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Doxa 70 Clone
Doxa 70 Clone
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Old 13th April 2009, 07:18 PM   #1
valo is offline valo  Norway
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Default Doxa 70 Clone

Hi

Is ther someone here that has cloned an Doxa 70 ?

I have the schematic, but i do not have the skills to make an PCB
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Old 13th April 2009, 07:30 PM   #2
stinius is offline stinius
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Default Re: Doxa 70 Clone

Quote:
Originally posted by valo
Hi

Is ther someone here that has cloned an Doxa 70 ?

I have the schematic, but i do not have the skills to make an PCB
Try contacting Roar Malmin.
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Old 13th April 2009, 08:24 PM   #3
valo is offline valo  Norway
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Default Re: Re: Doxa 70 Clone

Quote:
Originally posted by stinius


Try contacting Roar Malmin.
Yeps that guy knows a thing or 2 about the Doxa 70, but i dont think he can or will help make an PCB layout.

did trye to post the schematic here but the pdf file is too big
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Old 13th April 2009, 08:39 PM   #4
valo is offline valo  Norway
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Here is the shematic have a look at it this is an amp that sound realy nice and dont runs that hot
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Old 14th April 2009, 01:01 PM   #5
coder2 is offline coder2  Ukraine
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I do not know what is the Doxa70, sorry.
But at first sight the provided schematic seems incomplete. And I think it contains errors.

Where are T1, T3, T4 going?
Why collector of Q26 is torn?
Where is the bias for NPN Q2? - it cannot be biased by NPN Q20.
The same question about Q23 and Q5.
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Old 14th April 2009, 06:54 PM   #6
Roar Malmin is offline Roar Malmin  Norway
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I have stated in an earlier post that this schematic, as shown, is flawed, and an amplifier based upon said circuit, will not work.
Why clone it at all, when you can buy a fully functioning unit for a pittance?

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Roar
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Old 14th April 2009, 07:02 PM   #7
valo is offline valo  Norway
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First reason to clone it is just for the fun of it, and i guess it will cost more than an used Doxa70

Do you have schematic/service manual ?
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Old 14th April 2009, 07:45 PM   #8
Roar Malmin is offline Roar Malmin  Norway
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I guess that your kind of fun differs from mine.

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Roar
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Old 14th April 2009, 07:57 PM   #9
stoc005 is offline stoc005  United States
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Default Re: DOXA-70

Just for fun I looked up the BD245C here in the US. Digikey does not sell it and Mouser considers them obsolete. You'd have to update the BOM with modern parts to really build it, I think.

However, the circuit does have some merit, IMHO. I like the front end and the fact that this is a true DC amp, other than the one input coupling cap. No bipolar/'lytic cap in the feedback path. No miller caps on the Vas....No frequency compensation caps at all. No output zobel... No output inductor....hummmm. Not a big fan of pots, other than the pot in the Vbe circuit. P1 is probably a "zero-the-output" pot. Don't know what Q26, Q27 do either. Missing a few other parts to make it a "commercial" amp, IMHO.

It looks like a solid 70 WPC/8 ohms (+-38volts) and with 5 outputs per side, 4 ohms should be no problem and maybe 2 ohms wouldn't bother it too much.

I will input it into LT_Spice with modern SMT transistors and see how it works. Should answer any stability questions as well. Check back in a day or so.

Bill
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Old 14th April 2009, 08:23 PM   #10
valo is offline valo  Norway
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Its old yes, but an verry good amp, i did buy an 70signature new, it did sound realy good but i sold it after a fea yeares...maybe it was an mistake

anyway i feel like its not verry popular to clone this amp for the fun of it , so i will consider to clone it......
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