Mix Bus Compressor from scratch

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Yes, when I started the project I was in remission, now it has come back and I start a course of immunotherapy next week. In addition I have arthritis in both hands and some carpal tunnel problems in my right, probably caused by a lifetime of DIY!!!

I still have to get this mix bus to the finish line though
best
DaveP

Thanks dave for all your hard work

I’ve always enjoyed working with you

And I use your audio boxes every week. I’ve had four songs on radio two this year that use your boxes
Ian

 

[DaveP]

I’ve always enjoyed working with you

We have been working together for eight years now and it has been one of the most rewarding relationships of my life.....Thank You!
Those "boxes", as you charmingly call them, were built to last, unlike myself! You are blessed with a great pair of ears and you can hear things that I can't, so I'm very grateful for the important feedback you have given me, which has helped me to build the gear for you with the sound that you want.
All the best
Dave

 

[DaveP]

Back to the Signal to Noise ratio:-
First of all I have listened to it on headphones and I can hear nothing, that means very little, but it is a basic first check.

I noticed that the noise was modulated on the unhelpful 162kHz sine wave from Allouis, if I shorten the horizontal time, I can measure the noise at 2mV peak to peak. CORRECTION. with the base cover on its about 1.2mV This works out at 424uV rms. With an output of 1.6V into 600 ohms, this works out at 71.5dB unweighted, I hope this will be enough!
best
DaveP

 

[JohnRoberts]

Yes, when I started the project I was in remission, now it has come back and I start a course of immunotherapy next week. In addition I have arthritis in both hands and some carpal tunnel problems in my right, probably caused by a lifetime of DIY!!!

I still have to get this mix bus to the finish line though
best
DaveP

Good luck with your health issue.

Getting old sucks...

JR

 

[5v333]

is the oscilation present when power is switched off and no in/out connections?

Just trying to understand what the conditions were...

 

[DaveP]

is the oscilation present when power is switched off and no in/out connections
Just trying to understand what the conditions were...

The 162kHz oscillation is present on the scope on the most sensitive settings even when the mix bus comp is turned off and the probe disconnected. From that I've deduced that it has nothing to do with the mix bus comp, but its just interference due to pick up from the Allouis Long Wave transmitter.
best
DaveP

 

[5v333]

Then you must have suffered from this since long before. Right?

 

[DaveP]

Then you must have suffered from this since long before. Right?

Actually no, it was not a problem when I made the 627, it is something that has just started recently.
best
DaveP

 

[Stevie342000]

Actually no, it was not a problem when I made the 627, it is something that has just started recently.
best
DaveP

How about a cardboard box lined inside and out with aluminium foil tagged to earth with a cut out so you see the screen on the oscilloscope, yes an idea pardon the pun thinking outside of the box here, just an idea.

 

[Script]

Just guessing : maybe-inductor based LP filtering somewhere? Or just gain stage filtering to keep hi-FQ stuff out?

 

[Ike Zimbel]

The 162kHz oscillation is present on the scope on the most sensitive settings even when the mix bus comp is turned off and the probe disconnected. From that I've deduced that it has nothing to do with the mix bus comp, but its just interference due to pick up from the Allouis Long Wave transmitter.
best
DaveP

Can you put a ferrite clamp (or two...) on the scope probe?

 

[5v333]

I always get a 60hz wave form (not pure) on my scope when my probe is not connected to anything.

 

[Brian Roth]

Can you put a ferrite clamp (or two...) on the scope probe?

I dunno if a ferrite clamp will have much effect at 162 kHz....

That is a powerful signal ....800 kW currently. However, I don't know how longwave signals propagate 200 kM away.

https://en.wikipedia.org/wiki/Allouis_longwave_transmitter

Bri

 

[mik]

Increasing the value of the grid stop resistors might help since it involves RF

 

[DaveP]

Increasing the value of the grid stop resistors might help since it involves RF

There are no grid stop resistors at the moment, but you have a point.
best
DaveP

 

[ruffrecords]

https://en.wikipedia.org/wiki/Allouis_longwave_transmitter

Bri

Almost certainly ground wave propagation so over the horizon would be no problem. There is a licence free band at 160KHz in the USA:

https://hackaday.com/2021/10/19/the-low-down-on-long-wave-unlicensed-experimental-radio/

Cheers

ian

 

[Brian Roth]

Almost certainly ground wave propagation so over the horizon would be no problem. There is a licence free band at 160KHz in the USA:

https://hackaday.com/2021/10/19/the-low-down-on-long-wave-unlicensed-experimental-radio/

Cheers

ian

Since Dave said he is 200 kM away from the site, it's interesting to contemplate what the RF field intensity is near the site which could cause "reception" at that distance. Figuring it drops via the inverse square law, it must be a gazillon mV per meter in Allouis! lol

Bri

 

[ruffrecords]

Since Dave said he is 200 kM away from the site, it's interesting to contemplate what the RF field intensity is near the site which could cause "reception" at that distance. Figuring it drops via the inverse square law, it must be a gazillon mV per meter in Allouis! lol

Bri

Reminds me of the story of the guy who lived near a newly erected TV transmitter mast. He wound some turns of wire around his loft and managed to run his lights off it. He was only found out when neighbours in his "shadow" complained of poor reception after dark.

Cheers

Ian

 

[DaveP]

In the late 60's I played with band at a gig very near the big transmitter on the hill just south of London. When we turned on our Selmer amps we got radio and TV stations loud and clear. 68k grid stoppers could not overcome it!
best
DaveP

 

[DaveP]

The project is now finished and ready to pack for shipment, these are the final schematics.




Thanks to everyone who has supported me in this project, you are what makes GroupDIY great.
Look out for audio samples in the weeks to come.

These are my previous projects with approximate dates and serial numbers:-
Altec 458A 2016
001 SA39B 2013
002 28CO 2014
003 RS124 2016
004 U73B 2015
005 LA2D 2016
006 EQP-1A 2016
007 660 (1st) 2017
008 HarmonicR 2017
009 V241-76 (1st) 2017
010 660 (2nd) 2019
011 OP6 2019
012 RCA96A 2020
013 UE-100 2021
014 627 2022
015 Bridge Comp 2023
016 Mix bus Comp 2024

Some of these have been "from scratch" projects but others have not.

All the best
DaveP