Salas hotrodded blue DCB1 build - Page 294 - diyAudio
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Old 16th March 2013, 09:17 AM   #2931
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O yes.. That was a couple of years ago - Great amps.. A lucky new owner has them..
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Old 16th March 2013, 09:45 AM   #2932
Salas is online now Salas  Greece
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Real size speakers, that's good.
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Old 25th March 2013, 01:01 AM   #2933
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Nick do you have an opinion for using a single 0,47uF FT3 teflon instead of K75-10 2,2uF bypassed by 0,1uF as output?
Provided that my amp is 220k input, so there should be no bass issue with the 0,47uF cap...
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Old 25th March 2013, 09:03 AM   #2934
Salas is online now Salas  Greece
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FT3 is good on its own you should try and decide. The phase is going to turn 5deg @ 20Hz and the -3dB point will be just under 1Hz. With the previous value there was almost no phase turn @ 20Hz. Those are the typical differences.
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Old 25th March 2013, 12:48 PM   #2935
mantha3 is offline mantha3  United States
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This would be a nice option on a Khozmo attenuator... I think this is a new option

Click the image to open in full size.
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Old 25th March 2013, 05:47 PM   #2936
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I'm thinking about building in a boozehound phono preamp with a hotrodded DCB1. Any reason I can't tap into the shunt regulated power supply to power the phono? It's happy with anything between 12V and 24V DC so I think this would be ok. All I would have to do is add a switch for the line/phono RCA connectors.
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Old 26th March 2013, 03:37 PM   #2937
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It s also time for me to start testing output resistors, so Niko I need your help better optimizing their value.
If I remember correctly from one of your previous posts, you suggested feeding a wave into the buffer and checking for oscillations. If everything seems ok then try to lower the output resistor values (and output impedance) until oscillations appear, and then go a bit up until it's fixed.

Do you mind sharing a bit more about this testing rig? What should be attached to the output? Cable only? amp? dummy load equal to amp impedance? What should the test input wave be?
I have no generator, so I will have to use something like a plain wave generator either from my pc or my phone.
Also, could I use trimmers to find the lower value for the resistors?

Are these lower values dependent only on the input impedance of the amp, or by the interconnects as well?

Thanks again for your invaluable help
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Old 26th March 2013, 03:44 PM   #2938
Salas is online now Salas  Greece
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You need a clean square wave generator in the audio band at least with the fastest rise time you can have, the IC cables to be used, a dummy of the amp's input resistance and capacitance to terminate the IC cable. You need not see ringing on the edge of the square wave as you test lower output series resistor values.
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Old 26th March 2013, 03:45 PM   #2939
Salas is online now Salas  Greece
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Quote:
Originally Posted by oneplustwo View Post
I'm thinking about building in a boozehound phono preamp with a hotrodded DCB1. Any reason I can't tap into the shunt regulated power supply to power the phono? It's happy with anything between 12V and 24V DC so I think this would be ok. All I would have to do is add a switch for the line/phono RCA connectors.
The DCB1 is 10V out though.
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Old 26th March 2013, 04:57 PM   #2940
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In trouble with 2 hotrodded DCB1

Built 4 during last 3 months : two were perfect at first fire up and 2 others were not.

All semi conductors come same batch:BC550C,BC560C ,BC517G and ixys diodes from Digi-Key

Transformers 14-0-14 120va;and get 20.5VDC on can, resistors 10 ohm 5w , diodes from Ed.Lafontaine, IRFP240/9240 from an other DIY member etc. , 2sk 170 from Spencer

On one DCB1 the 5 diodes on 9240 side don't light on ; the other the 5 +3 diodes on same side (9240) don't light:

So at first ; what I am looking for ; what components I must suspect.

Where is DCB1 diagram on DIY

Thanks for your help.
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Last edited by Praudio; 26th March 2013 at 05:02 PM.
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