Hi p robertson,
many thanks
I will buy parts and start this weekend.
what the size of your heatsink and VA of the transformer?
kp93300
many thanks
I will buy parts and start this weekend.
what the size of your heatsink and VA of the transformer?
kp93300
Hi all I have built the class A doz,and can confirm that it has that JLH full,rounded class A sound. The bass seems punchier and dynamic. Here are some pcb/overlay traces if anyone is interested.Good luck
You can use any jFET input opamp. Check the datasheets.
Yes you can, as long as the dissipation in the output transistors is taken care of.
You are welcome. I achived fine results with P2P connection on veroboard, hope you get the same or better.
btw, I have designed a simple single layer PCB for the direct coupled DOZ. Will post it as soon as it's finished.
Made a start!
Made a start on my DOZ today. Mounted power switch, volume pot, power connector, fuse, transformer, choke and filter capacitors. Now to make the main circuit
Class A Audio Amplifier - Power supply completed. by John - Sparkie ツ, on Flickr
Made a start on my DOZ today. Mounted power switch, volume pot, power connector, fuse, transformer, choke and filter capacitors. Now to make the main circuit
Class A Audio Amplifier - Power supply completed. by John - Sparkie ツ, on Flickr
Hello Shaan,
Thanks for the circuit diagrams, photos and the very informative discussion.
I am curious: in an earlier post in 2009 (# 25 in the thread "DOZ-Death of Zen amp from Rod Elliot") you were very critical of DOZ. Did you make any modifications to Rod's original circuit this time, to make it perform better? Or am I missing something here?
btw I am glad to know that 2N3055s are good enough - and even better - for this amp.
Thanks,
Reji
Thanks for the circuit diagrams, photos and the very informative discussion.
I am curious: in an earlier post in 2009 (# 25 in the thread "DOZ-Death of Zen amp from Rod Elliot") you were very critical of DOZ. Did you make any modifications to Rod's original circuit this time, to make it perform better? Or am I missing something here?
btw I am glad to know that 2N3055s are good enough - and even better - for this amp.
Thanks,
Reji
Hahaha, yes I did get awful result from DOZ at that time... 2009... my first attemps. But you see that was not the shaan of 2012, right? I now know what mistakes I made building it - I used a cheap 5watt wirewound resistor as the 0.1ohm at the emitter of the upper transistor(which I measured with a multimeter in 2011 to be around 3.6ohm
), it became hot during listening, which it should not be. But due to my ignorance and lack of experience I couldn't suspect it. Also I used some cheap chinese electrolytics in the feedback path, bootstrap and the output; pretty ridiculous when I think of it now. Of course it had to sound bad. I wish the resistor or the power transistors blew; then I could have had a chance to understand what I needed to understand. Finally, the layout was also non-standard for this circuit. Did you see the PCB plan in one of my last posts here? I used the same design in the stereo direct coupled DOZ on a veroboard. It sounds great! Now a days I use expensive electrolytics made by an Indian company "Keltron". These electrolytics have given fine sonic results be it a simple class-ab amp, Lazycat's SSA, JLH or DOZ. The power resistors I use are metal film 2watt type. I experimented a good deal with different parts, I learned a good deal, I got good sound. It just wasn't supposed to happen in 2009 . What I now know is that - All amplifiers sound "great", when built correctly.Funny thing- I ran the new DOZ amp using the same pair of ST made TIP3055s that I used in that 2009 experiment. Did they go through mutation?!
Hi Shaan,
Many thanks for the explanation. Recently I too came across a similar issue while I was building a Philips 40 W amp. I replaced the power supply filter caps (12000 microF, 100 V, one for each channel) with another brand, and the sonics improved right away. Funny thing is, the swapping was only for aesthetic reasons and I was not in the quest for any sonic changes. However the audio got "cleaned up": my subjective assessment is that the original caps were introducing TIM distortion in the amplifier.
Keltron is a Kerala Govt company based in Trivandrum. At one time time they were reporting losses; anyway good to know they continue to make good capacitors as before. Actually with the proliferation East Asian caps, I hardly see them in Bangalore these days !
cheers,
Reji
Many thanks for the explanation. Recently I too came across a similar issue while I was building a Philips 40 W amp. I replaced the power supply filter caps (12000 microF, 100 V, one for each channel) with another brand, and the sonics improved right away. Funny thing is, the swapping was only for aesthetic reasons and I was not in the quest for any sonic changes. However the audio got "cleaned up": my subjective assessment is that the original caps were introducing TIM distortion in the amplifier.
Keltron is a Kerala Govt company based in Trivandrum. At one time time they were reporting losses; anyway good to know they continue to make good capacitors as before. Actually with the proliferation East Asian caps, I hardly see them in Bangalore these days !
cheers,
Reji
Found an interesting old photo. See the attachment. In the left is a simple pure SE class-A follower amp and in the right, that DOZ of 2009. You can see cleanly that the left circuit has a big Keltron cap at the output and the right board has a blue "Samwha" cap. The left board sounded superb, the right sounded the opposite. You can also see the dreaded 0.1ohm(3.6ohm)/5watt white resistor on the right board. That thing had a +-5% print, but measured beyond 100% tolerance, it was flying at +3600% of the printed value... 
ROFL!
Let me tell you how I dirtied my hands with these bad capacitors. I used to buy Samsung caps at that time from the retail shop(I still have 4 of them). One day they showed me these "Samwha" caps and said these are the new "imported" "substitute" caps and should do the job without any problem. Those samsung caps gradually vanished and these "imported" trashcaps became the new standard here! Of course not in the high-end audio dept., these are prefered mainly by TV repair mechanics. A 4700uF/25V cap costing Rs.16; can you imagine? On the other hand the Keltron thing costs Rs.30 for 25V and Rs.42 for 35V.
ROFL!Let me tell you how I dirtied my hands with these bad capacitors. I used to buy Samsung caps at that time from the retail shop(I still have 4 of them). One day they showed me these "Samwha" caps and said these are the new "imported" "substitute" caps and should do the job without any problem. Those samsung caps gradually vanished and these "imported" trashcaps became the new standard here! Of course not in the high-end audio dept., these are prefered mainly by TV repair mechanics
. A 4700uF/25V cap costing Rs.16; can you imagine? On the other hand the Keltron thing costs Rs.30 for 25V and Rs.42 for 35V.Attachments
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Shaan,
Yes, there is lot of "imported" stuff these days. The "Samwha" of course looks better than the the Keltron in the photo (that un-appealing colour of Keltron caps has never changed as far as I know), and also being cheaper, one might end up buying them. My bad electrolytics also were imported (and expensive as well).
I was not aware of the perils of the white wire-wound high wattage resistors; now I know !
btw now I am quite keen on the Mosfet power follower; just read Rod's article. Saw your contribution there as well.
cheers,
Reji
Yes, there is lot of "imported" stuff these days. The "Samwha" of course looks better than the the Keltron in the photo (that un-appealing colour of Keltron caps has never changed as far as I know), and also being cheaper, one might end up buying them. My bad electrolytics also were imported (and expensive as well).
I was not aware of the perils of the white wire-wound high wattage resistors; now I know !
btw now I am quite keen on the Mosfet power follower; just read Rod's article. Saw your contribution there as well.
cheers,
Reji
Yes, in the next 3 years you wont be the shaan of 2012 either. You will have more experience then. And you may change your opinion also
All good things to those who wait. I waited, 3years. I got some good knowledge.
Yes, in the next 3 years you wont be the shaan of 2012 either. You will have more experience then. And you may change your opinion also
Jay, please. Don't post here if all you can do is chanting philosophical words. Open a new thread if you feel like you have to do it anyway. In this thread only talks about your DOZ build, and No fortune telling. Period. Please don't post anything OT or I'll have to report it to the mods. You can of course read the first post more carefully.
We all learn from mistakes...isn't it the normal way of things..
Shaan, I see that you have made the class A amps DOZ, JLH and MPF. Assuming the right power supply, preamplifier and decent 8 Ohm speakers we can get (two-ways with Philips 8" woofer and dome tweeter, say), which of these three would you prefer? I am considering low volume level listening of typical Indian film music, pop, and western classical in a 12' x 16' room.
Right now I have a couple of pretty good class AB amps (one DIY and one purchased). Purchased system is a Marantz (SR5003), and it performs really well with a Marantz CD player (DV-18) as source. But I'm seriously thinking of an adventure into DIY Class A just to understand the sonic differences, and hence this question !
Thanks,
Reji
Shaan, I see that you have made the class A amps DOZ, JLH and MPF. Assuming the right power supply, preamplifier and decent 8 Ohm speakers we can get (two-ways with Philips 8" woofer and dome tweeter, say), which of these three would you prefer? I am considering low volume level listening of typical Indian film music, pop, and western classical in a 12' x 16' room.
Right now I have a couple of pretty good class AB amps (one DIY and one purchased). Purchased system is a Marantz (SR5003), and it performs really well with a Marantz CD player (DV-18) as source. But I'm seriously thinking of an adventure into DIY Class A just to understand the sonic differences, and hence this question !
Thanks,
Reji
Philip,
I prefer the DOZ of course. But, I absolutely do not recommend it to anybody. I say, build it if you are curious, listen your favorite music through it and then keep it if you liked the output or discard it if it's not upto your expectations. What "I" like or hate is totally a personal preference and I think you should not take my likings into your consideration for a possible candidate for your own amplifiers, whatever music you like to hear. I like all kind of music, from Indian classical to dubstep. And I love listening them through DOZ, more than any other amps I built. I don't have those expensive systems like Marantz etc., but have listened to many of the expensive instruments at many places, mostly at my friends' and relatives' homes and recording studios; they sound very appealing. I wanted to build something which could give me the same pleasure. I built that something, love its sound. But you may well hate it. I may well run into making remarks like how "warm" "sweet" "firm" or "fat" the DOZ may sound but if I do so then this thread has gone down the drain.
I simply can not/should not convince you about the sound of DOZ. But Rod Eliott can teach you what you need to know before starting to evaluate the sound of a particular amplifier. Read through his site and you will have 50% clear idea of that "Class-A" sound, the rest you will underestand when you build your own class-A. I, however can tell you these, SE class-a sounds different from PP class-a, pure SE sounds different from phase-splitting SE(like DOZ), symmetrical class-a sounds different from assymetrical class-a, VFB class-a sounds different from CFB class-A.
DOZ's high amount of low order distortion makes its sound pleasureable to my ears, so I listen to it.
I prefer the DOZ of course. But, I absolutely do not recommend it to anybody. I say, build it if you are curious, listen your favorite music through it and then keep it if you liked the output or discard it if it's not upto your expectations. What "I" like or hate is totally a personal preference and I think you should not take my likings into your consideration for a possible candidate for your own amplifiers, whatever music you like to hear. I like all kind of music, from Indian classical to dubstep. And I love listening them through DOZ, more than any other amps I built. I don't have those expensive systems like Marantz etc., but have listened to many of the expensive instruments at many places, mostly at my friends' and relatives' homes and recording studios; they sound very appealing. I wanted to build something which could give me the same pleasure. I built that something, love its sound. But you may well hate it. I may well run into making remarks like how "warm" "sweet" "firm" or "fat" the DOZ may sound but if I do so then this thread has gone down the drain.
I simply can not/should not convince you about the sound of DOZ. But Rod Eliott can teach you what you need to know before starting to evaluate the sound of a particular amplifier. Read through his site and you will have 50% clear idea of that "Class-A" sound, the rest you will underestand when you build your own class-A. I, however can tell you these, SE class-a sounds different from PP class-a, pure SE sounds different from phase-splitting SE(like DOZ), symmetrical class-a sounds different from assymetrical class-a, VFB class-a sounds different from CFB class-A.
DOZ's high amount of low order distortion makes its sound pleasureable to my ears, so I listen to it.