TonyW

Re: Cavendish
« Reply #20 on: October 10, 2018, 03:52:16 PM »
I got it working!
There are still a couple of issues
low 60hz hum
little more  Headroom would be nice, I don't know if by removing the 15k's and adding a jumper wire across  the 5532 is the correct way to proceed with this, no one seems to give me a direct answer on this, all they say is to remove them.
The sound-well it's got a little thicker sound then before.
Hope this post helps someone that purchases a Cavendish board.


scott2000

Re: Cavendish
« Reply #21 on: October 10, 2018, 05:07:46 PM »
Great! I'm still at a loss as to how it works but it's irrelevant to me. I'm guessing it's single ended /unbalanced or something??? Just confusing because, from my limited knowledge, it almost looks like your omitting the negative polarity from the output circuit by leaving that stuff vacant.....would be nice to know for sure......

anyway, The manual says to take the ground from the Cavendish board to a spot on the GSSL close to the opamps..... Hard to tell where yours is going from the pic...... maybe hum from this???

Thanks for the updates! Glad it's working


TonyW

Re: Cavendish
« Reply #22 on: December 17, 2018, 03:08:19 PM »
Just an update, after using this on my drum bus for a little while I determined  this dish thing belongs in the trash can . Total crap I spent a lot of money buying parts for this project also. Stay away from it.
Removed it from the GSSL and sounds much better. You also get no real  help from the people who sell it.

TubeMonkey

Re: Cavendish
« Reply #23 on: December 18, 2018, 02:10:04 PM »
that's quite opposite of my experience.  Sounds great and really adds a lot of meat imo.

TubeMonkey

Re: Cavendish
« Reply #24 on: December 18, 2018, 02:32:59 PM »
I don't have time for the next few days but can probably help you out: dont give up just yet

Potato Cakes

Re: Cavendish
« Reply #25 on: February 11, 2019, 11:46:25 AM »
Remove the jumper wire across the 15k on the main PCB board. Then give it a go...


Thanks!

Paul
« Last Edit: February 11, 2019, 11:51:03 AM by Potato Cakes »

TonyW

Re: Cavendish
« Reply #26 on: February 13, 2019, 02:05:49 PM »
Hi Paul

Have you installed this Cavendish in a GSSL?  I since removed it from the GSSL, and it's in a box came close to trashing it, but didn't yet.
Thanks for your advice , I tried jumpering the 15k,removing it, and re-installing it.
The hum is very present when you set the make-up gain up to where it should be level wise.
I have gone thru this whole circuit board even made a schematic.

Thanks for responding

Tony

Potato Cakes

Re: Cavendish
« Reply #27 on: February 13, 2019, 03:18:57 PM »
Hi, Tony,

I do actually have one installed and am currently using it in a session. I did a write up on it in the GSSL Add On thread regarding this and a couple of other mods I did to this circuit (https://groupdiy.com/index.php?topic=65232.0). The 15k resistors on the output are feedback resistors that are being replaced on the Cavendish board with the resistor and trimmer to allow you to match output levels, so the ones on the main board are to be left empty. I would also recommend doing all of your connections between the boards via the IC connections except for ground. Go over to the Add On thread and see if any of that info helps. I can assure you this board works great. Also, you should know the guys at Expat have made many invaluable intectual and product contributions to this forum for the benefit of many.

Thanks!

Paul

TonyW

Re: Cavendish
« Reply #28 on: February 13, 2019, 03:59:27 PM »
Thanks, Paul
I will try again when I get some time. did you see my post about the unity gain resistors?https://groupdiy.com/index.php?topic=71466.0

Potato Cakes

Re: Cavendish
« Reply #29 on: February 13, 2019, 04:31:48 PM »
I did not.

If you look at the schematic, the 27k resistors are between the VCA out and output op amp. You can swap that to 15k or put a trimmer in there to fine adjust the level and find out what that resistance is. But you shouldn't have to crank your output pot all the way to get a good level if you have 27k in there currently. This tells me that something else must be going on. Swap the resistors first and see if this gets you where you want to be.

Thanks!

Paul


Rob Flinn

Re: Cavendish
« Reply #30 on: February 13, 2019, 04:48:27 PM »
Just been reading this thread.   Regarding your 60Hz hum.  Looking at the first pic you posted of your unit you do seem to have the API output transformers remarkably close to your power transformer.     Most people would get them as far away as possible .....
regards Rob

TonyW

Re: Cavendish
« Reply #31 on: February 13, 2019, 05:36:45 PM »
Thanks again Paul

The 27k's are actually at the input of the VCA, I did change the resistors to 15k and It made a difference
No longer need to crank the make-up gain.

Thanks Rob for chiming in, I will try the Cavendish one more time and move it as far away from the PS transformer.

Rob Flinn

Re: Cavendish
« Reply #32 on: February 13, 2019, 05:55:57 PM »
Thanks Rob for chiming in, I will try the Cavendish one more time and move it as far away from the PS transformer.

If it still hums try rotating the mains transformer or the cavendish board.     I had a hum issue with a 4 channel Neve mic amp I made once.  I tried all sorts of earthing mods.  Tore out all my nice neat wiring that took ages.  In the end it was the mains transformer...............
regards Rob

Potato Cakes

Re: Cavendish
« Reply #33 on: February 13, 2019, 06:08:10 PM »
Thanks again Paul

The 27k's are actually at the input of the VCA, I did change the resistors to 15k and It made a difference
No longer need to crank the make-up gain.

Thanks Rob for chiming in, I will try the Cavendish one more time and move it as far away from the PS transformer.

One step fin the right direction. Excellent.

Yes, input to VCA is what I really meant. I was trying to recall the schematic from memory and got that part backwards.

Thanks!

Paul