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  »  New  To Milq builders: corrections, simplification, modifica..  Talking about amp…....  Melquiades Amplifier  Forum     16  73207  05-17-2007
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04-26-2007 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 21
Post ID: 4273
Reply to: 4263
The last nigh stupid DIY apathy…

 Romy the Cat wrote:
Still, doing whatever crazy and Macondo-dedicated things I will be doing with one stage I will have my full-range Milq as a tested reference trying to get result no worse then the one that I got from a “default” Melquiades …
The last deep nigh after midnight I was comfortably sitting with my Cat on my couch playing 1938 Bruno Walter with Wiener Philharmonic recording of Mahler IX and Handel’s Messiah by Swedish Radio with Stockholm Bach Chorus. The Macondo both channels were done more or less properly calibrated and were driven by my 3-chenals Super Milq…

It was quite serious, rich and meaningful Sound the Sound the ignited within me lethargy to destroy the Super Milq, pulling form it the MF output transformer for the single-stage Melquiades. The Sound was so balanced and so “compiled” that to take it apart would be an act of real barbarianism. Frankly speaking I was so comfortable and so contented that I was wondering if I even what to go for the single-stage Melq… Sure it might be interesting to try to see what would happen  but it would open a Pandora box for many other prospective “issues”.

It is quote nice as it with no extra efforts invested… I do not know… I will not hurry this case…. If someone make for me the necessary uncompromised MF and HF output transformers then I would make the single-stage Melq. If not then I will keep what I have now and will keep bitching that the world is the place filled with mean and non-cooperative people….

Ah, how wonderful would be if I could write a check to someone and that someone would bring the build amp in my room in a few weeks/month…

The Cat….


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
04-26-2007 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 22
Post ID: 4277
Reply to: 4267
The single-stage clipping.
The maximum power I can get as now from the single-stage Milq is at 3.4V, not at 3.0 and it is still well under one watt. I think I would need a little more to get some pick power. I need to play a little more with 6E5P’s operation point to find it’s best current/voltage ratio for the single-stage operation and to get a little more power However, at this point I notice one very interesting thing that differentiate it form Milq. When I drove Milq with excessive grid current into deep distortions the amp near horizontally clipped the summit of the waves. The single-stage Milq when it severely overpowered clips very … I would say differently on the scope. It is very round and smooth… Well you watch yourself. The fist one at 3.4V is the last none distorted value…




"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
04-27-2007 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 23
Post ID: 4280
Reply to: 4277
Single-stage 6E5P: more notes in dairy.
Dima and I spent today quite a time experimenting with different operation of the Single-stage Milq. We drove it from my Fluke 409D with resistor bias, loaded with 12.8:1 into 12R.

Playing with bias, voltage and current we tried to find an operation with reasonable power, to have identical current and voltage clipping and absolutely symmetrical (V vs. A) halves of the wave. In the end we concluded that with my 15-16Ohm the 170-200V and 30-40mA is near ultimate operation (for single stage). We were able to get whole 2Watts with very sympatric V vs. A clipping. Probably in my case I will stay with 1.6-1.7W..

I also, tried the Zero base operation as ML8 suggested. Sure, I lost a lot of power and the amp began to operate in very severs voltage deficiency. Here is 4V overload with 115V on plate:

Another interesting test: trying to bypass the resistor between plate and screen. I was not able to detect with my scope any oscillation but I have a slow scope – juts 100MHz. hat I detected that with moving my heads neat the tubes and stressing the tubes the plate current was fluctuating within 3-4mA. With 4R resistor between plate and screen the problem did not manifest itself and the tube had a complete immunity to it’s environment.  Over the weekend I will be loading the thing to the real drivers, find the V vs. A against the real load and listen the Sound...


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
04-28-2007 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 24
Post ID: 4286
Reply to: 4280
Listening the Single-stage 6E5P

Now I re-listen all the things the we try to measure. To surmised everything I have to tell that Dima’s way to looks for optimum operation point of the tube (setting balance for voltage vs. current sufficiency) turned out to be very successful as I did not see absolutely no discrepancies between auditable and measurable. As long the tube has the identical and symmetric current and voltage clipping it does sound the best. I have no idea why audio  people create so much “cult” about finding the best operation points for tubes and why any controversy exist – it look so simple and so unambiguous – for one stage of course.

Anyhow, I was not able to listen the Single-stage 6E5P with horns. The tolerable volume level I got driving Vitavox with 0.6-0.7V… VERY far from any dangers regions. So, I took 16R speaker with 90dB sensitivity and drove it with Single-stage 6E5P. First - the 0 bias on the tube – it was absolutely unusable, sorry ml8…

The best sound I got from this tube with ~ 6.5-6.8W dissipated on plate. More power made the  sound more stiff less power made… less power…Now current vs. voltage (with 16R load) keeping the same power. More voltage and less current made Sound “brown”, more compressed and in a way “inverted”.  More current and less voltage made it sound suffocated. In a way deficiently in voltage or current both produced that over- damping effect at upper bass and lower midrange but that over-damping sounded different for voltage and different for current. It is have to explain in words but it is VERY much the same as over-damping of bass when we adjust VTA of cartridge vs. lighting of bass when we change the tracking mass.

Ironically the best subjective sound I got in the best measurable point. I did a few blind tests  with different tubes when I was trying to set subjectively the best sound adjusting bias without looking at miliampermeter of the plate current. In all cases, finding this operations point and then driving the amp into distortions I has the perfect symmetrical pictures of voltage vs. current. It all was at the same current but at different bias settings (from minis 3.1V to minis 3.8V). So, the “magic” number was 175V and 38mA…

Now is the quandary… Do I have to for the Single-stage Milq pre-select the tubes or I need to put bias adjustment in there? Perhaps only for upperbass channel where I “might” be important. Now is the biggest question: now important all of this? All those experiments took place with amp outputting 3V but during it live the Single-stage Milq will do less then 1V. I do not have a full range 109dB system to assess subjectively how will sound. Listening single channels I can say that the deviation form perfect voltage vs. current setting is WAY less (if any) auditable at 0.7V. So, I need to think how important it might be in the real world.

The caT


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
04-29-2007 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 25
Post ID: 4289
Reply to: 4241
Returning back to basics.

Jim, returning back to the subject of tube testing….

I do not know if you have seen my most recent obsession; the idea of driving my Macondo with 1.8W of a single 6E5P:

http://www.goodsoundclub.com/LatestPosts.aspx?ThreadID=4241

So, what I learned is that all 6E5P, regardless of vintage and lever of being used up have the same 30 times gain. So, it is a drastic improvement over the very uneven gain of 6C33C. Still, all 6E5P have different ability to produce current – the stupid Russian tubes! So, sine I know the exact operation point for this tube and sine I will have the adjustable base for each channels of the single stage Melquiades then what might OBJECTIVELY indicated to me the life span of the 6E5P? The cathode emission? The transconductance? The use of getter? The darkening of the glass? Where would be an objectively correct point when a tube consider “gone”: 10% less of cathode emission, 30% less of cathode emission, 50% less of cathode emission? Is it wary from tube to tube and some of the sound fine with 50% less of cathode emission and with less bias?

Rgs,
The Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
04-29-2007 Post does not mapped to Knowledge Tree
hagtech


Hawaii
Posts 117
Joined on 02-13-2006

Post #: 26
Post ID: 4290
Reply to: 4241
pulse tube
With this tube I would think cathode emission limits lifetime.  Stepping back a moment, I'm guessing this tube is designed for radar operation.  Maybe in an aircraft.  The spec sheet definately talks only about pulse mode of operation.  Maybe it was a driver for a pulse radar transmitter?  What this means to me is that there are some sacrifices made in the tube.  It has a very limited maximum average power dissipation.  This had to be done in order to keep the structure small enough that it would operate at the desired RF frequencies.  It has very high pulse current capability, so the cathode must have extremely high emission, or plate gets starved and curves fall over.

So I have an idea.  For class A operation, the cathode emission is way too high.  We cannot run at the high peak currents because the plate will melt.  Or at least overheat and cause secondary emission problems, glow, etc.  Therefore, I suggest starving the filament.  Let's think about running this tube with 5V heater.  I'll run some sweeps to see what happens to the curves.  I think adapting the tube from pulse operation to continuous mode is no problem.  The lower emission is still enough for our needs, and it has the side benefit of greatly increasing lifetime.

Most importantly, I think we have to keep the plate dissipation way down, like 6W or so.  Cannot let the G2 get too hot. 

I like the direction you are headed.  This tube will sound better and more natural than the 6C33.  But might lack "authority".

jh
04-29-2007 Post mapped to one branch of Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 27
Post ID: 4291
Reply to: 4241
The 6E5P-E vs 6E5P.

 hagtech wrote:
Stepping back a moment, I'm guessing this tube is designed for radar operation.  Maybe in an aircraft.  The spec sheet definately talks only about pulse mode of operation.  Maybe it was a driver for a pulse radar transmitter?  What this means to me is that there are some sacrifices made in the tube.  It has a very limited maximum average power dissipation.  This had to be done in order to keep the structure small enough that it would operate at the desired RF frequencies.  It has very high pulse current capability, so the cathode must have extremely high emission, or plate gets starved and curves fall over.

Jim, I think you look at different datasheet. The 6E5P never meant to be used for pulse operation. The Datasheet said that it was designed for broadband amplification of HF.

http://www.goodsoundclub.com/PDF/6E5P.pdf

The 6E5P was use in railway radios transmitters, in portable SW radio stations, in some consumer radios in 60s and reportedly in TV applications. The 6E5P did have a version specialty dedicated for impulse operation. It called 6E5P-E. It has visibly the same constriction but extra short balloon:

http://www.goodsoundclub.com/PDF/6E5P-E.pdf

A few years ago I foolishly bought 100 of them (I think I paid 8c per tube) and they turned out to be VERY different sonically then the 6E5P and I found them unusable (about which I warned in the Melquiades article). BTW, you might see them on the picture:

The number 2 on the left in the first row is the 6E5P-E. The number 4 on the left in the first row is a normal 6E5P.

 hagtech wrote:
  So I have an idea.  For class A operation, the cathode emission is way too high.  We cannot run at the high peak currents because the plate will melt.  Or at least overheat and cause secondary emission problems, glow, etc.  Therefore, I suggest starving the filament.  Let's think about running this tube with 5V heater.  I'll run some sweeps to see what happens to the curves.  I think adapting the tube from pulse operation to continuous mode is no problem.  The lower emission is still enough for our needs, and it has the side benefit of greatly increasing lifetime.

Well, sine there is not need to fight with impulse mode I do not think it is the problem. However, the idea to starve filaments I very interesting. For LF horns I would need the full 6.wW on plate but for HF horns I need a fraction of watt and I might drop the heater voalsh, prolonging the tube lives. I will also make some Dima’s voltage vs. current tests (BTW, I found it VERY cool approach) with lover heater voltages.

 hagtech wrote:
  Most importantly, I think we have to keep the plate dissipation way down, like 6W or so.  Cannot let the G2 get too hot.

In my experiment I would say that up to 6.8W it behaved reasonably and more or less proportionally increase power with inverse voltage. I have to note that went I drove my 109dB upper bass horn with minus 10dB digital off my 5V DACK at 13:1 and having 6.6W on 6E5P’s plate then I took a think blanket and patched the mouth of my horns because it sounded louder then civil defense bombing alarm. I presumed that it offset the horns resonant frequency quite aggressively but it was the only way to test it under the live condition. With a “tampon” in the mouth that horn would be too violent to be with it in the same room.

 hagtech wrote:
  I like the direction you are headed.  This tube will sound better and more natural than the 6C33.  But might lack "authority".

Well with 109dB sensitively there are very many rational to go into the direction I ma going… how it will manifest itself in Sound I have no idea. I personally less care about “lack of authority". It is 109dB and I need just 0.7 V to pump into my speaker to get listening level. I more concern about ability of this single tube (and it is VERY fast tube) to play “slow” and produce the necessary “acoustic like” and “dynamically viscose” harmonic pattern. It did it with two stages but I do not know if it will with single stage. The individual channel looked like sound fine but how it will be in context of the whole installation only God knows…

The caT


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
04-30-2007 Post does not mapped to Knowledge Tree
hagtech


Hawaii
Posts 117
Joined on 02-13-2006

Post #: 28
Post ID: 4294
Reply to: 4291
input voltage
For a single driver, looks to me like you need an input signal of at least 3Vrms.  A lot of linestages can do that, so a single tube power amp seems both reasonable and interesting.  Yes, I was looking at wrong data sheet. 

You know, for somebody just taking a snapshot of a bunch of tubes for a forum post - it's really quite good.  Has that Ansel Adam's look.  I'd swear you used film.

jh
04-30-2007 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 29
Post ID: 4295
Reply to: 4294
The little Melquiades, the pictures and the illusive transformer core…

 hagtech wrote:
For a single driver, looks to me like you need an input signal of at least 3Vrms.  A lot of linestages can do that, so a single tube power amp seems both reasonable and interesting.

What actually I discovered the last week makes me VERY enthusiastic. I usually drive my horns with under 1V that… make it possible to drive then with …. preamp. Sure it doe not pump a lot of current but still it is possible sine I need no bass and no electric cones damping. Anyhow, I was experimenting with the single-stage Milq (the full gazed version not the prototype) and ended up trying with my Denon D30 mini-system. As I told before the D30 is amazing crap but still I have a bunch of small monitors that the D30’s 22W amps drives… So, I took the D30 headphone output and drove with it the single-stage Melquiades. To my great surprise the result was nothing short of stunning – I absolutely did not expect it. Sure it was not able to drive it with a lot power – increase of volume sent Sound to ugly clipping but at very low volume the Milq absolutely overridden the D30’s sound making it to sound very large, VERY dynamic (…and it is with the Celestion SL-600!!!!), surprisingly colorful and very inversing…. I was very pleased and puzzled with this effect….

BTW, Jim (and others) I have difficulties to source the necessary transformers for HF channels of single-stage Melquiades. Do you know any sources that sell the amorphous core for transformers in small quantities?

 hagtech wrote:
You know, for somebody just taking a snapshot of a bunch of tubes for a forum post - it's really quite good.  Has that Ansel Adam's look.  I'd swear you used film.

Not really it was an old image that I took from the bottom of the Melquiades pages.

http://www.goodsoundclub.com/Melquiades.aspx


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
04-30-2007 Post does not mapped to Knowledge Tree
cv
Derby, United Kingdom
Posts 173
Joined on 09-15-2004

Post #: 30
Post ID: 4300
Reply to: 4295
Amorphous cores for Melquiades spud amp
Hi Romy,
I dunno if you mean the C-core materials itself or the completed transformers... if the former (perhaps a poor term in this context), then
http://www.elnamagnetics.com
have what you are looking for.
Seach for AMCC - these are the Metglas C-cores you are after...

Also, if you are able to limit the LF before the power stage, I would very strongly suggest trying a custom OPT from Sowter in the UK on a 100% mumetal EI core for the S2.... expensive but something magical about the sound.

If we agree on the spec beforehand, we may even be able to come to an arrangement where I purchase them from you if you don't like them so you're not risking much. Feel free to PM me if you are interested.

Best,
cv
04-30-2007 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 31
Post ID: 4301
Reply to: 4300
The core materials, the problems and the solutions...

 cv wrote:
Hi Romy, I dunno if you mean the C-core materials itself or the completed transformers... if the former (perhaps a poor term in this context), then http://www.elnamagnetics.com have what you are looking for. Seach for AMCC - these are the Metglas C-cores you are after...

Well, Bud do not mind to wind HF transformer if e find an interesting raw core… I hardly doubt I will find anywhere a ready to go transformer with my custom DSET HF specifications…

 cv wrote:
Also, if you are able to limit the LF before the power stage,

Well this it VERY big subject. As you remember in two stages Milq I was not able to high pass the amps at line level as it created very wrong sound. I have a number of hypnotizes about the resume and the single stage amp would be a good playgroup to try it. I do intend to high pass it if I could. There is a great chance that in the two stages Melquiades the high pass was not possible die to the application in the given topology. I spent a LOT of time to experiment with it.

 cv wrote:
I would very strongly suggest trying a custom OPT from Sowter in the UK on a 100% mumetal EI core for the S2.... expensive but something magical about the sound.

Chris, can you point to the specific model of the Sowters OPT?

 cv wrote:
If we agree on the spec beforehand, we may even be able to come to an arrangement where I purchase them from you if you don't like them so you're not risking much. Feel free to PM me if you are interested.

Point out the exact model. It is not about the price but rather about the quality of result. I would rather have Bud’s, Lundahl and Sowter transformers for S2 in order to see which will work better. Interesting is that I feel that the S2 channel will be the most prominent transformer in the amp… the only concern I have that my experience with amorphous core is very positive and I afraid that I will not have the dynamics and the “harmonics not affected speed” with any none-amorphous lamination… BTW, if you propose to “agree on the specs” then does it mean that you will be trying the single stage Milq


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
04-30-2007 Post does not mapped to Knowledge Tree
hagtech


Hawaii
Posts 117
Joined on 02-13-2006

Post #: 32
Post ID: 4302
Reply to: 4301
eliano
I think Jack Eliano of Electraprint can custom wind something for you.  Or maybe Mike at Magnequest.  At under 5W, the core does not need to be very big, so cost of exotic materials go down and bandwidth and magnetic coupling go up.

jh
05-01-2007 Post does not mapped to Knowledge Tree
op.9
Planet Earth
Posts 68
Joined on 01-26-2007

Post #: 33
Post ID: 4303
Reply to: 4301
Sowter
I use Sowter model 9550 for my treble horns. (Changing over to these was the biggest single improvement I've ever made). Brain is very good to deal with and will make anything to your specs. He has huge experiance with OPT design.

Oneday I want to compare my sowters with the (amorphous) Lundahl LL9206 at 20:1 in a parafeed arrangement, with an air-core choke. Could be interesting...


cheers,

op.9



everybody used to call me James in my past other-worldly life.
05-01-2007 Post does not mapped to Knowledge Tree
jessie.dazzle


Paris, France
Posts 456
Joined on 04-23-2006

Post #: 34
Post ID: 4304
Reply to: 4302
Transformer hunt continued
Romy,

I have contacted Automatic Electric (AE Europe in the Netherlands) requesting a quote for transformers meeting your specs. The AE site says they can do custom amorphous core transformers to spec. Currently waiting for a reply. I will post the info as soon as I have it.

jd*


How to short-circuit evolution: Enshrine mediocrity.
05-01-2007 Post does not mapped to Knowledge Tree
Ronnie
Stockholm
Posts 81
Joined on 06-30-2005

Post #: 35
Post ID: 4306
Reply to: 4304
AE Anniversary

jd: I'm celebrating the 1 year anniversary of my order for custom transformers from AE Europe.
It suits me fine that they haven't delivered (because I don't have the $ now), but you may want to be ...less than overly optimistic.

I don't know about the waiting time with Tribute transformers.
Perhaps Dave Slagle (www.intactaudio.com) could do the job?

05-01-2007 Post mapped to one branch of Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 36
Post ID: 4307
Reply to: 4304
Some thoughts about transformer for my MF channel.

First of all thanks to all who assist me with this project, including those who did not post here.

Jim, Electraprinted Jack is great guy but he does not believe in exotic cores, very unfortunate because I like to deal with him.

Jessie, you are right I did forget the AE Europe source. It would be interesting what they say. BTW, I would need all secondary sections all go outside with marked polarity….….

op.9, could you in term of subjective impressions and associations describe what your Sowter did with the Sound of you treble horns?

Still, without exclusion of all other opportunities, I would like Bud to bid with his transformer wounded around an amorphous stick or amorphous bagel…

Anyhow, I would like to share some my concerns about the transformers for Vitavox S2 channel. A common thinking about famous transformer would not be really applicable in my case as I did not see anyone judge transformer in context of DSET use. Within a very low power, within very small size and within a very limited frequency range it would not be difficult to make a very good transformer but then the question would be: how to make it to sound in a seatrain way. This is the zone in wish I have absolutely no experience which buttons to push and no knowledge what ingredients to mix. I less case about the transformer for tweeter channels – there is not a lot of sound there but with the midrange with S2 driver the transformer in this project would be a very interesting subject.

Let me I explain my objective for this transformer. In my mind  (the mind of user bit the designer) in this transformer should be 4 entities that should be properly balanced:

1) Harmonics
2) Speed
3) Dynamics
4) Connectivity

HARMONICS is hardly the properties of the transformer itself but rather the plate loading via transformer. So the secondary sections should be stuck out allowing remapping the sections on fly. Still, read about the “speed”.

SPEED should be maximum possible. However it is a different speed then juts unloading the tube, striping the harmonic tails and converting SET into the crappy OTL sound. Usually in “betters” SETs the output stage loaded slightly les and it create the feeling of speed. I do not like it. Along with this “speed acceleration” the sounds slightly flatten the parabola with which the notes roll it their pitches. As the results it create slightly “flat” (musically) sound. The speed that I am taking about should not interfere with harmonic pattern. It should be maximum speed of exchange of information but it should be absolutely indifferent to harmonics. Still, read about the “dynamics”

DYNAMICS should at it max as well but there is more to it. The speed of information exchange should be identical (or different) at different dynamic ranges. I do not know if at minus 60dB the speed of information exchange should be identical to the minus 20dB. It might be that it should have own speed deviation… However, when it sounds I know that it is wrong when it sounds wrong.  Some transformers do change the speed of information exchange at different dynamic ranges but they do it according to wrong algorithms. I do not know what the right algorithms are: I am not in the business of design the things but in the business of bitching about others. Anyhow, for my transformer I would like it to be able to have own dynamic intelligence and know what speed to demonstrate at wish dynamic level, still keeping the dynamic window as wide as possible. Still, read about the “connectively”.

CONNECTIVITY – this is the key. The connectively is something that differentiate a right transformer from anything else. What is important also that a good transformer should have absolutely maximum connectivity with absolutely maximum speed and dynamics. So, what the connectively is all about? The connectively is the association between the events that being transmitted via a transformer. The individuals sounds, properly harmonically structured at this max speed and with no compression it not enough. In music notes have inferred references to other notes and even if to virtually cut out of music the referred notes (along with their harmonists) then the referencing notes still will imply the removed notes. Bad transformers have no speed and no dynamics but if the bad transformers do have speed and dynamics (with correct harmonics) then they have no connectively between the notes. With bad transformers sound feel like a porcupine’s back with a zillion individuals needles stick out of Sound and each needle do not know about the sharpness of other needles. In a good transformer each needle of event (would it be a note or a pause) are kind of managed by one mind, the same mind that manages the speed and dynamics. Also it is very important that the connectively should not be loosing itself at high and low dynamic levels… In a way a transformer in it’s connectively should be more like Michelangeli play….

Well, I would love to tell you that I know HOW to do it but I do not know. The only one transformer that I have seen that had the absolute maximin of connectively, speed and superbly smart dynamics were the Expressive Technology transformers. Well, it would be very interesting to find the transformer for my S2 channels that would be able to do the same. It looks like that within a limited bandwidth the task should not be  too difficult…

Rgs,
Romy the Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
05-01-2007 Post does not mapped to Knowledge Tree
cv
Derby, United Kingdom
Posts 173
Joined on 09-15-2004

Post #: 37
Post ID: 4308
Reply to: 4306
LF limit in single stage and Sowter mumetal cores
Hi Romy,

Agreed about the S2 transformer being the most prominent  it is here I think that mumetal will shine. I should have said that I was referring to the upper S2 covering 1k-12k or so.

I wasn't too clear earlier - when I suggested rolling off LF for the S2, I didn't mean at the x/o frequency. I was thinking more around 200Hz or so. This will ease the work of the single stage melq and on the mumetal, which can't handle the flux that comes with LF. It may be difficult to get 2W at 500Hz with the biggest core Sowter can do.

Actually, that applies to the usage of all small core transformers - you must limit LF before the output stage or risk saturating the core; even if the speakeror OPT doesn't see any LF power, it's the voltage swing on the primary that determines the core flux.

The exact Sowter model I used was custom but all of Sowters stuff is in a way. Just need to spec out the Lpr, turns ratio, dc current and power at given frequency and if possible they will build it at no extra cost to the "standard" models.

Alas I have no time these next coulple months to build anything but would like to try it out when my horns are eventually delivered.

My concerns in giving the mumetal an unequivocal recommendation is not that you may simply prefer amorphous, but rather that it could sound rather different to amorphous (esp. with the lower S2 driven by amorph).... hence my offer to purchase them from you if unsuccessful. That mumetal core material is getting more expensive and difficult to get hold of. I can use the OPTs for a 6e5p spud or I can always use a diffeent bobbin with the laminations and restack them for a different application!

The issue I had with my mumetal OPTs is very noticeable magnetostriction - core singing along with the music. But they had a rather larger airgap which wouldn't have helped.

Anyway, the offer stands - if you'd like to try them at cv's risk, just let me know the spec and I can optimise with Brian.

Also bear in mind that the winding geometry and materials affect tone. To my mind, the masters here are Pieter from Tribute and Dave Slagle, both of whom build wonderful transformers. Bud has some fascinating ideas but I have not been lucky enough to hear his ironware yet.

regards
cv


05-01-2007 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 38
Post ID: 4309
Reply to: 4308
The Sowter’s mumetal transformers for Milq?

Chris,

I head a lot a lot of good thing about Pieter from Tribute and I would like to recruit him for the s2 transformer. We send last week to him an email and he did not reply. I heard from many other people that it is a very typical for his communication pattern. So, it dificalt if he is not accessable to communicative? I do not know also how Bud’s amorphous transformer would be, I do not think he knows either but he is not only accessable but also abuseable. :-) since I have very limited ides what I need technically it is very important to me that someone could listen all my "verbiage" and in his mind to convert it into the implementable specifications...

Anyhow, I if you feel that it worth try then I do not mind to try the Sowter’s mumetal transformers. I was also thinking about the 200Hz from bottom, 50mA gap. Let presume that I WILL BE ABLE to high-pass it at line level and that the MF stage will NOT handle the full range signal. Then the key would be to have the minimal amount of turns in primary, preserving best coupling with objectives to serve the necessary ratio (since we have no heavy inductance demands). About the ratio. I would like to have 12:1 with half-&-half. It means that all secondary sections should go outside to some kind of mapping board and if I connect half of then in serial and half of them in parallel then I would like to get in this setting 12:1. Fell free to convert what I meant to say into a format that would be more comprehendible for the Sowter guy. Feel free also to suggest what I am thinking wrong.

Rgs,
Romy the Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
05-01-2007 Post does not mapped to Knowledge Tree
cv
Derby, United Kingdom
Posts 173
Joined on 09-15-2004

Post #: 39
Post ID: 4310
Reply to: 4309
Sowter spec for mumetal OPTs: iteration 1

Allo

Pieter is super-talented and a great guy; if you are a Larry David fan he looks a bit like his Dutch cousin...

The only problem is that he has a long waiting list... I don't think you would get the OPTs any time soon.

If we will try Sowters then I would suggest:

Primary inductance of about 2H, for use above 1kHz.

Turns ratio of 12:1 would give you a 2.4k load with 16 ohm secondary.

With a gap of 50mA, I reckon on the order of 1-2W may be possible at 500Hz - let's see what Brian thinks once spec is complete. Not sure the biggest mumetal core they have will handle much more.

As for secondary configuration, if you don't need the facility to play with taps, you are generally better off without all the connection options as you don't have to re-terminate all the secondary options. (The secondary will always need to be sectioned internally). If you do have taps, it's vital to use the entire secondary or else the tx is suboptimal.
Sowter have a range of options, scroll down at:

http://www.sowter.co.uk/2se.htm

So you pick any option except the "tapped" one! I don't understand why you want to insist on half series/half parallel connections when internally, the secondary is made of more than 4 sections? Just because the "mapping board" has 4 sections coming out of the tx...

Anyway, I will email Brian and see what he reckons.
cv

05-01-2007 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 40
Post ID: 4311
Reply to: 4310
I think we spoke about it in past

I would defiantly avoid any taps by any cost, regresses how “advanced” they are implemented. On the page that you referred the first configuration, with secondary sections sticking outside, looks like a reasonable to me.

Yes, the 2.4k to 3.0K load with 16 ohm secondary would be fine but only in the middle of that first configuration. I would like to have at least one, one a half kOhms up and down. As I undusted the re-termination and remapping of secondary does not affect sound in any way.

One of the reasons why I do not know where to lend because I do not know what kind “contrast” Brian’s transformer will give. If case of “contrasty” sound it would be nice to drop I would say 500R and to load the tube slightly harder. It is really does not cost money and do not affect sound. So, why not to have this option…

BTW, Chriss I have two questions,. What will be the range of the prices for this MF transformer and what you thoughts I might do for HF channel transformer (>12K and up). I think we spoke about it in past:

http://www.goodsoundclub.com/Forums/ShowPost.aspx?postID=634#634

Rgs,
The caT


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
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