Official 33609 builder's tread. See 1st page for updates.

[promixe]

Wow, there's been some discussion going on here! =) For some reason I stopped getting thread updates in the email... Weird.. Anyway:

RuudNL, thanks for your contributions to this thread. I have a few questions:

I replaced the intermediate transformer by a differential amplifier.

Did you happen to use OPA2604 for this? Did you wire it as single-ended positive only supply?

But even in the original state (without my addition), the LF distortion of my compressor is lower than the version of for example Promixe, as you can hear in the posted examples.

Would you have an opinion as to why your unit differs so much in LF distortion handling even with identical sidechains? What component are you referring to that would give erroneous superimposed harmonics onto CV?

Also, I think you might have mentioned earlier that you added 10:1 ratio mod to your compressor, is this correct? Or am I mistaking you for someone else? Did you calculate the values for that mod or did you use "empirical method" of just plugging in resistors and measuring until it matched the response? =)

Thanks!

 

[mata_haze]

Igor,
what are the compatible NEVE (original) opamps that can be used on this project?
I have a couple of B512 which I would like to use.

Best,
Mattia.

 

[Igor]

BA340/BA440 are the Neve ones.
It is possible to use other discrete opamps, like 990 etc, with additional components,
it was discussed here. I never had experience with B512.

 

[mata_haze]

Hello,
i have fired up my 33609 just now.i am having troubles on the very first line up point = unity gain.
I have done the "bias" to 280mV (across R44), left it there 15 more minutes and then injected (using a Neutrik A1) 0.775V into the unit, compressor and limiter in bypass but overall unit enganged.
even with the trimmer at maximum I am still -1.5dbu under unity gain.
is this right?!?!?!

I have done a check of all static voltages and they all seems in within specifications on the signal path section, the only ones which are a bit off are those in the compress ratio section. here is the list from Left to right

first voltage is what is supposed to be,second voltage is what I am getting

Tr3 base 17V = 17.78
Tr3 Collector 17.6= 18.43
TPA 4V= 3.46
Tr4 base 17V = 17.79
Tr4 Collector 4V=3.75
TPD 11.6 = 11.69

Tr2 Base 4.1V=3.2
Tr2 Emitter 4.7V=0.56
TR2 collector 0.64V=3.8
TR15 collector 9.9V=11

TR8 emitter (TP E) 0V=0.6

TR9 base 0.6V = 0

R2 23.8v= 23.85
R2 (Tr9 collector) 23.3V = 23.53

TR6 Emitter 20.4V= 20.42

TR10 base 7V =7.14
TR10 collector 17.4V = 17.4
TR10 emitter 6.4V = 6.5
TR11 emitter 2.5V = 1.63
TR7 emitter 23.7V = 23.85
TR7 collector 0V = 0

TR12 0.6V = 0.58
TR1 collector 0V = 0.1

I suppose the section where the compressor threshold is (due to the fact that is not lined up) could be all over the place?!

I am using st.ives 31267 at the input primary series secondary series.
Carnhill VTB 9045 in the interstage primary series secondary parallel
carnill VTB 9056 at the output.

The sine at the output (when the circuit is enganged, but compressor and limiter are in bypass) looks perfect. but I have tried to probe it (referenced to ground and to PIN3 after the input transformer) but I am not able to see much..

IGOR...what mistake am I making?!?!

Best,
Mattia.

 

[rob_gould]

Are you measuring between hot and cold pins at the output?  You should be measuring between hot and cold, not hot and ground. 

I made this mistake.  It's covered in some detail earlier in the thread.  As I recall (it was a good while ago for me) I had the same symptoms as you, and this was the reason...

 

[mata_haze]

Are you measuring between hot and cold pins at the output?  You should be measuring between hot and cold, not hot and ground. 

I made this mistake.  It's covered in some detail earlier in the thread.  As I recall (it was a good while ago for me) I had the same symptoms as you, and this was the reason...

Hi Rob,
I am using the Neutrik A1 to measure I believe it does it between hot and cold, but anyway, when the unit is in full bypass the gain it's absolutely fine, it drops 1.5 dB when enganged...so if the neutrik was not measuring correctly it should show both ways..

shouldn't?
??? ??? ??? ??? ??? ???

M.

 

[mata_haze]

couple more considerations:

-I have replaced the BA340 (Igor version) with a commercial equivalent but no change, therefore this roules out the op-amp.
-when the compressor section and the limiter sections are in bypass (but the unit is enganged) the only resistor responsible for the gain is R40, which sets the negative feedback (can anybody confirm?). I have checked and measures 1K3 as per schematic.
-on RV2, does that affect the BIAS of the bridge? if so shall I twick it a bit in order to see if it changes the impedance of the bridge and then come back to the line up procedure?

any help will be VERY MUCH appreciated 

this is all very interesting, I am getting to know the unit..I am just dying to get it working and use it  :

Best
Mattia

 

[Igor]

-I have replaced the BA340 (Igor version) with a commercial equivalent but no change, therefore this roules out the op-amp.

OK, both works than

-when the compressor section and the limiter sections are in bypass (but the unit is enganged) the only resistor responsible for the gain is R40, which sets the negative feedback (can anybody confirm?). I have checked and measures 1K3 as per schematic.

This is right. Just to confirm, you did not installed parts for use with 990 family of opamps
(they printed from bottom side on silkscreen, with suffix J, like RJ1, CJ1...etc).

-on RV2, does that affect the BIAS of the bridge? if so shall I twick it a bit in order to see if it changes the impedance of the bridge and then come back to the line up procedure?

No, it doesn't. Or shouldn't

Just to be sure, measure CV at LINK point is 0v.

I have done the "bias" to 280mV (across R44), left it there 15 more minutes and then injected (using a Neutrik A1) 0.775V into the unit, compressor and limiter in bypass but overall unit enganged.
even with the trimmer at maximum I am still -1.5dbu under unity gain.
is this right?!?!?!

No. Please check transformers are connected right, and all resistor's values where audio passes.

Tr3 base 17V = 17.78
Tr3 Collector 17.6= 18.43
TPA 4V= 3.46

OK, what is on TPB?

The rest seems fine as well

I am using st.ives 31267 at the input primary series secondary series.
Carnhill VTB 9045 in the interstage primary series secondary parallel
carnill VTB 9056 at the output.

I am not familar with Carnhills. Ratios are: input: 2:1, interstage 1:2, output 1:2.5
In general, this should work, check again transformer's ratios.

The sine at the output (when the circuit is enganged, but compressor and limiter are in bypass) looks perfect. but I have tried to probe it (referenced to ground and to PIN3 after the input transformer) but I am not able to see much..

When measuring with scope the out, connect pin3 to gnd and measure at pin2 of XLR.

IN/OUT PCB connectors (3-pin Molex, 2.5mm pitch) are btw 1+;2gnd;3-

Dunno. Really, dunno. Bit of patience, check everything and you will find wrong resistor or wrong connection or something like this. Check at primary of out. trafo there's 8db less than at its secondary.
Check when you feed 0db in, at interstage's secondary w/o compression there's -25db.

Good luck and keep us informed!

 

[mata_haze]

Hello,
done some checking and measurements.
all the resistors on PCB  are 100% correct,same for capacitors and their orientation.

output and pin 3 of the XLR (cold) shorted for the scope to be able to read.ground of the scope connected here.

here is what I have got (even though it's quite hard to read as the signal is really really small):
TPC= 100 mVpp (approximately) which should be about -17.7dBu (instead of the -25dBu that the schematic suggests)
TPD= 800 mVpp (note that my RV1 it's on ful at the moment) which should be -8.8dBu (instead of the 8dBu that schematic suggests)

TPA has 3.46VRms
TPB has 4.16VRms
CV to ground (chassis and therefore PSU 0V) has a constanto 90mV regardless of threshold or Ratio settings)

I also have done a full line up of the unit and it is in within specifications...apart from this 1.5dB of loss..
  
: : : :

I have noticed that R31 on the schematics it's  a 560 ohm while it becomes 680 on the PCB

question: do the two front PCB boards (compressor control and limiter control) affect the overall gain when the compressor and the limiter are not switched in?
the carnhill I am using should give +8dB at the output, having said that the gain at TPD it's already quite high...so where is it getting lost?!

puzzled...
:-\ :-\ :-\

M.

 

[mata_haze]

BUMP!

 

[Igor]

TPD= 800 mVpp (note that my RV1 it's on ful at the moment) which should be -8.8dBu (instead of the 8dBu that schematic suggests)

Schem suggests -8db

Are both (original and replacement) BA340's have same gain loss?
Maybe...it somehow loaded too hard? Try to remove output cap
next to BA340 (470uF) and see what happens at TPD-if there will be significantly more signal,
check trafo, resistors, etc. I think something wrong at BA340 stage. I asked before
about components for use 990 family of opamp, they should not be installed, please confirm.

TPA has 3.46VRms
TPB has 4.16VRms

It is OK, but they should have closer dc voltages.

CV to ground (chassis and therefore PSU 0V) has a constant 90mV regardless of threshold or Ratio settings)

Try to connect CV to ground and see what happens. I don't remember if there were some tens of
mv of dc at my units or no, but....worthy to try.

I have noticed that R31 on the schematics it's  a 560 ohm while it becomes 680 on the PCB

Doesn't matter; there are some different manual versions, this resistor does not affects gain,
it sets attack time for compressor.

question: do the two front PCB boards (compressor control and limiter control) affect the overall gain when the compressor and the limiter are not switched in?

If there's no compression, answer is no. They should be connected when adjusting the unit.

the carnhill I am using should give +8dB at the output, having said that the gain at TPD it's already quite high...so where is it getting lost?!

tpd should be -7.5...-8 db depending on trafo's load... I suppose somehow BA340's out is loaded too hard.

 

[mata_haze]

Hi Igor,
sorry I forgot to answer: none of the components for the 990 family are in (marker "J"),

Yes, both original and your BA340 have same gain loss, this points to the circuit around it correct?
I am going to remove the 470uF output cap and I will check all the components around there again.
will keep you posted,

Thank you ,
Mattia.

 

[Igor]

Great. We need to figure out where /at which stage/ gain is lost. Let us know about 470uf!

 

[bradbivens]

I'm getting close to being finished with the unit.  The audio section sounds great and the test proc is going without a hitch.  The only problem is my meter is displaying reduction in the wrong direction (compression makes needle go to the right).  I tried flipping the +/- on the meter connection with no luck.  Any ideas?

Brad

 

[ultra-alex]

mine too. seems like a pretty normal behaviour... 

 

[Igor]

This is the way 33609 meter works.

 

[StudioSQ]

so just got it finished after being in my project bin for like 2.5 years. it sounds great, i have original marinair input transformers and edcors for the rest. i love the edcors and they are sooo cheap. i really love this thing.

 

[Biasrocks]

Looking forward to building this guy.

As a result of some of the research I was doing regarding this project I came across this which goes into some detail about the distortion inherent in the 33609.

http://www.uaudio.com/webzine/2009/march/doctors.html

It basically says that the 33609 is capable of up to 10% harmonic distortion.

Mark

 

[dmp]

I finished up my build with only one mistake. I had one of the electrolytic caps backwards and got popping when I turned the gain switch. With that fixed, I was able to calibrate it just like the instructions and it seems to work really well. Hurrah!
I ran the audio samples through to compare to the distortion others were seeing (test1,2,3, then 4a). I got a very similar result for 4c & 4d - hearing the same kind of distortion. I'm not sure if the output from my soundcard is the same, but it was really heavy compression & limiting. The meter was going to 20 dB at times. I used Carnhill transformers. I haven't changed R10 as recommended yet.
It is not a musical distortion to my ears, it sounds more like clipping or a ground issue between the audio and sidechain paths.

 

[Biasrocks]

Does anyone have any 1N4153's they could spare?

Unfortunately my boards, which I bought second hand did not include them and Newark / Farnell has no stock here in Canada.

I'm doing a stereo build and I'm looking for 8 matched or a bunch that I can match up.

Mark