the Poor Man 660 support thread

[tommypiper]

Moby, what are you referring to?  Are you making some PCBs?

Can someone point me to info about the mid/side feature?  Somehow I've not seen it before.

(Yes, I tried a search...)

 

[lolo-m]

Moby, what are you referring to?  Are you making some PCBs?

Can someone point me to info about the mid/side feature?  Somehow I've not seen it before.

(Yes, I tried a search...)

The mid/side feature is a M/S matrix encoder/decoder. Originally, Fairchild incorporate this for vinyl disk cutting. The mechanical reading of a vinyl can make the diamond jump if the L/R/Mono are too different.
Nowadays, CD can be engraved without any problem without controlling how much are different L and R. So the M/S matrix feature nearly disappeared from the mastering compressors. Some still use it to compress more or less the two parts of a stereo signal (mono part / pure stereo part). It can help to tame a vocal too loud or to open the stereo of a mix for example...
It is the lateral/vertical function (meaning side/mono word to word)

 

[Kingston]

Kingston,
Although I disagree with your previous harsh words on it not being a Fairchild I will be a good sport

my gripe is just using the panel in this context is a bit of a fraud really. Technically it is very impressive with custom sheet metal work. It's a perfect panel, and congratulations for that.

Here is the M/S network

pm me if you want the BRD for Eagle CAD.

Thanks for showing this. It was as I suspected. There's basically one unused relay in there, but I understand this was probably a good choice for layout reasons.

No need for any Eagle files. I still draw my PCB's manually in CAD.

Mikko, if you need that board I can add that to the list  

Sometime after x-mas, I'll show you the drawings.

 

[Moby]

Moby, what are you referring to?  Are you making some PCBs?

Sorry is i confused you, yes, I helped couple of projects (Lolo's SCAMP and Mikko's MK7 project) with PCB manufacturing because I have good local shop.
Regarding M/S yes it's a bit obsolete mastering process but it's still really helpful if you have problematic mix to master, like Lolo mentioned in his explanation.

Sometime after x-mas, I'll show you the drawings.

No prob mate  ;D

 

[Kingston]

the most important modern use of mid-side processing in this type of configuration is the control of stereo image. Channel gain controls turn into mid-side faders, and you can compress the mix mid and side parts separately. Very smooth stereo image corrections possible. Also more drastic enhancement tricks.

This is usually much more effective than any monkeying around with various stereo link options.

 

[tommypiper]

Thanks for the explanations, Lolo, Moby and Kingston.   8)  Is there a straightforward way to implement the M/S in this project?  (I don't want to copy anyone's work, unless they offer it.)  

I've been wanting to work with M/S encoding,,,, and I knew there was M/S in the original 670 but I wasn't sure how to fully implement it in the PoorMan version !  So I'm thrilled to see Chuck doing it and Kingston working on it.  

I'd love to try and build it, but is there some information about how to implement it somewhere?  Chuck, did you just copy from the original drawings?  How did you come up with the relay system?  I don't think I could design a relay system from scratch... cheers.

 

[Kingston]

Just look at the original fairchild 670 schematics. it's all there. The most important part is to realise is the fact you can't use the plain edcors for this. You need dual primary windings on the make up gain amp input transformers, and dual primary and secondary windings on the make up gain amp output transformer. You *could* hack the edcors to get it done, but they probably aren't going to perform adequately in this configuration. Lundahl, and many others will.

Then you need a 10-pole double throw switch (not gonna find one), or 5 DPDT relays switched by SPST switch. lots of options.

 

[TheGuitarist]

I know sourcing parts is a big part of DIY,

but i'm having alot of trouble finding the 24 pos 2 deck switches for the gain and threshold.

I've found the switch on the elma website, and the smd resistor loaded one looks like the one i need (i hope, please correct me if i'm wrong)

I just can't seem to find anyone who stocks them... do i have to contact elma directly? Just a little confused.

 

[capnspoony]

Hello all,

I have a few comments that maybe someone can shed some light on.  

All edcor iron including the power transformer.  I have no heat problems but got a beast of a coil resistor and a lot of ventilation.

1) I find that this unit to my ear adds some odd mid frequencies say 4-600.. I hear a good bit more low end that I LOVE but at the same time strapping this along an entire mix I hear it attacking vocals in a bad way... anyone else experience this?

2) I feel like my attack knob barely does anything.  If i swing it from one extreme to the other I can barely hear a difference.  All the way to the left feels a bit more open than all the way to the right presumably a faster attack to the left (counterclockwise).  

All and all I like this piece but as of now I just don't see it beating out other gear I've made in the past and am not entirely blown away by it.  I greatly appreciate all the hard work that has gone into the design but... well I've already said my piece but am wondering if there's anything I've overlooked or if this is the general vibe felt by others?  

Is there any way to do a test on the attack pot to make sure its working okay?  I certainly hear a difference but its not as drastic as I'd like to hear.  I have a scope and generator but wouldn't know a test to show this is working

anyway here are some pics

cheers
best
Richard  

 

[Kingston]

Your time constant pot behaviour is completely normal. It is very subtle. By the way it's not really an attack pot. As far as I know it only sets the speed one half of the "dual release" caps. The original analag time constant network has a long auto/dual release, and that pretty much undoes whatever the pot would do in a more direct time constant network (ie. 1 resistor and a 1 cap).

Lots of info and choices have been posted on time constant network modifications.

Your mid frequency problems might be similar to the distortions I have experienced, if you would not mind reading back about 5 pages. Basically related to badly matched tubes and/or amplification asymmetries cause by the edcors. But you must measure and scope them to know better. Otherwise it's just speculation.

All and all I like this piece but as of now I just don't see it beating out other gear I've made in the past and am not entirely blown away by it.  I greatly appreciate all the hard work that has gone into the design but... well I've already said my piece but am wondering if there's anything I've overlooked or if this is the general vibe felt by others?  

pretty much sums up my feelings as well. Certainly lives up to the "poorman" name. It will take a shitload of upgrades and modifications to get it to behave.

 

[idylldon]

All and all I like this piece but as of now I just don't see it beating out other gear I've made in the past and am not entirely blown away by it.  I greatly appreciate all the hard work that has gone into the design but... well I've already said my piece but am wondering if there's anything I've overlooked or if this is the general vibe felt by others?

pretty much sums up my feelings as well. Certainly lives up to the "poorman" name. It will take a shitload of upgrades and modifications to get it to behave.

I have to agree.  I will have to get more tubes to see if matching them closely helps to mitigate the distortion I'm hearing when I try to run a mix through it.  It does have its charm on individual instruments, though, but I really wanted to have something I could strap across the 2-buss other than my GSSL when I wanted a change of flavor. 

Cheers,
--
Don

 

[inputoutput]

Agree.  So I just ordered four LL1676. Don´t know when I´ll have the time to install them, but I´ll record some "before and after" tests for you all when that time comes.  Probable very subtile differences.

Can they be installed in reverse too (as 10K:600). Can I go for eight LL1676?    Any opinions, or tips before I smack ´em in?

 

[radiance]

This beats me....

...such a simple circuit
....quite a few successful builds (well, we don't know for sure but there are no complains)
.....quite a few problematic builds
.......no consensus on what seems to be the matter with the problematic builds
........some have heat problems, some don't...

My build is going at snails speed right now and these problems don't sound very encouraging.

I think we should make a list with possible problems.
These are the ones I've read about so far (except from the usual suspects such as bad shielding, not enough space, layout, grounding etc. etc. ):

-Underspecced Power transformer
-Badly matched tubes
-Varying 5687 specs
-Varying Edcor audio transformer specs,  (not sure...)
-Wrongly wired Edcor audio transformer (as in: bad quality control @ Edcor)

 

[capnspoony]

Hey Guys,

thanks for the quick response back.  I'm certainly going to look into this unit sounding like it has the common cold.  I suspected edcor to possibly be the culprit and then I'll move to the tubes. I agree a list of similar ailments would be helpful to others here.  I need to spend a few hours looking back in this thread - I haven't been through it because it was just finished and it works "fine" 

I'll try and complete some sweeps of my iron in the meantime and go from there.

Also, I'm in the same boat - wanting to strap something else other than my gssl along mixes, which does work great BUT this was intended to be my alternate for strapping and would love to get it up to snuff.

Best
Richard

 

[benlindell]

Ok guys, last time I want to triple check I'm going to make up my rotary switches correct, Let me know if this diagram is correct

 

[benlindell]

bump for a confirmation.

thanks.

 

[khstudio]

I haven't been around here for a while because (as some of you know) I had my share of problems with my build but I must say I learned a LOT about Vari-Mu comps!

Just to recap, I'm running my unit with just ONE tube in the side-chain & it works well & keeps my unit running MUCH cooler.. especially the PT.

I spent soooooooo much time on this thing... WAY more than I've ever had to with anything I've ever built. After finding that the "Tubes" (Philips) were the culprit I switched to "Tung-Sol"

I did everything I could from matching tubes, changing PT & swapping Edcore TX's & I found that the PM670 is what it is.

I had to say fuck it & put it in the rack (even though it DOES have a little too much distortion/color for full 2 buss material.
What I do like it on the most is Bass guitar... Regular guitars, vocals, etc... are sometimes cool too.

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.

I wish I could clean up a little bit of the distortion that occurs MOSTLY WHEN COMPRESSING!!!
The RAW gain, with NO Compression on my unit sounds pretty good.

If anyone finds a nice alternative to the Edcore TX's, PLEASE let us know... maybe this would help with the "Sound or distortion" I'm getting, who knows ???

For those of you who that have questions about my build, problems, setup, fixes etc... you'll have to read back in the thread.
I don't have time or energy to retype it all.

One thing I dropped the ball on was posting the voltage chart of my own build but it did match what Don, idylldon posted.

 

[radiance]

it DOES have a little too much distortion/color for full 2 buss material.

AFAIK forum member dagoose uses his unit for mastering  :-\

http://www.groupdiy.com/index.php?topic=28274.msg415199#msg415199

...at least it's there in the rack. Dunno if it sees much use.

 

[khstudio]

it DOES have a little too much distortion/color for full 2 buss material.

AFAIK forum member dagoose uses his unit for mastering  :-\

http://www.groupdiy.com/index.php?topic=28274.msg415199#msg415199

...at least it's there in the rack. Dunno if it sees much use.

I checked that link & he said he used it but had low end issues... not to mention, none of us know the "Standards" others go by or what they consider good or normal sounding.
From the feedback I read on this thread, there are PLENTY of comments about distortion.
I did not post back here to argue my point, findings... or "opinions".

BTW... did you build your unit yet & actually listen to it?

 

[dagoose]

it DOES have a little too much distortion/color for full 2 buss material.

AFAIK forum member dagoose uses his unit for mastering  :-\

http://www.groupdiy.com/index.php?topic=28274.msg415199#msg415199

...at least it's there in the rack. Dunno if it sees much use.

Kinda true but i must also confess that i just use it when i want 'some' color, it's far from clean.  
When i use it for mastering the meters are hardly moving and it really doesn't work on most material because of the distortion that starts when compressing more then 2 / 3db..
I also noticed that the low end is lost a bit..
It is indeed still in the rack but hardly used, in the beginning i was really happy with it but now? i don't know..  :-[

EDIT: just saw khstudio's reply. Indeed, loss of low end things like that..
But for some reason i still like it though..