Integrated Amp Reviews

Interesting how your findings re - using the 4 ohm taps echo Martin Colloms' conclusions when he tested Quicksilver tube amps in HiFi News back in the 80's.

Nice review.

How would this perfrom with a 16 ohm load? Valencias, for example.

Both these GoldenEar (EPDRs of 2.15 ohms at 59Hz and 1.53 ohms at 135Hz), and Kef(EPDRs of 1.66 ohms between 135Hz and 140Hz) speakers were not the best load for a tube amp such as this to be reviewed with, it may have faired a lot better with speakers with easier loads.
Both the GoldenEar and Kef have EPDR impedance loads down below 2ohms in areas where power is needed measured by JA himself.

Cheers George

I understand Stereophile can only use the speakers they have on hand at the time. But maybe it's time to have 2 pairs of resident speakers, easy load, and hard load, to give the readers a bit better indication of how amps really sounds with both loads?

Cheers George

Sorry, this is off-topic, but since this is the most recent entry by JA, I thought it may get prioritized in the "Reply to" email notification system ;)

This query is about JA's Measurements of DACs ... notably:

"Fig.8 DAC brand-model-x spectrum of 50Hz sinewave, DC–1kHz, at 0dBFS into 600 ohms (left channel blue, right red; linear frequency scale)."

I've often noted JA refer to this as a "punishing" test and if a d/a unit performs well, it is "bomb proof".

I assume -- correct me if I'm off -- that this is because DAC's output is not "experiencing" its expected high-Z pre-amp load? Hence, it's output stage is forced to drive more current, concomitantly "overloading" that stage a bit. Yes?

Does the output stage exhibit thermal stress (heat, FLIR glow)? Is this a bit like amplifier clipping?

Thanks in advance for JA/anyone's feedback!

"Does the output stage exhibit thermal stress (heat, FLIR glow)? Is this a bit like amplifier clipping?"

Very much so, there are some amps that have stupid low input impedances 1khom-10kohm as yes this taxes some sources output stages./ Gone are the great days when the industry standard input impedance for amps was 47kohm, and tubes were 100kohm and anything could drive them.

Cheers George

Many tube amplifiers I know drives speakers better than what their spec wattage may suggested. However, this particular amp may be opposite? Not sure how to interpret that this amp struggles a bit at the specified impedance terminals. My question is does I/50 exhibit clipping with the moderate load which is normal for many modern speakers?

"I was alarmed to read "Installation of the DAC Module should only be attempted by electronic technicians or other qualified service personnel."

Since the amp chassis contains high voltages, they obviously needed to cover their posterior.

I was very interested in purchasing the amplifier until I found out, balanced inputs beyond 2v are not compatible with the i50. Most every DAC that has a fully balanced design, sounds best from its balanced output and nearly all have normal out voltages over 3volts. The i50 is not even compatible with Audio Research’s own DAC9 if balanced connections are employed. It was likely a design oversight to incorporate balanced inputs on the i50.