jessie.dazzle wrote:

For now, the amplifiers I use are a pair of Lamm M1.1s (was going to look for a pair of used ML2s, but more and more considering building a pair of Meliquaides). Using the M1.1s with a pair of V.A. Parsifal/Encore (direct radiating) speakers there is a little background hiss, but nothing you would hear from the listening point.

First of all about the Lamm M1.1. It is a common knowledge that SS PP amps is very much not the correct amp to use with horns but here we enter a little secret of mine. It is known that ceramic drivers do not do good HF and particularly in horns. However, when you drive the ceramic horn driver with SS PP amps then the drivers begin to sing. I had some very good results with Lamm M1.1s and various none-alnico drivers.

jessie.dazzle wrote:

However with the S2s, this background hiss is much stronger; the level is constant and does not rise or fall with volume adjustment. It can be heard from well beyond the listening point. The hiss is equally present in all (4) S2s I have, so I don't think it is a question of the driver. With the S2s I can hear much further "into" the hiss, and observe all kinds of detail (fluctuations in the electricity?).

Jessie, this is very normal behavior of S2. The S2 has 22dB more sensitively then Parsifal/Encore. In addition you drive S2 with 20 times more power and gain then they should be driven, and with the amp (Lamm 1.1 that is not partially quiet. What do you want form those drivers. They have no noise  - then juts present to you what was given to them.

jessie.dazzle wrote:

The hiss remains when disconnecting the ground wire for all circuits powering the system. My question now is... Do other S2 users have the background hiss when using appropriate SET amps? Is it possible that the M1.1s generate more hiss? I should also mention that the associated preamps are either an L1 or an L2. I recently replaced all tubes in both pre and power amps (hiss present with both L1 and L2, so the preamp is probably not the source of the hiss).

Ok, what you have for noise perspective is the worst combination for a high sensitively system. 80% of your noise comes from Lamm L1 or an L2. They are MOSFET preamps and MOSFET have own MF output noise that is not depending form the volume control (it is not gain noise but the indispensable MOSFET noise). It is not auditable with 90dB sensitive acoustic system but with 110dB sensitive and too much gain in power amplification the noise is right in your face. Bypass the Lamm preamps and you loose most of the think MF hiss. The minor noise that will be left will be own Lamm M1.1’s noise. This amp is also quite noise for high sensitively speakers. The solution could be various. Find low noise 5W-10W power amp and drive it with Lamm preamp. The amplitude of the hiss will go all the way down. Bypass the Lamm preamps and use any low power amps and the noise will be gone for good. In the end do not forget the S2, according to this paper has 10W max power handling. Could you believe now severely you discharge this magnets when you drive them with 110W of PP power? Anyhow, even with Lamm preamps and reasonable power/gain power amp (20-24db no noise gain) you will not be able to be bothered by Lamm L1 or an L2 MOSFET’s hiss. ML2 is very-very quite amp, virtually silent, there are many other SETs… but when you go into the world of properly assembled (and consequentially quietly operating) single ended amplifiers then you will not have any hiss issues with your S2 drivers.

Jessie,

A few hints. If you are moving from Parsifal/Encore and LammM1.1 world into the world of SETs and Horn then do not be in hurry to commit yourself and do not create to yourself artificial addictions.

When I talk about artificial addictions I mean that you deal with some “effective” tools now and do not become preoccupied with the performance of those “items” but rather think about Sound as a whole. There are a lot of Morons out there who created for themselves the subjects of bogus worshiping (would it be WE, RCA, Vitavox, Klangfilm and many others…) However, ONLY final result might be justification for anything and the final result does not depend from those “items” but rather implies the combining and integration of all elements of your playback. So, think in context of entire system and observe the benefits of that S2, or anything else ONLY in context off whole Sound of your installation. If you do so then you will be ahead of 99% of the freaks who do audio.

When I talk about “do not commit yet” I mend do not go at this point for an expansive SET. Get a cheap SET, make your horns and spend some time to optimize your horns. THEN, when your acoustic system will be more or less organized (even not perfect) THEN bring better single-ended triode amplifiers and observe how beneficial they might be. To listen a SETs on Parsifal is false thing to do. If you read too much Lars Fredel doodles about the subject then be advised the he was a fool and quite imprudent lair. (In his room the LammM1.1 on Parsifal killed ML2 but it was not what he was writing).

You might also consider different options of you know what kind of horn installation you made. Perhaps you would need to go for DSET that fundamentally MUCH prefers direction to go. $10.000.00 that you prepared to pay for ML2 is a lot of money. A par of Melquiadeses might cost $3.000, but might be made even less, I would say $2.000. Evan if you pay $1000-$1500 to someone to build the thing than you end up with ~3.000-$4.000, no feadback SET that will be doing more interesting then a single Lamm ML2. Interesting that advising is I do not use my ego as a motivation but rather I consider Milq's quality of sound AND the most important thing: flexibility.  You will have money and the "design space" to go for dSET and will be able to optimize the transformers to drive the dedicated channels + to use the line level filters… A single pair of ML2 (old version)  does perfectly fine, it is absolutely the  best commential SET out there, and it is VERY educational amp to live with but  by building any serious horns you will very fast overgrow the ML2’s ability to be flexible…

Rgs,
The Cat

You would not have ‘limitations imposed by of a pair of SET amps such as the ML2s”. ML2 would do fine, juts make sure that it would be older ML2 before 2001-2002 production. You try the Melqs then, the parts are not a problem at all. Everything is very much available not expensive. Theoretically is possible substantially simplifying the Melq. You can use input caps everywhere beside the second stage. Go for smaller last capacitors in filter and combine the positive bias supple with supply of the first stage. If you will be driving down to 40Hz then you might go away with those simplifications with practically no harm to sound. I made the Melq Support Forum available specially for people who wish pursue the amp and I would provide all necessary assistance, including pointing out where to get the approved :-) parts. Everything is really perfectly shippable but be advised that I do not care about the “parts sounding” and voicing amplifiers THAT way. Use any good quietly commercial parts, preferably not “audiophile grade (they are mostly crap) and you would be fine. I am sure that you would be able to get everything you might need right in there…

The caT


PS: the following posts went toward the Milq amplifier and have no relation to the subject of Hiss of S2 driver. Therefore, the thread was spited and the continuation might be found at:

http://www.goodsoundclub.com/TreeItem.aspx?postID=2686

From Email that I got today:

“….. I see that you are considering trying the metal diaphragm again in your S2s. I am using the metal diaphram for the moment (it is all that i have), but have the terrible ringing problem, especially on female vocals. Sounds like the diaphragm is hitting something and the voice just rings for a moment... How are you going to get rid of this if you use the metal again, or are you just going to use for the fundamental channel?? “

There are 4 reasons why the S2 drivers have “terrible ringing”.

1) Dirt in gap. It could be fixed by cleaning the gap.

2) Improper centering of cone when the cones rib the walls of the gap. (Or the dirt in the gap). It could be fixed by re-centering the diaphragm. Be advised that it might be trickier with specific S2 drivers then with others.

3) Natural ringing of the metal diaphragms. The Vitavox older metal suspended diaphragm had own quite brutal top, I have written about it a lot in past. However, I would not characterize it as “terrible ringing” but rather as very minor mechanical distortions. I have also to testify that I have witnessed my metal diaphragms sound very clean, so this subject is under investigations: amplification, electricity, roll off and so on… A plastic suspension cone has no such effect but it has other problems (response, secondary resonance, etc…)

4) The faulty cones. Do not forget that the metal suspended diaphragms are over 50 year old and many of them worked not in greenhouse-like home environment driven by a low power SET but in movies theaters, driven by >100W PP crap, in many instanced with pentodes output.. The S2 is 10W driver and they were severely stressed on the fields. The aluminum cones have a have tendency to develop internal crack when they over-stressed – you do not see it but it’s there. That crack has own “terrible ringing” effect. This problem made Altec in past to move from fully aluminum cones on this 802 driver to the symphonic (plastic) suspension on their 808A drivers. Still, with proper amplification the full Altec’s aluminum do sound much more interesting, though can not handle a lot of power….

RonyWeissman wrote:

There's a shop in south of france that can clean and recharge the S2s, and he'll do some testing of the drivers at same time. I hope that solves it.

jessie.dazzle wrote:

Buy or make a good non-magnetic flat-blade screwdriver (I made one from a solid stainless steel rod... use a "hollow grinding" technique and make sure the tip is a nice fit... not all "stainless steel" is non-magnetic)... If you try working on the driver with a normal magnetic screwdriver, you will be fighting a very strong magnetic field that wants to suck the tool straight through the non-replaceable diaphragm. You don't need this, you need to be free to concentrate only on torque.

Please whatever you do, do not stick in the gap anything metal. By doing it you short the gap eclectically and you are discharging the magnets. Use the only plastic or wood scrubbers not metal. (I use the tips of the cable fasteners- very continent). In fact 95% of all dirt might be handled without any tools just using marking tape, which is essential for any gap cleaning.

jessie.dazzle wrote:

One more thing you might consider... There is quite a serious Vitavox user in Italy who applies a thin film of machinists oil ("3in1" for example) to the edge of the metal diaphragm (just the edge... the part that gets clamped) and on the screw threads... He tightens the screws with a minimum of torque. The oil I assume allows sealing the diaphragm, without torquing the screws too tightly. It may also slightly damp diaphragm resonances. I have not yet tried it, but the logic appeals to me. (I need to get this guy's contact info).