Re: Transistors
Does that sound like a reasonable approach? ...Or at least is it a reasonable compromise for an impatient fellow like me?
Given the above, I'm not going to make any trannie changes today - today I'll just be working on getting the heat down, allowing me to test changes to the resistance and voltage in the output stage. Assuming that goes well, tomorrow I hope to fix the trannie matching in the one amp that still isn't well matched, and look at the current mirror (higher Hfe, and trimpot adjustment to match voltage).
Thanks - that's what I figured.sandyK said:
What I've been doing so far is about 3-4 hours of listening each day, and one single change in between. 3-4 hours is enough for a concerto, a symphony, a jazz instrumental album, a jazz vocal album, and a mix of other stuff. 60% of this I keep constant each time (partly because it's stuff I really like, and partly because I find it easy to pick up differences this way), and 40% I vary (partly to keep things interesting, and partly in an ongoing quest to find what music best shows differences).
Does that sound like a reasonable approach? ...Or at least is it a reasonable compromise for an impatient fellow like me?
Given the above, I'm not going to make any trannie changes today - today I'll just be working on getting the heat down, allowing me to test changes to the resistance and voltage in the output stage. Assuming that goes well, tomorrow I hope to fix the trannie matching in the one amp that still isn't well matched, and look at the current mirror (higher Hfe, and trimpot adjustment to match voltage).
to stay with the original design the Vre should be kept the same even though you chose to change the Re value.jp_howard said:
However, the increased Vre you have adopted possibly performs better than what the designer chose. I can't understand why he chose such a low Vre, unless keeping the heatsink cooler helped compensate for the temperature undercompensation.
If you increase Vre to ~20mV you will dissipate more power at quiescent conditions. This may require a bigger and/or more efficient heatsink.
Roender has found that the NJLs do perform well at 17mVre and 20mVre. Experiment to your ears' satisfaction, but watch temperatures.
Re: Transistors
Pity you missed the group buy of bc546c that went through last year.
The BC546 are probably b grade. It is unusual to find bc546c at retail outlets.jp_howard said:
Pity you missed the group buy of bc546c that went through last year.
Re: Re: Transistors
Andrew
You are correct about the BC546C being hard to find, at least Downunder.
But who needs a group buy for this lot of genuine ON BC550C from RS Australia ? (+10% GST locally)
545-2254
Transistor,bipolar,NPN,BC550C
Available in Production Packaging
Each
1+ $0.10
25+ $0.07
100+ $0.03
Live stock check
Check a different quantity Local Stock Technical data sheets ON Semiconductor BC550CG Small Signal NPN TO92
AndrewT said:
Andrew
You are correct about the BC546C being hard to find, at least Downunder.
But who needs a group buy for this lot of genuine ON BC550C from RS Australia ? (+10% GST locally)
545-2254
Transistor,bipolar,NPN,BC550C
Available in Production Packaging
Each
1+ $0.10
25+ $0.07
100+ $0.03
Live stock check
Check a different quantity Local Stock Technical data sheets ON Semiconductor BC550CG Small Signal NPN TO92
Hi,
the bc550c and bc560c are pretty standard and fairly easy to source.
It's the bc546c and bc556c that are much more difficult to source.
However the 550/560 are specified to a better noise value than the higher voltage 546/556. In other words they should be selected for their particular duty, not swapped willy nilly.
the bc550c and bc560c are pretty standard and fairly easy to source.
It's the bc546c and bc556c that are much more difficult to source.
However the 550/560 are specified to a better noise value than the higher voltage 546/556. In other words they should be selected for their particular duty, not swapped willy nilly.
Re: Re: Transistors
Oh I see - I hadn't noticed the grades. Yes you're quite right, they are b grade.AndrewT said:
Would it be fair to say that in circuits where the higher voltage of the 546 is not required, the 550 is always a better option (at the same grade), since it has a better noise spec? Especially since it's easier to find at C grade?AndrewT said:
If not - can you explain what other issues would need to be considered?
Re: SC ULD2
I also discovered that my little baggie of 15 bc550c's actually contains only 3 bc550c's, the remainder being unrelated parts that jaycar seems to have filed rather poorly. So all in all, not a great step forward in this particular project!
Anyway, that did give me the opportunity to instead try replacing the opamps in my DAC, which it turns out are a big improvement (NES5532AN - muddy; LM4562NA - too bright; OPA2134 - OK but not thrilling; OPA627AU - just perfect!) I was a bit surprised by that result, since in my headphone amp I really liked the LM4562NA.
A good plan, but a poor implementation... I thought I'd try and be clever and do a tap this time in the heatsink, rather than use screws, and all I managed do to was snap the tap bit. I snapped it when it was fully screwed in, and there's nothing to 'grab' to wrench it out. Since I didn't buy a spare tap, or a spare heatsink, that's the end of tonight's attempt! I think I know what I did wrong however (didn't drill a deep enough hole in the first place, then pushed too hard on the tap to try to force it deeper).sandyK said:
I also discovered that my little baggie of 15 bc550c's actually contains only 3 bc550c's, the remainder being unrelated parts that jaycar seems to have filed rather poorly. So all in all, not a great step forward in this particular project!
Anyway, that did give me the opportunity to instead try replacing the opamps in my DAC, which it turns out are a big improvement (NES5532AN - muddy; LM4562NA - too bright; OPA2134 - OK but not thrilling; OPA627AU - just perfect!) I was a bit surprised by that result, since in my headphone amp I really liked the LM4562NA.
if noise is higher prioity than voltage then 550/560 is better than 546/556jp_howard said:
If gain is more important than all else, then c grade is better than a or b grade.
Choose what seems most important from the list of characteristics.
It's not just noise, voltage, gain, there's lots to compare.
Re: Re: SC ULD2
No, don't be silly, that would take too long and I would have forgotten what the previous set ups sounded like.
I just swapped the opamps around and accepted what ever rubbish came across with wanted audio signal.
of course you optimised the power supply and circuit for each opamp when you did this comparison.jp_howard said:
No, don't be silly, that would take too long and I would have forgotten what the previous set ups sounded like.
I just swapped the opamps around and accepted what ever rubbish came across with wanted audio signal.
Sc Uld2
Jeremy
I snapped a tap in one of the heatsinks of my Class A amplifier. Luckily, it was for the top cover.
I have also been caught by not thorougly checking every part I take out of a Jaycar drawer. In that case, it is mainly due to other customers.
Regarding the opamps, many are sensitive to the actual PSU.
As you will have already noticed, the LM4562HA doesn't really shine, unless the power supply has a really low impedance way past the audio band. I also found the LM4562 too fatigueing in the SC Studio Series Stereo preamp.One day I will get around to putting a JLH Power Supply add-on in line there too.
I think another lesson to be learned from experience with the metal can LM4562HA, is that as many people have found, it can get too hot to keep your finger on for more than a few seconds when used with +-15V rails. It needs a TO5 heatsink slipped on, or some other kind of heatsink fitted. All this suggests that the LM4562HA has much better thermal management. In fact it has been shown by an Electronics engineer from Rockhampton in Queensland, that the normal LM4562 audibly benefits from fitting some kind of heatsink too. Other people have remarked that the LM4562HA also has a markedly lower DC offset voltage than the LM4562. Perhaps this is also due to the better thermal management?
The normal LM4562 die must feel like it is wearing an overcoat in summer !
SandyK
Jeremy
I snapped a tap in one of the heatsinks of my Class A amplifier. Luckily, it was for the top cover.
I have also been caught by not thorougly checking every part I take out of a Jaycar drawer. In that case, it is mainly due to other customers.
Regarding the opamps, many are sensitive to the actual PSU.
As you will have already noticed, the LM4562HA doesn't really shine, unless the power supply has a really low impedance way past the audio band. I also found the LM4562 too fatigueing in the SC Studio Series Stereo preamp.One day I will get around to putting a JLH Power Supply add-on in line there too.
I think another lesson to be learned from experience with the metal can LM4562HA, is that as many people have found, it can get too hot to keep your finger on for more than a few seconds when used with +-15V rails. It needs a TO5 heatsink slipped on, or some other kind of heatsink fitted. All this suggests that the LM4562HA has much better thermal management. In fact it has been shown by an Electronics engineer from Rockhampton in Queensland, that the normal LM4562 audibly benefits from fitting some kind of heatsink too. Other people have remarked that the LM4562HA also has a markedly lower DC offset voltage than the LM4562. Perhaps this is also due to the better thermal management?
The normal LM4562 die must feel like it is wearing an overcoat in summer !
SandyK
Re: Re: Re: SC ULD2
I have no idea how to optimise the circuit or power supply for each opamp, nor did I even know this was necessary (although, now that you point it out, I do recall Alex mentioning elsewhere that the lm4562 is fussy about power supplies). However, this does explain why the opamp I decided I liked best came out the winner - it was specifically suggested by the guy that designed the DAC as a suitable upgrade.
I'm not sure what I did to deserve the sarcasm, but since I first picked up a soldering iron only a month ago (and had never even touched a resistor or capacitor at that time!), you can generally assume that if I do something silly, it's due to my inexperience and inability in this field, not due to laziness or apathy.AndrewT said:
I have no idea how to optimise the circuit or power supply for each opamp, nor did I even know this was necessary (although, now that you point it out, I do recall Alex mentioning elsewhere that the lm4562 is fussy about power supplies). However, this does explain why the opamp I decided I liked best came out the winner - it was specifically suggested by the guy that designed the DAC as a suitable upgrade.
Re: Sc Uld2
That's interesting that you found the same thing. Would you expect that a JLH add-on might even be used effectively with a DAC?sandyK said:
Yes, I found that too when adding it to the headphone amp. I only tried the lm4562na in the DAC however, since the additional lm4562ha's that a kind chap is sending me haven't arrived yet.
Jeremy
My heavily modified Musical Fidelity X-DAC V3 was supplied with an
AC plugpack. I have gained huge improvements by supplying it from an external +-15V dual regulated PSU , which incorporates a non current limited JLH PSU add-on. I imagine that there are many other shunt regulators that would give similar results, but most are Voltage specific, whereas the JLH is capable of passing through the full voltage, but much cleaner,very low impedance, and over a wide bandwidth. This also helps with clock stability in the DAC.
SandyK
My heavily modified Musical Fidelity X-DAC V3 was supplied with an
AC plugpack. I have gained huge improvements by supplying it from an external +-15V dual regulated PSU , which incorporates a non current limited JLH PSU add-on. I imagine that there are many other shunt regulators that would give similar results, but most are Voltage specific, whereas the JLH is capable of passing through the full voltage, but much cleaner,very low impedance, and over a wide bandwidth. This also helps with clock stability in the DAC.
SandyK
Re: Re: Re: Re: SC ULD2
Swapping opamps proves nothing about the abilities of each.
It can be interpreted as sarcasm if you wish, but the message is very clear.jp_howard said:
Swapping opamps proves nothing about the abilities of each.
No interpretation is required for the phrase "of course you optimised the power supply and circuit for each opamp when you did this comparison", when you are already aware that I did not. This is clearly sarcastic.AndrewT said:
No-one claimed that it does. I simply documented my experiences this evening, without any claim as to its implication. Thanks to the information provided by you and Alex, I now understand the reason for these observations (i.e. in my headphone amp, which has been carefully tuned for the lm4562ha, this opamp sounds best, whilst in the DAC the opamp it was tuned for sounds best).
Such an outcome is, I'm sure, obvious to the many experts on this forum. However, for me it is quite an eye-opener; I have read some comments on other sites that claim that opamp choice is not important, and that any claims otherwise are purely imaginary - such comments are not backed up by tonight's listening.
Andrew,
Either you are supremely inept at forum communications, or you are using it to promote one upmanship. I know you to be a decent, intelligent fellow, and I cannot understand your behaviour.
Jeremy is an extremely successful businesman, only 35, with a voracious appetite for knowledge and a very sharp mind. He is also very personable, and I do not understand why you goad him with these 'I told you so' situations.
Please lay off, understand that others here are learning as he goes, and that Jeremy and this group of people deserve respect and admiration for making the effort to learn a difficult craft.
Someone recently commented that only a handful of people here actually build and listen to their creations, and that most are rusted on to critical comment and subjective observation. That's cool, but I remind you Jeremy has built something, is working hard to overcome the pitfalls of construction and design, and is rapidly absorbing the technology. I have NEVER seen anyone as adept on a PC as Jeremy, and I assure you he is learning very quickly. I say he should be congratulated, not upbraided for failure to '...optimise the power supply'.
Cheers,
Hugh
Either you are supremely inept at forum communications, or you are using it to promote one upmanship. I know you to be a decent, intelligent fellow, and I cannot understand your behaviour.
Jeremy is an extremely successful businesman, only 35, with a voracious appetite for knowledge and a very sharp mind. He is also very personable, and I do not understand why you goad him with these 'I told you so' situations.
Please lay off, understand that others here are learning as he goes, and that Jeremy and this group of people deserve respect and admiration for making the effort to learn a difficult craft.
Someone recently commented that only a handful of people here actually build and listen to their creations, and that most are rusted on to critical comment and subjective observation. That's cool, but I remind you Jeremy has built something, is working hard to overcome the pitfalls of construction and design, and is rapidly absorbing the technology. I have NEVER seen anyone as adept on a PC as Jeremy, and I assure you he is learning very quickly. I say he should be congratulated, not upbraided for failure to '...optimise the power supply'.
Cheers,
Hugh
I presented a scenario as a conversation.
It seemed to be a humorous way to get the point across.
JP interpreted it as sarcasm.
That's up to him.
AKSA accuses me of "goading". That is simply untrue.
I am not into one upmanship.
I associate with learners all the time.
I am used to hearing how they interpret, understand and reach conclusions and how they respond to both closed and open questioning.
My comments and the way they were presented were not a put down.
I am not going to apologise for alleged misbehaviour.
The message was and remains important.
It got through and riled someone. Possibly because after the fact it now seems so obvious.
I can't help that.
I will do all I can to help the community.
I too come here to learn.
I know I have learned a lot from my fellow Members and I have a lot more to learn.
I recognise that there are many topics that I will never be able to comprehend. That is not your fault. It is my failing.
If I am
It seemed to be a humorous way to get the point across.
JP interpreted it as sarcasm.
That's up to him.
AKSA accuses me of "goading". That is simply untrue.
I am not into one upmanship.
I associate with learners all the time.
I am used to hearing how they interpret, understand and reach conclusions and how they respond to both closed and open questioning.
My comments and the way they were presented were not a put down.
I am not going to apologise for alleged misbehaviour.
The message was and remains important.
It got through and riled someone. Possibly because after the fact it now seems so obvious.
I can't help that.
I will do all I can to help the community.
I too come here to learn.
I know I have learned a lot from my fellow Members and I have a lot more to learn.
I recognise that there are many topics that I will never be able to comprehend. That is not your fault. It is my failing.
If I am
then I have to live with it.
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