I've had a think about it, and decided that what I need is a few prototypes... I guess there is no better way to see which design I prefer, other than trying them myself.
I'll give My Ref a go first and see how it compares with my current LM3875 Gainclone. Then I'll have a think about that nested design (which I'm kind of afraid to try, because I won't have a PCB for it, and I have no confidence in my practical electronics knowledge at all).
And then finally, I'll see if I can still be bothered (lol), choose the design I like best and go nuts with it, silver and all. By the way, I really like silver... even if it had no electrical advantage over copper I'd still go for it because it simply looks beautiful. And it's very easy to plate it over copper.
I would also like to apologise to anyone who finds my manners offensive. I am used to writing in strictly moderated forums, and also I tend to get really attached to my ideas (which, I guess, is never good for a healthy discussion).
Thanks again for all your responses.
I'll give My Ref a go first and see how it compares with my current LM3875 Gainclone. Then I'll have a think about that nested design (which I'm kind of afraid to try, because I won't have a PCB for it, and I have no confidence in my practical electronics knowledge at all).
And then finally, I'll see if I can still be bothered (lol), choose the design I like best and go nuts with it, silver and all. By the way, I really like silver... even if it had no electrical advantage over copper I'd still go for it because it simply looks beautiful. And it's very easy to plate it over copper.
I would also like to apologise to anyone who finds my manners offensive. I am used to writing in strictly moderated forums, and also I tend to get really attached to my ideas (which, I guess, is never good for a healthy discussion).
Thanks again for all your responses.
Dear Leon,
Promise is promise. I simulate here for you a concept of a nested chip-amp. The difference between normal and nested, is the almost 20 dB. better S/N ratio of the nested one! The output impedance nested is almost 2uOhm, wich will result in a dampingfactor of over a million
Chip amps with smart feedback techniques, like this one can outperform many discrete designs and sound trully phenomenal in my opinion.
With kind regards,
Bas
Promise is promise. I simulate here for you a concept of a nested chip-amp. The difference between normal and nested, is the almost 20 dB. better S/N ratio of the nested one! The output impedance nested is almost 2uOhm, wich will result in a dampingfactor of over a million
Chip amps with smart feedback techniques, like this one can outperform many discrete designs and sound trully phenomenal in my opinion.
With kind regards,
Bas
Attachments
The input doesn't need a ground reference from the source and the output does not pollute the ground return.
It is far from obvious that these improvements are beneficial sound wise. If it indeed sounds better and not just different, it's hardly because of the lower output impedance.
A little summary about the LM3875.
Input noise : from 2uV typical , which is fairly good to 8uV max, wich is not
good at all....
Slew rate : from 11V/uS typical, which is not an extra value, but still enough,
to 5V/uS worse value, wich is clearly much worse than any discrete design and
somewhat lacking for a 50W amp.
Even the typical value of 11V/uS is in no way compatible with a hig end credo...
The 3886 show better value for the slew rate, but nothing extraordinary,
and a noise that can reach 10uV, slightly higher than the max value of
the 3875...
With such "perfs" , these amps, although good enough for general purpose,
can in no way match a good discrete design...
Input noise : from 2uV typical , which is fairly good to 8uV max, wich is not
good at all....
Slew rate : from 11V/uS typical, which is not an extra value, but still enough,
to 5V/uS worse value, wich is clearly much worse than any discrete design and
somewhat lacking for a 50W amp.
Even the typical value of 11V/uS is in no way compatible with a hig end credo...
The 3886 show better value for the slew rate, but nothing extraordinary,
and a noise that can reach 10uV, slightly higher than the max value of
the 3875...
With such "perfs" , these amps, although good enough for general purpose,
can in no way match a good discrete design...
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Dear analog,
Wel I built chip amps with a comparable feedback concept as I showed above. In a nested feedback in my opinion, the sound is improved day and night over the standard one. And most noticeable, the bass, and sub-bass is so much tighter. Like you put an out of focus picture in focus. Not to invoke a new discussion, but I truly believe the much higher dampingfactor is cause of this. The improved S/N ratio gives room for better micro detail information. I would say build one yourself to hear the difference, it must be heard
I never want a standard chipamp anymore after I heard this.With kind regards,
Bas
Yes, I agree, and balanced power amps seem to be widely used for high end headphone amps. Odd they're not that common for speaker amps. Must be the cost I guess. [/QUOTE]
Hammond used this design in their organs, balanced amps fed from a balanced source. The source in their case was a the tone wheel. A typical schematic has three parallel wires with signal flow left to right the center wire is ground, top and bottom wires are 180 deg out of phase. This runs through coupling transformers and right into the speakers.
Hammond built this into speaker cabinets. A typical cabinet had three of these balanced amps and three sets of speaker drivers. We'd call this today a "balanced tri-amp." In the 1950's these sold for about three times the price of a new car. Some large installations might use four cabinets. It was a good design. All the cables running to the cabinet were balanced line level, no hum pickup. and there was never a cross over needed as each amp fed only one driver.
I don't think this was a new idea even in 1950. But it was un-common for home HiFi because of the cost.
Hammond used this design in their organs, balanced amps fed from a balanced source. The source in their case was a the tone wheel. A typical schematic has three parallel wires with signal flow left to right the center wire is ground, top and bottom wires are 180 deg out of phase. This runs through coupling transformers and right into the speakers.
Hammond built this into speaker cabinets. A typical cabinet had three of these balanced amps and three sets of speaker drivers. We'd call this today a "balanced tri-amp." In the 1950's these sold for about three times the price of a new car. Some large installations might use four cabinets. It was a good design. All the cables running to the cabinet were balanced line level, no hum pickup. and there was never a cross over needed as each amp fed only one driver.
I don't think this was a new idea even in 1950. But it was un-common for home HiFi because of the cost.
Uncle,
No offense taken. Perhaps I was too harsh, but I wanted you to at least consider the My Ref before summarily dismissing it. It was designed and fine tuned by a person who is interested in achieving the best sound possible from these marvelous chips. If you try one, I hope you are as pleased with it as I am with mine. If not, don't hold back--I'll deserve your scorn.
All these discussions about exotic configurations put a scare into me, too. They all seem complicated and fussy, with no proven kits readily available. I know very little about electronics, but found this amp economical for what it provides and easy to build, and easy to improve with better parts, which seems to be your goal, as well. That's why I was so insistent, perhaps too much so. I apologize for being pushy, but I'm trying to get the word out.
A couple weeks ago, I had the opportunity to hear my amps through $18,000 Eggleston speakers (88 dB, 6.3 ohm). They are every bit as good as, in some ways better than, multi-thousand dollar commercial offerings, lacking only the gobs of wattage that some audiophiles crave (in my opinion, to an excessive degree), but none of the authority or refinement.
Peace,
Tom E
No offense taken. Perhaps I was too harsh, but I wanted you to at least consider the My Ref before summarily dismissing it. It was designed and fine tuned by a person who is interested in achieving the best sound possible from these marvelous chips. If you try one, I hope you are as pleased with it as I am with mine. If not, don't hold back--I'll deserve your scorn.
All these discussions about exotic configurations put a scare into me, too. They all seem complicated and fussy, with no proven kits readily available. I know very little about electronics, but found this amp economical for what it provides and easy to build, and easy to improve with better parts, which seems to be your goal, as well. That's why I was so insistent, perhaps too much so. I apologize for being pushy, but I'm trying to get the word out.
A couple weeks ago, I had the opportunity to hear my amps through $18,000 Eggleston speakers (88 dB, 6.3 ohm). They are every bit as good as, in some ways better than, multi-thousand dollar commercial offerings, lacking only the gobs of wattage that some audiophiles crave (in my opinion, to an excessive degree), but none of the authority or refinement.
Peace,
Tom E
Uncle_leon,
I have built an amp using the LM3875 chips running them with at 25 vdc (18v ac) powering 2 floorstanding speakers, Monitor Audio BR6. The sound is quite amazing and detailed for the simplicity of the circuit. I plan to bi-amp the speakers for even better quality. I also was quite surprised when a friend and me listened to my amp and compared it to his Arcam Alpha 9 pre amp, power amp and bi amped Totem Sttaf speakers. All I can say is that he was a little bit gutted with his system and the amount of money it has cost him after listening to a cheap chip amp setup.
I have built an amp using the LM3875 chips running them with at 25 vdc (18v ac) powering 2 floorstanding speakers, Monitor Audio BR6. The sound is quite amazing and detailed for the simplicity of the circuit. I plan to bi-amp the speakers for even better quality. I also was quite surprised when a friend and me listened to my amp and compared it to his Arcam Alpha 9 pre amp, power amp and bi amped Totem Sttaf speakers. All I can say is that he was a little bit gutted with his system and the amount of money it has cost him after listening to a cheap chip amp setup.
Thanks madisonears.
The reason I initially looked unfavourably upon My Ref is that it seemed "too complicated to be good". My belief is that the "directness" and immediacy that I so love in my minimalist Gainclone comes from its extremely short signal path and extremely low component count (there is a total of 6 capacitors and 6 resistors in my whole amp - no protection circuits, no filters, no controls - other than a single Noble pot for volume control).
If you tell me the ability to convey emotions is retained in My Ref, while improving in other fields, that will definitely be enough to convince me to give it a go. Another thing I would love is if it was possible to make it as wonderfully compact and modular as Peter Daniel's kit can be, as I based my ideas for the case around that.
Portreathbeach - my amp is also running off +-18VAC, and I also want to go down the bi-amping alley. My amp was actually bi-amped, but then I fried two out of four channels, leaving me with ordinary stereo I would say the difference is quite perceptible, especially dynamics are significantly improved when bi-amping.
The reason I initially looked unfavourably upon My Ref is that it seemed "too complicated to be good". My belief is that the "directness" and immediacy that I so love in my minimalist Gainclone comes from its extremely short signal path and extremely low component count (there is a total of 6 capacitors and 6 resistors in my whole amp - no protection circuits, no filters, no controls - other than a single Noble pot for volume control).
If you tell me the ability to convey emotions is retained in My Ref, while improving in other fields, that will definitely be enough to convince me to give it a go. Another thing I would love is if it was possible to make it as wonderfully compact and modular as Peter Daniel's kit can be, as I based my ideas for the case around that.
Portreathbeach - my amp is also running off +-18VAC, and I also want to go down the bi-amping alley. My amp was actually bi-amped, but then I fried two out of four channels, leaving me with ordinary stereo
I would say the difference is quite perceptible, especially dynamics are significantly improved when bi-amping.
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When the original GainCard came out it had a reputation for an immediate, hi resolution sound. In fact, quite remarkable for what the LM3875 is supposed to be.
Many people put that down to the small signal path and minimalist design (although they forget about the many components inside the chip!!). In fact, it's all of that plus the one thing they don't often mention - that the LM3875 is an extremely well designed power amp in its own right with a number of excellent design features and a benign distortion spectrum when not clipped.
The more you move away from that ideal the less the amp can be called a Gainclone. It's not a clone, it's a completely different amp.
I've built minimalist LM3875 Gainclones using the best components and point to point wiring. Equally important, if not more so, is the PSU. Currently I biamp my two-way speakers with the classical 2,200uF Peter Daniel type PSU for the tweeter amp and a high capacitance regulated PSU using Pedja's discrete regs for the bass amp. Again, no pcbs just hardwired.
Believe me, they sound nothing short of amazing. I don't want anything better than this, although I might try balancing the amps when I get the funds.
Forget about endlessly looking for the best solution. There isn't really one but this is pretty close. Build one and try for yourself.
Many people put that down to the small signal path and minimalist design (although they forget about the many components inside the chip!!). In fact, it's all of that plus the one thing they don't often mention - that the LM3875 is an extremely well designed power amp in its own right with a number of excellent design features and a benign distortion spectrum when not clipped.
The more you move away from that ideal the less the amp can be called a Gainclone. It's not a clone, it's a completely different amp.
I've built minimalist LM3875 Gainclones using the best components and point to point wiring. Equally important, if not more so, is the PSU. Currently I biamp my two-way speakers with the classical 2,200uF Peter Daniel type PSU for the tweeter amp and a high capacitance regulated PSU using Pedja's discrete regs for the bass amp. Again, no pcbs just hardwired.
Believe me, they sound nothing short of amazing. I don't want anything better than this, although I might try balancing the amps when I get the funds.
Forget about endlessly looking for the best solution. There isn't really one but this is pretty close. Build one and try for yourself.
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I've recently had a chance to compare my Gainclone to a recapped Creek 4040 amp.
The Creek had cleaner treble, more bass (albeit far less controlled) and a lot better detail retrieval. But believe me I was so happy when I finally switched back to GC - because it doesn't just play music like Creek - it plays emotions as well. It involves you, grabs you right by the heart.
That is something I definitely want my future "hi-end" amp to do as well.
The Creek had cleaner treble, more bass (albeit far less controlled) and a lot better detail retrieval. But believe me I was so happy when I finally switched back to GC - because it doesn't just play music like Creek - it plays emotions as well. It involves you, grabs you right by the heart.
That is something I definitely want my future "hi-end" amp to do as well.
Dear,
Sound perception is a very personal thing. But in my opinion a good amp doesn't have emotion. The musicians, and producer who created the record put their emotion in their masterpiece, it is up to the amp to transfer that emotion as good as possible, without add or hold back anything. For me an amp that holds back details, isn't good enough. The other side could be, that the Creek amp had some worser on-even harmonic distortions which clarify certain details more then original intended.
With kind regards,
Bas
Now that... I do understand... and more than most on here
What does it look like on a 'scope ? asks jrn77478
Well for me it produced by this,
http://www.diyaudio.com/forums/solid-state/119151-my-mosfet-amplifier-designed-music.html
and looks like this, post #157
http://www.diyaudio.com/forums/soli...t-amplifier-designed-music-8.html#post1545959
Sorry I know it's not a chip amp, but this is what sonic heaven looks like... quite why it sounds as it does though is the unanswered question
Sebastiaan - of course it is amp's only role to convey whatever was in the original recording. The thing is, with most amps emotions get "lost in translation". I cannot tell you why Gainclone of all amps can do it better than others. Perhaps there are other kinds of distortion that evade measuring equipment, and yet our hearing picks them up. That's why certain things, even though ridiculous from electrical point of view (the so called audiophile "vodoo"), sometimes work. There are still many things scientists don't quite understand about how our hearing works, and what exactly makes for a "good" sound.
jrn77478 - you need to get out more you know
Mooly - Thanks! I've had a look at your amp, but that schematic looks just plain scary to me No way in hell I'd be able to build that myself without very precise, step-by-step instructions
jrn77478 - you need to get out more you know
Mooly - Thanks! I've had a look at your amp, but that schematic looks just plain scary to me
No way in hell I'd be able to build that myself without very precise, step-by-step instructions 
Hi,
Sorry to have gotten off track in the slagging match.
I would suggest bridge/parallel for that, probably 6pcs LM3886 or 3pcs LM4780.
With a big enough powersupply and heatsink they will drive anything in terms of voltage/current capability, excluding original Apogee Scintilla.
This means kits or Semi-Kits.
This is not a bad choice.
HOWEVER, if you already biamp, why not go fully active.
If using (for arguments sake) a modified DCX2496 Digital Crossover you could interface directly from the DAC Chips to the Power Amplifiers, using bridged gainclones on all channels.
Match the Chipamp's gain to get clipping when the DAC clips. Maybe add a volume control (could be Dallas/Maxim DS1666 Chip based - this tracks well and sounds good and is easily remote controlled) and you have an excellent system.
Use LM3875 (effectively Bridged - BTL) at lower voltage and with small value PSU Capacitors for the MF & HF Driver, and parallel LM3886 (again effectively Bridged - BTL) at higher voltage with a big Snubberd PSU for the bass.
This would allow a very nice floorstanding 3-Way speaker with digital X-Over and chip amps that I would suspect could show many conventional "super high end" High End systems a thing or two on all fronts.
Class A bias will help some especially on getting smoother treble. I do not find gainclones to be lacking detail, may be your volume control, preamp of some part choice in your current setup.
Well, I am not sure about that. Mains transformers can be shielded quite effectively. Placing the supply externally means you need a cable between amp and supply and in order to make the separation meaningful you need a fair bit of distance. Now you add extra resistance of the cables and connectors in the supply and you have to put bigger capacitors locally at the chip.
Equally, an external preamplifier will only mean extra signal degradation due to extra cables and connectors.
I feel the "best" is always dependent on the context. I have yet to find a single "universally good" component that really, genuinely improves things reliably each and every time in any context.
I have at home a "Gainclone" that I feel sounds very good and is a reasonable competition for my Tube Amp sonically speaking. It has a little more power, but even with that there is not a lot between the two Amplifiers, especially once I compensate the gainclone for having a lower output impedance than the tube amp.
Yet funnily both Amplifiers use VERY different parts choices.
The tube Amplifier is full of Metal Film and wirewound (non inductive) resistors, has silver foil coupling capacitors and film type power supply capacitors, silver wire (all comparably "bright" sounding component choices).
The Tube Amplifier is push-pull class A with only local feedback around the 6550/KT88 output stage, low impedance concertina phasesplitter with 5687 and ECC83/12AX7 single ended gainstage.
Here I use an external passive controller (Noble Pot, silver switch, silver RCA jacks), also all silver wired and silver interconnects are used.
By Comparison the Gainclone uses copper CPU Coolers for heatsinks with "plastic tab" LM3875 and is full of Elna Silmic Capacitors in the Powersupply, AB Carbon Composite resistors for the signal circuit and copper wire.
I used 2 X 3,300uF/50V per channel with seperate rectifiers (but a single 25V-0V-25V secondary transformer) because a) I had them and b) they sit neatly between the "low capacitance" concept of the original gaincard and the normal "Big Cap" approaches, also sonically. Wiring is all copper, potentiometer is a Panasonic carbon/plastic motorised type.
FWIW, I put this into a broken and unrepairable Audio Innovation Alto Amplifier Chassis (yes, the chrome version), making the Amp look as stunning as it sounds.
Sonically either Amp is excellent on my floorstanders (10" Woofer, 5" Wideband & circular magnetostat/ribbon tweeter, all first order crossovers at 350Hz and around 12KHz, 90dB/2.83V/1m, around 25Hz LF extension in room.
I would avoid silver with solid state gear in general and gainclones specifically.
Good choices.
Yes, I like to use the same principles as much as possible.
I would still consider going fully active. I would, where it not for the fact that I am involved in developing commercial high end gear, which means I need a home system that is fairly "compatible" to allow me to evaluate new products and/or perform long term testing.
My frist work with Chipamp's was actually an active speaker I build in the mid 1980's, it included the TDA2030 in bridged and current boosted mode for two 8" Woofers (later with motional feedback a'la Backes & Mueller), a bridged pair of TDA2030 for the 5" Wideband Driver and initially a single TDA2030 for thr plastic dome tweeter, later replaced by a piezo tweeter (these are better than their reputation if used right) driven by a bridged pair of TDA2030.
Crossover was initially 3rd order sallen key filters looped around the TDA2030 as in the SGS Thomson Application Note for the TDA2030 (where you also find the current boost transistors).
Later this was replaced by two cascaded first order sections with a PNP and NPN transistor follower respectively buffering the first and second section for 2nd order filters with no lowpass on the wideband driver and pure inverting mode chipamps following a "Phase-splitter".
This speaker did remarkably well, for it's time, and I suspect it would still do well today.
So, if you build for yourself only, consider going fully active.
Ciao T
Sorry to have gotten off track in the slagging match.
I would suggest bridge/parallel for that, probably 6pcs LM3886 or 3pcs LM4780.
With a big enough powersupply and heatsink they will drive anything in terms of voltage/current capability, excluding original Apogee Scintilla.
This means kits or Semi-Kits.
This is not a bad choice.
HOWEVER, if you already biamp, why not go fully active.
If using (for arguments sake) a modified DCX2496 Digital Crossover you could interface directly from the DAC Chips to the Power Amplifiers, using bridged gainclones on all channels.
Match the Chipamp's gain to get clipping when the DAC clips. Maybe add a volume control (could be Dallas/Maxim DS1666 Chip based - this tracks well and sounds good and is easily remote controlled) and you have an excellent system.
Use LM3875 (effectively Bridged - BTL) at lower voltage and with small value PSU Capacitors for the MF & HF Driver, and parallel LM3886 (again effectively Bridged - BTL) at higher voltage with a big Snubberd PSU for the bass.
This would allow a very nice floorstanding 3-Way speaker with digital X-Over and chip amps that I would suspect could show many conventional "super high end" High End systems a thing or two on all fronts.
Class A bias will help some especially on getting smoother treble. I do not find gainclones to be lacking detail, may be your volume control, preamp of some part choice in your current setup.
Well, I am not sure about that. Mains transformers can be shielded quite effectively. Placing the supply externally means you need a cable between amp and supply and in order to make the separation meaningful you need a fair bit of distance. Now you add extra resistance of the cables and connectors in the supply and you have to put bigger capacitors locally at the chip.
Equally, an external preamplifier will only mean extra signal degradation due to extra cables and connectors.
I feel the "best" is always dependent on the context. I have yet to find a single "universally good" component that really, genuinely improves things reliably each and every time in any context.
I have at home a "Gainclone" that I feel sounds very good and is a reasonable competition for my Tube Amp sonically speaking. It has a little more power, but even with that there is not a lot between the two Amplifiers, especially once I compensate the gainclone for having a lower output impedance than the tube amp.
Yet funnily both Amplifiers use VERY different parts choices.
The tube Amplifier is full of Metal Film and wirewound (non inductive) resistors, has silver foil coupling capacitors and film type power supply capacitors, silver wire (all comparably "bright" sounding component choices).
The Tube Amplifier is push-pull class A with only local feedback around the 6550/KT88 output stage, low impedance concertina phasesplitter with 5687 and ECC83/12AX7 single ended gainstage.
Here I use an external passive controller (Noble Pot, silver switch, silver RCA jacks), also all silver wired and silver interconnects are used.
By Comparison the Gainclone uses copper CPU Coolers for heatsinks with "plastic tab" LM3875 and is full of Elna Silmic Capacitors in the Powersupply, AB Carbon Composite resistors for the signal circuit and copper wire.
I used 2 X 3,300uF/50V per channel with seperate rectifiers (but a single 25V-0V-25V secondary transformer) because a) I had them and b) they sit neatly between the "low capacitance" concept of the original gaincard and the normal "Big Cap" approaches, also sonically. Wiring is all copper, potentiometer is a Panasonic carbon/plastic motorised type.
FWIW, I put this into a broken and unrepairable Audio Innovation Alto Amplifier Chassis (yes, the chrome version), making the Amp look as stunning as it sounds.
Sonically either Amp is excellent on my floorstanders (10" Woofer, 5" Wideband & circular magnetostat/ribbon tweeter, all first order crossovers at 350Hz and around 12KHz, 90dB/2.83V/1m, around 25Hz LF extension in room.
I would avoid silver with solid state gear in general and gainclones specifically.
Good choices.
Yes, I like to use the same principles as much as possible.
I would still consider going fully active. I would, where it not for the fact that I am involved in developing commercial high end gear, which means I need a home system that is fairly "compatible" to allow me to evaluate new products and/or perform long term testing.
My frist work with Chipamp's was actually an active speaker I build in the mid 1980's, it included the TDA2030 in bridged and current boosted mode for two 8" Woofers (later with motional feedback a'la Backes & Mueller), a bridged pair of TDA2030 for the 5" Wideband Driver and initially a single TDA2030 for thr plastic dome tweeter, later replaced by a piezo tweeter (these are better than their reputation if used right) driven by a bridged pair of TDA2030.
Crossover was initially 3rd order sallen key filters looped around the TDA2030 as in the SGS Thomson Application Note for the TDA2030 (where you also find the current boost transistors).
Later this was replaced by two cascaded first order sections with a PNP and NPN transistor follower respectively buffering the first and second section for 2nd order filters with no lowpass on the wideband driver and pure inverting mode chipamps following a "Phase-splitter".
This speaker did remarkably well, for it's time, and I suspect it would still do well today.
So, if you build for yourself only, consider going fully active.
Ciao T
Dear Thorsten,
Sorry everyone for going off topic, but is to interesting to let go. If you wish we can open a new topic about this. Do you have any information of above and/or schematics? That would be really interesting since I didn't see DIY MFB with chipamps yet.
Thank you.
With kind regards,
Bas
Hi,
First, this Speaker was build behind the iron curtain on the wrong side of the Berlin Wall and when I left in some haste and under cover of doing something in early '89 it, documentation and many other interesting pieces of personal, family and of course my audio history where left behind and never recovered...
What I remember on the MFB thing is that over years from around 86 I was messing with bridge schemes to sense the drivers back EMF (what rythmik now does), but I found that when the bridged was correctly set up for best results the heating of the driver coil and the inductance change as the coil travelled caused the bridge to unbalance and for smoke coming out of voice coils, things to go bang and all that stuff. I had a fair few woofers reconed at the time.
What I eventually implemented successfully was the classic German "electret microphone glued to the cone" scheme covered here a number of times. Using a chipamp was really incidental. The origin for me was a mid 80's publication of the west german "Funkschau" magazine. My own publication for the east german DIY electronics mag was rejected because I was considered politically unreliable and referenced western sources..
Well, much water under the bridges across Elbe, Oder and Spree since those years.
Ciao T
First, this Speaker was build behind the iron curtain on the wrong side of the Berlin Wall and when I left in some haste and under cover of doing something in early '89 it, documentation and many other interesting pieces of personal, family and of course my audio history where left behind and never recovered...
What I remember on the MFB thing is that over years from around 86 I was messing with bridge schemes to sense the drivers back EMF (what rythmik now does), but I found that when the bridged was correctly set up for best results the heating of the driver coil and the inductance change as the coil travelled caused the bridge to unbalance and for smoke coming out of voice coils, things to go bang and all that stuff. I had a fair few woofers reconed at the time.
What I eventually implemented successfully was the classic German "electret microphone glued to the cone" scheme covered here a number of times. Using a chipamp was really incidental. The origin for me was a mid 80's publication of the west german "Funkschau" magazine. My own publication for the east german DIY electronics mag was rejected because I was considered politically unreliable and referenced western sources..
Well, much water under the bridges across Elbe, Oder and Spree since those years.
Ciao T
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