Servo-Sound made in Belgium - Page 8 - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 10th October 2012, 11:48 AM   #71
troystg is offline troystg  United States
diyAudio Member
 
troystg's Avatar
 
Join Date: Apr 2004
Location: In a dream... Please don't wake me.
Wouldn't be complete without Mr. Eraths work.

lweusersgroup : LWE Loudspeakers Users Group


http://groups.yahoo.com/group/lweuse...unt=20&dir=asc
__________________
Troy
Thinking positive doesn't make things better, it makes you a better person.
  Reply With Quote
Old 10th October 2012, 12:11 PM   #72
diyAudio Member
 
steph_tsf's Avatar
 
Join Date: Mar 2008
Quote:
Originally Posted by troystg View Post
Wouldn't be complete without Mr. Eraths work.
Agree !
Attached Files
File Type: pdf US3449518.pdf (340.2 KB, 79 views)
File Type: pdf US3493682.pdf (185.6 KB, 33 views)
File Type: pdf US3497621.pdf (181.1 KB, 31 views)
File Type: pdf US5086473.pdf (436.6 KB, 34 views)
File Type: pdf ERATH LWE Speakers.pdf (325.2 KB, 57 views)
  Reply With Quote
Old 10th October 2012, 12:25 PM   #73
troystg is offline troystg  United States
diyAudio Member
 
troystg's Avatar
 
Join Date: Apr 2004
Location: In a dream... Please don't wake me.
I have a few of Mr. Eraths units and I am hoping that one day someone will be able to do the same with a DSP instead of the reactive components and combine it with a good class D amp such as the Hypex nCores...

If you would like one of his units to "disect" please let me know and I can send it to you.
__________________
Troy
Thinking positive doesn't make things better, it makes you a better person.
  Reply With Quote
Old 10th October 2012, 03:19 PM   #74
diyAudio Member
 
steph_tsf's Avatar
 
Join Date: Mar 2008
Quote:
Originally Posted by troystg View Post
I have a few of Mr. Eraths units and I am hoping that one day someone will be able to do the same with a DSP instead of the reactive components and combine it with a good class D amp such as the Hypex nCores.
A DSP inside the feedback loop would introduce a delay that would impair stability. On the other hand, putting the DSP outside the feedback loop, as preamp, would ruin Mr. Erath's concept as doing so the system would operate like a digital Linkwitz transform.

Quote:
Originally Posted by troystg View Post
If you would like one of his units to "dissect" please let me know and I can send it to you.
Before sending a whole unit, it would be interesting to "virtually regenerate" the four patents filed by Louis W. Erath, using LTspice simulations.

1) the US3449518 patent filed 1965 Sept. 15 about current drive, special feedback networks and optical feedback for bass reinforcement at quiet listening levels (did KM ServoSound got some inspiration from this ?)
2) the US3493682 patent filed 1966 Nov. 21 about a new standardized way to connect a loudspeaker to a power amplifier outputting a voltage (the speakers contains the required frequency compensation network, that the amplifier uses in his feedback loop - now tell me what's happening in case of long unbalanced wires ?)
3) the US3497621 patent filed 1967, June 19 about more refined optical feedback circuits for extending the bass boost at quiet listening levels (did KM ServoSound got some more inspiration from this ?)
4) the US5086473 patent filed 1989, Nov. 27 about a feedback system for a subwoofer using current in the feedback path, and a RLC series network also.

After this, we may try "virtually regenerating" a few commercial products sold by Louis W. Erath :

5) the "Model 1" with a normal power amplifier lightly modified for accessing its feedback network
6) the LWE 2A1 Speaker with LWE Amplifier
7) the little "Erath Electronic Suspension" box applied to some standard power amplifier and some standard closed box featuring some Q and Fc.

Viewed from here, the most appealing circuit is the one disclosed in the US5086473 patent filed 1989, Nov. 27.
Being filed in 1989, it comes after thousands and thousands of KM ServoSound systems sold in Europe. Most people will then infer that such patent is worth nothing.
Actually such patent has a high value to my eyes because unlike the KM ServoSound, we find no additional active components. The whole equalization gets done using passive components, and I find this very reassuring, very refreshing compared to the Linkwitz Transform (pre-equalization requiring one opamp), or compared to some complicated feedback requiring opamps, attempting to operate as "velocity feedback" (see JC Bodot "Zippy" in France).

Concerning the US5086473 patent filed 1989, Nov. 27, there is something unclear to me. Is the power amplifier (#38) a conventional power amplifier outputting a voltage, or is it supposed to output a current ? Why is it represented as distinct from the differential input stage (#60) ? Let us read the patent text : "A current signal is delivered to the drive coil (#34) by a broadband audio amplifier (#38)."

Finally one may ask if it is feasible to wire a power amp as Linkwitz transform, for getting a "power Linkwitz transform with voltage gain". Only using resistors and capacitors. No coils, no transformers, no opamps. If this is the case, I'm sorry for Louis W. Erath.

Speaking about JC Bodot in France, that man issued a kind of (biased ?) technical summary about "velocity feedback", before imposing his own "wideband velocity feedback".
One can read it here : http://ddata.over-blog.com/xxxyyy/1/...ack_Ch1_M1.pdf
Unfortunately it is in french.
There is question about bridges used to generate the electronic feedback of the power amplifier, namely the "Voigt bridge", "Maxwell bridge" and "Anderson bridge".
Unfortunately, JC Bodot failed to provide a bibliography and references, so after reading his prose, I still don't know who are Voigt, Maxwell and Anderson, and I still don't know if one of those were the inspiration source for KM ServoSound.

Time to open a few new threads on diyAudio ?
- Louis W. Erath patents and devices, illustrated by LTspice simulations
- towards a "power Linkwitz transform with voltage gain"
- the Voigt bridge, the Maxwell bridge, the Anderson bridge, the KM ServoSound systems, the Louis W. Erath systems confronted to compliance nonlinearities, magnetic nonlinearities, factory dispersion, thermal effects and ageing: are they "speed feedback" systems, or are they equalizers ?
- the JC Bodot "Zippy" in France : is this recycling, improvement, or innovation ?
Attached Images
File Type: jpg Erath Compensator.jpg (81.2 KB, 178 views)
  Reply With Quote
Old 10th October 2012, 04:55 PM   #75
troystg is offline troystg  United States
diyAudio Member
 
troystg's Avatar
 
Join Date: Apr 2004
Location: In a dream... Please don't wake me.
Mr. Erath developed another circuit that worked full range before he died. He made a few units to put in his new Trout powered speakers and made me the only external bi-amp version to use with some Hypex UcD amps. I started the active system but had to put it in storage when I came to Europe for a contract. I hope to pull it out of storage (been a year or so) and get started on it again shortly.

Referring to this one

4) the US5086473 patent filed 1989, Nov. 27 about a feedback system for a subwoofer using current in the feedback path, and a RLC series network also.

I have one home unit and two car units that utilize this circuit. I can offer you one of the car units(uses +/- 15vdc) to play with when you are ready.
__________________
Troy
Thinking positive doesn't make things better, it makes you a better person.
  Reply With Quote
Old 10th October 2012, 09:02 PM   #76
diyAudio Member
 
steph_tsf's Avatar
 
Join Date: Mar 2008
Quote:
Originally Posted by troystg View Post
Mr. Erath developed another circuit ... I hope to pull it out of storage (been a year or so) and get started on it again shortly. Regarding the US5086473 patent filed 1989, Nov. 27 ... I have one home unit and two car units that utilize this circuit. I can offer you one of the car units(uses +/- 15vdc) to play with when you are ready.
The best advice I can give you is to avoid spreading those elements over the world. Try keeping them together, with all cabling, documentation and correspondence in a secure & discrete storage. If there is a cost associated to the secure storage, you'll find people including myself willing to donate money. If some equipments sold by Mr. Erath never had a proper schematic on paper (how possible?), a wiring diagram or a service manual, it is never too late for making them. Let's take an example. If you email me decent pictures from a decent digicam, well in focus, of the PCBs (I mean the fully equipped PCBs), solder side and copper side, plus some other pictures like the power supply wirings and control wirings, I can manually process those pictures, deliver the corresponding schematics, and deliver a simulation using LTspice. Kind of stuff I did with great fun and pleasure with that old KM amplifier 10a (Servo Sound), back in 2008.
  Reply With Quote
Old 11th October 2012, 06:55 PM   #77
dapepe is offline dapepe  Belgium
diyAudio Member
 
Join Date: Aug 2010
Location: Belgium
Quote:
Originally Posted by steph_tsf View Post
Getting rid of the 20mH inductor in the 1:10 immobile voltage synthesis.
See attached picture.

A possibility is to use a ground-referred inductor synthezised by a gyrator. But then, the difficulty is to current feed this ground-referred inductor. I don't want to end up with weird components like OTAs in open-loop or with BJTs in open-loop (aka Nagra tape amplifiers). I need a practical solution based on one or two TL071 or audio-grade opamps.

Another possibility is to 1/p shift the stage. The three resistors become three capacitors. The inductor becomes a resistor. The issues with this approach : loss of DC path for the opamp feedback, small load impedance seen by the opamp at high frequency, possible issue with the capacitor used at the input. Such circuit may operate if adding a serial resistor at the input (say, 100 ohm) and adding a parallel resistor as negative DC feedback (say, 1000k). It could be the TL071 is unable to handle such uncommon arrangement. I'm not sure that faster is better, in such uncommon arrangement, making me doubt about the TL071 (he hates being loaded) and the OPA134 (he is maybe too fast).

Any other idea ?

This difficulty is maybe the reason of the "black box" inside the Servo-Sound. Maybe the Servo-Sound is an accurate bridge feedback with no big concerns about tracking the DC coil resistance (I'm not sure elvee is right in his approach), but with a nice trick (or private joke) for replacing a coil by some organized silicon. In such active box, containing the electronics, a non-copper electronic coil is highly desirable, with no vibration induced distorsion and no risk of detuning. In this context I think that the Servo-Sound "black box" is containing an emitter follower used as poor man's gyrator for implementing the coil, plus a Nagra-inspired (Nagra patented maybe ?) BJT arrangement outputting an AC current (not a voltage) feeding the ground-referred synthezised coil (and associated resistors). Plus an emitter follower, as output buffer.

Is anybody on earth knowing what's inside the Servo-Sound "black box" ?

Thanks in advance,
Steph
Hello steph,

I managed to find out what is in the blackbox of the air preamplifier. The box is made of resin or epoxy. I googled and find out that aceton would deluate the resin or epoxy. Indeed it worked, if you let the blackbox one hour in the aceton, you can scrape off the epoxy. It is a long process but worth doing it. I found 4 resistors, 2 electrolytic capacitors and a 3 piece coil. The aceton made the blue surrounding of the capacitors unreadable. I used a esr/ capacitor meter to find out the cap values.
Hopes this helpes.
I noticed you are from belgium ? Well i am.
Regards,
Peter
  Reply With Quote
Old 14th October 2012, 07:01 AM   #78
diyAudio Member
 
steph_tsf's Avatar
 
Join Date: Mar 2008
Quote:
Originally Posted by dapepe View Post
I managed to find out what is in the blackbox of the air preamplifier. The box is made of resin or epoxy. I googled and find out that aceton would deluate the resin or epoxy. Indeed it worked, if you let the blackbox one hour in the aceton, you can scrape off the epoxy. It is a long process but worth doing it. I found 4 resistors, 2 electrolytic capacitors and a 3 piece coil. The aceton made the blue surrounding of the capacitors unreadable. I used a esr/ capacitor meter to find out the cap values.
Great! What blackbox are we talking about? KM amplifier 10a or KM amplifier 15b?
  Reply With Quote
Old 23rd October 2012, 08:25 PM   #79
dapepe is offline dapepe  Belgium
diyAudio Member
 
Join Date: Aug 2010
Location: Belgium
Default blackbox

Hello,

I'm talking about the one that is the pre-amplifier ( see attached fotos) BUT my description will help you to find out what is in any blackbox ( servo sound , KM )

Detail : the blackbox is just plastic and is surrounding the epoxy.

If you squeeze the plastic , it comes off, and shows you a brown epoxy box.

Also interesting : on the KM-52 speaker , there is no blackbox on the double-sided pcb !!
Attached Images
File Type: jpg component ID.JPG (966.3 KB, 118 views)
File Type: jpg IMG_0035.jpg (792.1 KB, 105 views)
File Type: jpg IMG_0036.jpg (828.6 KB, 97 views)
File Type: jpg IMG_0037.jpg (1,001.4 KB, 92 views)
  Reply With Quote
Old 23rd November 2013, 10:41 PM   #80
dapepe is offline dapepe  Belgium
diyAudio Member
 
Join Date: Aug 2010
Location: Belgium
More then 1 year later after last post , any news , anyone ?
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Ultra sound transducer for servo feedback subwoofer? e96mlo Subwoofers 28 11th July 2013 04:59 PM
Philips made in Belgium, new production engels Multi-Way 40 22nd July 2010 02:20 AM
Hello from Belgium pigsnoot Introductions 3 13th June 2009 09:44 PM
..didn't know how they sound till i made me one.. tmyr Planars & Exotics 137 26th November 2006 09:01 PM
home made surround sound Hitman Digital Source 7 22nd December 2002 06:15 AM


New To Site? Need Help?

All times are GMT. The time now is 11:39 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2