why dont you confuse me next time 
i allready have 1 833 here, ill buy another and try it.
then try the OPAs and see if i can tell a difference.
I dont even know where to get OPAs from :/
Carlamart: its only an 24v24 supply, regardless. it simply wasnt enough gain and I couldnt achive anywhere near full power (20-25watt)
i allready have 1 833 here, ill buy another and try it.
then try the OPAs and see if i can tell a difference.
I dont even know where to get OPAs from :/
Carlamart: its only an 24v24 supply, regardless. it simply wasnt enough gain and I couldnt achive anywhere near full power (20-25watt)
in my experience you only need high quality opamps if gain >1. So if you are building a buffered pre with no gain (=1) opamp selection doen't matter that much.
When building an active crossover i couldn't distinguish between opa2132, ne5532 and a number of other, both high quality and crappy opamps.
When building an active crossover i couldn't distinguish between opa2132, ne5532 and a number of other, both high quality and crappy opamps.
mAJORD said:why dont you confuse me next time
I dont even know where to get OPAs from :/
I have seen some postings before that implied that the OPA parts were harder to find and pricier in walk in in Australia for some reason. OPAxxxx are TI (Texas Instruments) parts.
ESP has them available. It is listed on there the price list page near the bottom.
carlosfm said:
OK
Agreed.
One thing that we should keep in mind though as far as recommendations on this forum is that many of these things are a matter of degree and there is always a dismissing return effect at play. You have communicated unambiguously that for the LM833 you think it is sort of a cliff and that it should never be used. So you have a yes/no recommendation on this. But bear with me as I try to make a general point.
In general I think that we have to keep in mind there are different budgets and different goals that exist and it is more useful to more people if the continuum of possibilities is presented. The price difference between nice sounding choices and high end parts will be fine for some and out of project $ goals for others.
So while "what is the best part" discussions are useful, hopefully we can agree that "here is a continuum of possibilities" discussions are very valid and valuable to a large number of people.
BTW: My opamps are properly bypassed, as is good practice.
returning to the first topic of the thread, I keep on needing a schematic for my preamp with opa627... 
isn't there a link?? Is it something like this http://diyaudio.com/forums/showthread.php?postid=197110#post197110 ? 
Thanks, Matteo
isn't there a link?? Is it something like this http://diyaudio.com/forums/showthread.php?postid=197110#post197110 ? Thanks, Matteo
carlosfm said:moving_electron,
There are high-end op-amps that are cheap.
OPA2604 and LM6172 are cheap and very good indeed.
Why use the much inferior LM833?
Are we talking cents here?
In looking up prices it is interesting to see that the NE5532 price has dropped quite a bit over the last year I believe. So the NE5532 price is now nearly identical to the LM833 which based on your recommendation makes the NE5532 a better candidate on the low end on.
Prices seem to vary widely in different locals but from Digikey US prices (no tax) for small quantities of DIP parts:
OPA2604AP $4.28
LM6172 $3.80
OPA2134 $2.63
NE5532 $ .84
LM833 $ .78
Regarding the premium vs. non premium parts I think that it depends on budget. Sure for most people the ~ $7.00 price difference for a 2 chip preamp will not break the bank. It is only $7.00 and so it is not that costly to "upgrade". I think we can agree though that it is $7.00 that will not go elsewhere.
But consider an active crossover with baffle step correction and a notch filter etc and imagine that the number of op amps is 22. The cost to use the premium devices is ~ $77. Tax in many locals would raise this even higher. This may not be a consideration for you but may be a consideration for others. Perhaps the $70 allows for the purchase of much better tweeters and an upgrade to the midrange drivers on a speaker project etc.
Even on the preamp where the cost difference is much less the considerations may still be there for some. Maybe you were never a starving student, but I can remember trying to figure out how $40 was going to feed us for a few weeks. At that time the lower cost parts would have looked like a pretty good way to go in a preamp project.
The best deal for crossovers until recently was to use quad chips, but nowadays there are less and less around. Good quality ones I mean.
In any case, you can see that Marchand has an improved version using better chips. OPA2134 if I am not wrong. And using several chips on a xover will also be a weak link if the chips are not that good.
Carlos
.....could this design be adapted to became a preamp (less gain...right?)????
MINT
if you insist on using opa627's use this
adaptor
wouldnt it be nice...a battery powered, buffered, 627 and cheap! based preamp?
one more question, what would an apropiate gain for a gainclone for this example..
/just in case...i have no relation with any of the vendors.
MINT
if you insist on using opa627's use this
adaptor
wouldnt it be nice...a battery powered, buffered, 627 and cheap! based preamp?
one more question, what would an apropiate gain for a gainclone for this example..
/just in case...i have no relation with any of the vendors.
wouldnt it be nice...a battery powered, buffered, 627 and cheap! based preamp?
one more question, what would an apropiate gain for a gainclone for this example..
[/B]
The Tangent circuit is very nice, but has some drawbacks for this application.
1) It's intended for portable use, so it's powered by 18VDC splitted by an additional circuit to create a floating ground. This is really unnecessary for a GC application, where you will power it off the wall. Even if you power it with batteries, you will be better served by two 12v batteries directly powering that stage, with no floating ground. If powering off the wall you will need a good regulator to power the preamp.
2) The BUF634 version they use is the SMD version, which can't operate in class A. Same as DIP version.
Carlos
carlosfm said:
Of course it may happen! And I am very much aware of that.
But you are introducing another element in your supply that introduces other problems, like influencing impedance. Currents go through this split element.
Also powering from +/- 9v chips that can take much more is interesting for small chips, where heat can be a problem, and battery power. But if you have a healthy floor mounted supply (battery or AC sourced), why use a supply splitter?
Carlos
carlosfm said:Anyway Carlos...
Did you make the pre?
Not yet. I already did some tests with IGC and NIGC versions, using 1000uF and 2200uF respectively. The IGC sounded a lot better, at least in the highs and mids. All of them fed directly from a Marantz player with no buffer or preamp.
But I am working on a few preamp versions to try and interchanging some ideas over them with Pedja.
When I get more results I will get back here. Right now I am waiting for some toroidal transformers, which in Brazil you have to special order because they do not carry stock.
When they get here things will start rolling again.
Carlos
Alcaid,
The (usual) error you have on your layout is that you have the two electros on the same side of the op-amp.
Each one must me ON each of the supply pins, with the bypass cap right next to it ("glued" to the op-amp).
And the BUF634 needs the same treatment.
I put the BUF on the right side of the op-amp.
The caps are behind the BUF634.
This way it's very near the op-amp, so the feedback loop is short.
The (usual) error you have on your layout is that you have the two electros on the same side of the op-amp.
Each one must me ON each of the supply pins, with the bypass cap right next to it ("glued" to the op-amp).
And the BUF634 needs the same treatment.
I put the BUF on the right side of the op-amp.
The caps are behind the BUF634.
This way it's very near the op-amp, so the feedback loop is short.
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