the Poor Man 660 support thread

[benlindell]

And the 1062ohm resistor from each deck get tied together and sent to the PCB correct?

 

[RayBlack]

Hey there,

I'm new here and need some orientation. Would like to build a Stereo Compressor for my 2bus, and the PM660/670 seems to be the perfect match.
Any information of the total costs of building the standard analag design, with a simple enclosure ?

Thanks!
Ray ;D

 

[Kingston]

RayBlack, read this whole thread.

This is not a good build-by-the-numbers project AT ALL.

It's evident on every single page.

 

[radiance]

Hey there,

I'm new here and need some orientation. Would like to build a Stereo Compressor for my 2bus, and the PM660/670 seems to be the perfect match.
Any information of the total costs of building the standard analag design, with a simple enclosure ?

Thanks!
Ray ;D

A very rough estimate would be between 500 and 900 euro, maybe even more.
It depends on the quality of the parts used (rotary switches, meters, knobs), the amount of add-ons you want (slow start heater PSU, side chain booster board) and if you want a nice case + engraved frontpanel.

 

[skal1]

Hi

the poorman is causing my proceeding  compressor to low signal .


1}set up is ,daw to compressor , tx 10k:600 output impedance into input tx 600:10k of  poorman  into mixer,  why am i see signal loss in the first comp?


2}set up is ,daw to compressor  ,tx 10k:600 output impedance into mixer, no signal drop in this set


is the poorman causing  a loading issue ?


skal1

 

[skal1]

Bump need some help on the above issue


skal1

 

[lolo-m]

Hi
the poorman is causing my proceeding  compressor to low signal .

1}set up is ,daw to compressor , tx 10k:600 output impedance into input tx 600:10k of  poorman  into mixer,  why am i see signal loss in the first comp?

2}set up is ,daw to compressor  ,tx 10k:600 output impedance into mixer, no signal drop in this set

is the poorman causing  a loading issue ?

skal1

Your mixer input seam to be high impedance :
When you connect your comp to the PM670, you've got 2 transformers connected together. A loss of 6dB is perfectly normal in this case as the power avialable on the secondary of the compressor is divided into the PM670 input transformer primary and the compressor transformer secondary winding (600 ohm into 600ohm). The load of the compressor is 300 ohm (600 // 600).
When this compressor output transformer is connected to a high impedance load, the total (or close) power is avialable on the mixer (600ohm into 10k ohm). The load of the compressor is 600ohm (600 // 10k).
This 6db loss used to be an evidence in the past as all the input had a real 600ohm impedance, but nowadays it isn't that evident as most of the line inputs have got a 10k impedance. All the nowadays professional gear outputs are designed to be able to drive a 600ohm load but with a level loss.

PS: if I'm right, PM670 input impedance is around 1Kohm.

 

[skal1]

hi lolo-m



i took the mixer out of the set up and the level of the first compressor is still showing the same signal lost  when the poorman is connect.

What do think is wrong here?

skal1

 

[lolo-m]

hi lolo-m

i took the mixer out of the set up and the level of the first compressor is still showing the same signal lost  when the poorman is connect.

What do think is wrong here?

skal1

Your mixer has got a high impedance input. PM670 has got low impedance input.
The "problem" isn't your mixer. The "problem" comes from the compressor out to PM670 in . To be honest you don't have any problem if the loss is around 6dB with the poorman inserted between the compressor and the mixer. Simple ohm law applies there:

P = R x I x I

If R is divided by 2 it will result in a U divided by 2...

PS : Are that the chains you tested :
1°) DAW into compressor into PM670 into mixer
2°) DAW into compressor into mixer
If they are , and if the loss is around 6dB on the first chain, I think it is normal.

 

[skal1]

hi lolo-m

i took the mixer out of the set up and the level of the first compressor is still showing the same signal lost  when the poorman is connect.

What do think is wrong here?

skal1

Your mixer has got a high impedance input. PM670 has got low impedance input.
The "problem" isn't your mixer. The "problem" comes from the compressor out to PM670 in . To be honest you don't have any problem if the loss is around 6dB with the poorman inserted between the compressor and the mixer. Simple ohm law applies there:

P = R x I x I

If R is divided by 2 it will result in a U divided by 2...

PS : Are that the chains you tested :
1°) DAW into compressor into PM670 into mixer
2°) DAW into compressor into mixer
If they are , and if the loss is around 6dB on the first chain, I think it is normal.

1°) DAW into compressor into PM670 into mixer ,gives me signal loss on the first comp
2°) DAW into compressor into mixer  no signal loss
3°) DAW into compressor into PM670 output  not connected  ,gives me signal loss on the first comp


does this like right lolo-m?

skal1

 

[[silent:arts]]

skal1,

looks like you first comp (what model btw?) can't drive the input impedance of the poor man.
doesn't matter, but might be a problem with the true bypass boards (jumping level).

 

[lolo-m]

Yes it seam to be right if the signal loss is around 6dB...
This is one of the reason that make the studio electronics manufacturers avoid transformers ( even if the main reason is the cost of transformers ).
To get a connection without too much loss between 2 transformers, we should have an output impedance of less than 150 ohm to feed the 600 ohm input transformer of the following gear... With tubes, it become really tricky to get this kind of impedance on the output ...

And bump, BTW what is this comp ?

 

[skal1]

Yes it seam to be right if the signal loss is around 6dB...
This is one of the reason that make the studio electronics manufacturers avoid transformers ( even if the main reason is the cost of transformers ).
To get a connection without too much loss between 2 transformers, we should have an output impedance of less than 150 ohm to feed the 600 ohm input transformer of the following gear... With tubes, it become really tricky to get this kind of impedance on the output ...

And bump, BTW what is this comp ?

That it now now more tube comps for me  :

[/quote]
And bump, BTW what is this comp ?
[/quote]

chas and dave comp  ;D


hey thanks for  insight lolo-m


skal1

 

[skal1]

ok i am back again, i did not really understand lolo-m theory ,so i took out the poorman input transformer with the gain switch still on  and directly connected to the out of the chas&dave .

everything seems OK ,until you start turn the gain switch  connected to the transformer  , the vu on the chas&dave moves down when the gain switch  is turned ccw and up when turned cw.


It seems like the gain switch is acting like an attenuator for chas  ,should this be happen ?


sorry for the botheration.


skal1

 

[radiance]

Would be nice to see a little schematic of the output stage from the chas. I find impedance always hard to grasp ... and a schematic would really help...

Also, it seems the VU from the chas is connected directly to the signal, no buffer....

 

[emrr]

PM660 input impedance is 1800 ohms.  It's defined by the 30K attenuator.  If you have a 10K:600 in front of that (between your other comp and the PM660), then your other comp is seeing roughly 30K as it's load.    You should not see any loss because of that, unless you are using a single 12AX7 (or similar) as a line output stage.  I think you have another problem. 

(30K actual) 10K:600 / 600:10K / 30K attenuator

If you are seeing 7 dB loss, you could say that your other comp has an output impedance of 30K (6dB power matching loss), and the other 1 dB is accounted for by the quoted transmission loss of the Edcors. 

 

[lolo-m]

everything seems OK ,until you start turn the gain switch  connected to the transformer  , the vu on the chas&dave moves down when the gain switch  is turned ccw and up when turned cw.

It seems like the gain switch is acting like an attenuator for chas  ,should this be happen ?

Should this happen  ? NO
It seam your attenuator isn't connected properly. It looks like you connected the wiper to the transformer. Edcor's pins 5 should be connected to one end of the resistor ring, 8 to the other resistor ring, the other end of each ring resistor tied together and connected to the CV, and wiper to the grids....

 

[skal1]

:-[ i think your right  lolo-m , when i originally wired the switch it was made in rev :'( and i had to do some jiggery pokery to make it work in the right direction.

i will have to order some new resistors to night .

its sounds right lolo-m ,even tho the switch works  properly

@emrr  how do you work out this reflected impedance thing, heres some thing i was reading last night when i was trying to figure out what you were taking about , might be good for the others how have problems with impedance,

http://www.radioremembered.org/outimp.htm

Skal1

 

[lolo-m]

The simplest thing to know about transformers is :
1°) A transformer hasn't got any impedance.
2°) A transformer is used to match impedance by refflecting a different impedance than the real load.
3°) Refflected impedance is (ratio X ratio), Voltage change is given by the ratio.

For example (EMRR)
10K/600 connected to 600/10K really means 4/1 connected to 1/4 so if the end impedance is 30K:
30K /(4X4) X(4X4) = 30K
Other example :
Load is 600 ohm
If the output transformer connected to this load is a 2:1
The electronics connected to the transformer primary will "see" a load of 600 X (2X2) = 2400 ohm and the Voltage on the load (secondary) will be 1/2 voltage of the primary's.

 

[mich]

1°) A transformer hasn't got any impedance.

- But a transformer is optimized to work at a certain impedance - thats why we have a 600/600 and a 10K/10K.
- My understanding of this is that the DCR will be very different between the 2 transformers in the above example.