Official 33609 builder's tread. See 1st page for updates.
- Thread starter Igor
- Start date
Help Support GroupDIY Audio Forum:
Built with ll1540, ll1528, APP992 opamp, and some '80s Jensen output transformer.
All the bc184, 214 changed to 550-560.
Very good sounding compressor with a noise level about -100-110 db at 0db.
It was difficult to calibrate, I had to change one resistor on the input to have correct values for the Lundahl.
For those who also have the meter problem while calibrating I have a solution:
I had a misunderstanding in Igor's calibration procedure.
After having the 3V from the calibration circuit I had to adjust the contol voltage trimmer to have -8db on the output.
After it I had to adjust the calibration voltage to have -20db on the output.
Adjust the meter trimmer to see 20db gain reduction.
And after it Igor says: go back to..... No, I shouldn't have to go back and repeat.
In the Neve calibration procedure there is no need to repeat loops.
In the first step you calibrated the control voltage and in the second the meter full scale reading, and that's it, go for the next step!
Maybe it will help to someone else, it was a huge amount of time getting to this result
Cheers
All the bc184, 214 changed to 550-560.
Very good sounding compressor with a noise level about -100-110 db at 0db.
It was difficult to calibrate, I had to change one resistor on the input to have correct values for the Lundahl.
For those who also have the meter problem while calibrating I have a solution:
I had a misunderstanding in Igor's calibration procedure.
After having the 3V from the calibration circuit I had to adjust the contol voltage trimmer to have -8db on the output.
After it I had to adjust the calibration voltage to have -20db on the output.
Adjust the meter trimmer to see 20db gain reduction.
And after it Igor says: go back to..... No, I shouldn't have to go back and repeat.
In the Neve calibration procedure there is no need to repeat loops.
In the first step you calibrated the control voltage and in the second the meter full scale reading, and that's it, go for the next step!
Maybe it will help to someone else, it was a huge amount of time getting to this result
Cheers
Trench Recordings
Well-known member
I'm about to start this project. I took some scans of pcb boards if anyone is interested.
https://www.dropbox.com/sh/vs4jnqez8scuo8c/AADE-wYuCyXvxEb9WBFGmv2Ma?dl=0
https://www.dropbox.com/sh/vs4jnqez8scuo8c/AADE-wYuCyXvxEb9WBFGmv2Ma?dl=0
Biasrocks
Well-known member
Thank you, now I can resurrect the bad channel in my build. The BA340 was a thorn in my side for this build.
Mark
Mark
Trench Recordings
Well-known member
There is a bunch of 1/8 watt resistors on the bom around the switches and on the ba340 Opamp. Is this ok or should I go up to 1/4 watt ?
chefducuisine
Well-known member
There is no need to order 1/8 watt resistors. You can use 1/4 Watt resistors without a problem here. You need to bend them tight so they don't touch the front panel of your case when the whole PCB is being installed.
Have Fun - This is a really useful compressor!!!
Have Fun - This is a really useful compressor!!!
Trench Recordings
Well-known member
RuudNL
Well-known member
Did somebody ever measure the distortion at 40 Hz, at different ratios and release times?
My 33609 sounds reasonable with avarage program material, but produces audible distortion with bass guitars.
Distortion values at 4 or 5 dB gain reduction would be very interesting!!!
(Of course distortion will be higher when using fast release times on bass signals, but even with longer release times the distortion is present.)
The distortion MUST be produced by a ripple on the control voltage, because when I use DC as control voltage, the distortion produced by the diode attenuator is very low.
My 33609 sounds reasonable with avarage program material, but produces audible distortion with bass guitars.
Distortion values at 4 or 5 dB gain reduction would be very interesting!!!
(Of course distortion will be higher when using fast release times on bass signals, but even with longer release times the distortion is present.)
The distortion MUST be produced by a ripple on the control voltage, because when I use DC as control voltage, the distortion produced by the diode attenuator is very low.
RuudNL
Well-known member
Tonight I was still thinking about the different release times of the DIY 33609 and the distortion problem.
Suddenly I realized that I had seen a different circuit for the release bias voltage...
This morning I took a look at the schematic of the Neve 33314/B compressor/limiter, and I noticed that is it 99.9% the same as the 33609, but with one exception!
The 33314/B uses not ONE, but TWO diodes for the release reference voltage!
Since the BAX13 is also a silicon diode, this will give a higher voltage over the two diodes than over the single D11 (1N4148) in the 33609.
IMHO this will result in a longer release time and maybe (hopefully!) in a lower distortion.
I will test this modification and report the results. Interesting!
EDIT: Tested the DIY 33609 with two diodes. This brings the release reference voltage from +0.61 to +1.22 V.
Difference in release time and distortion is minimal.
I noticed that to obtain the same distortion values as the 'official' Neve 33609, I have to increase the limiter release capacitor from 10 uF to 15 uF (10+4.7uF), and the compressor release capacitor from 10 uF to 33 uF (10+22uF).
Of couse this will have an influence on all release times. Let's see if this is workable!
Suddenly I realized that I had seen a different circuit for the release bias voltage...
This morning I took a look at the schematic of the Neve 33314/B compressor/limiter, and I noticed that is it 99.9% the same as the 33609, but with one exception!
The 33314/B uses not ONE, but TWO diodes for the release reference voltage!
Since the BAX13 is also a silicon diode, this will give a higher voltage over the two diodes than over the single D11 (1N4148) in the 33609.
IMHO this will result in a longer release time and maybe (hopefully!) in a lower distortion.
I will test this modification and report the results. Interesting!
EDIT: Tested the DIY 33609 with two diodes. This brings the release reference voltage from +0.61 to +1.22 V.
Difference in release time and distortion is minimal.
I noticed that to obtain the same distortion values as the 'official' Neve 33609, I have to increase the limiter release capacitor from 10 uF to 15 uF (10+4.7uF), and the compressor release capacitor from 10 uF to 33 uF (10+22uF).
Of couse this will have an influence on all release times. Let's see if this is workable!
Attachments
Trench Recordings
Well-known member
Anyone know how to calibrate this unit ? Can't find instructions.
Thanks
Thanks
jensenmann
Well-known member
Anotherone finished:
I´ve used Marinair T1442 at the input, OEP interstage and Carnhill VTB9056 at the output. Happy camper
I´ve used Marinair T1442 at the input, OEP interstage and Carnhill VTB9056 at the output. Happy camper
prescott said:Built with ll1540, ll1528, APP992 opamp, and some '80s Jensen output transformer.
All the bc184, 214 changed to 550-560.
Very good sounding compressor with a noise level about -100-110 db at 0db.
It was difficult to calibrate, I had to change one resistor on the input to have correct values for the Lundahl.
For those who also have the meter problem while calibrating I have a solution:
I had a misunderstanding in Igor's calibration procedure.
After having the 3V from the calibration circuit I had to adjust the contol voltage trimmer to have -8db on the output.
After it I had to adjust the calibration voltage to have -20db on the output.
Adjust the meter trimmer to see 20db gain reduction.
And after it Igor says: go back to..... No, I shouldn't have to go back and repeat.
In the Neve calibration procedure there is no need to repeat loops.
In the first step you calibrated the control voltage and in the second the meter full scale reading, and that's it, go for the next step!
Maybe it will help to someone else, it was a huge amount of time getting to this result
Cheers
I have finished my compressor but have some problems with calibration
Cannot complete step 3.3 : setting unity gain with unit switched in but comp and lim bypassed. With RV1 at max i can't get over -0.5dB
I have used the lundahls for input and interstage, you are mentioning a resistor change, would be useful if you can point me in the right direction
Thanks in advance
I am scratching my head with this compressor. I have gone through all 47 pages of the thread and found some guidelines for troubleshooting the unit, which made me understand the circuit a bit better, yet i cannot make it work perfectly
Everything seems to be fine fine and also i don't have any particular problem with calibration steps, besides the unity gain is off by half dB
I have followed again the signal path and compared the readings to the schematic. I have attached the schematic in case someone can have a look
- at the input transformer secondary i have -8.4dB vs -6dB on the schematic - i have used a lundahl ll1540 wired 2:1
- at the interstage transformer secondary (TP_C) I have -28dB instead of -25dB - lundahl ll1528 wired 1:2.5
- the output of the ba340 is -6.5dB with the preset gain at maximum.
- the output transformer is a sowter 8403 wired 1:2 and i have -0.5dB at the output so even with the ba340 gain at maximum I cannot get to unity gain
I believe i need to change some resistor to match the lundahl transformers but I am wondering if would be better tweaking the input or the interstage ?
Everything seems to be fine fine and also i don't have any particular problem with calibration steps, besides the unity gain is off by half dB
I have followed again the signal path and compared the readings to the schematic. I have attached the schematic in case someone can have a look
- at the input transformer secondary i have -8.4dB vs -6dB on the schematic - i have used a lundahl ll1540 wired 2:1
- at the interstage transformer secondary (TP_C) I have -28dB instead of -25dB - lundahl ll1528 wired 1:2.5
- the output of the ba340 is -6.5dB with the preset gain at maximum.
- the output transformer is a sowter 8403 wired 1:2 and i have -0.5dB at the output so even with the ba340 gain at maximum I cannot get to unity gain
I believe i need to change some resistor to match the lundahl transformers but I am wondering if would be better tweaking the input or the interstage ?
dmp
Well-known member
beatnik,
If you had to decrease the gain more than the trimmer allowed, you would want to change R34 so you can properly set the gain with RV1. The trimmer combined with the resistor form a voltage divider. But since you are maxed out on the trimmer and are below gain, you need to go back to the drawing board a bit.
I think, because you are using different transformers, you cannot get the required transformer step up the compressor needs. I would suggest going back and verifying how you have them hooked up and what ratio you are getting. t2 should step down 1:2 and t1 should step up 1:2.5. You should be able to get these exact ratios with the ll1540 and ll1528. But you need to hook up the windings correctly. With the extra step up of 1:2.5 vs 1:2 you will be over at the trimmer and just need to bring it down a smidge to be calibrated.
The relationship between dB and transformer gain is dB=20log(vs/vp) where vs/vp is the turns ratio (secondary voltage over primary voltage). If you have a 1:1 transformer, the gain is 0 dB.
I built this compressor with Carnhill iron and it is a fantastic piece of gear. Keep up with it cause you'll be happy when it's done.
The transistors on the output amp need heatsinks or they fry.
If you had to decrease the gain more than the trimmer allowed, you would want to change R34 so you can properly set the gain with RV1. The trimmer combined with the resistor form a voltage divider. But since you are maxed out on the trimmer and are below gain, you need to go back to the drawing board a bit.
I think, because you are using different transformers, you cannot get the required transformer step up the compressor needs. I would suggest going back and verifying how you have them hooked up and what ratio you are getting. t2 should step down 1:2 and t1 should step up 1:2.5. You should be able to get these exact ratios with the ll1540 and ll1528. But you need to hook up the windings correctly. With the extra step up of 1:2.5 vs 1:2 you will be over at the trimmer and just need to bring it down a smidge to be calibrated.
How do you expect to get +8 dB from a transformer wired 1:1?
The relationship between dB and transformer gain is dB=20log(vs/vp) where vs/vp is the turns ratio (secondary voltage over primary voltage). If you have a 1:1 transformer, the gain is 0 dB.
I built this compressor with Carnhill iron and it is a fantastic piece of gear. Keep up with it cause you'll be happy when it's done.
The transistors on the output amp need heatsinks or they fry.
dmp
Well-known member
Here is the data on that transformer:
http://www.sowter.co.uk/specs/8403.htm
"Twin primaries may be connected in series or parallel permitting a 1:1 or 1:2 or 2:1"
You want a 1:2 step up, per the info at the start of this thread:
hi dmp, thanks for your reply
i have the transformers wired correctly. sorry the output is in fact 1:2 that was just a typo. i have edited the previous post
I could probably tweak r34 as you suggested for having a higher gain at the input of ba340 but could be possible the problem is in the stages before that ?
the input transformer is a Lundahl LL1540 wired 2:1 and at its output i have -8dB - shouldn't be to expect -6dB ?
Could be possible that the input transformer resistor values are not suitable for the Lundahl LL1540 ?
After the input transformer all test points are -2dB lower than nominal value, so I am wondering if I fixed this first the rest of the gain stages will match the schematic values ?
i have the transformers wired correctly. sorry the output is in fact 1:2 that was just a typo. i have edited the previous post
I could probably tweak r34 as you suggested for having a higher gain at the input of ba340 but could be possible the problem is in the stages before that ?
the input transformer is a Lundahl LL1540 wired 2:1 and at its output i have -8dB - shouldn't be to expect -6dB ?
Could be possible that the input transformer resistor values are not suitable for the Lundahl LL1540 ?
After the input transformer all test points are -2dB lower than nominal value, so I am wondering if I fixed this first the rest of the gain stages will match the schematic values ?
dmp
Well-known member
Pull the transformer and check that it is 2:1 outside the circuit?
it's a bit hard to desolder the lundhal transformers from the pc board. i believe it's wired correctly
this is the LL1540 datasheet
http://www.lundahl.se/wp-content/uploads/datasheets/1540.pdf
I have wired it this way
pin 2+3 output +
pin 1+4 output -
pin 5+7 joined together
pin 6 input +
pin 8 input -
pin E gnd
I have tried replacing resistor R34 next to the preset gain trimpot. I used 47K instead of 7K5. With this value I can get the compressor to match unity gain but the calibration of the gain reduction meter seems can't be done correctly. I don't know if this two issues are dependent on each other
this is the LL1540 datasheet
http://www.lundahl.se/wp-content/uploads/datasheets/1540.pdf
I have wired it this way
pin 2+3 output +
pin 1+4 output -
pin 5+7 joined together
pin 6 input +
pin 8 input -
pin E gnd
I have tried replacing resistor R34 next to the preset gain trimpot. I used 47K instead of 7K5. With this value I can get the compressor to match unity gain but the calibration of the gain reduction meter seems can't be done correctly. I don't know if this two issues are dependent on each other
RuudNL
Well-known member
Did someone in the meantime come up with a real solution for the LF distortion problem some people seem to have?
Despite all experiments, the distortion at low frequencies is much higher than in the original Neve 33609.
Here are the distortion figures I have measured at 50 Hz and 100 Hz at 6 dB gain reduction:
Limiter, 50 Hz, 6 dB gain reduction:
50 mS - 1,84% THD
100 mS - 1,08% THD
200 mS - 0,62% THD
800 mS - 0,24% THD
Limiter, 100 Hz, 6 dB gain reduction
50 mS - 1,00% THD
100 mS - 0,59% THD
200 mS - 0,34% THD
800 mS - 0,15% THD
Compressor, 50 Hz, 6 dB gain reduction
100 mS - 2,66% THD
400 mS - 0,84% THD
800 mS - 0,49% THD
1500 mS-0,33% THD
Compressor, 100 Hz, 6 dB gain reduction
100mS - 1,34% THD
400mS - 0,42% THD
800mS - 0,25% THD
1500mS-0,17% THD
The distortion is clearly audible on bass signals.
Although some people say that the DIY 33609 works fine (yes, it sounds good on midrange frequencies), I am sure that this is a common problem with a lot of DIY 33609's. Any input is welcome!
Despite all experiments, the distortion at low frequencies is much higher than in the original Neve 33609.
Here are the distortion figures I have measured at 50 Hz and 100 Hz at 6 dB gain reduction:
Limiter, 50 Hz, 6 dB gain reduction:
50 mS - 1,84% THD
100 mS - 1,08% THD
200 mS - 0,62% THD
800 mS - 0,24% THD
Limiter, 100 Hz, 6 dB gain reduction
50 mS - 1,00% THD
100 mS - 0,59% THD
200 mS - 0,34% THD
800 mS - 0,15% THD
Compressor, 50 Hz, 6 dB gain reduction
100 mS - 2,66% THD
400 mS - 0,84% THD
800 mS - 0,49% THD
1500 mS-0,33% THD
Compressor, 100 Hz, 6 dB gain reduction
100mS - 1,34% THD
400mS - 0,42% THD
800mS - 0,25% THD
1500mS-0,17% THD
The distortion is clearly audible on bass signals.
Although some people say that the DIY 33609 works fine (yes, it sounds good on midrange frequencies), I am sure that this is a common problem with a lot of DIY 33609's. Any input is welcome!
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