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

@bifwynne  Not sure what you feel is deficient with the ARC Ref 150SE specs. If you care to elaborate, please do

Thanks for not getting at me since you own these amps. All I am saying is that Bill was on a mad quest for low distortion and high damping and achieved that in the one amp I called out for that. My only negative was its complexity. See if you can find that post. 

What I feel is deficient is exactly what JA thinks. Somtimes us folks do agree.  https://www.stereophile.com/content/audio-research-reference-150-power-amplifier-measurements. What interesting to me is that most audiophiles agree with each other by disagreeing with the technical people. It is still a mystery to me why people without technical knowledge want to disagree with technical people who are making this stuff (for better or worse). Sometimes I feel like im just fueling the fire.

JA does me a great favor when he tests an amp, then I dont have to. I have 400 pages of test notes on 200 amps and preamps that I have measured over the past 35 years. Testing an amp is a laborious task if you really want to get into whats going on. 

For you and everyone out there. There are things going on in certain combinations of amps and speakers that cannot be easily predicted. However these effects are rarely present in a good amp with good performance measurements. I have tricks that go beyond what JA does. For instance I put a 0.1 uf cap (similar to some speaker cables) across the output of a big Adcom amp while was on the bench and luckily connected to an AC Line amp meter. When i touched the cap against the output terminals the 10 amp meter pegged and i quickly disconnected the cap. I just holding it. Didnt get hot though 1200 watts was going somewhere and that somewhere was the transistors. 

I know some people have unknown Birdies going on in there system. Birdies are brief supersonic oscillations that occurr on specific parts of the wave at specific levels. If you drive a simple woofer directly that is the easiest way to see them and they sound like clipping but you are not clipping. 

I have personally, in my own store in the 1980s, watched a BIG Levinson ampifier smoke when connected to a high end speaker cable that had some parameter (perhaps capacitance) that the amp didnt like. It just sat there as little trails of smoke came out, and frankly I was amused.

I know im off topic but... motto is. Just because an amp passes the 2 uF load test (somewhat standard) does not mean it is stable into smaller capacitances that might be present in many cables. Whether you like lamp cord or not, It is the proper constructin for a speaker cable. Just not exotic enough for most. Hey man, its just wire.

Anyone else smoked and amp with a speaker cable? 

@cardiffkook

Roger said....  I put the proper cord on my RM-9 but now people want me to put an IEC on there so they can use theirs. I did opimize but thats not good enough for the PC and fuse people. May I also offer that a captive cord has one less pair of connections

Cardiff said.
That is what I suspected you would say. I have tested expensive upgraded power cords in my system and never noticed any improvement or difference. I notice large differences between amps, preamps, cartridges, cartridge loading and even in minor changes of speaker toe in. But in my system, I have yet to hear any difference between pc's. I am not saying there are no differences, just that I haven’t heard any so far in my system, compared to the cord included by the manufacturer.

I think we need to hear more from the people like Cardiff who have tried powercords and not heard any difference. I will allow it because we have heard quite enough from the pro side, too much. Lets try to balance the issue. Lets give voice to those, like Cardiff, who can clearly dissern difference in his system.

Anyone who has bought a power cord and owns an SPL meter, or oscilloscope or any measurement equipment is welcome to report their findings. I have reported mine. 

Anyone who has spent over $100 on cables and has no SPL meter had better go get one. :)

@prof    Actually, the talk of switchers raises another question I'd like to direct to Robert:

I have more than one amp I like to use for my system. It's a minor pain to switch the cables, but it sure would be nice to have a switcher where I could switch between amplifiers to the main stereo speakers. (So interconnects would lead from one output of my preamp to my main amplifiers, and out the other output to a second amp. Depending on which amp I wanted to use I'd just flip a switch.

At one point I did a bit of research and saw some candidates, but for the most part they looked awfully cheap, which left me hesitant.

Would you say a fully transparent switcher of the type I'm describing could be built?

Yes we have one, can make you one with a volume control to balance the gain of the two amps so they play the same loudnes. They, God willing, you flip back and forth, on the same speaker please, and hear of not hear the differences between the two amps. This is exactly what we are doing.

Then you can invite your friends over and really have some fun. You will likely find what we have found.. Some amps sound very similar with differences too small to be sure they are real and some amps let you know pretty quickly what they are up to. We find good correlations with measurements.

What are your two amps.

@ramtubes

You’re gonna hate me: My amps are Conrad Johnson Premier 12 monoblocks and an old Eico HF81.

BTW, since you asked about hearing "the other side" for power cords:

I was cured of power-cord-fever early on. I had been given a selection of Shunyata power cords to try, from their least expensive to very expensive. I didn’t think I heard any difference between the less expensive Shunyata cables and my 15 dollar power cable (On CD players, etc). But I thought the most expensive cable seemed to obviously change the sound. (Darker, smoother, more lush). To double-check I had a pal help me do a blind test between that cable and the 15 dollar cable. Once I didn’t know which cable was being used, all the "obvious" sonic differences I thought I was hearing vanished and I couldn’t tell them apart. Saved a bunch of money there! I haven’t worried about pricey cables since. (I’ve gone on to blind test other components, sometime identifying differences, sometimes not).

@krelldreams   Roger asked for specs... the only spec I know of is “1.2k” hand written on the bottom of the case. This was only a test anyway since I’d need more than the single input this one provides. I was not aware that Music Reference made passive devices (?).

 I am considering both tubed and solid state phono preamps. Any design parameters that I should be paying attention to? Any designs to avoid? I currently only need one for a high-output MC cartridge (MM gain and loading), but I plan on trying other cartridges in time as well. I’m not opposed to getting a step up device if a cartridge I get in the future needs one.

BTW, i looked up the Axiom. If you have an ohm meter just connect it to the input jack and output jack and get some numbers. Non of them are good for long runs as we all know. If yours is 1.2 K ohms thats a rather low number unless the source is much lower. 

For  you preamp you need to focus on S/N ratio and RIAA accuracy and distortion which should be nill. If you find a measured review I will look at it. You want at east 60-70 dB signal to noise ratio at the output of YOUR cartridge. 

We might build a few phono preamps on special order. The one I have developed for Clio has is all tube start to finish, 3 gains, 12 loadings, tape EQ available (he likes 15 ips tape). It uses only 4 tubes which I am rather proud of as most will use more and give you more trouble. 

I tried a FET front end some years ago and just did not like it. A Low noise FET is about the same noise as a SLN 6922, so there is no noise advantage there. You can get the lowest noise with transformer inputs, but then you have to deal with placement issure and the sound of the transformers.