the Poor Man 660 support thread

[alexc]

That tube sub plus the time constant mods (from bluebird) make this quite an impressive unit.

Just starting to listen to it on submixes and program where a characterful limiter is needed.

Am building a channel strip : the Orange 86 + 6AS6 saturation -> Angelfire 3band EQ -> Poorman Limiter

Should be fun. Just about ready to start the chassis!

 

[radiance]

I finally tried the 6N5P sub (as suggested by Kingston) - and am very impressed by the improvement.

Same here...
For me, matched tubes (6N5P's in my case) plus a healthy heater PSU solved all my problems...being distortion and weird channel, knob and meter interactions. The healthy heater PSU part involved an extra heater voltage toroid and bigger supply caps (3300 uF, was 1000uF) on my slow start heater boards which are each fed by there own bridge.

Also, the side chain booster with custom time constant caps and resistors made the poorman so much more usable, at least for me.... 
I tried the original Fairchild values but they were not for me...I like fast release times...

 

[mitsos]

well, it's nice to see people saying good things about this build! Mine is (still) not done, but I've still got hope. Last time I tested it, I had some hum issues which I think is just insufficient heater capacitance... found some more caps now, and I'm break this out again soon and try it out, then get some 6n5p's..

What are the bluebird timing mods? I tried a T-attenuator on the input (IIRC he was the first to bring that up even though it's the way the Fairchild was wired) instead of the stepped switch, seems to work well, although I can't be 100% sure it's OK until I solve my hum problem. Much easier to wire anyway

 

[radiance]

What are the bluebird timing mods?

see attached...

 

[idylldon]

What are the bluebird timing mods?

I believe most of this is from bluebird with some other info from other folks (sorry, didn't note who wrote what):


The Main mod I wanted to suggest has to do with the time constants.

I just wasn't getting the flexibility out of the attack and release I wanted.

So I started off by adding a switch to change C4 (10uF) I used these values.
10uF, 6.8uF, 4.7uF, 1uF

I still felt like the attack knob wasn't changing the time constant enough.
I glanced over the original 670 schematic and realized it has a resistor in parallel with the time constant caps not in series that changes.

EDIT I'm sorry there are also resistors in series with the capacitors in addition to parallel. these would have an effect on attack time. EDIT

So basically I PUT (RV7) IN PARALLEL WITH (C4).

I put RV7 on a 5 position switch and used these values:

25K, 65K, 150K, 470K, and an open position (you could use 2 megs)

The higher the resistance the longer it takes the cap to discharge through it. longer release. the smaller the cap the shorter time it takes to fill up. shorter attack.

switching up the combination of the two makes for a lot of flexibility.


Voltage rating of caps:  there is no high voltage in this stage.  In my opinion you are fine with - let's say 63V.

I wanted to mention an easy way to get a good range of time constants without big changes is to just use the resistor values I mentioned earlier in parallel with the 10uf cap. You don't really have to change the cap value to get a good variation of release times. It has a lot more effect than the stock 10K pot in series with the 10uf cap.

I've scaled back to three caps. 10uf, 6uf, and 2uf.  Also using just three resistors in parallel with the caps. 68K, 470K, and 3m (or no resistor).  With those caps and resistors you can simulate the first three or four time constants of the real 670.

I've been using the 2uf and 68K in parallel setting the most. this is closest to the fastest fairchild setting. its great on bass drums vocals, just about anything. I'm sure its not the exact same because of the weaker sidechain but I'm loving it

I should also mention that I don't EVER use the Analag/Rowans original time constants because they are WAY too slow I used "Bluebirds" advise & set up a 2uf cap with various "switchable" resistors for release times. I think 68k, 180k & 470k then one position with just the 2uf (no resistor). My position 5 is blank for now & 6 is Rowans 10uf. These combination's work GREAT for vocal, bass... most things really.
Note to everybody: in Analag's design, the faster attack is with the 10K pot set at 10K... The lower it's value, the longer is the attack or to be precise the softer is the attack... The release time is function of the program which charged the network. More clearly, if the comp compress during a short time, the 10uF will be charged during a short time and the release will be quite fast. If the comp compress during a long time, the 10uF will be charged more and its discharge (release) will be longer... It is an adaptation with really interesting attack/release of the position 5 and 6 of the Fairchild.

The original design has far too long release times for my taste. I tried to measure the release time, got bored, went for lunch and when I came back the meter returned to 0vu. About 25 minutes i think.  (joking)

So, I took out c4, jumpered it and substituted it with different capacitors and resistors in parallel.

At the moment I have:
1u2 // 50k
3u3 // 100k
4u7 // 150k
5u6 // 1meg
6u8 // nothing
10u // nothing

Mind you, these are just values I had in hand. I installed them in order to start aurally tweaking the beast.  BOOM!!!  I haven't taken it to the studio yet, but listening at home I can easily see the poorman becoming my favorite compressor.

Beautiful compression action, especially with those short release times.


So based on what you explained (thanks by the way), my table:

Slow attack                                    Fast attack

      10uf  6.8uf  4.7uf  2uf  1uf  0.5uf
        None  2M  470k  150k  65k  25k

Slow release                                  Fast release

Bluebirds schematic can be found in this post:

http://www.groupdiy.com/index.php?topic=29056.msg369127#msg369127

Back to me.  I did a similar mod to mine based on Kevin's (khstudio) suggested values, which I've forgotten right now but maybe he'll chime in to mention them.  This TOTALLY transformed the compressor into something FAR more usable and flexible.  Even though I loved my 670 from the beginning, I REALLY love it now.

Cheers,
--
Don

 

[mitsos]

wow, thanks guys, that's a lot to digest.. gonna try to finish this thing up soon. It's been boxed up since I moved....

 

[idylldon]

gonna try to finish this thing up soon. It's been boxed up since I moved....

You won't regret finishing this one up.  I used mine all day in the studio today and it makes me smile every time I run pretty much anything through it.  Today it was lead guitar.  The ol' Poor Man worked like a charm.

Cheers,
--
Don

 

[dingo]

hello!
have my pm 670 under test
just one channel at time because a faulty 600/10.k edcor transf.

voltage are :  on 245 rail - got 243 v
                    on 136 rail -  ... 130-132v
slow start heather  6.3 v
and -17 and +17
tube are matched

the unit sound ok  no distortion no hum  ;D
rv3 -2,4v  rv6 -4,5v
the problem is when shut down  and turn on again after a while ???
the voltage on 245rail drop down to 40 or 50v
q4 irf840 is my main problem
all the other transistor are ok
d7 is ok
have tried 6 of them...all gone!!  and same problem after power off  and power on after discharge
now i need to order more irf840  can IRFB11N50APBF be the more powerful substitute?
have read most of support thread and all the problem on the psu board
and something about C6 47uf eletrolitic on psu board should be film cap 0.47uf it is  right?
do i need  to change this cap i am using 47uf 400v eletrolit.
on 136 rail  my voltage are fixed on 130v  do i need to tweak this  for 136v  can use a trimmer on r9?
thanks!

 

[radiance]

the problem is when shut down  and turn on again after a while ???
the voltage on 245rail drop down to 40 or 50v
q4 irf840 is my main problem

Maybe try a bigger heat sink? This is just a wild guess, but since your saying that even after discharge you have this problem, it might have something to do with the transistor still being hot or so??
Does it get hot during start-up?

and something about C6 47uf eletrolitic on psu board should be film cap 0.47uf it is  right?
do i need  to change this cap i am using 47uf 400v eletrolit.

Analag suggested a 0,47uF film cap, or even no cap at all...

on 136 rail  my voltage are fixed on 130v  do i need to tweak this  for 136v  can use a trimmer on r9?
thanks!

I should leave it at 130V....but you can use a trimmer on R9 if you really want the 136V I guess...

 

[idylldon]

and something about C6 47uf eletrolitic on psu board should be film cap 0.47uf it is  right?
do i need  to change this cap i am using 47uf 400v eletrolit.

As radiance pointed out, analag suggested changing this out, but I have the 47mfd in there and haven't experienced any problems. 

What have others done with the cap in this position?

Cheers,
--
Don

 

[dingo]

hello Radiance
the main problem is around irf840 Q4
when start up q4 is normal in temperature after 1hour or more is quite hot have a big heat sink there!will try bigger one
but compressor still work
then shut down ...and maybe turn on the day after ...and voltage drop to 50v sometime....sometime less
Q4 measure strange values  around the legs
change q4 to a new one  turn on ...voltage are ok  and sound ok .... but after new start  same issue!!
now must order more irf840 for other test
will try  change c6  or bypass it
other suggestion?
thanks!

 

[kazper]

http://www.groupdiy.com/index.php?topic=28274.msg520053#msg520053

Voltage chart prior to modifications

Analag recommended:

1) Remove or make C6 a film cap under 1uF and suggested 0.47uF Film

2) Break the trace between D3/D4 and C1. I suggest a 10W wire wound 50R or more, shunt C1 with about 150K or less. You will have to go off board with these.
Illustrated :
http://www.groupdiy.com/index.php?topic=28274.msg520306#msg520306

 

[radiance]

...and maybe turn on the day after ...and voltage drop to 50v sometime....sometime less
Q4 measure strange values  around the legs
change q4 to a new one  turn on ...voltage are ok  and sound ok .... but after new start  same issue!!
now must order more irf840 for other test
will try  change c6  or bypass it
other suggestion?
thanks!

Very strange indeed....beats me..

Yes, try changing C6. Also, are you able to test Q4 in any way?
The idea is to take a fresh irf840, put it in the poorman and turn it on. Now turn it of and remove the irf840 so you can test it out of the circuit.

I don't know if this is going to work but try putting a couple (two or more) of NTC's in series  between the toroid and the IEC inlet.
These NTC's are used to limit inrush current and might help to ease the start-up load for the irf840.

I used some NTC's  in my mixer PSU which has 3 toroids. The inrush current was so high that without the NTC's I had to use a fuse that was way to high.

Did you measure the voltage before Q4 during start-up? Best way to do this is with a DMM with a so called record function.

 

[living sounds]

Hi,

I'm finally, finally attempting to finish my PM670. Main voltages on the PSU are OK, but the slow start heater once connected to a channel only puts out 100mV and 200mA. I can set it to 6.3V only when it's not connected to the channel. Couldn't find any obvious mistakes. Both slow start heaters behave this way? What to do?

Thanks in advance!

 

[radiance]

Hi,

I'm finally, finally attempting to finish my PM670. Main voltages on the PSU are OK, but the slow start heater once connected to a channel only puts out 100mV and 200mA. I can set it to 6.3V only when it's not connected to the channel. Couldn't find any obvious mistakes. Both slow start heaters behave this way? What to do?

Thanks in advance!

What toroid are you using? Have you tried powering just powering 1 channel? Or are you building the mono version?
These slow start heater boards need SERIOUS heat sinks.
Also, to get near DC from these boards the 1000uF caps are not going to cut it.
I've found 16V 3300uF panansonic caps that DO for the same footprint. Whit the 1000uF caps I had 0,8V ripple, now it's 0,02V or less..
With the 1000uF caps I could not get the heaters above 6V, now I can get 7V easily...all with poorman boards connected.

Here a link to my earlier heatsink troubles...

http://www.groupdiy.com/index.php?topic=28274.msg508277#msg508277

 

[dingo]

hello Radiance!
thanks for the info!!
what value is better for ntc?
transformer  is the toroidal one from silent art
yes i have tested q4 irf840  in the circuit and all the voltage are ok at first start up , one channel only ,all tubes.
all the other irf840 used before ,off the board measure different
values between each leg using a simple diode tester function on my multimeter
all after the voltage drop!
irf840 have a big heat sink isolated

slow start have 3300uf on and regulators are on heat sink and all fixed in a big piece off aluminium used for separate the psu.toroid from
rest of the boards
ordered a pack of irf840  and will try!!
i would try to change input tranny and maybe out
what do you think about use sowter 4383 ? or maybe jensen jt6110k-b
have listen the edcor600:10k and to my ear are to much in hi-frq range!!
have finished etch scamp booster prototype and will try it

 

[living sounds]

Hi,

I'm finally, finally attempting to finish my PM670. Main voltages on the PSU are OK, but the slow start heater once connected to a channel only puts out 100mV and 200mA. I can set it to 6.3V only when it's not connected to the channel. Couldn't find any obvious mistakes. Both slow start heaters behave this way? What to do?

Thanks in advance!

What toroid are you using? Have you tried powering just powering 1 channel? Or are you building the mono version?
These slow start heater boards need SERIOUS heat sinks.
Also, to get near DC from these boards the 1000uF caps are not going to cut it.
I've found 16V 3300uF panansonic caps that DO for the same footprint. Whit the 1000uF caps I had 0,8V ripple, now it's 0,02V or less..
With the 1000uF caps I could not get the heaters above 6V, now I can get 7V easily...all with poorman boards connected.

Here a link to my earlier heatsink troubles...

http://www.groupdiy.com/index.php?topic=28274.msg508277#msg508277

Thanks! I'm using the group buy torroid, too. After the big rectifier I get around 11V DC at the input of the slow start heater PSU. Right now I'm using just one PM660 channel for testing. The heater PSU gets warm (regulator, big resistors), but not excessively. With the heater PSU connected to the PM660 channel the voltage drops to minimal amounts (ca. 0.1 V), and no amount of turning the heater trimmer can change that (unconnected I can set it to anywhere between 0 and 11V DC). The input voltage at the heater PSU remains at 11V.

 

[dingo]

hello radiance!
have found this ntc:

    * TERMISTORE, NTC, 10R, 5A
    * Tipo termistore:NTC
    * Resistenza:10 OHM
    * Beta Value (K):1208
    * Operating Temperature Rangea -55°C a +170°C
    * Operating Voltage Range:265V
    * N. of Pins:2
    * SVHC:No SVHC (18-Jun-2010)
    * Beta Value Lower Limit Temperature:25°C
    * Body Diameter:16mm
    * Current Max:5A
    * Lead Length:32mm
    * Lead Spacing:7.5mm
    * Operating Temperature Max:170°C
    * Tensione operativa:265V
    * Package / Case:Radiale
    * Power Dissipation Ptot Max:3.9W
    * Resistance Tolerance:± 20%
    * Serie:B57238
    * Temperature Upper Limit Beta Value:100°C
do you think it is ok

 

[radiance]

hello radiance!
have found this ntc:

    * TERMISTORE, NTC, 10R, 5A
    * Tipo termistore:NTC
    * Resistenza:10 OHM
    * Beta Value (K):1208
    * Operating Temperature Rangea -55°C a +170°C
    * Operating Voltage Range:265V
    * N. of Pins:2
    * SVHC:No SVHC (18-Jun-2010)
    * Beta Value Lower Limit Temperature:25°C
    * Body Diameter:16mm
    * Current Max:5A
    * Lead Length:32mm
    * Lead Spacing:7.5mm
    * Operating Temperature Max:170°C
    * Tensione operativa:265V
    * Package / Case:Radiale
    * Power Dissipation Ptot Max:3.9W
    * Resistance Tolerance:± 20%
    * Serie:B57238
    * Temperature Upper Limit Beta Value:100°C
do you think it is ok

Yes..that will work. However, I'm not sure this will fix your problem. It won't make it worse though;-)
You might want to check the components  surrounding q4 as well. Maybe a wrong value or a faulty diode??

This PSU design is way over my head. Maybe someone else more knowledgeable can chime in? 

 

[radiance]

Thanks! I'm using the group buy torroid, too. After the big rectifier I get around 11V DC at the input of the slow start heater PSU. Right now I'm using just one PM660 channel for testing. The heater PSU gets warm (regulator, big resistors), but not excessively. With the heater PSU connected to the PM660 channel the voltage drops to minimal amounts (ca. 0.1 V), and no amount of turning the heater trimmer can change that (unconnected I can set it to anywhere between 0 and 11V DC). The input voltage at the heater PSU remains at 11V.

Have you tried taking 2 tubes out?