| briangt PSU 1 transformer, 2 PSU, how to? - Click HERE for Original Thread |
| sansbury |
So I have the BrianGT dual mono kit, most recent iteration. There are two PSU/rectifier boards. I am assembling one channel first to verify things.
One question that comes up is that the first PSU board I have has terminals to connect 4 wires to off the transformer. I have a Avel trafo from parts express and am following this wiring diagram from another thread:
http://www.diyaudio.com/forums/atta...tamp=1121283775
This shows all 4 secondary wires going into one PSU board. My question is, using one transformer, do I not use the second PSU board at all, or is there another way to wire this up? |
|
|
| Mayday |
I split the secondarys like this:
 |
|
|
| sansbury |
| Beautiful- Thanks! |
|
|
| ianpengelly |
The only problem I have found is that you might experience hum due to the two channels interacting through the transformer with this set up. I think the Dual Mono Brian GT kits are designed to be used with either 1 power supply board or 2 transformers. I wrote a thread about it:
http://www.diyaudio.com/forums/show...&threadid=95451
Fingers crossed you don't run into this problem, but I did and it bugged me for ages until I figured it out. Now I am waiting to fit the second transformer. |
|
|
| Apex Jr |
I had my webguy put a picture of hookup of the
toroids I have in stock on the website
www.apexjr.com/miscellaneous.html
1/2 way down
Thanks to Troy St Germain
Steve @ Apex Jr. |
|
|
| Mayday |
Looks like this now, and no more humming either...it's completely quiet.
Dual trafos is clearly the way to go with these dual-mono kits.
Noticed sound improvements aswell.
Fan isn't hooked up, don't know that I need it yet. |
|
|
| AndrewT |
Hi,
no hum.
How did you connect the two audio grounds to the safety earth? |
|
|
| Mayday |
Used this as stargnd, and connected them to it and safety gnd to it aswell.
 |
|
|
| ianpengelly |
Mayday,
Glad you had good results from moving to two transformers... I'll be off to the garage today to try and get mine modified.
Andrew,
I am ashamed to say I still haven't got round to building a disconnecting network. |
|
|
| AndrewT |
| quote: | Originally posted by Mayday
Used this as stargnd, and connected them to it and safety gnd to it aswell.
|
| quote: | Originally posted by ianpengelly
Mayday,
Glad you had good results from moving to two transformers... I'll be off to the garage today to try and get mine modified.
Andrew,
I am ashamed to say I still haven't got round to building a disconnecting network. |
Mayday has got it to work without a disconnecting network.
Look back to his amp photo and you can see his grounding wires going to the tag strip just above the CE label (right of centre). |
|
|
| Mayday |
| As you can see on the photo of my stargnd, all the solderpoints are connected to each other with a bit of copperwire(in this case silverplated) thats important. |
|
|
| ianpengelly |
| Andrew, that is how mine is effectively wired at the moment (from a grounding perspective), however, I am getting pops from my speakers when things like the fridge start. I am hoping that a disconnecting network will help to tame this, if not I'll be off out to get a filtered mains inlet. |
|
|
| Mayday |
| Sounds more like a wiring problem in your house. I'd get a filter with enough outlets for the entire stereo. |
|
|
| ianpengelly |
| I bought a russ andrews silencer plug in thinking that would help, but it hasn't. The stereo is plugged in directly adjacent to the fridge, when I move house in a couple of months I'll have to see if it is still as bad. |
|
|
| ppcblaster |
and what is your rail voltages?
Thank you |
|
|
| Mayday |
| in my case it is -+35V |
|
|
| ianpengelly |
2X22V for me.
I have just made the change over to two transformers and I am pleased to say no hum! And no pops and crackles last night despite not fitting my disconnecting network (ran out of time as Dr Who was on at 7:00, couldn't miss that!). So I am very pleased. I need to try it with music and see if there are any improvements made. :D |
|
|
| ianpengelly |
| Oops! sorry 2x22V transformers! So about 32V rails |
|
|
| ppcblaster |
Mayday,
How did you silverplate the star ground,
and what type, size wire
is recommended for the internal wiring?
Thank you |
|
|
| Mayday |
The stargnd is simply a solder support(don't know if that's even a correct name, just translated straight from swedish), I bought it silverplated, then i connected the solderpoints together using 0,8mm(diameter) silverplated copperwire.
Normally I'd use 0,6mm(diameter) solid silver with teflontubing as insulator as internal wiring, but this build was my first chipamp, I wasn't shure about soundquality so I didn't want to spend too much.
Wires from boards to stargnd are 1,5 square mm pure copper. Also from stargnd to safety earth. |
|
|
| tamasic1 |
I remember reading several different sources that said to be sure you use a 10ohm resistor between star and earth gounds if you were going to connect them together. Am I right on this?
Mayday, did you find those first heatsinks a little inadequate? :hot: |
|
|
| AndrewT |
Hi,
silver plated tag strip, or tinned tag strip.
Similar with the wire?
Which?
silver=Ag
Tinned=Sn+Pb |
|
|
| Mayday |
| quote: | Originally posted by AndrewT
Hi,
silver plated tag strip, or tinned tag strip.
Similar with the wire?
Which?
silver=Ag
Tinned=Sn+Pb |
What is tag strip? If it is the stargnd, thingy, I bought it as silverplated
The wire is silverplated 0,8mm copperwire. |
|
|
| Mayday |
| quote: | Originally posted by tamasic1
I remember reading several different sources that said to be sure you use a 10ohm resistor between star and earth gounds if you were going to connect them together. Am I right on this?
Mayday, did you find those first heatsinks a little inadequate? :hot: |
They functioned for musiclistening, with lid of the case, but would have been too hot to use without fans when cased up. |
|
|
| Mayday |
| quote: | Originally posted by tamasic1
I remember reading several different sources that said to be sure you use a 10ohm resistor between star and earth gounds if you were going to connect them together. Am I right on this?
Mayday, did you find those first heatsinks a little inadequate? :hot: |
I have not used a resistor between stargnd and earthgnd, didn't know you should. |
|
|
| AndrewT |
Hi Mayday,
the resistor between safety earth and audio ground is an optional item. It is not compulsory.
The resistor value can be set to near zero ohms (>=1sqmm copper wire) or in the range 2r7 to 22r. But if the resistor value alone would cause a high voltage across it when fault current flows then ANOTHER component MUST be placed in parallel to keep the voltage on the audio ground side at a safe level. The extra component should be able to survive kA of fault current until the mains fuse blows and the arc extinguishes. |
|
|
| Mayday |
| It's working fine without resistor now, so I'll just keep it that way. Thanks for clearing it up. |
|
|
| ianpengelly |
Andrew,
I got round to making and installing my disconnecting network and it consists of a 10W 10R resistor, 2 X 6A power diodes and a 100uF cap all in parallel. This seems to have tamed all the popping I was getting from my fridge etc. |
|
|
| AndrewT |
| quote: | Originally posted by ianpengelly
disconnecting network and it consists of a 10W 10R resistor, 2 X 6A power diodes and a 100uF cap all in parallel. This seems to have tamed all the popping I was getting from my fridge etc. |
Hi,
the 100uF is surprisingly large. It is more usual to be in the range 10nF to 100nF, to ensure it conducts HF.
I am surprised that attenuating at source was not completely successful, but maybe it needed just a bit more (I had not thought of this as an interference suppressor, but it obviously does not do nothing). I wonder if this is an indication that there might be somthing wrong with the fridge motor? |
|
|
| ianpengelly |
I couldn't find anything as low as 10 - 100nF when I was browsing Maplins, I may well replace it at a later date if I have any problems in the next house.
I am please that I have now proved my theory from the other thread, which is that using 1 transformer and 2 rectifier boards (from the Brian GT dual mono kits) results in an interaction that manifests itself as hum and it is solved by either using 1 rectifier board for both channels or using 2 transformers, one per channel.
As for the pop, I would expect it to be down to the switch in the fridge rather than the motor, just because of the type of noise it is, i.e. very short duration pop. Of course you could be right and there maybe a earthing problem with the motor. |
|
|
|
|
