Does anyone care to ask an amplifier designer a technical question? My door is open.

@analogluvr  Over voltage can cause mechanical hum in a transformer

Thanks for pointing that out. The flux (and thus mechanical buzz) of a transformer rises sharply at some voltage. That point is up to the designer. I try to get mine still quiet at 130 Volts but we are getting up to 125 now in our houses so might have to go higher and wind for 125 rather than 120. 

Small amounts of DC on the line make things worse expecially with torroids as they have no gap. 0,5 volts of DC is enough. We make a power cord with a device to block the DC. Ask Clio, or you can make your own. Im not trying to sell anything here or be accused by one who does. 

Power transformers are a pain in the ass. If you make them bigger to reduce the flux they make more noise due to larger size. Ive been around the block several times on this. All our tranformers are silent at 2 feet in a very quiet room. My thought is if you cant hear it at the listening position whats the problem? Who sits next to their power amp? If you want someting lower noise I can make it for you. 

Power transformers can become noisy with age. Spongy feet or a bed of sand helps a lot to decouple from the rack or floor. 

@iamisaf When units are powered on I hear a very mild hum noise from the amplifier unit, if connect amplifier directly to the wall outlet I don't hear any hum noise. If I do the similar setup other side in the basement I don't hear any hum when connected to wall outlet or thru panamax power conditioner.What might be the issue?

The two sides of the basement may be on opposite phases of your 120/240 line. Houses are wired to try to balance the load on each phase. One phase may have DC or slightly higher voltage. Why are you using a power conditioner anyway. I dont.

Sorry to say this is a horrible product. Anytime they bring all you phone, cable, power, God whatever into one box its a horrible idea. If you can send it back please do. Modern devices generally do not need surge protectors and they tend to catch on fire!!

 https://www.crutchfield.com/p_299M5300PM/Panamax-M5300-PM.html?awkw=75647650225&awat=pla&awn...

Hi there would appreciate some help, I am shipping my Macintosh intergrated amp 200watt plus my def tech bp7000 sc to Thailand to live with me ? Very dodgy mains power !!! I am toying with the idea of ups or stabilizer or whatever , for some protection ? Against voltage drop . The def techs have 1800 watt driven subwoofers x2 of course ? I know that the equipment will never be driven at capacity, as house would fall in , your thoughts on a possible soloution,,, thank you : skiramp

@ramtubes

I could really use some help betting a better grasp of amplifier/speaker interaction. Specifically, in what sense a speaker is "easy to drive" for an amplifier.

This seems to generally relate to two parameters:

1. Speaker sensitivity
2. Speaker impedance (and phase angles etc).

I’ve seen speakers with higher sensitivity but lower or wilder impedance termed "easy to drive" and speakers with lowish sensitivity but higher and smoother impedance being "easy to drive." So I’m trying to get a grasp on what it means...in practical and possibly sonic terms...when a speaker is "easy to drive"for an amplifier and what you get when trading off sensitivity vs smooth impedance.

To turn it in to a practical example:

I owned the Thiel 3.7 speakers. Here are the Stereophile measurements:

https://www.stereophile.com/content/thiel-cs37-loudspeaker-measurements

Note the 90.7dB sensitivity, but with it seems a fairly challenging impedance.

Then take the Joseph Audio Perspective speakers (a speaker I’m considering):

https://www.stereophile.com/content/joseph-audio-perspective-loudspeaker-measurements

JA measured a low 84dB sensitivity but with a higher/smoother impedance he deemed them "a very easy load for the partnering amplifier to drive."

So I’m trying to understand the practical/sonic consequences - higher sensitivity, vs lower sensitivity but an easier impedance load. What does this mean for the power requirements, or type of power for each?

I have Conrad Johnson 140Wside tube monoblocks


https://www.stereophile.com/content/conrad-johnson-premier-twelve-monoblock-amplifier-measurements


And I’m wondering which of those speakers would be "easier to drive" with the CJ amps, why, and in what sense.

(FWIW: the CJ amps seemed to drive my Thiel 3.7s great: tight, non-flabby base, etc).

Thanks for any wisdom you can impart!

ramtubes - So, you don't believe power cables make a difference other than connectors and isolation transformers are worthless?  Is that correct?