Minimal IC Preamp for my gainclone

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meo85

Member
Joined 2003
Hi to all! I've build recently a gainclone on the first Peter Daniel's schematic and now I've thought to build an IC preamp for it.
I've got any OPA627, so this could be the IC which I can use.
Anyone can indicate to me a good schematic for this purpose (line preamplifier)?
Thank you to all, excuse me for my poor English... :rolleyes:
bye bye, Matteo
 
Nuuk

Nuuk

Member
Joined 2003
decdun.me.uk
What is a preamp?

It is a volume control and, if required, a selector switch.

It can be passive with just the above components or active which is what will make the difference with a GC.

To make it active, you can use a simple buffer circuit like the one used on my opamp buffered GC.

So you may not see a preamp on that page but with the addition of the contols, there is enough information to build one! ;)
 
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mAJORD

Member
Joined 2004
well.. I tryed using my GC with no Preamp.. using line level (CD player) and with a gain of 20 it was no good, (as can be calculated)

not only that tho it sounded like **** .. BUT if there such a thing as running in the caps (im sceptical) , then that could have been the cause for the bad sound .



I was looking for a simple design aswell. but found nothing that wasnt 2 stage, I wanted to use a single LM833 . but in the end have ordered a PCB off ROD elliot sound here in australia, which includes balance and tone controls, and is 2 stage, ill use the 2 833s in it and see how they go first up.
 
C

carlmart

Member
Joined 2001
preciseaudio.com
mAJORD said:
well.. I tryed using my GC with no Preamp.. using line level (CD player) and with a gain of 20 it was no good, (as can be calculated)
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What supply voltage are you using? What is the output of that CD player? What is the sensitivity of those speakers?

A GC with at least +/-24VDC should move any speaker directly driven by any CD player.

mAJORD said:
not only that tho it sounded like **** .. BUT if there such a thing as running in the caps (im sceptical) , then that could have been the cause for the bad sound .
Click to expand...

Using at least 1000uF capacitors should provide plenty of bass. The minimum you should use are Siemens/Epcos caps.

mAJORD said:

I was looking for a simple design aswell. but found nothing that wasnt 2 stage, I wanted to use a single LM833 . but in the end have ordered a PCB off ROD elliot sound here in australia, which includes balance and tone controls, and is 2 stage, ill use the 2 833s in it and see how they go first up.
Click to expand...

Get away from the 833! At least use NE5532s, if you can't get any better. But there are many modern chips now that upgrade it. They are trickier to implement but sound better.

See if Rod's board provides some way to bypass the tone controls stage, and put a switch to do it. Balance control should be useful only on a very "unbalanced" room. If possible avoid it too.

Carlos
 
moving_electron

moving_electron

Member
Joined 2004
carlosfm said:


Just don't use the LM833, or the whole thing will sound as a kitchen radio.:bawling:
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carlmart said:



Get away from the 833! At least use NE5532s, if you can't get any better. But there are many modern chips now that upgrade it. They are trickier to implement but sound better.


Carlos
Click to expand...



I really would not be scared of using the LM833 in the design.

Numerous people use them in the ESP designs and swear buy them and some are using it exclusively. For example, nobody on his forum claims they can tell any difference between an LM833 implemented active crossover and an NE5532 or OPA2134 crossover and there are 7 op amps on the 24dB/octave crossover. I certainly am not able to tell any difference between one I implemented with LM833 and polyester caps and one I implemented with OPA2134 polypropylene caps.

Others report being happy using the NE5532. My point is that in several discussions of op amps on the ESP forums (Rod's site) the NE5532, LM833 and OPA2134 all come up with happy users. No one reports any issues with the sound through any of them.

One thing to note though is that the LM833 is a higher bandwidth device and in some designs such as the crossover, it needs some small caps added at a few points to defeat oscillation. That has not come up on the preamp I don't think but is something to look out for.

I have OPA2134 in my Project 88 board and my P06 phone preamp as I built them before trying the LM833. They sound great. I probably will keep using the OPA2134 when the number needed is small as I figure why not although it may be wasting several dollars.

I will probably keep using LM833 when the number is higher. Note the OPA2134 is available for sale on the ESP site.
 
C

carlosfm

Banned
Joined 2003
Something strange is happening here.
No difference?:eek:
Even the NE5532 is much better than the LM833!
Anyway, I junk both of them.
Seriously, I'm not really surprized that some people can't find a big difference for the OPA2134.
Designs like the Chu-Moy headamp that you can see on the HeadWize forum have all the instructions to use an OPA in a very wrong way.
The OPAs (or any modern / fast op-amp) like good bypassing.
Most os the times it's not the case.
I'm sorry, but if your pre is the one I think, the same goes for that.

Don't ask me how to properly bypass.
Use the search on this forum, I've said it plenty of times.
:angel:

Note: some people don't even have decent systems to take reliable conclusions.:bawling:
 
moving_electron

moving_electron

Member
Joined 2004
carlosfm said:
Note: some people don't even have decent systems to take reliable conclusions.:bawling:
Click to expand...


Oh I forgot, that's it, my system is so sucky that I can't hear that it sounds like a kitchen radio.
:whazzat:

We could probably go on for 20 posts with you describing perceived differences and saying others systems are so lacking or listeners so tin eared that they cannot hear the difference.

I could go on for 20 posts describing how my system is well above decent, about LM833 vs. OPA2134 not being an area to particularly worry about versus other areas of the system, and demanding blind A/B testing with sufficient number of individuals and all parameters including amplitude exactly matched and measured.

In the end you would claim vast differences and that even considering LM833 is a bankrupt inadequate implementation.

In the end I would claim there are a lot of other places to put your money where it will be noticable, and that me085 will be very happy with a LM833 based preamp.

But really now, lets not leave the impression that implementing with LM833 will "sound like a kitchen radio".

All that being said, I will point out what I said before, which is for my preamp where only a couple of opamps are needed I am using OPA2134 and may keep making that choice cause I have some on hand.

Note that there are those who consider the OPA2134 inadequate and way too low-end to be considered vs. more premium op amps. And so the cycle goes.....
 
C

carlosfm

Banned
Joined 2003
Nuuk said:

I wonder if we had a 'boot sale' of all the discarded opamps people have, how many we would actually have on offer! :bigeyes:
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My god, Nuuk, what an idea!:eek:
I mean, intead of junking these things we could sell them!:eek:

Guys, I have some BA4558s, 4560s, NE5532, OP176:eek:, LM833, NJM2114...
I sell them for the best offer above 100 Euros.:D

I need to buy some OPAs...:D
 
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