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Chip Amps Amplifiers based on integrated circuits

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Old 8th March 2003, 08:49 PM   #1101
Philo is offline Philo  United States
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When I mean "matched" I do mean output level or volume. I don't think it is your card causing the problem. Try increasing the resistor from the input to ground to around 75k-100k and see if that helps. What value cap do you have on the input? When I tried small voltage value film caps (100V)in my experiments, the sound was thin and anemic.
ksProject drivers?!?
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Old 9th March 2003, 06:34 AM   #1102
Peter Daniel is offline Peter Daniel  Canada
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Default Bridges to Babylon

Quote:
Originally posted by Philo
.

Peter, could you post a pic of your rectifier build? Did you make a PCB for them like your Alephs?
Here's how the bridges look. I placed the diodes in a way to achieve minimum connections. Two 4.7u N caps are on ea. rail between diodes.
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Old 9th March 2003, 06:39 AM   #1103
Peter Daniel is offline Peter Daniel  Canada
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K with A connect on the outside and this is where the 4 wires from secondaries go (through the large holes). Eight pins in the center are for 8 wires going to the amp. Two K and two A of four diodes pairs are connected with short wires on a components side. This is mounted directly to the rear panel of PS enclosure. I didn't really see a reason to make PCBs for that.
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Old 9th March 2003, 08:15 AM   #1104
Bricolo is offline Bricolo  France
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peter, did you try to bypass each diode with something like 22 or 100pF ?
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Old 9th March 2003, 01:00 PM   #1105
Cradle22 is offline Cradle22  Germany
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Hi!

Quote:
Originally posted by Philo
When I mean "matched" I do mean output level or volume. I don't think it is your card causing the problem. Try increasing the resistor from the input to ground to around 75k-100k and see if that helps. What value cap do you have on the input? When I tried small voltage value film caps (100V)in my experiments, the sound was thin and anemic.
ksProject drivers?!?
I do not use any cap right now... DC offset is always somewhere between 20 mV - 200 mV (according to how I wire the whole resistor / signal stuff).

kxProject is an open source implementation of soundcard drivers for the emu101k soundcard series, for example the audigy. It lets you control every single aspect of your card, and enables a totally free programmable (with already a lot of pre-fabricated modules) DSP on your card... I use it to actively control my system (crossover with any slope you like, compressor, equalizing...)
You can find it under www.kxproject.com

I will try increasing the resi to ground later on - if I at least understood it correctly, the volume should go up if I increase the resi to ground, while on the other hand decreasing the resi in series to input...?

Hope it works...

Bye,
Arndt
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Old 9th March 2003, 01:25 PM   #1106
Cradle22 is offline Cradle22  Germany
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Hi!

I just read in another thread (the one with the "humming" GC - wonder how a GC could have picked up Portishead ) that someone got rid of the hum when he disconnected signal ground from star ground...

But isn't signal ground supposed to go to star ground?

Or can I maybe put a cap beteen signal ground and star ground - would that help?

I can see that GC is a neverending story as far as modifications are concerned ...
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Old 9th March 2003, 02:13 PM   #1107
Cradle22 is offline Cradle22  Germany
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Call me confused...

Just tried a cap from input to ground, DC offset went up to about 15 V

After that I desoldered the cap, and put my first "original" humming configuration back in - just the 10 ohms resi in series to signal, no cap, no resi to ground, hooked everythin back up,

THE HUM IS GONE But don't know why - yesterday and today I only resoldered and resoldered and resoldered the resistors from signal, and the 1.7 cm long cable connecting it to input on the IC... nothing else

But another weird thing: It still plays too quiet! When I first listened to the GC and noticed the hum, the volume level was totally OK, now I have to put volume sliders to max to get at least adequate volume for my room...

So, back to soldering


Btw, just measure (I hope I did it right) impedance from the input (disconnected from amp, measured between signal pin and shield of the cinch connector), it was 79 ohms. Could that information help?
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Old 9th March 2003, 03:01 PM   #1108
Peter Daniel is offline Peter Daniel  Canada
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Here's the schematic of my bridge. Pins 1-4 create nodes on the DC side of the bridge for one rail; the other four pins, for the other rail. The 4.7 N caps (2 of them) are connected between pins 1 and 3, and 5 to 7. There are 8 wires from PS, and the ones from odd number pins go to one channel and the ones from even number pins got to the other channel. The grounds for both channels are connected on that board.
There are additional 4 x 1000u/50V caps in the amp (2 per chip). I didn't put any small caps across the diodes. First, there is not enough space, second pinkmouse tried it and reported that they soften or smear the highs. Another observation I made: I tried to use a nice 10A, Swiss made AC line filter with the PS and I didn't like it. I observed similar effects as PM reports.
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Old 9th March 2003, 03:10 PM   #1109
Mad_K is offline Mad_K  Norway
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How hot does the diodes get when playing at high volumes Peter?

I thought one had to heatsink them?
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Old 9th March 2003, 03:31 PM   #1110
Peter Daniel is offline Peter Daniel  Canada
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They are only barely warm. No need for heatsink.
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