the Poor Man 660 support thread

[elektrovolt]

okay, thanks

I am thinking of the 3U case with vented cover and two frontpanels (black and grey)

edit: ordered

still awaiting the edcors and rotary switches. also a nice pair of meters - those sifam meters are ridiculously expensive :? any thoughts ?

 

[Gachet]

Hi,

I have some problem troubleshooting the psu...
I have 186V and 106V instead of 245V and 136V.
I have double checked resistors ,changed the 3 mpsa transistors and the irf 820 but nothing changed.
Before regulator I have 324V and 188V.

What should I change or do?

Thanks

 

[Gachet]

:? nobody has an idea?

I am really in a deadlock.I need a few answers to understand how the psu is supposed to behave.
Can someone at least explain me what is going on around the irf 820 Q4?
What voltage do you have on pin 2 of Q4?

If Q5 is not fed with 245 V it won't be abble to supply 136V because of fixed gain, right?

thanks

 

[analag]

Check if D7 is the correct zener, then measure the voltage on the emitter of Q3.
Did you handle Q4 properly during installation?

analag

 

[Gachet]

Hi,
You mean that Q4 needs special care?
Like using proper heatsink with heat conducting grease?
Or discharge hands on earth before handling ?

At the moment I can't measure Q3 emitter voltage as I manage to rebuilt on a separate board all the things between C4 and R8.

I used 100 V 1.3W zener diode for d7


Thanks Analag.

 

[delaymix]

A number of issues not finish a good understanding of everything.

1) In relation to the previous statement that explains Volker about the split control of constant time in 6 divisions. I do not know very well if Volker to explain this is joking or serious ... my english is not good. I understand that the division is correct for a linear scale. In the case if so... would be 10K / (number of positions - 1);

0 position: 0 K
1 position: 2 K
2 position: 2.5 K
3 position: 3.3 K
4 position: 5 K
5 position: 10 K

Is this correct?
To perform this function, from the standpoint of sound would be better to use a logarithmic scale?

2) In relation to the rotary switch that controls the threshold. In terms of manageability, Is it better that the scale is linear or logarithmic?

3) I've thought about putting meters Sifam AL29WF. In this case, do we need a Zero control to adjust the starting point for measuring the gain reduction?

4) Does it make sense to see the meter in the GR and the output level? How could I do to commute between GR and the output level on the meter?
5) After reading the whole thread, I was not at all clear how to make the function link. In practical terms, What is the procedure for implementing the control link to a stereo unit?
Thanks.

 

[bernbrue]

[quote author="delaymix"]A number of issues not finish a good understanding of everything.

1) In relation to the previous statement that explains Volker about the split control of constant time in 6 divisions. I do not know very well if Volker to explain this is joking or serious ... my english is not good. I understand that the division is correct for a linear scale. In the case if so... would be 10K / (number of positions - 1);

0 position: 0 K
1 position: 2 K
2 position: 2.5 K
3 position: 3.3 K
4 position: 5 K
5 position: 10 K

Is this correct?
To perform this function, from the standpoint of sound would be better to use a logarithmic scale?.[/quote]

Simply solder five 2K resistors on a 2x6 Lorlin (pin 1-6) to get a 10K linear pot. Works fine!

2) In relation to the rotary switch that controls the threshold. In terms of manageability, Is it better that the scale is linear or logarithmic?

I think that a log scale is better here

3) I've thought about putting meters Sifam AL29WF. In this case, do we need a Zero control to adjust the starting point for measuring the gain reduction?.

Yes (trimpot parallel to meter)

4) Does it make sense to see the meter in the GR and the output level? How could I do to commute between GR and the output level on the meter?

Lorlin 2x6, connect meter to A and B, for GR from pcb to pin 1 and 7, for output level from output XLR (+/-) to pin 2 and 8 (add 3k6 resistor in series)

5) After reading the whole thread, I was not at all clear how to make the function link. In practical terms, What is the procedure for implementing the control link to a stereo unit?
Thanks

for stereo you connect the control signal of each channel (audio pcb) together, which is pin2 of PL1 in the schematic (the middle of the input gain control)

regards
Bernd

 

[nielsk]

Bernbrue,
you wrote in response to this question:


2) In relation to the rotary switch that controls the threshold. In terms of manageability, Is it better that the scale is linear or logarithmic?



I think that a log pot is better here

Does this mean you have tried the 24 position dual switch set up as linear and as log in this position and prefer the one set up as log? Or that you have found a 15K dual pot to work here and prefer a log taper?

thanks!

 

[bernbrue]

[quote author="nielsk"]
Does this mean you have tried the 24 position dual switch set up as linear and as log in this position and prefer the one set up as log? Or that you have found a 15K dual pot to work here and prefer a log taper?
thanks![/quote]

While prototype testing I first tried ordinary log and linear potentiometers. After that I decided to set up my 24 pos dual switch as a 15K log pot. Hope this makes it clear.
regards
Bernd

 

[Moby]

Lorlin 2x6, connect meter to A and B, for GR from pcb to pin 1 and 7, for output level from output XLR (+/-) to pin 2 and 8 (add 3k6 resistor in series)

If you disconnect VU how you achieve the first stage supply?

 

[mich]

If you disconnect VU how you achieve the first stage supply?

intresting question..the supply curent will still flow through the 22K resistor that is parallel to the meter (and into the CT of T2)- but that leads to think that the circuit (first stage) will behave different depending on the meter used?
because the meter is forming a parallel network with the 22K "droping resistor" and depending on its own DC resistence afect the curent geting to the anode of the tube?

 

[nielsk]

Thanks for the reply, Bernbrue
So are you happy with the way BOTH the input and threshold controls behave when when set up as log? Can you describe the different behavior of the threshold control between log and linear?

 

[khstudio]

[quote author="mich"]- but that leads to think that the circuit (first stage) will behave different depending on the meter used?
because the meter is forming a parallel network with the 22K "droping resistor" and depending on its own DC resistence afect the curent geting to the anode of the tube?[/quote]

I was also wondering the same thing... like how different meters "Could" affect the circuit.

BTW... would THESE meters from JLM Audio work?
http://www.jlmaudio.com/VU Buffer.htm

Would I need the "Buffer" circuit too?

 

[Moby]

because the meter is forming a parallel network with the 22K "droping resistor" and depending on its own DC resistence afect the curent geting to the anode of the tube?

Guys, I asked this question just after I saw the schematics. Answer "just the VU" is absolutely not adequate because every VU has internal DC resistance few Kohms. In parallel with 22k it's still few Kohms and voltage drop can be huge depending on current flow. That's not the same like original design, because everybody knows that original Fchild has ma meter instead of VU. Correct me if I'm wrong... Also, current is not steady it varies depending from GR that's why I expect ma meter on the place of VU (small internal resistance). Designers, please, lets clear this out. Can you give us voltage after VU connected or simply give us steady current in non GR mode so we can calculate the rest. I hope that I'm no asking too much :green:

 

[Larrchild]

The internal insulation characteristics of certain audio VU meters may not dig sitting at a few hundred volts above ground.
Careful.

 

[bernbrue]

[quote author="nielsk"]Thanks for the reply, Bernbrue
So are you happy with the way BOTH the input and threshold controls behave when when set up as log? Can you describe the different behavior of the threshold control between log and linear?[/quote]

Yes! With linear scale gain and threshold max is reached already in the first quarter of the turn, with log scale the range is spread over the whole turn. Concerning VU/GR switch I just explained how I would realize that, but in my prototype the meter (100uA) shows GR only. I realized that when the meter is disconnected, gain slightly decreases.
regards
Bernd

 

[veermaster]

Hi Bernd,
thanks for all the information. Did you realize those stepped attenuators as ladder types or even bridged H types?

 

[Moby]

Concerning VU/GR switch I just explained how I would realize that, but in my prototype the meter (100uA) shows GR only.

This thing makes me crazy. You can't connect ua meter directly to output and measure level. For that purpose you need Vu. On the other side if you go with the VU you must know which VU you choose since every model has his own internal DC resistance.
29W0-100UA0-30-1000ohm
29W0-1MA0-100 -50ohm
29W4-20MA0-100 -1ohm

and so on.... Now please read this! Voltage drop is not the same for 1000 and 1 ohm! Voltage drop is not the same with current of 10ma at 1000 ohm resistance and 1 ohm resistance and since this unit has dynamic current voltage will be changed a lot with 1000 ohm meter or less with 1 ohm. So, you can't say just VU or ua meter. Guys, you insist about MKP wimas in the sidechain because of fancy look and don't want to pay attention on the electronics-sonic details. I don't get this :evil:
And please give me the info of damned current of the first stage so I can choose the right meter and maybe save the time and money for the people who is just trying to connect this as Lego thing :green:

I realized that when the meter is disconnected, gain slightly decreases.

If you go with 1ohm meter you will not have that issue :!:

 

[bernbrue]

[quote author="Moby"]
This thing makes me crazy. You can't connect ua meter directly to output and measure level. For that purpose you need Vu. .....

So, you can't say just VU or ua meter. Guys, you insist about MKP wimas in the sidechain because of fancy look and don't want to pay attention on the electronics-sonic details. I don't get this :evil:
[/quote]

Dear Moby,
I´m not really motivated to answer questions that imply this insisting and offending tone. If you read my posting carefully you would have realized that I used a 100 uA amperemeter to measure gain reduction only, not level. There is no need to push things forward with :twisted: :evil: or other emoticons. I answered lots of questions twice, simply because people don´t read the infos. I receive pmails from people asking me to check their part lists and so on. That´s not my part and I´m not willing to do this. For my part, I can only report about my experience. I don´t know if you´ve already started the project, but concerning meters you should make your own tests.

Guys, you insist about MKP wimas in the sidechain because of fancy look and don't want to pay attention on the electronics-sonic details. I don't get this

Feel free to take whatever WIMAs your like, we do not insist on anything.

regards
Bernd

 

[Moby]

I´m not really motivated to answer questions that imply this insisting and offending tone.

Sorry but this wasn't offending tone. That's my reaction about mixing apples and oranges. If you remember I asked you twice about voltage drop around your meter and you never gave me the answer. Sorry but Vu, or 100ma meter can be a lot of different things. I'm sure that this design need a ma meter as GR meter but I don't have all my parts to do the test so I asked you. Is it so hard to put the voltmeter on the one side of your ua meter than on the other side and to give needed info, so I can order appropriate meter ? At the very end you gave the guy suggestion to switch VU (or ua meter, whatever...) to the output of the unit to measure output level and to feed the first stage through 22k resistor? If you ever gave me the voltages i asked I will calculate the huuuge voltage drop but now I can only imagine that.... :wink: OK , if you still think that my tone is offending how you going to describe your advice? Please think again about and be honest. P.S. I'm giving you a :guinness: :sam: anyway :wink: