I was never using Zobel network with chip amps, and never found the need for it. I've heard only of few cases when it was really required and some report that the amp actually sounds better without it.
CHG is for chassis ground connection. We put it there just in case somebody wanted to use different point for chassis ground hookup. Since recommended transformer is not CT but double secondaries, I don't know myself if it's better to connect chassis to that point or somwhere on rectifiers boards. I was always using negative output to connect with chassis (from both channel's binding posts to one point on chassis).
We use indeed separate diode bridges for each cap and we made return connections as close to the filter cap GND terminals as possible.
The suggested power connections seem to be indeed much better. It's always good when somebody comes with a fresh outlook. Any comments about creating loop with those connections and possible influence?
CHG is for chassis ground connection. We put it there just in case somebody wanted to use different point for chassis ground hookup. Since recommended transformer is not CT but double secondaries, I don't know myself if it's better to connect chassis to that point or somwhere on rectifiers boards. I was always using negative output to connect with chassis (from both channel's binding posts to one point on chassis).
We use indeed separate diode bridges for each cap and we made return connections as close to the filter cap GND terminals as possible.
The suggested power connections seem to be indeed much better. It's always good when somebody comes with a fresh outlook. Any comments about creating loop with those connections and possible influence?
Peter,
The improvement was quite noticable. This may have to do with my speaker cable (DNM/Reson), which is not shielded at all and quite long (low capacitance, high inductance, perhaps prone to catch up RF), but this is only an assumption.
Anyway, the treble got cleaner and smoother, and I decided to keep it.
Zobel
Best regards,
Oliver
so I may be the first one to report an improvement by using a Zobel; I use a GC based on Brian's 3875 kit. Initially I let it run in for about a week (without a Zobel) and then began serious listening for about a week, and after that fitted the Zobel.
The improvement was quite noticable. This may have to do with my speaker cable (DNM/Reson), which is not shielded at all and quite long (low capacitance, high inductance, perhaps prone to catch up RF), but this is only an assumption.
Anyway, the treble got cleaner and smoother, and I decided to keep it.
Zobel
Best regards,
Oliver
The Zobel Prize
There are no loop problems from the additional power traces.
Zobles:
I would think the guys from National know what they're doing. You cannot tell what speakers and cables that will be used with this. It is part of the high frequency compensation for the amp. Telling people that you don't need them and leaving them out of the design is irresponsible. Don't stuff the parts if you think you don't need them, but why sell amps or PCB boards that are not the original design, just on a personal whim without a clue for the engineering reason for their inclusion ....... oh I forgot, you're an experienced amplifier designer. I guess the inexperienced builders can tack the parts on top of the board if they are not in the PCB layout. :
Peter Daniel said:
There are no loop problems from the additional power traces.
Zobles:
I would think the guys from National know what they're doing. You cannot tell what speakers and cables that will be used with this. It is part of the high frequency compensation for the amp. Telling people that you don't need them and leaving them out of the design is irresponsible. Don't stuff the parts if you think you don't need them, but why sell amps or PCB boards that are not the original design, just on a personal whim without a clue for the engineering reason for their inclusion ....... oh I forgot, you're an experienced amplifier designer. I guess the inexperienced builders can tack the parts on top of the board if they are not in the PCB layout. :
No you're not.
No...... you're second guessing the guys at National and other competent amp designers know what a Zoble network does it put it in an amplifier for a reason.
What is a fast speaker cable? In terms of inductance, capacitance, and
dieletric constant of the insulation. What difference does being thick make to the speed?
Jamh said:
No...... you're second guessing the guys at National and other competent amp designers know what a Zoble network does it put it in an amplifier for a reason.
What is a fast speaker cable? In terms of inductance, capacitance, and
dieletric constant of the insulation. What difference does being thick make to the speed?
I'm not an experienced designer, but so far I didn't experience any problems regarding that. The same for at least 100 people who already built the kit.
Just out of curiosity, I installed Zobel on one of my amps right now, and the difference in sound is quite substantial. I can't say it's for worse, but it's definitely different. It seems like highs got cleaned out and are smoother, yet I can also detect coloration from a cap and resistor. I would have to listen more to decide what's better. But definitely worth investigating.
But those size resistor and cap might not be easy to place on the current board layout. I don't see any problem with mounting them directly to binding posts.
BTW, AudioZone offers a series resistor/capacitor jumper to those who have problems with matching speaker cables to the amp. So far there was only one such problem and Zobel network didn't help. Changing speaker cables eliminated that problem though.
Just out of curiosity, I installed Zobel on one of my amps right now, and the difference in sound is quite substantial. I can't say it's for worse, but it's definitely different. It seems like highs got cleaned out and are smoother, yet I can also detect coloration from a cap and resistor. I would have to listen more to decide what's better. But definitely worth investigating.
But those size resistor and cap might not be easy to place on the current board layout. I don't see any problem with mounting them directly to binding posts.
BTW, AudioZone offers a series resistor/capacitor jumper to those who have problems with matching speaker cables to the amp. So far there was only one such problem and Zobel network didn't help. Changing speaker cables eliminated that problem though.
Re: The Zobel Prize
I was under the assumption that the zobel could just attached to the binding post if there are problems with stability. This is what I have seen done on other designs, including the first amplifier I built a couple of years ago. I am clearly not an experienced designer of any sort, and am willing to consider any advice on this matter.
Also, what do you think about not having a feedback capacitor. On the National app note for the LM3875, it was marked optional, but it wasn't marked optional for the LM4780. I tried the LM3875 with, and without this capacitor, and didn't notice any difference on the scope. It is necessary to have this capacitor, with it providing unity gain at DC, and and also create a highpass filter with the inverting input resistor?
--
Brian
Fred Dieckmann said:
Zobles:
I would think the guys from National know what they're doing. You cannot tell what speakers and cables that will be used with this. It is part of the high frequency compensation for the amp. Telling people that you don't need them and leaving them out of the design is irresponsible. Don't stuff the parts if you think you don't need them, but why sell amps or PCB boards that are not the original design, just on a personal whim without a clue for the engineering reason for their inclusion ....... oh I forgot, you're an experienced amplifier designer. I guess the inexperienced builders can tack the parts on top of the board if they are not in the PCB layout. :
I was under the assumption that the zobel could just attached to the binding post if there are problems with stability. This is what I have seen done on other designs, including the first amplifier I built a couple of years ago. I am clearly not an experienced designer of any sort, and am willing to consider any advice on this matter.
Also, what do you think about not having a feedback capacitor. On the National app note for the LM3875, it was marked optional, but it wasn't marked optional for the LM4780. I tried the LM3875 with, and without this capacitor, and didn't notice any difference on the scope. It is necessary to have this capacitor, with it providing unity gain at DC, and and also create a highpass filter with the inverting input resistor?
--
Brian
I do..........
"I don't see any problem with mounting them to binding posts."
They are on the wrong side of the 0.1 ohm resistors and you are adding a lot of lead inductance in series with something that needs to be resisitive at high frequencies where the capacitor has become a very low impedance.. I would use a 1 watt metal film and a good 160V to 250V metalized polypropylene. Those don't take up much PCB and you could stand the parts on end and soldered the airbourne leads together if space is that tight.
"I don't see any problem with mounting them to binding posts."
They are on the wrong side of the 0.1 ohm resistors and you are adding a lot of lead inductance in series with something that needs to be resisitive at high frequencies where the capacitor has become a very low impedance.. I would use a 1 watt metal film and a good 160V to 250V metalized polypropylene. Those don't take up much PCB and you could stand the parts on end and soldered the airbourne leads together if space is that tight.
OK, I tried Zobel in my reference system and I have no doubts it degrades the sound. THe soundstage collapsed and the liveliness is gone, although highs "might" seem to be smoother.
Also, in this system the cables are probably an easier load, as in the first one I was using 1" copper foil, while here a more conventional cable is used, from DH Labs (Q10 if I remeber correctly).
I'd say, try Zobel for yourself, if it works for you, but don't assume it's really required because National's designers are using it
Also, in this system the cables are probably an easier load, as in the first one I was using 1" copper foil, while here a more conventional cable is used, from DH Labs (Q10 if I remeber correctly).
I'd say, try Zobel for yourself, if it works for you, but don't assume it's really required because National's designers are using it
Re: No you're not.
Thick as in gauge, and low inductance. My experience comes from trying and using my ears, as opposed to "accepting" competent engineers at National. You complain about the extra solder lead but don't wince at adding 2 extra components. I don't mean to say that Zobel networks don't have their place. If you find they help, by all means, go for it. In my system, the amps sound better without it. For what is worth, I use Jordan full range drivers with a 22 gauge 5N silver wire.
Fred Dieckmann said:
No...... you're second guessing the guys at National and other competent amp designers know what a Zoble network does it put it in an amplifier for a reason.
What is a fast speaker cable? In terms of inductance, capacitance, and
dieletric constant of the insulation. What difference does being thick make to the speed?
Thick as in gauge, and low inductance. My experience comes from trying and using my ears, as opposed to "accepting" competent engineers at National. You complain about the extra solder lead but don't wince at adding 2 extra components. I don't mean to say that Zobel networks don't have their place. If you find they help, by all means, go for it. In my system, the amps sound better without it. For what is worth, I use Jordan full range drivers with a 22 gauge 5N silver wire.
My experience comes from trying and using my ears*
"You complain about the extra solder lead but don't wince at adding 2 extra components."
They are not extra parts.......... they are part of the design.
* I hear that a lot from guys who know nothing about design. Unfortunately it's about issues where design choices make a difference. The Zobels belong in the design. One of the actual designers of amps based around these ICs has told me about all the problems people had have thinking that they can just leave the network out. I guess the next guy who trys this and has the amp oscillate can call you to tell him how to fix it without using the Zobels that are part of design.
'I'd say, try Zobel for yourself, if it works for you, but don't assume it's really required because National's designers are using it"
Just assume PD knows more than the guys that designed the IC. Here's someone else to call when your amp oscillates.........
"You complain about the extra solder lead but don't wince at adding 2 extra components."
They are not extra parts.......... they are part of the design.
* I hear that a lot from guys who know nothing about design. Unfortunately it's about issues where design choices make a difference. The Zobels belong in the design. One of the actual designers of amps based around these ICs has told me about all the problems people had have thinking that they can just leave the network out. I guess the next guy who trys this and has the amp oscillate can call you to tell him how to fix it without using the Zobels that are part of design.
'I'd say, try Zobel for yourself, if it works for you, but don't assume it's really required because National's designers are using it"
Just assume PD knows more than the guys that designed the IC. Here's someone else to call when your amp oscillates.........
Re: My experience comes from trying and using my ears*
That is interesting. I am an actual designer of amps based around those chips as well, and I can't tell you about the problems people have with amps oscillating.
Could it be that I'm using slightly different parts or different layout? Or maybe my grounding techniques are simply better? Or maybe it's just a pure lack, that a not experienced designer for some reason experiences once in a while?
It's not like I've built one or two amps. Those amps have been sold in quite substantial number, and I can assure you that there was no problem because Zobel was missing. We had the amps at the shows, we had them sent for reviews, the kits were built using the basic design, and I don't hear people have problems.
So what is your problem?
Fred Dieckmann said:
That is interesting. I am an actual designer of amps based around those chips as well, and I can't tell you about the problems people have with amps oscillating.
Could it be that I'm using slightly different parts or different layout? Or maybe my grounding techniques are simply better? Or maybe it's just a pure lack, that a not experienced designer for some reason experiences once in a while?
It's not like I've built one or two amps. Those amps have been sold in quite substantial number, and I can assure you that there was no problem because Zobel was missing. We had the amps at the shows, we had them sent for reviews, the kits were built using the basic design, and I don't hear people have problems.
So what is your problem?
Why it all this starts to remind the Aleph X thread, when Grey presented his schematic? You also said it won't work. Hundreds of people built it and it works fine. I'm really desappointed with your expertise.
And I don't care what National's designers suggest to use with the amp. I'm building amps my way and it shouldn't be your concern what my actual choices are. Buy it and try it out. Then talk about it.
And I don't care what National's designers suggest to use with the amp. I'm building amps my way and it shouldn't be your concern what my actual choices are. Buy it and try it out. Then talk about it.
National may recommend the Zobel to cusion the specifications of the op-amp. There have been and will always be designs that do not follow a manufactures reccomendations. This does not imply a poor design or an instable one either. It only requires care that you do not over drive the chip beyond its physical limits. I know a famous designer that did design his circuit outside the mfg specs, and even worked with the mfg to ensure it was a safe design. 20 years later my purchased model of this commercially produced amp is still going strong. (Wardsweb may know who I mean) There is an incredible amount of gamesmanship when it comes to a mfg writing a spec sheet.
Peter - keep on going!
Regards, David
Peter - keep on going!
Regards, David
Just your customers concern.........
There are people who have been building and selling Chip amps a lot longer than you have that have told me repetedly about the problems people run into by leaving the Zobel out of the design. If you actually look at a few schematics you will see that many amps use Zobel networks. I have buit chip amps. The LM1875s I built sounded better with a Zobel. I can only offer advice based on listening and sound engineering choices. I have a hard time believing you have sold hundreds of amps by the way. What you do with your own stuff is one thing, but offering design advice that will help insure the people have stable amps with many types of speaker loads and cables since to be good advice to me. But your the amp designer..... I guess you know best as usual. What do I know I am just a lowly EE who actually listens,measures, and advocates consistent performance and reliability . And, BTW I have been building and designing audio for about 30 years and was using parts that you seem to think are new discoveries, ten years ago. But then again I am not part of the Chip amp cult were building a circuit from the ap notes (and not even doing that right sometimes) in the data sheet makes one an amp designer.
There are people who have been building and selling Chip amps a lot longer than you have that have told me repetedly about the problems people run into by leaving the Zobel out of the design. If you actually look at a few schematics you will see that many amps use Zobel networks. I have buit chip amps. The LM1875s I built sounded better with a Zobel. I can only offer advice based on listening and sound engineering choices. I have a hard time believing you have sold hundreds of amps by the way. What you do with your own stuff is one thing, but offering design advice that will help insure the people have stable amps with many types of speaker loads and cables since to be good advice to me. But your the amp designer..... I guess you know best as usual. What do I know I am just a lowly EE who actually listens,measures, and advocates consistent performance and reliability . And, BTW I have been building and designing audio for about 30 years and was using parts that you seem to think are new discoveries, ten years ago. But then again I am not part of the Chip amp cult were building a circuit from the ap notes (and not even doing that right sometimes) in the data sheet makes one an amp designer.
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