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Old 16th June 2010, 07:21 PM   #3961
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Salas

Here a picture of my actual power amps:

Click the image to open in full size.

The mid horns and the tweeter are protected against DC with the big black caps, bypassed by sovjet caps.

One of those big caps is more expensive than one of the stereo t-amp boards...

Franz
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Old 16th June 2010, 07:27 PM   #3962
Salas is offline Salas  Greece
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Unfortunately good coupling capacitors are a layout and pocket killer. So I try to be inventive by carefully mixing what I have in my hobby box right now. Did many auditions against DC coupling to use that mix. I hope it will co work decently on that new phono board in the end. Has enough work to be done underneath the perf board still. Near finishing your reg?
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Old 16th June 2010, 07:33 PM   #3963
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Quote:
Near finishing your reg?
Not yet.

Next, I will make two stripeboards with a delay circuit, based on NE555, to get rid of the power up and down problem of the crossover by grounding the outputs of the active crossover.

Then, I can proceed safely to the shunt regulator.

And dont forget: I had to measure and adjust the levels and phases of my active crossover in the last two days.

Franz

Last edited by Franz Gysi; 16th June 2010 at 07:36 PM.
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Old 16th June 2010, 07:51 PM   #3964
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Quote:
Originally Posted by Salas View Post
You watch football and blow vuvuzelas, I experiment on phono.
Nice & neat master work as expected

What kind of output caps are you using?

Are you bypassing polipropylene ouput caps with teflon caps?

All RIAA caps are russians teflon not silver mica....T-1 15nF instead 16nF, 47nF are russians & real value is 47nF, I can't see russian model?

Last edited by merlin el mago; 16th June 2010 at 08:02 PM.
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Old 16th June 2010, 08:33 PM   #3965
Salas is offline Salas  Greece
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About output caps I don't know the maker. They are pull outs from a Chinese kit, they just have ''MPP'' on them. They happened to mix nicely with FT-1 bypass in my preliminary experiments on a DCB1's doubled output for DC VS Capacitors comparisons. In the RIAA I use ceramic C0G/NP0 as I wrote. They proved very decent subjectively and save layout size. Teflon is superior, I have compared, and it would be best if someone uses Teflon for Riaa filter too. This CCT has different values, lower impedance filter, so I got 30 33nF 50V 10% C0Gs and found exact values via paralleling. Its an experimental board, has many tweaks. Another problem for using expensive caps for the filter is having enough for reaching exact and matched values.
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Old 16th June 2010, 10:10 PM   #3966
massimo is offline massimo  Italy
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.... and 4 critters front end again
Expected gain? 60dB?
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Old 16th June 2010, 10:21 PM   #3967
Salas is offline Salas  Greece
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I use 9.5mA cascoded quads then 8.5mA 2nd stage then 7.6mA buffer with source CCS like B1. If it will pull as expected it may go 61.5dB. Don't know yet. Needs copper side wiring work, measurements, enclosure, and its 40C these days. I am experimenting on less noise possible and I hope that the high current 1.1k impedance first stage will prove gutsy enough to drive the 22K filter and charge up its 100nF caps with decent slew rate. Its a Guinea pig right now.
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Old 16th June 2010, 10:29 PM   #3968
massimo is offline massimo  Italy
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DCB1 output stage:nice idea
22 K filter: interesting as well. I like it.
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Old 16th June 2010, 10:33 PM   #3969
Salas is offline Salas  Greece
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Not DCB1, but B1. I use the 2nd stage drain voltage to center it and will show that DC on output with single polarity PSU. So it retains the output capacitors. Have shown how to integrate a B1 tail buffer early in the thread. I just wanna listen to this soup. Its not a proven unit yet.
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Old 16th June 2010, 10:37 PM   #3970
massimo is offline massimo  Italy
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Yes, sorry, my bad. It's a capacitor coupled stage
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