The feature that I am after is aimed at PA usage, and having a switch to turn it off makes the amp double purposed, so there is no interference from that circuitry when switched off for non PA use.
It would actually not be too complex to sense overheating from the heatsinks and use that info to also lower the drive level. In that case it would not be used to prevent clipping, but rather prevent over-driving into over-heating.
I'm not good enough yet at spice, but someone could simulate this and make it work.
There would be one opamp as a buffer from the input to the amp's drive input, a diode bridge with a few resistors and caps, a "vactrol" (LED/LDR opto-coupler). Wanting a balanced input, ahead of the follower buffer, there could be a balanced line receiver.
To simulate this properly, a spice model for such a vactrol would need to be found. Maybe that can be virtually done, if an exact model can't be found.
I see carver is using the NJM072S as the buffer follower, but it's basically the same thing as the TL072, and there are even better types available now.
They use SSM2141 as their line receivers. Those aren't too bad, probably much similar to texas' INA types.
It would actually not be too complex to sense overheating from the heatsinks and use that info to also lower the drive level. In that case it would not be used to prevent clipping, but rather prevent over-driving into over-heating.
I'm not good enough yet at spice, but someone could simulate this and make it work.
There would be one opamp as a buffer from the input to the amp's drive input, a diode bridge with a few resistors and caps, a "vactrol" (LED/LDR opto-coupler). Wanting a balanced input, ahead of the follower buffer, there could be a balanced line receiver.
To simulate this properly, a spice model for such a vactrol would need to be found. Maybe that can be virtually done, if an exact model can't be found.
I see carver is using the NJM072S as the buffer follower, but it's basically the same thing as the TL072, and there are even better types available now.
They use SSM2141 as their line receivers. Those aren't too bad, probably much similar to texas' INA types.
More expensive, more cabling, more devices, and they would have to be calibrated for the amps, or they are useless.
A few extra opamps and discreet parts at the amp's input can do that, for a lot less and no extra cabling, calibration and external device to buy.
And besides, where would the diy fun be in buying a device already made? 😀
Hi Nico,
Kindly read the reviews here
http://www.diyaudio.com/forums/solid-state/198500-symef-amplifier-108.html#post3808450
http://www.diyaudio.com/forums/solid-state/219354-1diffqc-amplifier-17.html#post3778255
Yes it is time you built yourself one, the wait has been rather long Nico 🙂 . There is no need to stay out in the cold any more 😉 Its time you felt the warm of SYMEF HAL: PauloPT - SYMEF.
kind regards,
Harrison.
Hi Spookydd,
Kindly read the reviews here
http://www.diyaudio.com/forums/solid-state/198500-symef-amplifier-108.html#post3808450
http://www.diyaudio.com/forums/solid-state/219354-1diffqc-amplifier-17.html#post3778255
Yes I agree that the white elephant must be investigated, when can we expect to hear a review on your build 😀
kind regards,
Harrison.
On a more serious note, the whole audio system chain must be modular. There is what is expected of the amplifier and there is what is expected of the line equipment and there is what is expected of the pickup equipment.
1. It is expected that the amplifier will be well behaved when handling the specified load.
2. It is expected that the line equipment will not overdrive the amplifier
3. It is expected that the source equipment will not overdrive the line equipment
By the time music flows through the speakers a lot of cooking has taken place. The most problematic source and pickups are guitars, drums and microphones, for these a compressor is a must.
You do not want your audience going deaf just because someone screamed into the mike or kicked the drums too hard. Set your compressor to be as pessimistic as possible above a certain signal level. When mixing also balance the signal levels.
kind regards,
Harrison.
1. It is expected that the amplifier will be well behaved when handling the specified load.
2. It is expected that the line equipment will not overdrive the amplifier
3. It is expected that the source equipment will not overdrive the line equipment
By the time music flows through the speakers a lot of cooking has taken place. The most problematic source and pickups are guitars, drums and microphones, for these a compressor is a must.
You do not want your audience going deaf just because someone screamed into the mike or kicked the drums too hard. Set your compressor to be as pessimistic as possible above a certain signal level. When mixing also balance the signal levels.
kind regards,
Harrison.
I will review all this stuff, the more info we have, the better the choices we can make.
I am working on several things at the same time, but that is a feature that I want in my amps such as the leach that I'm working on, and others...
I want the feature switchable, so it must be on during PA use, and off the rest of the time.
I think I will seriously draw from what carver has been doing, but likely with some differences. I will review all the various methods used and mke a choice that satisfies me.
This would not be a build on its own, as it's meant to be an integral part of something larger, but I will make this modular enough so it can easily be applied to something else. It won't be electronically entangled in other circuitry, so it can be viewed as as stand alone feature to include anywhere.
What needs to be understood is that it's never been meant to be a way to make an amp one that doesn't clip, as that is more than a white elephant, it just doesn't exist. What it is meant to be, is a way to make sure the amp is not pushed into clipping, or in a very limited way. That's done all the time and fairly well, by the likes of carver, crown, etc...
No need to reinvent the wheel, but since there aren't any good already designed stand alone circuits available out there for diyers, that I know of, then one needs to be designed.
All I have in mind is something as simple as possible, that is ahead of the amp but not "entangled" with it. By that, I mean that is doesn't get a feedback from the amp itself, which is one of the major reasons that I think can cause that pumping effect.
Hi Nico,
Kindly read the reviews here
http://www.diyaudio.com/forums/solid-state/198500-symef-amplifier-108.html#post3808450
http://www.diyaudio.com/forums/solid-state/219354-1diffqc-amplifier-17.html#post3778255
Yes it is time you built yourself one, the wait has been rather long Nico. There is no need to stay out in the cold any more
Its time you felt the warm of SYMEF HAL: PauloPT - SYMEF.
kind regards,
Harrison.
Dear Harrison,
Fortunately I never needed PCBs because my company makes me boards in a few hours when asked.
I did build one channel only almost two years ago but unfortunately it did not make the grade and ended in the junk pile.
Last year what remained of the assembly, spare PCBs and bag of components were given to a friend's son to be used in a school project.
I was later told by his father that he got good marks for his project while his buddies thought it was very cool and they used it at a class party.
.Those who wrote reviews regarding SYMEF may be honest compared to what they previously owned or read about.
Maybe it was purely pleasing you for giving them a free PCB.
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