Steve Dunlap said:
20Hz, 100Hz where does it stop switching? This is a can of worms again. Andy's comment involving the behavior of very weakly biased darlington transistors has little to do with the unusual bias arrangement and offered explanations of what is going on. Steve I'm sorry you are ill, I can't carry on an enthusiastic technical disscussion without feeling bad about that. This stuff is not all that important in the end.
scott wurcer said:
The distortion does go up some at the lower audio frequencies. You and Andy may have explained the cause of that. I really wish I could get back on the bench and test this myself. I'm not even sure if my equipment is still working correctly after not being turned on for two years. I just discovered my scope probe was bad when c2cthomas tried to calibrate it on Tuesday.
At least, into simulator (multisim 10) you inject 1 Hertz tone
the output measuring full power swing and monitoring current into the output transistors you perceive they never touch zero....always conducting.
This seems, at least to me, the output never switches off.
Sinus tone, with this frequency, takes time to the calculator to process all that stuff, maybe the current display i'm reading is ramdomic, but even this way i have tried several times...and i had never zero current....current was always crossing the colector to emitter junction into the power transistors, even when sinus signal approaches to zero... always current flowing....current seems to me is beeing modulated (goes higher and lower), the current, the bias current, and the off set measured with ground reference?....well..those ones variates....it is a zero reference "floating" system...... when bias aproaches to cutt into the output transistors the current is increased or decreased not to allow the output to cut, to go off, avoiding to stop conduction this way.... very interesting..i cannot understand exaclty how this works, but i can see the effects very clear into the simulator and also listening...people instantaneously say, while listening....
- "What a sound!"
A very good amplifier... superior without any doubt comparing to conventional designs..
Maybe i am too much simple, or too much ignorant..but really...not having zero current means the stage never switches off..because this means (when switches from "on" to "off") zero current will happens..in some moment no current will flow... exaclty during the period of time the transistor is cutted, when it is off the output transistors does not conduct any current...and we have always current there!
If other ones are switching...well... i could not find that and i really have not search for that...the output does not switch or i will have to complain to the Multisim 10 factory...my simulator will defective, bad or drunk.
Well.... as i use to say...if electrons spin clockwise or counterclockwise or if they have orange paint's belt or brown..if they are blue or not blue...those things are not very important to me...if someone has worries into such kind of details.... well...may be someone that will not have peace in his mind....nobody could see an electron..we know the effects, we know how to work with them..we know they exist..but we cannot see them.
regards,
Carlos
the output measuring full power swing and monitoring current into the output transistors you perceive they never touch zero....always conducting.
This seems, at least to me, the output never switches off.
Sinus tone, with this frequency, takes time to the calculator to process all that stuff, maybe the current display i'm reading is ramdomic, but even this way i have tried several times...and i had never zero current....current was always crossing the colector to emitter junction into the power transistors, even when sinus signal approaches to zero... always current flowing....current seems to me is beeing modulated (goes higher and lower), the current, the bias current, and the off set measured with ground reference?....well..those ones variates....it is a zero reference "floating" system...... when bias aproaches to cutt into the output transistors the current is increased or decreased not to allow the output to cut, to go off, avoiding to stop conduction this way.... very interesting..i cannot understand exaclty how this works, but i can see the effects very clear into the simulator and also listening...people instantaneously say, while listening....
- "What a sound!"
A very good amplifier... superior without any doubt comparing to conventional designs..
Maybe i am too much simple, or too much ignorant..but really...not having zero current means the stage never switches off..because this means (when switches from "on" to "off") zero current will happens..in some moment no current will flow... exaclty during the period of time the transistor is cutted, when it is off the output transistors does not conduct any current...and we have always current there!
If other ones are switching...well... i could not find that and i really have not search for that...the output does not switch or i will have to complain to the Multisim 10 factory...my simulator will defective, bad or drunk.
Well.... as i use to say...if electrons spin clockwise or counterclockwise or if they have orange paint's belt or brown..if they are blue or not blue...those things are not very important to me...if someone has worries into such kind of details.... well...may be someone that will not have peace in his mind....nobody could see an electron..we know the effects, we know how to work with them..we know they exist..but we cannot see them.
regards,
Carlos
Attachments
I know this is asking a LOT since few have completed assembly of these amps (exception is Carlos, Thomas and I think it was Phil) but I was hoping someone may have tried component substitutions where appropriate.
The Mauro My Ref. Rev_C has been tested extensively by Dario and he posted a list of worth while changes..
Has anyone tried it here?
Dario's suggestions for the Rev_C:
http://www.diyaudio.com/forums/showthread.php?postid=1818066#post1818066
I ask because I will be assembling mine shortly and would like to make the changes as I assemble it instead of having to disassemble and redo.
The Mauro My Ref. Rev_C has been tested extensively by Dario and he posted a list of worth while changes..
Has anyone tried it here?
Dario's suggestions for the Rev_C:
http://www.diyaudio.com/forums/showthread.php?postid=1818066#post1818066
I ask because I will be assembling mine shortly and would like to make the changes as I assemble it instead of having to disassemble and redo.
Hi Phil-
I have Steve's PCB's and will be building the 50 watt four output transistor version.
It will be the textbook version he originally designed, I am just looking to see if there are "suggested" component substitutions to get the most out of it.
I do not care to do circuit variations unless a problem was discovered with the original PCB's <which I do NOT think is the case>.
Thank you for checking into it.
Again, I am just looking for the critical individual parts that could be "upgraded" and would make the amp sound better. I would like to build it once and have it sound as good as possible.
I have Steve's PCB's and will be building the 50 watt four output transistor version.
It will be the textbook version he originally designed, I am just looking to see if there are "suggested" component substitutions to get the most out of it.
I do not care to do circuit variations unless a problem was discovered with the original PCB's <which I do NOT think is the case>.
Thank you for checking into it.
Again, I am just looking for the critical individual parts that could be "upgraded" and would make the amp sound better. I would like to build it once and have it sound as good as possible.
Hi Troy, I don't know if they improve the sound any but they made the bias and offset adjustments easier than using the single turn pots.
I got 'em from Mouser
652-3299Y-1-102LF
Bourns Multi-Turn Tr
1Kohms Standoffs
652-3299Y-1-103LF
Bourns Multi-Turn Tr
10Kohms Standoffs
BTW - using Steve's boards and standard parts my 50W Krills fired right up - a little trim up on the bias and everything was good to go. The offset adjustment didn't do much except clean up a itty bit of oscillation and I would up with them set to max.
I got 'em from Mouser
652-3299Y-1-102LF
Bourns Multi-Turn Tr
1Kohms Standoffs
652-3299Y-1-103LF
Bourns Multi-Turn Tr
10Kohms Standoffs
BTW - using Steve's boards and standard parts my 50W Krills fired right up - a little trim up on the bias and everything was good to go. The offset adjustment didn't do much except clean up a itty bit of oscillation and I would up with them set to max.
Well thank you for your input Thomas.
I will order those for the trimmers.
I certainly DO think it will work right out of the box, but I want to use the best "PRACTICAL" parts where applicable. This amp will be a reference amp for my son for years to come.
As an example, I do like the Dale RN55 / 60 resistors and Wima caps.
I will try to find all the components in the signal path and spend the money there and leave the rest of the components standard as in the BOM.
I will order those for the trimmers.
I certainly DO think it will work right out of the box, but I want to use the best "PRACTICAL" parts where applicable. This amp will be a reference amp for my son for years to come.
As an example, I do like the Dale RN55 / 60 resistors and Wima caps.
I will try to find all the components in the signal path and spend the money there and leave the rest of the components standard as in the BOM.
Hi Troy,
If you use the last schematic I posted you will be hard pressed to improve on the transistors. I feel the Toshiba are better, but many people can't get them. I switched to the Fairchild because they seem to be easier to get. Also, many people are afraid of the Toshiba transistors because of counterfeits. If you order from Mouser or Digi-Key that should not be a problem.
Some people prefer other brands of capacitors instead of what I have in the BOM. Use a brand you like better or trust more if you want to. You should check the parts listed in the BOM for cap lead spacing. For most caps, I list the highest capacitance that will fit the pad spacing on the boards. Other brands or types may have different lead spacing for the given values.
For C1 and C7 use the best cap you can in the values shown. C1 in the BOM is a polypropylene from Digi-Key that fits properly on the board. C7 has several possible lead spacings giving you more options on cap choice. The four main filter caps are standard spacing snap mounts. Use as large a cap as you are willing to pay for.
R26 and R27 should be a good quality multi turn type. Use the highest number of turns you can find that will mount in the space allotted. There is nothing special about the 1% resistors I show in the BOM. If you go with something else, check to see if it will fit. Not all resistors are the same size.
Remember, this was designed as an affordable amp with good sound. Any commonly applied part upgrade or tweak will work here as well. Those building with their own boards will have much more leeway in parts choice. The parts I have recommended are just that, recommendations. I will not be offended in any way by the choices made by builders.
If you use the last schematic I posted you will be hard pressed to improve on the transistors. I feel the Toshiba are better, but many people can't get them. I switched to the Fairchild because they seem to be easier to get. Also, many people are afraid of the Toshiba transistors because of counterfeits. If you order from Mouser or Digi-Key that should not be a problem.
Some people prefer other brands of capacitors instead of what I have in the BOM. Use a brand you like better or trust more if you want to. You should check the parts listed in the BOM for cap lead spacing. For most caps, I list the highest capacitance that will fit the pad spacing on the boards. Other brands or types may have different lead spacing for the given values.
For C1 and C7 use the best cap you can in the values shown. C1 in the BOM is a polypropylene from Digi-Key that fits properly on the board. C7 has several possible lead spacings giving you more options on cap choice. The four main filter caps are standard spacing snap mounts. Use as large a cap as you are willing to pay for.
R26 and R27 should be a good quality multi turn type. Use the highest number of turns you can find that will mount in the space allotted. There is nothing special about the 1% resistors I show in the BOM. If you go with something else, check to see if it will fit. Not all resistors are the same size.
Remember, this was designed as an affordable amp with good sound. Any commonly applied part upgrade or tweak will work here as well. Those building with their own boards will have much more leeway in parts choice. The parts I have recommended are just that, recommendations. I will not be offended in any way by the choices made by builders.
We'll be interested in see your results Troy. Steve helped me tweak my amps in and when we had bias set to less than 30mV (R26) he said that was close enough.
Using the scope we looked at the outputs to adjust R27 for minimum oscillations - noise etc. R27 did clean things up a bit - but things didn't need much cleaning up! I wish that we had a decent signal source so we could have ran some THD test - maybe next time.
Using the scope we looked at the outputs to adjust R27 for minimum oscillations - noise etc. R27 did clean things up a bit - but things didn't need much cleaning up! I wish that we had a decent signal source so we could have ran some THD test - maybe next time.
The Dale resistors are what I had in mind when I said not all resistors are the same size. Make sure they will fit. I used the Dale resistors in some of my more expensive amps. I liked the sound, however I had several that became noisy after a few days of burn in. I'm not sure what the problem was. That was years ago, so if the problem was the resistors, they may have corrected it by now. It is possible also that I could have damaged some of the resistors while forming the leads, but I never had the problem with any other brand.
c2cthomas said:We'll be interested in see your results Troy. Steve helped me tweak my amps in and when we had bias set to less than 30mV (R26) he said that was close enough.
Using the scope we looked at the outputs to adjust R27 for minimum oscillations - noise etc. R27 did clean things up a bit - but things didn't need much cleaning up! I wish that we had a decent signal source so we could have ran some THD test - maybe next time.
Hi Thomas,
Just to be correct, the 30mV I said was close enough was the DC offset. Less is of course acceptable. It depends on how steady your hand is while making the adjustment. This is where more turns are better.
My distortion analyzer has its own signal generator. I don't know why I didn't think of that while you were here. Maybe next time. It would still be best to do that with the amps in a metal case and soldered input connections.
Hi Troy --
I used the Dale RN60's on Steve's boards and they fit OK although there might have been one place where I needed to do some creative lead bending -- can't remember where though. I also used WIMA polypropylene and metallized polypro's and Nichicon Muse for the electrolytics (except the big filter caps) where I could. I didn't have alot of flexibility because I had to use 100V caps in some places.
You could use UF4007 diodes in the power supply instead of 1N4007s and Vishay 78-FE6D-E3 from Mouser for the 6A diodes. Get enough of the KSC1845s to match them for the input differential pair. Maybe get 20 as they're cheap.
Also, you might want to consider using the option on the board to use a cap to block DC feedback in case your son's preamp has any DC on the output. It's marked as C22 on the board.
I think that's about it......but probably not.
Phil
[added in edit -- Thomas, are you planning on starting a 50W builder's thread? The last few posts might be good there.]
I used the Dale RN60's on Steve's boards and they fit OK although there might have been one place where I needed to do some creative lead bending -- can't remember where though. I also used WIMA polypropylene and metallized polypro's and Nichicon Muse for the electrolytics (except the big filter caps) where I could. I didn't have alot of flexibility because I had to use 100V caps in some places.
You could use UF4007 diodes in the power supply instead of 1N4007s and Vishay 78-FE6D-E3 from Mouser for the 6A diodes. Get enough of the KSC1845s to match them for the input differential pair. Maybe get 20 as they're cheap.
Also, you might want to consider using the option on the board to use a cap to block DC feedback in case your son's preamp has any DC on the output. It's marked as C22 on the board.
I think that's about it......but probably not.
Phil
[added in edit -- Thomas, are you planning on starting a 50W builder's thread? The last few posts might be good there.]
Memory ain't what it used ta be!! 
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