| Peter Scowcroft |
I wish to modify my preamp to provide XLR outputs.
the only problem i have is i have no idea how to do it!!
Does anyone have any ideas?
I would need some basic instructions...preferably in crayon!
Thanks
Peter |
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| phn |
| What, you want to go balanced? Try this link for very basic information. But if you want to balance your system, that's for the more knowledgeable guys here. |
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| pinkmouse |
| What do you want to drive? There are several ways of doing this, some easier than others. |
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| Peter Scowcroft |
| I have an RB-970bx preamp and a Rotel RB-991 power amp with pretty XLRs on the back...does that help? |
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| Peter Scowcroft |
| I have checked the link phn. Interesting but unfortunatly it is about making the wires. I need to make the socket and manufacture something that will reverse the phase of one channel!! |
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| joensd |
Hi,
here´s one simple way to do it with an opamp.
(You´d only need the transmitter in figure1)
http://sound.westhost.com/project51.htm
You could also have a look at the BOSOZ from Nelson Pass but then you could omit your whole preamp. (nice article(s) anyway)
http://www.passdiy.com/legacy.htm
(balanced zen line stage; which is a class a preamplifier)
greets |
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| phn |
| "Crayon" kind of threw me. At least the other guys here dug up some interesting stuff. They always do. |
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| leadbelly |
Judging by the tone of your post, it sounds like what is the easiest way to do it would suit your needs best.
So, IMO, forget individual op amps and discrete designs and use a single chip solution like the DRV134. This is from the datasheet: |
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| Peter Scowcroft |
Hmmm the advice i was looking for was:
Buy this circuit board.
Solder the wires here, here AND here...not there though that would be silly.
Connect the power to the unit HERE and HERE.
turn on enjoy!
Could anyone offer advice on that level.
Sorry for sounding stupid, but lets face it I need lots of help!:bawling: |
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| leadbelly |
| OK, so it sounds like you want to build an external device to do the conversion? Opening up your preamp and tapping power out of it and putting in XLR jacks is out of the question? |
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| Netlist |
Ha ha... but this is Diy. ;)
Let me try:
1) Get a board with those little holes in it or glue the chip to the chassis of the amp and go P2P.
2) Buy the chip mentioned by leadbelly
3) Buy 2 X 1µF cap.
4) Look for +/-15V or whatever the chip needs as supply in the existing amp. Alternatively you could fabricate a new supply but lets keep things simple.
5) Disconnect the output from your amplifier and connect it to the input of the chip.
6) Connect the output of the chip to an XLR.
7) Drill a hole in the back of your amp to fit the XLR.
Done.
Edit: Double the mentioned parts as this is for one channel.
10 caps? Hmm... where would you need them Pinkmouse?
/Hugo :) |
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| pinkmouse |
| Use the DRV134. You will need the two chips, about ten caps, and about two square inches of perf board. You will also need to open up your pre, find the voltage rails for the preamp, and cut new holes for the XLRs. The last job will likely be the most difficult. If you give me a day or so I can draw you something up. |
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| pinkmouse |
| quote: | Originally posted by Netlist
Edit: Double the mentioned parts as this is for one channel.
10 caps? Hmm... where would you need them Pinkmouse? |
2x 0.1uf + 2x 47uf supply bypassing, and, say, a 2.2uf dc blocking cap on the input, per chip.
The DRVs work best with good bypassing, as they have to drive lines they need a little attention in that area.
It's half a circuit I'm building at the moment - give me ten minutes and I'll post a pic. |
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| Netlist |
| quote: | Originally posted by pinkmouse
It's half a circuit I'm building at the moment - give me ten minutes and I'll post a pic. |
Sure, take your time :)
Re caps: I hadn’t looked at the datasheet, now I see.
/Hugo :) |
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| pinkmouse |
| Here we go, this will be the Mk 2 version of my balanced pre/driver for my JBL monitors, the Mk1 version having been "borrowed" by a mate before I even had chance to plug it in! |
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| phn |
Netlist, be fair. Surely you wouldn't recommend that as a first DIY project. Isn't that what they invented the phono amp for, the newbies?
And I know you weren't too serious. But I just had to add my 2 cents. I think it's great that people try to do whatever they can themselves. Of course, if pinkmouse posts that pic (edit: done) it just shows what great place this is for people with silly questions like me. |
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| pinkmouse |
phn
I'll stick by my claim that this is very achievable, and the most difficult thing will be cutting the holes. For that you will need what is known as a cone cutter, drill pilot holes tom start, then open them out to the correct diameter with the cutter.
Thinking about it, you may not even need the 2.2uf caps, if you take a feed from the back of the existing phonos, then they are already likely dc blocked. So two little boards, with a chip and four caps on each. You can't get much simpler than that! :) |
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| phn |
pinkmouse, from what I have read elsewhere (being that I still wonder why more phono amps aren't balanced), what you say sounds perfectly fair. I probably expressed myself wrong.
Doing the soldering and stuff isn't that complicated. That I'm sure Peter Scowcroft will work out. I surely didn't want to discourage anyone. My argument was rather that even when you guys are going out of your way to make it clear and easy, you still can be hard to follow for a newbie. (That was what my first post was about. I can't teach this guy anything. All I could do was to refer to a very newbie friendly page that helped me understand how this balanced thing works.) Of course, all we newbies have to do is ask. But sometimes it's not easy to ask since you don't know how to phrase the question. Other times you have to ask some silly thing just to reassure you understand even when you are pretty sure you do. And you really don't want to be a pain.
Sorry for getting longwinded. |
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| pinkmouse |
phn
Your comments are very valid, and I understand what you mean. Although I may sometimes look like I know a lot, I consider myself still a newbie to electronics, and I still ask some really stupid questions myself, for the same reasons you do.
So try to be patient with us, and we'll try to be patient with you. Deal? :) |
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| Enzo |
I may have missed something, but if the whole point of this exercise is to be able to reverse the phase of one channel, why not reverse the speaker wires for that channel and move on?
That assumes you already can make a working connection between units other than through the XLR connectors.
If the point is that you cannot now connect the pre and power amps together, then I will shut up and watch. |
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| Peter Scowcroft |
Thanks for the help,
Pink mouse and netlist you both seem to be getting ideas forward I can understand.
I can quite happily cut holes in the back of my case (lets face it all you need is a bit of dynamite and some luck...or a drill.)
I am a semi compotent solderer though am prone to mistakes. (read below if you want to hear what the worst one was WARNING its pretty grim)
unfortunatly these are the things i cannot understand
"Use the DRV134. You will need the two chips, about ten caps, and about two square inches of perf board. You will also need to open up your pre, find the voltage rails for the preamp"
netlist I am stuck on the parts 2-4.
I have had NO electronics training EVER, i just know a bit of the thoery behind from taking chimistry at uni (which loosely relates to physics which is relevant).
Will both these circuits improve the quality?
If not is it possible to buy better quality components?
ok now for the painful story.
Sitting at my table soldering some wires with a HEAVY pair of bullnose pliers half off the table. Accidentally solder my finger (as you do). Elbow kicks back and hit pliers Hard. The pliers then sail into the air just missing my face (just to give you an idea how high they went before returning to the ground/my groin.
Well you can guess where they landed...to cut a long description short. I was wearing Jeans and the pliers still managed to draw blood! it hurt. |
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| pinkmouse |
Ouch!
Ok, can you open up your pre and take a couple of photos. That way, we can probably guide you in tracking down the power rails. I will sketch up a quick circuit diagram for the components in the next hour or so and post it here. It really isn't as difficult as we made it sound, Hugo and I were just discussing best implementation.
Oh, for the holes, I find shaped charges make the neatest cut! ;) |
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| Peter Scowcroft |
Pink mouse I was having a look at your circuit. I know I have only seen the top half but it does not really look that complicated!
I also connect the three surround channels of my PC directly to my second power amp (RB-993 also XLRd).
I have no volume control on the surround channels as i have no pre for them.
Am i right in guessing that your pretty circuit is essentialy a volume control with XLR outputs that takes unbalanced inputs?
I am quite good at following instructions (if the instructions are good) would you be able to tell me how to do it? (please, its worth a hugh and the knowledge that you managed to teach an ignoramous advanced electrical theory) |
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| Peter Scowcroft |
Hmmm shaped charges!
I think I am going to do dinosaur shapes.
I suddenly realised how hard opening up my case is going to be...I forgot i epoxied it to the bottom of one of my hifi shelves.
I had run out of room on my rack and couldn't be arsed to make a bigger one :D :D
I will get some photos somehow...I could unsrewthe top plate leaving that on my rack.
ooh have to goto work, see you later and thanks
Peter |
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| pinkmouse |
| quote: | Originally posted by Peter Scowcroft
...I forgot i epoxied it to the bottom of one of my hifi shelves. |
ROTFLOL!
Ok, I will post the driver part later today, and the Mk2 buffered version when finished and I have checked it all out. |
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| Peter Scowcroft |
Hi Mousey,
Any more progression on how to make my new toys? :(
I promise i won't greatly injure myself following them...much! ;)
It is not like I am using anything dangerous...like soldering iron, pliers!:xeye:, mains voltage electricity oh and not to mention a dinosaur shaped platic explosive! :hot: |
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| pinkmouse |
Oops, I knew there was something I had forgotten to do!:eek:
Will post it shortly!
Promise! |
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| pinkmouse |
Here we go!
The 0.1uf caps can be just about anything, though preferably MKP, and the electros anything from the indicated 47uf right up to 100uf or so, 25V rated. |
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| Peter Scowcroft |
I can borderline understand this. I'm at the border though on the wrong side =-(
I have a few questions!
1) Where do i connect the inputs signal and return. Which areas do i glue to the three XLRs, signal, inverse signal, return?
2)Where it says earth what do i stick that too?
3) there are some capasitors (i'm guessing because of the uF) one has a circle and a positive which i am assuming is a normal cap...what is the other one?
What do I ask for in the shop EXACTLY and what shop?
4) what is the chip called and where can i buy it?
5) you mentioned that this had to be connected to a power supply! Where do i connect it and what voltage?
6) as i probably will do a low grade test unit (depending on component cost) would it be possible to run that off a battery so i can fit it externally?
7) I have NO idea what this will cost, are there any components I can get of a better quality that will improve the sound?
8) Do you have a fave kind of beer because i will probably have to mail you a 6 pack to say thanks for the help!
9) Thankyou for the help so far.
p.s. It might be easier if you e-mail me at peterDOTscowcroftATtiscaliDOTcoDOTuk
thanks again |
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| pinkmouse |
That's ok Peter, no problem. I think this is also informative enough to keep it in the public domain, after all, I'm sure there are others out there with the same problem!
Anyway, answers...
1) For this you need to do a little research. On the back of your power amp it will give a polarity for the XLR connector. It will be either pin 2+, pin 3-, or the other way round. The + and - outs connect to the appropriate pin in the XLR connector. The third pin is for earth, we'll come back to that later.
2) Later... ;)
3) The capacitors with the circle around them are electrolytic, and have a positive and negative pin. They must be mounted the correct way or they will go bang! the third item down on this page is the kind of thing you're after. The other components are also capacitors, and the seventh item on this page will do the trick.
4) The chip is a Burr-Brown DRV134. I got them from RS components, but if you can't get them, I may have a couple spare.
5) The ideal supply would be run from your existing pre, +15v,-15v. We would have to track down the rails in your amp.
6) Yes, two 9v batteries would work fine for a temporary solution.
7) Not that much, probably about a tenner.
8) Ooh, now there's a question. I will have to think about that one...:)
9) No problem, anything for a fellow Yorkshireman.
p.s. You will notice that I haven't got back to earthing. That will be a whole installment in itself.. |
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| Peter Scowcroft |
For the Xlr it is a 3 pin connector. 33 kohm and 1 volt.
I can't see anything else apart from that =(
I am having a look round at maplins at the mo for gear.
oh for the love of god it is confusing!
What is the board you have glued your circuit called?
What wiring do you reccomend or should i use that conductive paint listed on maplins?
Remember i have NO electronics experience or training.
Are you a Black Sheep or Timmy Taylors man? |
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| pinkmouse |
Ok, well we will go with the UK standard for XLR, pin 3 hot, (if anyone knows this amp better, please chip in!). This means that the +output from the chip goes to pin 3, and the -output goes to pin 2. Pin one is earth. I am deliberately leaving earth connections 'till last, to avoid confusing you more than required. ;)
The board I use for construction is called Tripad board, and you can get about twice as much as you need for both boards for about a fiver from Maplins.
For wiring, for the most part we will use the pads on the board, and small interconnects cut off from the components once they are mounted. For the signal wiring, we need screened twisted pair. Don't bother buying this, send me your address and I will send you a couple of metres, I have a drum with the best part of 150m on, so I can easily spare you a little!
And now, a short intermission, while I eat my tea... |
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| pinkmouse |
| Tripad board. Ignore the dodgy soldering, I just bought a new roll of lead free stuff, and I'm not that pleased with it... |
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| Peter Scowcroft |
Ok to clarify i need for each channel:
GenElect 100uF 16V low profile electrolytic capacitors x 2
Polyester 0.1uF film capasitor x 2
Some tripad board
and of course some wire.
I have some Naim interconnect wire I am not using would that work? (4 core + shield)
I cannot find anywhere that sells the DRV134! any hints or do you have some spares i could purchace?
This sounds so exciting!
Did you have a good tea? cheezy beans on cheese and toast for me. |
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| pinkmouse |
Yes.
Yes.
Yes.
Probably.
I think so, just trying to sort out all my bits at the moment...
Good! You realise, this is the start of an addiction worse than any class A drug!
Yes thanks, home made Bombay potato with mushroom bahji last night, cheese on toast tonight. |
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| Peter Scowcroft |
I unfortunatly have never managed to make any homemade indian food that tastes anything near right!
I try though!
Never had any problem with cheese on toast though...actually I also had that for tea...and I burn't it. |
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| Peter Scowcroft |
Just a thought,
How will this mod affect the sound quality?
:confused: |
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| pinkmouse |
In theory, better! You will have much better noise rejection, and an optimised signal transfer.
It also means you may never have to buy an expensive interconnect again for that run, as XLR is not like phono,all reasonable cables sound identical, (IMHO). |
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| Peter Scowcroft |
Don't worry my interconnects wern't that pricey....apart from the £130 per metre ones....which is all of them!!
I liked the cable because it DID make the sound different!?
I am just going to chop the RCAs off and o a bit of resoldering.
Cant wait to try this.
Eventually I am going to stick something like this on the back of my CD player and run everything balanced the whole way through! |
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| Peter Scowcroft |
| just a thought...what interconnects do you use? |
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| dnsey |
| quote: | | I unfortunatly have never managed to make any homemade indian food that tastes anything near right! |
Off topic I know, but still DIY...
Look for a little paperback called 'The Curry Secret' - tells you how the restuarants do it, and it tastes exactly right
:yummy: |
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| pinkmouse |
Peter, mail me your address, I have stuff to send you.
Cables tomorrow, (well, later today...:)) |
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| AR2 |
Hello PinkMouse,
It would be great if you could post reverse solution as well - ballanced to non ballanced.
So we could have complete solution for future use.
Thank you
AR2 |
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| pinkmouse |
| One thing at a time! :) |
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| pinkmouse |
| quote: | Originally posted by Peter Scowcroft
just a thought...what interconnects do you use? |
I went through various brands, Audioquest, DNM, QED, but now I use home brewed ones using Van Damme installation grade balanced twisted pair, ( the cable I'm sending you). Phonos are an OEM non branded high quality thick gold plated type, very good, but a little tight to plug and unplug.
Has the parcel arrived yet? |
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| Peter Scowcroft |
| just gone to check the mail/1 |
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| Peter Scowcroft |
Sweet:
Newindian takeaway menu
Letter from mother in law
AND a mysterious package!!
Takeawa seems good.
The card was a valentines card...I am never goig to ge used to the fact that EVERYONE sends EVERYONE a valentines card in the USA. I got a c#valentinescard from 7 year old bo last year.
And the package containssome funky toys!
We have some nice wire 3 chips and 4 green things!
SWEET
Thankyou!
What are the green things? |
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| pinkmouse |
The 0.1uf caps. I had a bag of 200 here so I thought I could spare a few. And a spare chip doesn't hurt in case the first attempt all goes horribly wrong !
Have you unglued your preamp yet? :) |
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| pinkmouse |
| Have you got the rest of the bits yet Peter? |
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| Peter Scowcroft |
I am really sorry,
my wife has become very sickrecently and my priorities have changed.
Would it be possible to mail the parts back to you?
Sorry about this.
Peter Scowcroft |
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| pinkmouse |
| Peter, sorry to hear that. Don't worry about the bits, that's not important. I hope she gets well soon |
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| lgreen |
Sorry to hear about your wife.
If you ever get back to this and need help the items from pinkmouse are right on what you need. If you want to see something similar look at my RCA/mini to XLR box here |
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