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

@Daveyf, what model are the speakers and what model is the sub? Also...

I also have a REL sub hooked up to the amp, it is left, right and ground at the amp, as both the amp and the REL are balanced designs.

I presume you are using a three-wire cable to connect the sub’s Speakon connector to the outputs of the amp. Does "ground at the amp" mean that the ground (black) wire in the cable is connected to the amp’s chassis, or to a terminal that may be provided on the amp as a means of connecting to its circuit ground, or does it mean that the ground wire is connected to one of the negative output terminals of the balanced amp? And if the latter, is the ground wire connected to the negative terminal of the channel that produced sound when you misconnected the wires, or to the negative terminal of the channel that didn’t produce sound?

Regards,
-- Al

Ok, what would be the difference if they are isolated vs not isolated...would this have changed the way the amp behaved...or I guess the right side speaker? 

I've found over the years that its not wise to make too many assumptions. If you have a Digital Voltmeter, check the continuity between the woofer and HF sections (with nothing connected to it) and see if they really are completely isolated.

Thanks. The speakers are bi-wirable at the input, so I am assuming that without a connection at the terminal, which I have removed, that there is no common connection between the woofer and the tweeter. ( it’s a two way). Nonetheless, the right speaker did play, just not the left? I also have a REL sub hooked up to the amp, it is left, right and ground at the amp, as both the amp and the REL are balanced designs. I guess I got lucky and didn’t blow one channel at the amp...or worse that and both speakers! 

No damage, and from what I can surmise, due to luck- one of your connections was apparently loose, otherwise neither speaker would have played. Essentially on the non-playing side, it sounds like the output of the amp was shorted. Fortunately you caught it and sorted it out, so no damage to the amp.

This is assuming that the biwire connection on the loudspeaker employs a common connection between the woofer and HF section.

Would very much like your advice on what occurred to me a few days ago with my ss stereo amp.
I own a large stereo ss amp and speakers that both allow for bi-wiring. Four connectors per side and therefore I utilize two separate connectors per speaker cable per side ( four in total on each speaker and amp side). i normally connect two positive and two negative to each respective amp terminal and speaker terminal...left and right. A few days ago, I was re-inserting the amp back into the system and was NOT thinking! This time, I connected the amp correctly, BUT I connected the speakers as positive and negative connectors onto wrong terminals! So, what I ended up with was a positive connection and a negative connection X 2 ( per side) at the amp side ( correct) and a positive and negative connection for each terminal at the speaker end...one positive cable on positive, one negative cable on positive, one negative cable on negative, one positive cable on negative. This was done on both speakers!!! I powered up and noticed that I was getting signal only through ONE speaker, the right hand speaker, with no signal from the left hand speaker! What was going on??? Why signal at only one speaker with this bad connection scheme?
Luckily after much head scratching, I realized my mistake and corrected the hook up...and then both speakers were playing fine. Again, any idea as to why i had sound from one channel...and not both or any? Could I have done damage with this bad connection error?
Thanks for the reply.

Ralph, what is OTOH mean? Im a newbee.The cords with diodes make a difference when needed. I think I have been clear and consistant here.

OTOH: On The Other Hand; other slang acronyms you may find handy:
IMO: In My Opinion
IME: In My Experience
IIRC: If I Recall Correctly
YMMV: Your Mileage May Vary
If there are only diodes in the cord, there will be no conduction near the AC crossover point. Electrolytics are thus used as I mentioned prior so that the AC waveform is undistorted. However, it appears you are conflating two different subjects in your comment above.

Your amp draws heaps of current when played hard. Something heavy ga might help a little at full power. At idle Im not so sure. I note the current draw of the M-60 goes up quite a lot at full power testing.

How long can I run an M-60 sinewave at 60 watts into 8 ohms before the tubes get unhappy?

Not very long, but long enough so that organ pedal tones and the like can be reproduced without damage. The tube is linear with grid current.

Is it pure Class D or something else?

It is a good example of class D.

Are you familiar with Primare's UFPD power technology? Is it pure Class D or something else?

i’m late to thread but have a perplexing question. 
i own an expensive ss amp and leave it on 24/7.
i could turn it off when i’m not going to use it for a few hours as well as overnight. for amp longevity what is best? thanks

Hi Ramtubes,
In response to my query about damping you asked for a link to Hegel
which is:
 https://www.hegel.com/

You will see they describe what they put into their components,  also when looking up integrated amps, the damping factor is specified eg their starter amp H90 is only 2 x 60 watt in 8ohms but the damping factor is over 2000 therefore capable of handling above average difficult speakers (but not mammoth difficult speakers!) As they quote " The grip, or damping factor as it is called, is up to 20 times higher than the industry average. Ensuring a dynamic and powerful bass response, even on larger floor standing loudspeakers."  

"Musicality" term used to express a fatigue free listen . Still as resolving as anything but probably not boosting any frequencies . Hence fatigue free . No distortion as well .

@prof 

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.

***********GREAT QUESTION, EVERYONE READ THIS**************

Ill take this one speaker at a time. The 3.7 is THE speaker that birthed the RM9-SE and RM-200 designs. Those are AB2 designs that use positive grid voltage to extend the output current range of an AB1 amplifier. We had a MK1 RM-9 customer who was going through output tubes at an alarming rate. The speaker and his love of Miles was driving the tubes hard.

First, JA did not point out, as he now does that 2.83 volts is NOT the proper voltage for a 4 ohm speaker. Its 3 dB too high so the 4 ohm sensitivity of the 3.7 is 87 db. Its even worse because this it a 2.5 ohm speaker so take off another 2 and make it 85 dB. So its really not a very efficient speaker.

I made the RM-200 with taps down to 1 ohm for speakers like this to preserve the damping, reduce the tube stress and lower distortion. The 2 ohm tap on the RM-200 is ideal for this speaker. Mismatching the load on a tube amp makes it work really hard. This is a 2.5 ohm speaker so good luck. Many SS amps will not play this speaker well.

Thats your the gist of question #1. 

#2. Phase angle..

As the phase approaches 90 degrees the output devices have both full voltage and full current across them. The dissipation in SS or tube amps goes wildly high. SS amps are sure to current limit, tube amps just take it. This is why tube amps have a reputation for driving such loads at the 3.7 and ESLs.

Thats all for now. This great question deserves several parts. Anyone please feel free to ask as we go for clairfication.

@ atmasphere
In one post Roger says it doesn’t make much difference, OTOH in the very same post describes the power cords that he made up special and how anyone can do it. I have to assume that he felt it was worth doing

.
Ralph, what is OTOH mean? Im a newbee.The cords with diodes make a difference when needed. I think I have been clear and consistant here.

Your amp draws heaps of current when played hard. Something heavy ga might help a little at full power. At idle Im not so sure. I note the current draw of the M-60 goes up quite a lot at full power testing.

How long can I run an M-60 sinewave at 60 watts into 8 ohms before the tubes get unhappy?

"Musicality" is one of those oh-so-subjective terms with no agreed-upon meaning. But the same can be said about the incomplete sentence by khiak above ;-) . The "can" implies it is a question, but the "changes" negates that. Should the sentence read "Can changing the power cord to the amp change the musicality of the sound at the speakers?" (a question), or "Changing the power cord to the amp changes the musicality of the sound at the speakers." (a statement) ?

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

Do I detect a little nudge there?  I think isolation transformers are great when needed. I like balanced power which also isolates. These things have a good chance of reducing noise if one has noise.

My stand on power cords is entierly intellectual from an amplifier designer and transformer makers point of view. I know what is inside a transformer and how it works. When you know about transformers, house wiring etc. we can further discuss this interesting topic. 

@prof1   I also wonder how the introduction of a subwoofer alters the load to an amplifier. So say if you have a powered sub and you crossover to the sub from the mains at maybe 80 or 60 Hz. Once one has off-loaded much of the low frequencies to the sub, I wonder how much the main amp "sees" and if that, in effect, is like adding a more powerful amp in to the equation

.  

I assume you are using some crossover to rolloff the main speakers. Is that via and electronic crossover or the series caps found on some subs?  Makes a difference as to voltage the main amp still has to produce and thus clipping and IM distortion. The correct way is to rolloff the main amp at its input so it never sees the bass voltage. 

@khiak  Can changing the power cord to the amp changes the musicality of sound at the speakers.

Some think so.

Can changing the power cord to the amp changes the musicality of sound at the speakers.

@testpilot.

You can purchase this DC blocking board (link below)and populate it or buy one completed at the link below. Great double thick circuit board that is very high quality. The in and out pads accept 12gauge solid core wire which is also nice. Instructions and part lists also on the site. The board is a two layer design in parallel (70um thickness of each) so yes - it can handle current of 20A. The capacitance needed for 1kVA is 22000uf, but since the difference in the price is not big I’d prefer 33000uF. I think the board cost me something like $15-$18 shipped. The parts were only another $20 or so.

I use them in my isolation balanced power conditioners. I just built them right into the chassis. They quieted down the toroidal perfectly. Quiet as a mouse now and used to buzzzzz.....

Yes, I love my balanced power conditioners and will never take them out as the music simply sounds so much better with them in place. I find them to work wonderfully in many systems.

https://www.atlhifi.com/shop/bare-pcb/pcb-for-dc-trap-blocker-filter-for-toroidal-transformers-toroi...

As for the reference to light gauge cords not bringing home the bacon, what gauges are we talking about?

18ga for sure- not suitable for larger current draws. The wire gets warm along its entire length with a big enough amp- that suggests its limiting current, and certainly the voltage at the amp will not be that of the wall.

Connect two diodes back to back in parallel and insert in hot lead of power cord.

The diodes are bypassed by electrolytic capacitors, which conduct only when neither diode is conducting.

@stargazer3 For the OP what are the pros and cons in relation to damping for amplifiers; eg Hegel store great reliance for damping in relation to driving difficult speakers.

There is no con to high damping if done properly. However more than 20 will have little effect and may cause the designer to do some bad things to achieve it.  When a designer goes to maximize his favorite parameter he can go too far and other things will suffer. In this case stability from oscillation.  There are many amplifiers out there waiting for the wrong load and their own destruction.

I have seen many amps with very high damping oscillate into a 0.1 uF load which is typical of some speaker cables. Smoke and shorted output transistors was the result. The cause is too much feedback and assuming that if the amp is ok with the standard 2 uF test load it will be stable with smaller capacitive loads. Many well known amps are not. I tested an early ADCOM that took of with 0.1 uF. I did it for one second. A few more seconds would have been the smoke test.

Do you have a link to Hegel, I would like to read it?

@testpilot  How do you block DC.

Connect two diodes back to back in parallel and insert in hot lead of power cord. 

@skiramp 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

I dont know the specifics of  your equipment as to low voltage. Solid state amps I have designed work fine down to half line voltage. Some do not. Well designed switching supplies are low voltage protected but if not they smoke and burn up. 

Get a power regenerator with wide voltage tollerance and let it deal with it. I do mean regenerator like PS audio makes. IF it fails you can send it back. 

I would also question what you are doing with those big subs. Are you watching Das Bot.

I wish you well in Thailand. Its a lovely and exotic place I visited many years ago.

@atmasphere - I can't seem to find the reference you referred to on page 12. What I did find was this which Roger wrote:

I would have had the electrician put in several duplex outlets so no power strip is needed. Power strips vary in cost and quality but the expensive ones with big claims are just marketing. You have nice 10 Ga wire in the wall and then what?

Heres something Ive done. Get a bunch of reasonable power cords, like $20 each of various lengths. Cut off all the male plugs strip and hardwire the cut end directly to the 10 GA wire with a bussbar. Solder good solder lugs to the wires and screw them with a star washer to the bussbar. THe star washers are important. Now you have direct power cords and have eliminated one connection. Make some extras of course. The ones you arent using just coil them up.

I had custom power cords made that are 8 ft long, very flexible, supple, drape nicely and wont pull your smaller devices off the shelf. We have them if you need some.

Bottom line here. Its not the wire that matters. You have hundreds of feet of ordinary magnet wire in every transformer. What you gonna do bout that? :). All this power cord and power strip is just foolishness. Why do we need powercords that are a pain to run?

The custom power cords he is referencing in the quote above I believe to be 14 or 16 gauge, I'll have to check. I don't disbelieve your statement on connectors or power cords heating up, but I have never experienced it on any of my components including yours and Roger's amplifiers. As for the reference to light gauge cords not bringing home the bacon, what gauges are we talking about?

@testpilot  Take a look at the Isotek Synchro EVO3.

Thanks atmosphere. 


(I'm still interested in ramtube's view as well).

My room is on the smaller side: 15' x 13' wide and I listen at modest volume - typically 70 db to maybe 75, probably 90 at the most if I crank it more to listen from down the hall.

I also wonder how the introduction of a subwoofer alters the load to an amplifier.  So say if you have a powered sub and you crossover to the sub from the mains at maybe 80 or 60 Hz.  Once one has off-loaded much of the low frequencies to the sub, I wonder how much the main amp "sees" and if that, in effect, is like adding a more powerful amp in to the equation. 

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."

@prof
Tube amplifier power has traditionally been expensive. Inefficient loudspeakers as mentioned above only became possible in the era of solid state since that power is so much cheaper. Unless you are in a very small room, I'd consider a different speaker as 140 watts isn't a lot of power when dealing with a sensitivity that low, regardless of the 'difficulty' of the speaker.

@clio09

this is the power cord he was referring to that does make a difference under certain circumstances:

http://tubeaudiostore.com/pocoyoucanac.html

Otherwise as Roger noted in his last post just get a cord with good connectors.

Apparently though Roger sees or saw fit to build his own power cord setup using some pretty heavy gauge wire (see page 12); this suggests (if actions speak louder) that he does think they make a difference, else why go through the bother?

(FWIW a power cord with light gauge but good connectors will not bring home the bacon, generally speaking. I've seen power cords, not just the connectors, heat up.)


I first heard how dramatic a power cord can be at the 1990 CES in George Cardas' room. The impact and nature of the bass was easily heard by all present to be quite different and with more impact when stock power cords were replaced by a pair that George offered. I found it disturbing; at the time I just didn't understand what was happening (and it clearly was not snake oil as it was repeatable) but I also knew enough to not buy the explanations that were offered (which clearly **were** snake oil).


But in time I found out that all you have to do is to simply measure the effects a power cord has on an amplifier. Generally speaking, the more power the amplifier draws, the more you will hear differences between power cables. 

Sorry to say this is a horrible product.

Ouch!
Power in Los Angeles could be very problematic.
I added a 5300 in about 2003 and it was a significant improvement even though my amp had an internal LC power filter. At the time, I auditioned 2 Panamax, 2 Monster and 1 Furman. The Furman was best, followed by the 5300, then the Monsters and Panamax. Each added it's own coloration.

15 years later in Oregon with different electronics, it still works and I like what it does. Cable and other jacks remain unused.

Hello
 How can I use a Plinius SA 250 amp setup for 230v in the USA, thanks John 

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

I don’t think he is saying connectors make a difference sound wise as some people might lead you to believe. In other words a Furutech connector won’t sound any better than an Oyaide connector. He is saying just use good ones. For me that means the ability to get a snug fit with the outlet (I use Hubbell hospital grade) and a means to make a good connection with the wire (I use off the shelf "Oyaide" connectors I buy on Ali Baba).

@ramtubes, how do you make a power cord that blocks DC?

For the OP what are the pros and cons in relation to damping for amplifiers; eg Hegel store great reliance for damping in relation to driving difficult speakers.

It’s doesn’t really matter what he believes, that’s the way it is. 

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

@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!

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

@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...

@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. 

RM - NJL3281D

not exactly sure which Ayre used but they did not prove hyper reliable...
the Twenty series use a derivative of the Diamond circuit and I believe also switched away from the thermaltrak...

@atmasphere - this is the power cord he was referring to that does make a difference under certain circumstances:

http://tubeaudiostore.com/pocoyoucanac.html

Otherwise as Roger noted in his last post just get a cord with good connectors.

@tomic601 

  RM - took a hiatus from the book, restarted on page 59....junction temps....had a bad experience with ON Semiconductor thermal tracs.....I know you are a tube guy, can you comment about the diamond topology ?

Not sure what you mean by thermal tracs?  ON semi is making the Motorola parts. I dont know if there is anything new. Do you have a part #.

@corby2 Hello, I have a budget system I like. It has a 25 watt Will Vincent Balwin tube amp with Coincident Dynamites. I do not have an audiophile power cord. How much do audiophile power cords help with the amp? I was thinking of getting to Anticable stage 3 power cord. Thanks, Cory in Reno

Hi Corby,

Very few amplifier makers wind their own transformers, but I do. When I wind a transformer for a 25 watt amplifier it is about 150 feet of 24 ga wire. After I am done I really dont see how 12 feet of 18 or 16 or 14 ga wire will make any difference.

If you measure the resistance of the primary circuit of your amplifier it is like likely near 5 ohms given that it is 25 watts.

This is easily done by unplugging the amp, turning it on, putting an ohmmeter across the two prongs of the power plug. Now you will know the total resistance of the primary loop. The total resistance of the secondary loop (reflected to the primary) is similar to that so double what you just measured. Now ask yourself how much a power cord of 0.01 or 0.1 ohm or 0.5 ohm is going to make when added to that number.

The claims about RF shielding are absolute bullshit. Along with any other specious claims.

Just get a cord with good connectors.

@clio09
In one post Roger says it doesn't make much difference, OTOH in the very same post describes the power cords that he made up special and how anyone can do it. I have to assume that he felt it was worth doing.

Roger addressed this previously in the thread. The short answer is not much if at all. The power cord should be designed such that the ends provide good connections to your outlet receptacle and amp. It should also be of sufficient gauge so as not to cause a safety hazard. I believe the captive power cord on the Music Reference RM-9 was 14 or 16 gauge. Roger used 18 gauge lamp cord for Music Reference preamp and MC head amp captive power cords. I made my own 14 gauge power cords for my components. I bought male and female IEC connectors on Ali Baba and sourced some computer grade three conductor stranded wire. They were not hard to make and parts costs per cable were around $30.

Hello, I have a budget system I like. It has a 25 watt Will Vincent Balwin tube amp with Coincident Dynamites. I do not have an audiophile power cord. How much do audiophile power cords help with the amp? I was thinking of getting to Anticable stage 3 power cord. 
Thanks, Cory in Reno
 

Right you are clio. I just checked the listing, and it's closed. This one had a nice walnut base, which I hadn't before seen from Music Reference.

I'm pretty sure the unit for $2450 sold as well. A recent RM-10 buyer contacted us and indicated he purchased a unit that was in Cypress, TX which matches the location of the unit in question. Either way, good for both buyers for getting their hands on a such a nice amp.

@clio09, there have been two different RM-10 Mk.2 listed here recently, one at a much lower price than the other. The cheaper sold, the other is still listed at an asking price of $2450, I believe.

Over voltage can cause mechanical hum in a transformer