You mention that you used the Yamaha R-S700 receiver to drive the Revel M106 speakers you tested. Do you have any other recommendation for integrated amps in the $500 range?
– E. Lluveras
Unfortunately the number of, cheap, integrated amplifiers, which have good power amps is declining. You want to purchase a units with 20Hz – 20KHz power ratings, both channels driven, below 1% THD into 8 ohms and 6 ohms. The minimum power should be 80 Watts average (RMS power is not dimensionally correct) at both impedances.
Besides my Yamaha R-S700, I could identify only two other stereo integrated units available currently with a 20Hz – 20KHz spec into 6 Ohms as well a 8 Ohms and they are both Harman Kardon (HK3700 and HK3770). Although I have not tested them I have the schematics for both for both these products and I can see why Harman Kardon can specify the products over the full frequency range for both loads.
For AVRs I could find nothing with a full frequency 6 ohm rating even out to $2000. In that case I would push the 8 Ohm 20Hz – 20kHz rating to 100 Watts average and a minimum of 150 watts average into 6 ohms at 1kHz with THD less than 1%. That should be enough margin for that unit to produce 80 watts average 20Hz – 20kHz into 6 ohms.
Well designed, large floor standing speakers, with multiple woofers, that can go down to 20Hz in room, such as the Revel F208 or PSB Imagine T3, presents a more challenging load and a power amp with a 20Hz to 20kHz spec at 4 ohms may be required for best results. In todays market this requires a move to an independent power amp. With a mini-monitor and sub-woofer the requirements on the power amp are reduced. The amp in the sub-woofer is doing all the work below 60Hz.
While looking around websites I found many products under $1000 and some well above that specify power only at 1kHz. Often at 6 ohms, which is the load that will typically produce the will produce maximum average power at 1kHz. With wimpy power supplies an amps power at 1% distortion can drip quickly below 200Hz. A couple of times I found power specifications into only one channel. I even saw a THD spec of 10%.
I have no idea what is happening. Before 1974 most manufactures made power amp claims that wildly overstated the power a product could produce. Often the power amp could hold the specified power for 100msec with one channel driven at 1kHz at 10% THD.
Sometimes the product you took home did not even achieve the power they put on the box for the short term burst into 1kHz. Eventually they cooked up something called peak power which was defined as the power delivered at the crest of the sine wave not the average of over the whole sine wave cycle. In 1974 the FEDERAL TRADE COMMISSION stepped in:
16 CFR Part 432 – Trade Regulation Rule Relating to Power Output Claims for Amplifiers Utilized in Home Entertainment Products
This document required testing of both channels under continuous conditions with the frequency range of the test and distortion measured during the test reported. Also required was preconditioning test at fraction of the full scale power that maximized the amount of heat the amplifier could dissipate (as opposed to the full power case where most of the power gets to the speaker). This made sure the amplifier did not get too hot or go into early shut down.
In 2008 the FTC asked for comments on amending the law. One major manufacture wrote:
“I think the FTC should let the free market reign and avoid further burdensome regulation.”
Fortunately the FTC did not listen to this:
“The Commission has determined that it will not seek to amend the Rule to permit manufacturers to use the EIA/CEA-490-A standard as an alternative for rating the power output of multichannel amplifiers”.
The FTC did clarify that only 2 channels needed to be tested in multichannel equipment.
Ebay has allowed me to collect old stereo buying guides from the 60s – 70s. You can see power specs drop by an order of magnitude in 1974, especially for off brand products
I do not know of any additional rule changes but something has happened. I hope the government still has the power to enforce EIA/CEA-490-A and bring correct reporting back to the spec sheet.
Needless to say I would avoid purchasing any product that does not provide average power into at 8 ohms at less than 1% distortion, into 2 channels, 20Hz-20kHz.