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Old 6th June 2003, 08:38 AM   #11
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Hi!

I've still not had enough time to re-try building the DoZ, since I had to finish the P3A first

I think it will be delayed until late summer or fall, since my next project is a Zebulon Ultra subwoofer (man, 120l, 58 kg...!!!)

But I think that I will rebuild it step - by - step, not trying to find out what I did wrong the first time. So I will use my unstuffed second board, and unsolder the first one...

But do post your experiences, if you find out what you did wrong! I will always keep track of this...!

Bye,

Arndt
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Old 6th June 2003, 11:13 AM   #12
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Rod Elliot says to use a 1k charging resistor also...but I don't know how to connect it? From cap out to ground? in parallel w/ the cap? In series w/ the cap to speaker output? How big of a resistor? .5watt? or bigger? Thanks!

-Matthew K. Olson
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Old 6th June 2003, 11:26 AM   #13
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Default The missing resistor...

Quote:
Originally posted by Mattyo5
Rod Elliot says to use a 1k charging resistor also...but I don't know how to connect it? From cap out to ground? in parallel w/ the cap? In series w/ the cap to speaker output? How big of a resistor? .5watt? or bigger? Thanks!

-Matthew K. Olson
Connect it from cap out to ground!!...Use a 1W resistor for good sleep...


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Old 6th June 2003, 03:05 PM   #14
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Ok, also, would anything close to 1k work? bigger than 1k would have a slower capacitor charging...but would it have less effect on the sound? Would 750 ohms work? I'm just thinking about paralleling some .5watt resistors and need to know what would be best...also have to consider what I have Later!

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Old 6th June 2003, 03:19 PM   #15
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Quote:
Originally posted by Mattyo5
Would 750 ohms work?
Yes... this value is not critical...is job is only to charge the capacitor ...when there is no loudspeaker connected...

Not a very hard work!!!

Even a 1,5k will work...or 2.2k,in this last case a 0,5W resistor is enough...
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Old 6th June 2003, 11:31 PM   #16
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Ok, I paralleled 2 2.2k 1watt resistors and got 1.08k...and put this across the speaker out terminals...basically from the c3 cap output (speaker +) to ground (speaker -). Now I have less than .06v DC offset instead of 9v. :-D AWESOME! Now my only problem is that my toroidal that I just got is too high of a voltage...so I need to install some higher voltage caps. I have 50v caps now (BIG 80kuf computer grades) and I'm now running close to +60v-0 supply. So time to install my 80vdc 61kuF caps I have an 800 va avel 40+40 toroid right now. should be plenty Bias will be around 2.5-3.0 amps. Any idea how much power I'll get into 8 ohms? 40 watts or so sound right? Thanks!

-Matthew K. Olson
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Old 9th June 2003, 02:31 AM   #17
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Well...the amp works. Thats the short of it. I'm actually running the rails quite high...66v!!!! I know thats really high, and bias at 3.3 amps. But i have 8 transistors and big heatsinks. Should hold it fine. Anyway, the amp works, I get some hum so far, though i haven't had time to mess with it. I'm also using Rod Elliots circuit for a balanced receiver, and had to take this out of the circuit for now because it was giving me LOTS of distortion. So I'm running it unbalanced and sloppily biased. I'll get it running better soon enough, and post pics too. Don't worry ya'll!
This is going to be a sweet amp!

-Matthew K. Olson
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Old 9th June 2003, 06:00 PM   #18
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Ok, my house current has quieted down to give me a 53v rail. I have spent the past 2 hours trying to figure out a ground loop...the only thing that helps is lifting the ground. The chassis is grounded to the wall, but not to the main caps or the amp itself. I know that this is a no no...but its the only thing that seems to help. Anyway, initial impressions of the amp are that the highs are VERY nice...open soundstage...little light on the bass. Not sloppy at all...just...lacking? I have 2 2200uF panasonic FC caps on each output ...is this too little? I think this amp would be just great to biamp with...put this amp on the highs and do a gainclone or lm3886 (similar to gainclone) on the lows...it would be a great amp for sure! What a heater though...amazing how much heat this thing generates...especially with 3A+ bias. Pics soon.

-Matthew K. Olson
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Old 9th June 2003, 09:11 PM   #19
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Also...one other thing...would getting rid of the 1k output capacitor "charging" resistor work for getting my bass back? Its good, its deep, but its just not as loud. Soundstage is quite nice though

-Matthew K. Olson
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Old 9th June 2003, 09:26 PM   #20
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Matt...what size of transformer are you using....your caps are a wee bit small but should be ok if the transformer can carry the grunt
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