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Need an amp for low ohm speakers

Hear Here said:
That looks like a treasure trove of ancient kit best donated to an audio museum!

A quick count of boxes shows 10 of electronics and perhaps 6 speakers - and I can't imagine how many cables tie it all together! An impertinent question maybe, but do you want a museum collection, or do you want to close your eyes and just listen to music, at as good quality as your money can buy?

If the former, then continue with your quest for an ancient amp that is happy with low impedance speakers - there must be plenty to choose from and others can offer advice on models. If the latter, you'd really be better off with a simple but well-chosen all-in-one (streamer/amplifier and a pair of decent speakers - all bought "nearly new" of course. Ditch the record and CD collections too - you can hear it all from a subscription streaming service such as Quobuz or Tidal at as good or better quality than you enjoy now.

That's it - one box (no cables is another massive bonus and a big cost saving too) and a pair of good speakers chosen to work well in your particular room. :) or :facepalm:
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You have no idea, I have more! I really enjoy the hobby without spending huge money. As for content, I use a raspberry pi with a DAC “hat” and all of my music ripped from my cd collection in Flac (full) format. I have to agree with you in that a lot of the collection doesn’t sound that good. You can see the Dynaco ST-70 on the bottom left- when paired with the unseen PAS 2 preamp and dual AR2x speakers sounds pretty good. As for the museum, I donated some of my Hallicrafter and RCA short wave radios. That was really before my time.
 
Torin Krell said:
One of the pleasures of using a powerful vintage receiver is its nostalgia, elegance and simplicity. Perhaps instead of wiring in an extra amplifier it may be best to find a different and even better speaker system with a reasonably flat 8 ohm impedance. Using a new amp with a vintage receiver, to me, seems like missing the point of using vintage gear. I would suggest system matching over system patching.
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That is actually the plan. The receiver is too cool to disrespect with a different amp :). Do you have a suggestion for a good sounding set of 8 ohm speakers to match the 1280?
 
boXem said:
"Please don't take it personally" + sarcasm = classy. The usual internet equation. Anyhow...

Care to explain a bit more? I guess you understood yourself when typing, but this means nothing to me.

How loud do they listen? Which music style? In what kind of room?

I didn't overlook this metric and noted that this is for a single channel. It looks like the power supply is the limiting component, so we can assume that in stereo mode each channel will output 200ish W in 2R. To compare with modules that I know very well, that's a bit better that an NC252MP.
For my room, my speakers, my listening tastes, an NC252MP is more than enough in terms of power. But I have witnessed NC252MP based amps getting out of steam at very reasonable levels with very normal speakers in well damped rooms. An NC252MP is not an universal solution, neither is a single 3E A7.

Still to compare with my own experience and the hundreds of feedbacks I received, the 2R output power in mono mode is close to the one from the 1ET400A with a proper power supply. I heard only one or two complaints of missing current delivery with speakers that had a messy impedance. So A7, why not (pending proper cooling), but one per Infinity RS-2.5, not one for two.

To finish on this, it's quite easy to calculate the listening levels reached knowing the listening distance, speaker minimal impedance, speaker efficiency and amplifier voltage/current capability. Would be nice if ASR members were giving an answer like "such amplifier will allow you to reach that many dB with your speakers" instead of promoting the flavor of the month as a generic solution.


Don't want to enter the debate around the importance or not of high damping factor, just asking for data to backup a claim that is technically very dubious.
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Here, too, your assumptions are wrong. There was zero sarcasm in that, just math and basic physics.
For a square wave, the power supply power would be equal to the maximum continuous output power.
Since music is a sine wave, however, only a fraction of that power supply power is needed. In development, for normal music, a ratio of 1/4 to 1/8 power supply power is assumed for 1/1 sine power/peak power. With Class D, 1/4 should be on the safe side.

Based on your original calculation, the power supply would have to be at least twice as large for Amir's measurements, even for one channel, even without accounting for losses.

I don't want to argue with that.
I happened to know that the Pioneer SX 1280 shuts down after a short time even at low power levels of 40-50 watts at 4 ohms, and probably even sooner with these speakers.
Since this volume was apparently sufficient for the owner, I had absolutely no reservations about recommending the A7 as a stereo amplifier. This was not a statement I made lightly.
 
Ted G said:
Hello,

Fulfilling my teenage dreams, I purchased a Pioneer SX 1280 receiver. Unfortunately, even with 200 watts per channel it can't run the recently acquired pair of Infinity RS-2.5 speakers at high volume for very long before cutting out on protection. After doing some research, I found that the speakers can run down under 3 ohms when the bass kicks in and the receiver can't handle it. I'm considering getting a purifi or hypex based class D amp. The alternative is a used Adcom 555 or similar. I'd love a beefy Mcintosh but I've already dropped a lot on what I have :(. Also, rather than using the receiver, what is an inexpensive alternative pre-amp? I am not a purist as you can tell with the Bose 901's. Please hifi guru's lend your expertise!

View attachment 463229
Click to expand...
1752694316311.jpeg
 
This requires two words of exquisite brilliance. Because you clearly need the best. Don’t cheap out on this. Do it once. Do it right. Make those babies sing:

The Sovereign.

THE SOVEREIGN ® The ultimate monaural High End power amplifiers, in twin tower design

Ultra high precision and high power monaural power amplifiers. THE SOVEREIGN ® The best High End mono power amplifier twin towers. Ultimate Precision from Germany with no equals. Absolute State of the art technology by Thomas and Marita Hoehne. Elze, Germany
www.sovereign-amplifiers.com www.sovereign-amplifiers.com
 
Roland68 said:
Here, too, your assumptions are wrong. There was zero sarcasm in that, just math and basic physics.
For a square wave, the power supply power would be equal to the maximum continuous output power.
Since music is a sine wave, however, only a fraction of that power supply power is needed. In development, for normal music, a ratio of 1/4 to 1/8 power supply power is assumed for 1/1 sine power/peak power. With Class D, 1/4 should be on the safe side.

Based on your original calculation, the power supply would have to be at least twice as large for Amir's measurements, even for one channel, even without accounting for losses.

I don't want to argue with that.
I happened to know that the Pioneer SX 1280 shuts down after a short time even at low power levels of 40-50 watts at 4 ohms, and probably even sooner with these speakers.
Since this volume was apparently sufficient for the owner, I had absolutely no reservations about recommending the A7 as a stereo amplifier. This was not a statement I made lightly.
Click to expand...
No need to argue.
P = U RMS * I RMS = Z * i RMS * I RMS.
To get 400 W in 2R, you need 14 A RMS, whatever the signal shape. Signal shape will influence the peak value, 20 A for a sine.
A "10 A" power supply doesn't math. A 520 W power supply does.
Hopefully I went to look at the power supply label to have this story make sense. As you say, math and physics.
 
I like the idea of a fan because it's cheap and easy and you can probably try with any fan you have on hand before buying anything special.

BUT what works on a normal day MIGHT not work on a hot day in the summer. If you have a way of measuring the actual heat sink temperature you can make a good estimate of the temperature drop and maybe get an idea of how much ambient temperature it can take with and without a fan.


On the other hand... I also like the idea of a more "rugged" solution.
 
boXem said:
No need to argue.
P = U RMS * I RMS = Z * i RMS * I RMS.
To get 400 W in 2R, you need 14 A RMS, whatever the signal shape. Signal shape will influence the peak value, 20 A for a sine.
A "10 A" power supply doesn't math. A 520 W power supply does.
Hopefully I went to look at the power supply label to have this story make sense. As you say, math and physics.
Click to expand...
What power supply would be needed to achieve at least 2 x 200 watts at 4 ohms in a stereo amplifier?
 
For me I would kick out the crossover and go for active with DSP ...

End of OT.
 
Some years back, I picked up a pair of Crown XLS2500 for US$250 each (used of course) on ebay (from memory)

The XLS amps are specced for 1ohm speakers, and will handle pretty much any load with ease.

They are also commonly used by garage bands and various PA environments, and when these shutdown/retire, are often sold cheap.
 
Ted G said:
That is actually the plan. The receiver is too cool to disrespect with a different amp :). Do you have a suggestion for a good sounding set of 8 ohm speakers to match the 1280?
Click to expand...
Unfortunately all the reasonably efficient, high volume capable, vintage or semi-vintage speakers that I am found of apparently have an impedance that dips into 4 ohm territory at least through some of their range. Perhaps someone else has some suggestions.
 
IIRC Bryston amplifiers were able to drive 2 Ohm loads and could fit into a vintage setup.
 
Torin Krell said:
Unfortunately all the reasonably efficient, high volume capable, vintage or semi-vintage speakers that I am found of apparently have an impedance that dips into 4 ohm territory at least through some of their range. Perhaps someone else has some suggestions.
Click to expand...
Any KEF speaker from 1970s or early 1980s.
 
Buckchester said:
This requires two words of exquisite brilliance. Because you clearly need the best. Don’t cheap out on this. Do it once. Do it right. Make those babies sing:

The Sovereign.

THE SOVEREIGN ® The ultimate monaural High End power amplifiers, in twin tower design

Ultra high precision and high power monaural power amplifiers. THE SOVEREIGN ® The best High End mono power amplifier twin towers. Ultimate Precision from Germany with no equals. Absolute State of the art technology by Thomas and Marita Hoehne. Elze, Germany
www.sovereign-amplifiers.com www.sovereign-amplifiers.com
Click to expand...
Phew, for a second i thought they were way too expensive, but the price is for a pair;)

THE SOVEREIGN.
Ultimate High End monaural Power Amplifiers. EUR 198.950,- (pair)
 
AdrianusG said:
Phew, for a second i thought they were way too expensive, but the price is for a pair;)

THE SOVEREIGN.
Ultimate High End monaural Power Amplifiers. EUR 198.950,- (pair)
Click to expand...
I decided to get 200 Buckey amps instead
 
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