bruno2000
Well-known member
I run mine at 16V.
Best,
Bruno2000
Best,
Bruno2000
PYE Compressor/Limiter Thread *boards shipping* BOM up!
- Thread starter abechap024
- Start date
Help Support GroupDIY Audio Forum:
Spencerleehorton
Well-known member
Bruno and mdainsd,
Could you take some voltage readings and post please?
ive wound mine down to -16.20v now and no difference, have put output from protools through and getting loads of distortion, sounds like its just on the low end, so could this possibly be the output transformers?
well i've got no idea where the trimmers are now but i've tweaked and tweaked and have a pretty sound now!!!
R48 seemed to help the most, also the 10k trim, i will take readings from all trimmers once i've tweaked both channels!!
Finally starting to work and sound good!!
Could you take some voltage readings and post please?
ive wound mine down to -16.20v now and no difference, have put output from protools through and getting loads of distortion, sounds like its just on the low end, so could this possibly be the output transformers?
well i've got no idea where the trimmers are now but i've tweaked and tweaked and have a pretty sound now!!!
R48 seemed to help the most, also the 10k trim, i will take readings from all trimmers once i've tweaked both channels!!
Finally starting to work and sound good!!
Spencerleehorton said:
While I haven't built these exact PCBs, I used the same circuit from the PYE service manual.
I suggest that you read this thread from the beginning. There's a discussion on the threshold switch. This part is important for the correct gain staging inside the compressor.
EDIT: original unit ran on 16V. I'm running mine on 18V because of better performance. Other people answered you earlier.
May I also suggest that if you want to post something in addition to your previous post, you'd rather edit that post so we don't have half a page of your posts with just a couple of sentences in each please.
Spencerleehorton
Well-known member
i will consider my hands well and truly slapped!! lol, thanks for all your wise words, i will edit my posts and read again this post from the start to understand about the gain staging.
The compressor now is sounding really good, think i just have to move the txf nearest the psu as i can hear a little hum on that channel.
thanks everyone, sorry about all the posts!!
The compressor now is sounding really good, think i just have to move the txf nearest the psu as i can hear a little hum on that channel.
thanks everyone, sorry about all the posts!!
Spencerleehorton
Well-known member
I have just read on page 3 of the thread that the gnd should be tied together to B+?
At the moment there is nothing from B+ to IEC but i am getting continuity.
Just to confirm though, would it be better for B+ to goto IEC gnd or XLR gnd?
and could this be why i'm getting some hum?
and Yes i'm getting loads of mobile phone interference!!
and to reply to the previous comment about the threshold control, i think i understand now, the input and output are put onto a switch pot, i dont have this, i have 2 x pots.
At the moment there is nothing from B+ to IEC but i am getting continuity.
Just to confirm though, would it be better for B+ to goto IEC gnd or XLR gnd?
and could this be why i'm getting some hum?
and Yes i'm getting loads of mobile phone interference!!
and to reply to the previous comment about the threshold control, i think i understand now, the input and output are put onto a switch pot, i dont have this, i have 2 x pots.
Spencerleehorton
Well-known member
Im getting a lot of hum!, both channels , would someone be able to explain the correct gnd scheme please?
and also does anyone have any info on how to make the stepped attenuator,
i have a couple of 24 switch 4 pole switches i could use, just need to know layout of resistors.
regards
Spence.
and also does anyone have any info on how to make the stepped attenuator,
i have a couple of 24 switch 4 pole switches i could use, just need to know layout of resistors.
regards
Spence.
bruno2000
Well-known member
Spencerleehorton said:
Email sent w/ r values for switch.
Best,
Bruno2000
Spencerleehorton said:
You need to connect IEC ground to chassis (metal enclosure). Then connect B+ to this point. B+ is the ground reference. Take B+ from the PSU filter cap and connect it to the chassis, this should cure your hum issues.
Ian (ruffrecords) has an excelent paper on grounding that's worth reading:
http://www.customtubeconsoles.com/diy
Theory folder.
Spencerleehorton
Well-known member
thats perfect, thank you, i also need to change my stand offs to plastic, once ive done i will then attempt the attentuator!!
Also Just to clarify, im using 2 x 18v 30VA transformer which is powering both channels, is this too little?
Only getting hum on the right channel, clean as a whistle on left channel?
Could someone explain the whole threshold switch and gain control please.
As on the original schematic the gain pot just looks like a dpdt switch?
Update(27/07/2017)
also today after doing the gnd from the C10 cap, the right hand channel seems to have hiss as well as a little low end hum, where as the left channel is silent.
when i match the level of hiss on both channels, the right hand channel is down about 15db on the mixer, so its quite loud!!
regards
Spence.
Also Just to clarify, im using 2 x 18v 30VA transformer which is powering both channels, is this too little?
Only getting hum on the right channel, clean as a whistle on left channel?
Could someone explain the whole threshold switch and gain control please.
As on the original schematic the gain pot just looks like a dpdt switch?
Update(27/07/2017)
also today after doing the gnd from the C10 cap, the right hand channel seems to have hiss as well as a little low end hum, where as the left channel is silent.
when i match the level of hiss on both channels, the right hand channel is down about 15db on the mixer, so its quite loud!!
regards
Spence.
Spencerleehorton
Well-known member
Im going to run each pcb from 18v - 0v rather than having the secondaries in series and daisy chaining, hopefully this will fix the hum and hiss?
also could be a dodgy transistor, will do some voltage comparisons and see if i can spot it!!!
also could be a dodgy transistor, will do some voltage comparisons and see if i can spot it!!!
Spencerleehorton said:
It's not clear how you're powering the unit. 30VA should be plenty. Each channel consumes about 0.12A, which translates to roughly 2VA at 18V. 4VA for 2 channels.
The hum in just one channel tells that you probably have a ground loop. Make sure that each channel has only a single connection to a common ground point. They shouldn't share any other ground except this one point.
Spencerleehorton
Well-known member
The only gnd points I have are on input which attaches to xlr socket, c10 + is linked to both pcbs to star gnd and input pot and output pot both have gnd.
Missed the output xlr gnd connection by any chance ?
Also the pcb provides 3 connections for the input XLR, i assume one of them is gnd, if you connect the gnd on the input XLR socket to the chassis then dont use the gnd connection on the pcb (assuming the shield wire connects to the xlr socket gnd)
Also the pcb provides 3 connections for the input XLR, i assume one of them is gnd, if you connect the gnd on the input XLR socket to the chassis then dont use the gnd connection on the pcb (assuming the shield wire connects to the xlr socket gnd)
Spencerleehorton said:
Maybe that's me but I still don't get your power and grounding scheme.
Input/output XLR's pins 1 should tie directly to chassis ONLY. You don't bring that connection to your clean audio ground. Now, are you powering 2 boards from a single PSU or what? Or do you link each C10+ to your common GND? What does "input pot and output pot both have gnd" mean? Of course they should have GND, but they should have connections to your audio GND, not common point.
You may also compare voltages in the hissy channel agains the clean one and see if they match. Maybe it's not a ground issue at all.
marcn said:
This is probably not a huge deal in the transformer balanced outputs. The GND on the XLRs is used for shielding only, it isn't (and shouldn't) used as a common GND reference between the devices as in unbalanced connections. So if the shield is not connected to chassis, you loose a protection of the screen, but I doubt that this can make a hiss in one channel 15dB louder than in another.
Spencerleehorton
Well-known member
sorry yes, i have both the output and input pin 1 to star ground.
input xlr shields goes to gnd on pcb
star ground to C10 + on pcb 2 then daisy chained to C10 + on pcb 1
Im now going to change the mains transformer so each pcb gets 18v feed rather than windings in series.
then i will check transistors, as i suspect its the transistor making the hiss.
regards
spence.
input xlr shields goes to gnd on pcb
star ground to C10 + on pcb 2 then daisy chained to C10 + on pcb 1
Im now going to change the mains transformer so each pcb gets 18v feed rather than windings in series.
then i will check transistors, as i suspect its the transistor making the hiss.
regards
spence.
Spencerleehorton
Well-known member
now i have changed the mains transformer to feed each channel with 18v/ 0v there is no hum, just some hiss now to try and track down.
The hiss difference is about 4db now so i'm very nearly there.
The hiss difference is about 4db now so i'm very nearly there.
Spencerleehorton
Well-known member
Its seems I’m not out of the woods with this compressor, channel 2 has a sawtooth sound at 700hz, I’ve check the sound using a signal generator and it sounds exactly like a sawtooth rather than anything else, its maybe triangle but not sure.
Channel 1 is ok, bit of hiss but i would expect this without the correct gain/threshold control which i haven’t done yet.
I will go through all the transistors and see what voltages look like now on bottom of circuit to see if anything looks off?
I have set the oscillator to exactly 250khz now as i have a meter for setting this.
regards
Spence.
Channel 1 is ok, bit of hiss but i would expect this without the correct gain/threshold control which i haven’t done yet.
I will go through all the transistors and see what voltages look like now on bottom of circuit to see if anything looks off?
I have set the oscillator to exactly 250khz now as i have a meter for setting this.
regards
Spence.
peskado said:
Apparently Abe gave all the boards he had from the most recent PCB runs to Dan from Collective Cases in order to cover his outstanding debts to him. I lodged a claim to get the payment I made to AC Sound back from my credit card company, and received a refund which I then used to buy boards from Dan instead.
http://collectivecases.com/?product_cat=pcb
I know this is not ideal, but I suspect it's your best option - I don't think you'll see your order fulfilled by AC Sound in the near future :-(
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