Paradise Builders

Keith, that's good news, the dmm I had was way off as well, 50+/- on any given sample.

Has anyone else tried the caps to stop the oscillation yet? Any advice on most suitable cap type for the job, I probably have that value lying round in styrenes.

Yes, and it worked, my advice (as in http://www.diyaudio.com/forums/analogue-source/218625-paradise-builders-99.html#post3318195) is 470p for Cc1 and 2.7n for Cc2 (see attached schema). Hessener will soon have a updated assembly guide. Cc1 may be as large as 2.2n but I do not think that this is needed.
 
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The protection diodes must be protected (I thought) also I want to use this thing to measure floating items in power amplifiers running of +/- 70V. For this purpose I may even need higher values for these resistors. They, and the two 500ohm values will be switchable. Any other thoughts on this? Currently it is just a simulator-prototype.

yes, you are right. these resistors will add noise eventually, and to measure higher voltages this should turn into a voltage divider which then may need compensation (talked about this at length in the elektor article, only the resistors were much higher there. 1n4148 is a good choice, very low capacitance.
other than that the circuit looks just fine. have you checked the common mode range in your simulations?
 
yeah :) the shunts do work. i just have 2x18V trafo with just provisory 2000 uF per rail.
before i connect the rest:

there is a 10k resistor in the input which is also drawn on PCB. but this is NOT the one mentioned in the instruction for loading the input?
i do have to solder another 10k resistor between input gnd and input, right?
thank you for answering,
stefan
 
i will use a benz glider in the end. it is recommended for a 22k load.


ah, ok, the 10k resistor for testing is "the" load resistor that will remain in the end? so maybe a different value for an other cartridge?

and btw, the outputs shuld be shortet for testing? i know that for power amps.

tnx
stefan
 
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What type of benz glider ?

What is the output of this cart ?

Why do you want to short the output of the amp ?

The 10k resistor present in the circuit is NOT the cart load resistor... it is part of the circuit intended to null input offset.

Yo must connect a parallel resistor to the input to serve as cart load resistor.

You can try 22k but I doubt it will be the best option... If you are using a 0.4mV glider, I would consider loading it around 1200r, if you choose the 0.8mV glider, I would choose around 2400 ohm.

The high output glider (2.5mV) is not very well suited to this circuit.
 
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Hi guys, just fired it up today. Running into some troubles. Voltage at +/-18v steady. DC off set is wandering +/-0.3V. I would leave it on for it to settle for next few days, input off set trim down to zero. One of the chanel when i measure at pin 6 of IC reads about 6V, so as the test point of the 6800uF cap. The other chanel IC pin 6 measures 0.5V . Where should i check ?
Quan
 
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Hi guys, just fired it up today. Running into some troubles. Voltage at +/-18v steady. DC off set is wandering +/-0.3V. I would leave it on for it to settle for next few days, input off set trim down to zero. One of the chanel when i measure at pin 6 of IC reads about 6V, so as the test point of the 6800uF cap. The other chanel IC pin 6 measures 0.5V . Where should i check ?
Quan

That was quick - you only just recieved the parts on christmas day !! :D

Pin 6 of the servo opamp is its output, and this voltage indicates how hard he has to work to correct the offset. So for the time being there is nothing too wrong. The 6V is a little on the high side, but lets just see and wait a couple days.

Just checking - the 6800uF caps should only see about 0.7V, whereas the 4700uF caps should see 14V, (and there should be no big deviation on either), is this what you are seeing?
 
That was quick - you only just recieved the parts on christmas day !! :D

Pin 6 of the servo opamp is its output, and this voltage indicates how hard he has to work to correct the offset. So for the time being there is nothing too wrong. The 6V is a little on the high side, but lets just see and wait a couple days.

Just checking - the 6800uF caps should only see about 0.7V, whereas the 4700uF caps should see 14V, (and there should be no big deviation on either), is this what you are seeing?

Hi Alfred, i could not wait and got stuck into it:D. The voltage measured at the 6800uF cap is the same as the voltage on pin 6 of the op-amp ie 6V, the other chanel measured about 0.5V so as the op-amp.
Quan
 
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Hi Alfred, i could not wait and got stuck into it:D. The voltage measured at the 6800uF cap is the same as the voltage on pin 6 of the op-amp ie 6V, the other chanel measured about 0.5V so as the op-amp.
Quan

something is very wrong with this board, here some more questions:
which 6800uF cap has the high voltage, C6 or C7?
can you measure the voltages across R5, both ends?
what are the values of VCASCL and VCASCH?

many thanks in advance
 
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Ok Alfred, the measured voltage was at the test point next to the 6800uF cap.
The Vascal measured +14.6V and -14.51V. The measured R5 voltages are-0.621V and + 0.47V.
Quan

that looks reasonable, lets see what the opamp pin 6 voltages will be in a couple days. have you checked if your amplifiers actually amplify? I think that (apart from the LV noise) they should be working fine.... (but please verify your system is not DC coupled, or your woofers will see some interesting movements.....)
 
that looks reasonable, lets see what the opamp pin 6 voltages will be in a couple days. have you checked if your amplifiers actually amplify? I think that (apart from the LV noise) they should be working fine.... (but please verify your system is not DC coupled, or your woofers will see some interesting movements.....)

Thanks, i wasn't game enough to try it but will do soon as long the DC offset settle down a bit more. Currently it is still wandering around up to 0.2V mark. i will measure the pin6 of the IC in a couple days then report.
quan