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- Jan 27, 2012
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- 8
Looks fantastic Dave !
Mix Bus Compressor from scratch
- Thread starter DaveP
- Start date
Help Support GroupDIY Audio Forum:
rock soderstrom
Tour de France
I don't want to hijack this thread but since we've been talking about cutting sheet metal accurately at home, here's a little update on my saw jig.
It works well, here for example an FR4 PCB, which is also not so easy to saw. Sheet metal works as well.
What I recommend is:
Guide rods better made of stainless steel, aluminum is a bit too weak for that job.
Turn the saw blade around so that it works against the base plate.
Otherwise it works well
...and all this on the washing machine
It works well, here for example an FR4 PCB, which is also not so easy to saw. Sheet metal works as well.
What I recommend is:
Guide rods better made of stainless steel, aluminum is a bit too weak for that job.
Turn the saw blade around so that it works against the base plate.
Otherwise it works well
...and all this on the washing machine
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You have not hijacked the thread Rock, it's all about making a practical project and sharing techniques, so well done.
The chokes are now in place, choke loading was common in the past and they appear to give a vintage quality to the sound.
The busbar and earthing is now in place. Note that the green wire from the IEC mains input is bolted to the chassis bottom right behind the angle. The busbar passes through the chassis grommet and only connects to the chassis at one point, the input sockets.
The power supply is like a mini star ground with all the earthing points on the busbar between the two big caps. Leading off from that, the main busbar goes past all the tubes supported from their central spigots, then it earths at the chassis on the input sockets. This is the RCA earthing arrangement (attached) which is also recommended by Jensen's Bill Whitlock, I use it because it works!
best
DaveP
The chokes are now in place, choke loading was common in the past and they appear to give a vintage quality to the sound.
The busbar and earthing is now in place. Note that the green wire from the IEC mains input is bolted to the chassis bottom right behind the angle. The busbar passes through the chassis grommet and only connects to the chassis at one point, the input sockets.
The power supply is like a mini star ground with all the earthing points on the busbar between the two big caps. Leading off from that, the main busbar goes past all the tubes supported from their central spigots, then it earths at the chassis on the input sockets. This is the RCA earthing arrangement (attached) which is also recommended by Jensen's Bill Whitlock, I use it because it works!
best
DaveP
scott2000
Well-known member
Wow.. Just keeps getting better every time I see one of these projects...
Where do you get your focus? You on some choline supplements?
Where do you get your focus? You on some choline supplements?
I have made a few changes, I changed the output transformers to some bigger ones that now sit on the top.
They are still 15k:600 but they have some shielding to avoid pick-up from the power supply. They also give me more space on the inside for the output caps.
I have started adding components and I keep a tight check on the wiring progress with schematics like this:-
Left Channel
Right Channel
The right channel is more complicated because of the HT line. I am in two minds whether I need C1, I think it may hold the CV anyway, comments welcome.
You will notice I have numbered the tubes to help me add the right components. With a project like this I try to keep things as clear as possible to avoid stupid mistakes!
DaveP
They are still 15k:600 but they have some shielding to avoid pick-up from the power supply. They also give me more space on the inside for the output caps.
I have started adding components and I keep a tight check on the wiring progress with schematics like this:-
Left Channel
Right Channel
The right channel is more complicated because of the HT line. I am in two minds whether I need C1, I think it may hold the CV anyway, comments welcome.
You will notice I have numbered the tubes to help me add the right components. With a project like this I try to keep things as clear as possible to avoid stupid mistakes!
DaveP
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Johnny1234
Well-known member
Hi Dave, i have a few questions. If you want to answer you can say yes no or the value.
#1 What value is the input level pot.
#2 What power transformers are you using.
#3 If I lift the input to the side chain feed, will it put the unit in bypass mode.
#4 Where do the v.u. meters feed from.
#5 Is there any plan for a gain reduction meter.
BTW I plan on using 100k pot for attack and 1meg for release.
Many Thanks and Happy Easter
Johnny1234
#1 What value is the input level pot.
#2 What power transformers are you using.
#3 If I lift the input to the side chain feed, will it put the unit in bypass mode.
#4 Where do the v.u. meters feed from.
#5 Is there any plan for a gain reduction meter.
BTW I plan on using 100k pot for attack and 1meg for release.
Many Thanks and Happy Easter
Johnny1234
Happy Easter to you too.
#1 Dual 100k lin pots.
#2 B+ is a Triad VPT230-110 25VA from Farnell 1785731. Heater is a Multicomp 230-2x6V also from Farnell 1675043
#3 Yes, but increasing the threshold will also switch off the side-chain.
#4 VU meters are fed from the output.
#5 No, the VU meters are set to a level, then the threshold reduced until say -3dB is achieved.
I use a switch for attack/release so that notes can be kept of the setting. Pots will be fine.
best
DaveP
#1 Dual 100k lin pots.
#2 B+ is a Triad VPT230-110 25VA from Farnell 1785731. Heater is a Multicomp 230-2x6V also from Farnell 1675043
#3 Yes, but increasing the threshold will also switch off the side-chain.
#4 VU meters are fed from the output.
#5 No, the VU meters are set to a level, then the threshold reduced until say -3dB is achieved.
I use a switch for attack/release so that notes can be kept of the setting. Pots will be fine.
best
DaveP
Johnny1234
Well-known member
Johnny1234
Well-known member
If you are enjoying what you do, maybe a part time apprentice would help and pass your legacy on to another generation.
Johnny1234
Well-known member
Note to DIY'ers in countries with 120 volt mains. Use the Vigortronix VTX-146-015-206 part #99AC4549 instead of the Multicomp 230-2x6V.
Hi Guys... an interesting thread. I just finished a re-build, and some mods, to an RCA BA6A Limiter... needed to do a quick refresher on Vacuum Tubes before I did! 
Johnny1234
Well-known member
As far as I can tell, the 6BK8 is the American EF86, the EF83 is a very special tube that has a a semi- remote charateristic but it keeps the plate current constant.
I remind you that this compressor has yet to be proved to work yet!
best
DaveP
I remind you that this compressor has yet to be proved to work yet!
best
DaveP
The left and right stereo amps are now finished except for the input pots. The side-chain is finished except for the threshold and the CV supply.
I only just had enough tags for all the components, you can never have enough for prototype designs!
When I finish cleaning up little snippets and vacuuming it out, I will check it over for mis-wires and if its ok I will fire it up to check the voltages.
There remains the attack and release switches to do.
best
DaveP
I only just had enough tags for all the components, you can never have enough for prototype designs!
When I finish cleaning up little snippets and vacuuming it out, I will check it over for mis-wires and if its ok I will fire it up to check the voltages.
There remains the attack and release switches to do.
best
DaveP
I have finished enough of the circuit to turn it on!
I put dropper resistors in the power supply based on a safe estimate but to get the required voltages I have changed some values from the original.
These are the revised circuits as of today with the correct resistor values.
The threshold control varies the voltage at the cathode of V5 as shown from 16-35V
With all the right voltages, I can now fit the attack/release switches and start dynamic testing
best
DaveP
I put dropper resistors in the power supply based on a safe estimate but to get the required voltages I have changed some values from the original.
These are the revised circuits as of today with the correct resistor values.
The threshold control varies the voltage at the cathode of V5 as shown from 16-35V
With all the right voltages, I can now fit the attack/release switches and start dynamic testing
best
DaveP
Johnny1234
Well-known member
Hi Dave,
Many many thanks for sharing all your information on this project. I am excited to see you final results.
It's name shall be P------- MBC.
Many many thanks for sharing all your information on this project. I am excited to see you final results.
It's name shall be P------- MBC.
