the pimp / mod the Poor Man 660 thread
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lolo-m
Well-known member
I made a board layout for my second mod. I will share it. It is single-sided so I would like to know if it's worth to make some professional boards. The thread is here :
http://www.groupdiy.com/index.php?topic=32406.0
http://www.groupdiy.com/index.php?topic=32406.0
mikeyB
Well-known member
It's getting late and I can't find what I thought I had seen - maybe another thread -but didn't someone mention using a hybrid poweramp chip to replace the valve sidechain? Will this affect the sound drastically?
nite nite - need sleep!!
nite nite - need sleep!!
lolo-m
Well-known member
lolo-m
Well-known member
A few days ago, looking the amazing results Rotheu had on his PM660, I realized that there was maybe an "all tube" pimp that can be done on the Analag's PM660...
The first stage of the real Fairchild SCamp is a 12AX7 in class B mode. On Analag's design, this stage isn't present. I didn't scope (yes, I know, I should have ;D) the SCamp, but I'm quite sure the PM670 SCamp is a classic push-pull amp. So I added this missing ( ??? ) stage... And the result is: it seams to work !!!
I will have a lot of shows in the next 15 days so I won't be able to check this idea correctly untill next month. If someone wants to test it, it is quite simple. Look the Fairchild schemo and copy the first stage, then connect the output to the "threshold connector". Use the Threshold pot output to feed the 12AX7 grids.
Analag, am I right to think the 5687 are in pure AB mode ? I don't have anything to simulate the 5687 so...
The first stage of the real Fairchild SCamp is a 12AX7 in class B mode. On Analag's design, this stage isn't present. I didn't scope (yes, I know, I should have ;D) the SCamp, but I'm quite sure the PM670 SCamp is a classic push-pull amp. So I added this missing ( ??? ) stage... And the result is: it seams to work !!!
I will have a lot of shows in the next 15 days so I won't be able to check this idea correctly untill next month. If someone wants to test it, it is quite simple. Look the Fairchild schemo and copy the first stage, then connect the output to the "threshold connector". Use the Threshold pot output to feed the 12AX7 grids.
Analag, am I right to think the 5687 are in pure AB mode ? I don't have anything to simulate the 5687 so...
lolo-m
Well-known member
My last investigations on this mod aren't really revelant :-\... I only managed to add a DC threshold with this mod so I give up...
Anyway, for poeple who want to implement the "missing" DC threshold (not sure it is really a missing point but more Analag design wish), there's a way to do it with the SCAB (SCAmp Booster)... I will fix this Tuesday or Wednesday and post results here :
http://www.groupdiy.com/index.php?topic=32965.0
Thank you again Analag and Silent Arts for this wonderfull comp !
Anyway, for poeple who want to implement the "missing" DC threshold (not sure it is really a missing point but more Analag design wish), there's a way to do it with the SCAB (SCAmp Booster)... I will fix this Tuesday or Wednesday and post results here :
http://www.groupdiy.com/index.php?topic=32965.0
Thank you again Analag and Silent Arts for this wonderfull comp !
lewilson
Well-known member
- Joined
- Aug 9, 2005
- Messages
- 218
Hello all,
I have found the Russian 6n5p tube to be a nice sub for the 6bc8 tube, Much smoother fuller compresion and overall a better quality tube than the american tubes. Its the same pinout as the 6bc8 but uses more filiment current.
I have found the Russian 6n5p tube to be a nice sub for the 6bc8 tube, Much smoother fuller compresion and overall a better quality tube than the american tubes. Its the same pinout as the 6bc8 but uses more filiment current.
It will be nice if you can post some sound samples, 6N5P against 6BC8lewilson said:
lolo-m
Well-known member
Is it a direct substitute ? I mean did you just plug them with the same settings or did you change the 2 bias settings ? I bought some to have different compression flavours on my 2 PM670...lewilson said:
khstudio
Well-known member
I'm gettin close. I'm also lucky that my brother can make me Vinyl stickers.
Pos 1 thru 5 will be some of Blue Bird's & Pos 6 will be stock... should be cool & give enough options.
Pos 1 thru 5 will be some of Blue Bird's & Pos 6 will be stock... should be cool & give enough options.
khstudio
Well-known member
See Below
khstudio
Well-known member
I posted a Blank - VOLTAGE CHART for everyone to download & hopefully fill out & post.
these measurements will help others troubleshoot none working units & narrow down problem areas.
Also confirm if your unit is working properly.
these measurements will help others troubleshoot none working units & narrow down problem areas.
Also confirm if your unit is working properly.
khstudio said:
buschfsu
Well-known member
kev,
i have a 2 deck 6 position switch for my TC that works with my purusha case. Can you share how you wired yours? looks like you jumpered the 10uf on the board? is that right?
Also my purusha case has a hpf knob silk screened on the back. did i miss a thread on this? anyone have one built this way?
thanks
i have a 2 deck 6 position switch for my TC that works with my purusha case. Can you share how you wired yours? looks like you jumpered the 10uf on the board? is that right?
Also my purusha case has a hpf knob silk screened on the back. did i miss a thread on this? anyone have one built this way?
thanks
khstudio
Well-known member
I will try to make a drawing as soon as I have time... it's not too hard.
I think if you read back I mentioned what values i used & I like them a lot!
I think if you read back I mentioned what values i used & I like them a lot!
khstudio
Well-known member
This is part of an email I sent to Rowan concerning using only ONE 5687 in the sidechain:
Thanks for the info...
Do you see any downside to the one tube side chain at all?
What about charging the 10uF Cap?
This comp really pulls a lot of current & if it reacts the same with 1 or 2 tubes I wonder why it even has 2 to begin with.
My next question should be about the possible need to adjust the cathode resistor for the single tube operation.
lolo-m said:
Thanks for the info...
Do you see any downside to the one tube side chain at all?
What about charging the 10uF Cap?
This comp really pulls a lot of current & if it reacts the same with 1 or 2 tubes I wonder why it even has 2 to begin with.
My next question should be about the possible need to adjust the cathode resistor for the single tube operation.
khstudio said:I must say I'm really surprised that no one else is having issues with a HOT Edcor Power transformer.
Here are the readings:
Total Heater Current draw = 5.27 amps
15 min = 98 deg F
30 min = 110 deg F
45 min = 115 deg F
60 min = 120 deg F
90 min = 128 deg F
120 min = 135 deg F
At this point the PT is too hot to keep your hand on for more than 5 seconds... if that!
Here are the readings with "Just ONE Tube in the Side Chains" - Both Ch:
Total Heater Current draw drops from 5.27 amps to 3.58 amps
15 min = 95 deg F
30 min = 98 deg F
45 min = 103 deg F
60 min = 106 deg F
90 min = 107 deg F
120 min = 107 deg F
MUCH Better, no?
noulou
Well-known member
Right! Pimping time!! ;D
First of all, many thanks to lewilson for the Russian valves tip. I tried them and they work great as a 6bc8 sub. I have to say I also prefer the sound to the american valves. East-West 1-0.
I am thinking of upping the supply voltage to them, like bluebird did with his 6ba6s.
I think 200v should be cool with them, what do you all think?
http://www.mif.pg.gda.pl/homepages/frank/sheets/049/6/6BC8.pdf
http://www.mif.pg.gda.pl/homepages/frank/sheets/113/6/6N5P.pdf
Now, with the all important time constants...
In my opinion, this is where it's at!
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. ;D ;D
(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 favourite compressor.
Beautiful compression action, especially with those short release times.
Who cares about 50 watt sidechains and sub-microsecond attack times?
If I wanted to completely trap the transients I'd turn to a digital limiter, which can also look into the future.
I don't think I have a need for lolos boards after all. I say let some of those sneaky transients through!
I'll report back once I tweak those time constants even more. (hopefully with sound examples).
First of all, many thanks to lewilson for the Russian valves tip. I tried them and they work great as a 6bc8 sub. I have to say I also prefer the sound to the american valves. East-West 1-0.
I am thinking of upping the supply voltage to them, like bluebird did with his 6ba6s.
I think 200v should be cool with them, what do you all think?
http://www.mif.pg.gda.pl/homepages/frank/sheets/049/6/6BC8.pdf
http://www.mif.pg.gda.pl/homepages/frank/sheets/113/6/6N5P.pdf
Now, with the all important time constants...
In my opinion, this is where it's at!
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. ;D ;D
(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 favourite compressor.
Beautiful compression action, especially with those short release times.
Who cares about 50 watt sidechains and sub-microsecond attack times?
If I wanted to completely trap the transients I'd turn to a digital limiter, which can also look into the future.
I don't think I have a need for lolos boards after all. I say let some of those sneaky transients through!
I'll report back once I tweak those time constants even more. (hopefully with sound examples).
lolo-m
Well-known member
khstudio said:
In stock TC network (as in Fairchild's pos 5 &6) the SCAmp charges the cap paralleled to the grid resistor first. This gives you the attack time ( in Analag's it is a 220nF). Then it charges the rest of the circuit... Less power will certainly mean in Analags' TC network only less release (or a weird release action)...
Paralleled tubes in push pull technology gives you more power and more linearity....
khstudio
Well-known member
Do you have any tips you could share about how best to test the release times?
I'd like to do a comparison once I get my unit back up & running.
Thanks for you help.
Do you mean slower, faster or what?
I'd like to do a comparison once I get my unit back up & running.
Thanks for you help.
Do you mean slower, faster or what?
lolo-m
Well-known member
Certainly a faster release as the cap won't be charged enough but certainly too with a fast peaky reduction and a release time starting at a different gain reduction... I don't know how it can sound...
All this is what I suppose, I can't say this is what happens...
All this is what I suppose, I can't say this is what happens...
khstudio
Well-known member
Cool... The reason I'm asking is, before my unit went down I had tried it both ways but settled on the Single side-chain tube because of the heat (or until I got it situated) I had recorded a few different tracks with each setup + I still remember how it felt... especially on this one Bass track I'm working on.
I do think it was a little better sounding with both tubes... something is a little strange with the release I think but can't put my finger on it.
I will say that it still does work very well... just maybe not optimal.
Thanks.
I do think it was a little better sounding with both tubes... something is a little strange with the release I think but can't put my finger on it.
I will say that it still does work very well... just maybe not optimal.
Thanks.
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