Moondogs have arrived!

[Marvel]

I had amps that were pretty quiet on my cornwalls, but also pretty noisy on the LaScalas. The Las are just really revealing.

My experience with hiss has been that it has always been in the tubes. Noisy tubes. The biggest culprits in my system were the preamp tubes.

I am sure that the K77s wouldn't be as bad, and these have Bob's CT125s in them. No doubt that the LS are very revealing.

The preamp (Merlin) is incredibly quiet.

[NOSValves]

Craig,

Haven't seen you around much. Hope things are getting back on an even keel.

Bruce

Bruce,

At the current rate I expect things to even out with the work load some time in 2010 LOL!! God I hate being way behind. That is why I'm tryin to stay off the forums. Other then being way behind all is well.

Craig

[Parrot]

Craig,

It isn't an unlikeable thing for sure. Just different. I don't listen at really loud volumes anyway. If I do 90db it is getting up there for me, so they work well. Symphonic music will go on tonight. I am sure the Bach will be okay. Brahms maybe. Shostakovich may push a little bit more. The later one gets and the larger the orchestra...

I don't just listen to the 'little girl with guitar' music. The soft compression is okay. Pleasant would be a word some would use-- other may say mushy (where is Paul?). I'll live with them for a while and try a lot of different material on them.

Here I am! "Mushy" is actually the description I got from, of all people, Mobile Homeless. I want to give credit where it is due.

[Marvel]

LOL

MH would say that, wouldn't he? It's okay. I think it is a bit above 'mushy.' I'm certainly not into the snob factor with all this stuff. If I like it, I like it. If not, then I'll change. Doubt I'll buy those high priced cables, stones, etc. Maybe I could fill the room with an inert gas, and have an oxygen line running to the sweet spot. Would that change the sound?

Bruce

[Parrot]

Not to leave an erroneous impression for anyone, Mobes didn't say Moondogs in all of their 3.5 W glory per se were mushy. He wasn't being that specific. He was talking about clipping characteristics of tubes vs SS.

*****

I was saying that I dont think a tube amp gets HARD when it clips compared to SS. IT just starts get more mushy and compressed. Meanwhile, SS amps clipping sound TERRIBLE and hard like GLASS. I was SORT of disagreeing with Rick in his "it will sound HARD" comment. I think we both agree that tube have better clipping characteristics. Not sure if I am totally with the reasons he listed as I think it more to do with the valve vs transistor.

kh

*****

[jazman]

Bruce,

I think the hum may be the result of less than proper tube/pin contact. I have had that problem with Sovtek 2A3s. Hold them at the base of the tube and see if any gentle movement affects the hum. I also suspect the hiss is a result of tube issues. I do remember reading a remark from Eric that the rectifiers tested on the low side. That can be a source of "soft" bass response. I do not have hum, nor hiss, and I'm using Khorns.

Klipsch out.

[Speedball]

Way to go Bruce! ...............new gear......[Y]

[Marvel]

Last night, after supper, after being out for a while, my youngest (well, he's turned 21 now!) and I came home to the stereo. I put in the EH Gold 2A3s. Let the 'dogs' warm up for a while as we did a few other things in the house. Then we put on his recording of the Bruckner Symp. no. 7.

We were quite satisfied with the playback. THis symphony (and recording) has lot of dynamics and is very full. Would it have had more slam with the higher powered ss? Probably (should I even go so far as to say not doubt). However, it was beautiful and never seemed to be lacking. They ae definitely keepers.

'nuff for now. Got to finish up the crossovers and get them in the system.

Bruce

[leok]

Bruce,

Quick thought about the hiss. The Moondogs alone have more than enough Voltage gain to develop their whopping 3.5W output from a 1V line source. If you're using a preamp all that preamp gain is simply adding noise and has to be padded down to a fraction of a Volt before being fed to the Moondogs anyway.

Try a passive attenuator instead of the active preamp. or-

Bypass the first stage of 6SN7 in the Moondogs .. easy mod for anyone who does that sort of thing. I just looked at the schematic and one disconnects C7 from V2-1 and connects the input to V2-1/R5 instead of V1-1/R1. That will reduce the Voltage gain by a factor of about 17. I've done it but needed an active preamp to make it really work.

If it works you can pull V1 from the circuit altogether.

Of course if you like it the way it is you can just listen to it.

Leo

[Marvel]

Leo,

I was going to disconnect the preamp last night and put some shorting plugs on the inputs to the amps, just to see if the noise persists. I just didn't get to it. However, there doesn't seem to be any added noise fom the Merlin at all. I'll still check it out further. I can't hear it from the couch anyway (not a good sign in some respects, as my son still can -- although faintly).

Bruce

[Erik Mandaville]

Bruce:

I think Leo has really good advice re: gain and extra noise/hiss. The output of a CD player alone is enough to drive the Moondogs into the clipping range, and a passive preamp can work very well. I used one for quite a awhile when the proximity of components in the system allowed for very short interconnects (about 18" from CDP to Moondogs). The hole in the chassis plate, now occupied by the BNC input for the regulated DC filament supply, was once occupied by a 50K ohm volume control. This worked very well for a few years, and as Leo mentioned, dropped the noise floor significantly (and it wasn't bad at all before I did this).

Some may say they currently use active preamps and experience absolutely ZERO hiss, but all preamps are not the same in this respect. What's sort of ironic about an active preamp, is that more often than not they're used to attenuate a source signal (except in the case of phonostages). For an experiment, and using an older pair of speakers, I once took the full-strength signal from our former CD player and ran it straight into the amps to see how loud it would really be. I got my answer!

On the other hand, I have preferred an active linestage when things were arranged so that the longer IC runs brought about the need for one -- mainly as a way of obtaining the much lower output impedance needed to drive the long cable.

BTW: You have really wonderful rectifiers on that amp. They did test slightly low, however all voltages in the circuit were exactly where they should be when I measured them. They probably still have a good bit of life in them.

I really like these low-powered triode amps, but they are not IME able to reproduce LF info. with the same authority and impact as a more powerful amplifier -- transistor or vacuum tube. For me, they just can't, but I'm willing to accept that for the majority of music we listen to. What they can give in bass response is not at all that bad, anyway!

Bruce: If just for kicks you wanted to try a passive attenuator, Radio Shack has everything needed for the 30/45 minutes it would take to make one. If the Merlin is like the Peach, it's an awesome preamp; but that's not the point. This would just be for an experiment to see what happens -- and for an easy/fun weekend project to try out...sometime down the road if you feel like it.

Another alternative would be to use an inline fixed attenuator between the Merlin and the Moondogs. There are some other tradeoffs with this, but the input impedance of the Moondogs is high enough to give you a little headroom in this respect.

And maybe we should just leave it alone so you can enjoy your new amps! Classic 2A3 amps at that!

Erik

[Cut-Throat]

Some manufacturers encourage lifting safety grounds to prevent ground loop hum, but I can give as many or more instances where cheating the earth ground is very strongly discouraged. Ultimately, I would rather have a slight, low-level hum that vanished when music was playing than compromise the built-in safety features of my components.

Erik,

While I agree that you should try to avoid cheater plugs if you can, I don't believe that they are the 'safety hazzard' that some folks make it out to be.

If you look at the problem of a ground loop in a stereo component, most can be eliminated by unhooking the CD player, The TV, The pre-amp etc. - The reason is of course is that these provide another path to ground. By lifting the ground with a 'cheater plug', you have removed that components path to ground and it will be grounded via the CD player, The TV, The Pre-amp. - The only way that the chassis of a component will become hot is if the circuitry of that component would fail and it could not find a path to ground. But of course, if you leave the other components plugged in, it will find another path to ground. Then adding a GFI circuit to your Stereo Gear, will probably make it safer than someone's that has not 'lifted the ground'

I have heard of these 'safety hazzards' many times before from people that ride motorcycles without a helmet!! - Using a cheater plug with a single appliance is not recommended, but using a cheater plug in a stereo system with a myriad of cables, interconnects, speaker wires, coax - electricity will 'know' how to find a ground before it 'lights up' your chassis.

I would much prefer the 'exteme low noise floor' obtained by lifting the ground, than accept any additional noise caused by multiple ground paths. Statistically a lot less dangerous than driving a car, and I don't plan on giving that up either! - But, I think you'd have to be a bit nuts to ride a motorcycle!

[Erik Mandaville]

Kevin:

"Erik,

"While I agree that you should try to avoid cheater plugs if you can, I don't believe that they are the 'safety hazzard' that some folks make it out to be."

That's fine. Do whatever you like.

If I at any time in the past suggested this practice, which I may have, I strongly advise against it. As I said above, Kevin, you are free to do what you want.

Since this is a public forum, there might be an instance where the safety of someone's component very much relies on that earth ground connection. And then the owner removes it, and one day picks up a live chassis with both hands, walking in bare feet on concrete. That person might not be able to run to the forum ever again to advise others not to do it.

I'm not willing to take that chance.

Erik

[Cut-Throat]

Kevin:

"Erik,

"While I agree that you should try to avoid cheater plugs if you can, I don't believe that they are the 'safety hazzard' that some folks make it out to be."

That's fine. Do whatever you like.

If I at any time in the past suggested this practice, which I may have, I strongly advise against it. As I said above, Kevin, you are free to do what you want.

Since this is a public forum, there might be an instance where the safety of someone's component very much relies on that earth ground connection. And then the owner removes it, and one day picks up a live chassis with both hands, walking in bare feet on concrete. That person might not be able to run to the forum ever again to advise others not to do it.

I'm not willing to take that chance.

Erik

Hi Erik,

Then you would also probably never want to suggest that someone go on a 'roadtrip' to pick up a pair of Khorns or drive to Electronics Shop to pick up a component, because you and I both know that statistically driving a car on America's roadways are more dangerous than using a 'cheater' plug on a stereo system.

Just trying to keep things in perspective! - We do tend to 'over' bloat things around here!

[Erik Mandaville]

Hi, Kevin

Okay.

I'm sure you're looking forward to the arrival of your new 45 amps from W. Labs. They should be fun.

Erik

[Marvel]

Okay, lifting the groung had no effect on the hum. I haven't disconnected the CD player to check that as a ground loop issue, but will later. Unplugginf the Merlin gets rid of the hiss. It is a very quiet preamp, but the noise drops off when it is unplugged.

I'm going back to listen to some music now. I've been recording a re-broadcast of our local symphony. Straight off the FM into the PC via the M-Audio Audiophile 2496 card. Sounds great.

Tonight was Edgar Meyer playing his Concerto for Bass in D. He is a genius. Also the Sibelius Symphony no. 2. And a third piece (world premiere) by a beautiful composer Clarice Assad, Brazilian Fanfare. The music was good too.

Bruce

[mikebse2a3]

Just one caution with cheater plugs and Televisions. I repaired many Televisions because of this practice so be carefull.

A lot of Televisions circuit designs in the last 10 years use what is refered to as a Hot Grounded Chassis and when you service them you must use an isolation transformer for safety. The AC plugs on some of these TVs are two pronged with one Blade wider than the other so that terminals such as RCA Jacks and such will remain wired to neutral of the AC Voltage. If you use a cheater plug and reverse the AC connection you will put the RCA Connections at the (120V AC Hot potential) and then when anything with a grounded RCA (ie: CD Player, Cable, Receivers, ETC...) is connected you will damage the Television and possibly the componets you hook to it.

mike[]

[jt1stcav]

Well, I have nothing technical to add to this thread...all I can say Bruce is enjoy your "new" Moondogs (as I'm well aware you have thus far)![]

Viva le SET!

[Marvel]

Just one caution with cheater plugs and Televisions. I repaired many Televisions because of this practice so be carefull.

A lot of Televisions circuit designs in the last 10 years use what is refered to as a Hot Grounded Chassis and when you service them you must use an isolation transformer for safety. The AC plugs on some of these TVs are two pronged with one Blade wider than the other so that terminals such as RCA Jacks and such will remain wired to neutral of the AC Voltage. If you use a cheater plug and reverse the AC connection you will put the RCA Connections at the (120V AC Hot potential) and then when anything with a grounded RCA (ie: CD Player, Cable, Receivers, ETC...) is connected you will damage the Television and possibly the componets you hook to it.

mike[]

After spending some time working oh three phase motor controllers, I am well aware of the possible dangers of missing grounds or changing the grounding path of equipment. I simply used a single IEC cord with the ground pin removed. It was then easy to be insterted the correct way into my outlet strip. A short five minute test showed me it didn't make a difference. It has been removed, cut in half and thrown away.

We have a huge box of IEC power cords where I work. I can always get more of them if I need them.

I may build a pad over the weekend, to cut the gain between the preamp and moondogs.

It really doesn't matter. More than anything, I am enjoying the music.

Bruce

[Erik Mandaville]

Mike:

Thanks for that caution. That was my concern, that the practice of defeating the earth ground connection might become generalized: Whenever a ground loop exists, whether the symptoms are rolling-bar-distortion on TV screens or hum in audio, that cheater plugs will be the quick (and only) cure for the problem. Or that someone might think it would be good to, once and for all, completely rid a system of ground loop plague by using two-prong cheaters on every component that uses a grounded plug.

I have been shocked hard in the past (a sensation I don't particularly like), and will take your advice. Using a single dedicated power strip has helped, but another more effective and safer way of of isolating ground connections, which is what cheater plugs accomplish, is to use something like this:

http://www.hometheaterhifi.com/volume_7_4/furman-it-reference-balanced-ac-12-2000.html

This is an example, not an advertisement. There is also some useful information that describes briefly and simply some of the causes of ground loop problems. There are also much less expensive options.

Bruce: Strings can sound incredible on these SE triode amps. I have a pair of Wright 2A3 monoblocks here now that I like very much. It uses a direct-coupled driver to cathode follower into the 2A3 which, while seemingly not having quite the drive as the Moondog (as mentioned above), has very good frequency response and inherently low noise due to the low impedance coupling. Classical strings and guitar are what we have been listening to mostly, as well as Bill Frisell, Bill Evans, the Carnegie Hall recording of the Thelonious Monk Quartet and John Coltrane, and some others. For me, the midrange tone of this kind of amplifier is a very acceptable compromise to its slightly softer bass response.

BTW: I also tested these amps in stereo with my own tube preamp, and found more gain related noise/hiss than with the Lexicon processer in two-channel mode. I'm interested to know how that padding works for you. You once sent me some excellent information on that subject! I should have remembered that when I suggested those inline attenuators.

Erik

PS to Others: Don't forget to fasten your seatbelts when you drive out to pick up the big horns. If you take the bike to check them out first, wear a helmet!