center will be around 100db or so and the L/R will be around 98db. So with music listening and movie watching I wont need much power. BUT I have always wanted to build a much larger amplifier for my subs. I will be using pro audio 18's in simple sealed cabinets. LT circuit and thats all. BUT they need a LOT of power to hit Xmax. (18 Sound 18LW2500)

So for the first amp I will only need about 16-30watts and be plenty happy. I could use a simple 4watt amp on the center and be happy also. I am mainly looking at having enough power for music listening. Add in EQ and I will want to have some headroom leftover. So this will be the first type pf build I would like to do. Was looking at your guides and the F4 or possibly F5v2(I believe its called) might be my first try.

The subwoofer amp will have to slowly come together. Gathering parts and reading as much as possible. I dont think I will be able to afford to build an amp that is big enough to punish my 18's but half way would be nice. I dont intend on breaking anything I just like to have 3db's or more of headroom if I can in all my amps. And for now I only have Class D and Class H amps that I have used.

So this is what I am going by. BUT I also might stick with pro audio amps for the subs and these Pass designs for smaller wattage needs.

Last edited by chrapladm; 13th November 2014 at 10:17 PM.
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Old 14th November 2014, 09:03 AM   #30
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by chrapladm View Post
........... The center will be around 100db or so and the L/R will be around 98db. .................
So for the first amp I will only need about 16-30watts and be plenty happy.................
50W to 60W into 98dB/W speakers are likely to give adequately loud reproduction on very dynamic audio.
You might get away with as little as 20W to 30W into the 100dB/W speaker.

These maximum powers will allow transient peaks to get close to 110dB @ 2.5m listening distance.

A single 18" will struggle to get close to these levels unless you keep it very close to you and it has a highish Xmax..
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