matjans said:
Thanks.
I'm currently using an LM-675. It's made unity gain stable by way of noise gain compensation. That's what the RC network across its + and - inputs is for. It's set so that it has a gain of 10 at around 500kHz, but a gain of 1 (or techincally, -1 since it's inverting) at DC and throughout the audio band.
The same technique can be used for other chip amps.
se
yldouright said:
Actually, you can have your cake and eat it too.
One of the neat properties of a good input transformer is that it can give you exceedingly high noise rejection even when fed from a wholly unbalanced source.
The Jensen JT-11P-1 for example can give you 100dB of common-mode noise rejection when fed from an unbalanced source (compared to 107dB from a balanced source). And because its input is floating, it can readily accept either unbalanced or balanced inputs
So, you don't need to use a balanced amplifier scheme and you don't have to mess with your sources.
And if you don't want to pay for something like a Jensen JT-11P-1 or a CineMag CMLI-15/15B, I've heard some people report good results using the less expensive Edcor transformers.
se
Steve Eddy
I hear noise reduction figures used all the time without the accompanying applicable bandwidth. Foe example, the LM3875 has 120dB of noise rejection but only at the lower frequencies so I'm not so sure your cake will satisfy as a complete meal. I've just been introduced to Mauro Penesa's gainclone circuit and am still reading about it. This presents yet another amp section candidate for this project.
I hear noise reduction figures used all the time without the accompanying applicable bandwidth. Foe example, the LM3875 has 120dB of noise rejection but only at the lower frequencies so I'm not so sure your cake will satisfy as a complete meal. I've just been introduced to Mauro Penesa's gainclone circuit and am still reading about it. This presents yet another amp section candidate for this project.
yldouright said:
First, those 120dB figures are with the two inputs shorted together and driven from a single source impedance. In a realworld scenario, the line impedances don't balance nearly so precisely and for electronically balanced inputs, the CMRR figure degrades quite rapidly with greater impedance imbalances.
To get that kind of figure in the real world, you'd have to hand trim the line impedances to within a fraction of a percent.
And yeah, the figures are typically given for lower frequencies, but then it's the lower frequencies, i.e. power line frequencies, that are the most prevalent source of noise in the audio band which couples into the line via loop inductance.
But transformers also provide galvanic isolation which can eliminate noise from ground loops and chassis leakage currents.
Can't say I'm familiar with that one. Got a URL?
se
damn lies and statistics
Steve Eddy
You elaborated my point perfectly. The specification only tells a part of the story, to know anything useful you have to read how they came up with the number. Building the integrated gainclone as I described it here will give us the opportunity to address the line impedence issues you disclosed in your post.
Steve Eddy
You elaborated my point perfectly. The specification only tells a part of the story, to know anything useful you have to read how they came up with the number. Building the integrated gainclone as I described it here will give us the opportunity to address the line impedence issues you disclosed in your post.
If you figure the additional parts for a separate preamp, the Mauro designs are actually sparse. I think carlosfm has stated many times that all the gainclones he has tested so far need a separate preamp. From reading his posts, I don't think he has decided which pre is his favorite yet but please correct me carlosfm if you have finally settled on the perfect match for all the gainclones.
carlosfm
The point of my last post was to highlight the fact that the Mauro design saves you the parts you will need with a separate preamp. Have you also tried the AD811 and other video amps? When you compare the preamp to the OPA627 buffered gainclone, do you find a great difference? I believe I read that you couldn't decide between the buffer and a dedicated pre for some time. What characteristic finally made you decide on the AD815 pre?
Russ White
I am leaning toward the NIGCWIPC as my solution because of its greater simplicity. I think your post refers to the "my reference" design you are currently offering in a group buy. The point of this thread is to come up with a best bang for buck integrated.
The point of my last post was to highlight the fact that the Mauro design saves you the parts you will need with a separate preamp. Have you also tried the AD811 and other video amps? When you compare the preamp to the OPA627 buffered gainclone, do you find a great difference? I believe I read that you couldn't decide between the buffer and a dedicated pre for some time. What characteristic finally made you decide on the AD815 pre?
Russ White
I am leaning toward the NIGCWIPC as my solution because of its greater simplicity. I think your post refers to the "my reference" design you are currently offering in a group buy. The point of this thread is to come up with a best bang for buck integrated.
yldouright said:
I have always use a standalone pre, because I prefer to have short speaker cables, and the power amp in a central position between the speakers.
I have used a buffered power amp because it was inverting topology, and it worked better that way.
The AD815 is superior to the OPA627 (even biased to class-A) and to my previous OPA627+BUF634 pre.
The AD815, besides very detailed, is very clean.
The cymbals are impressive, the treble is gorgeously clean, no blurring, no tizzzzz, no grain.
An experienced drummer would recognize a Zildjan cymbal.
Bass is very tight too, midband very open and natural.
filholder said:
When will those guys stop?
I hope this will cheer you up:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=40783&highlight=
Most of the thread talking alone...
Thanks Carlos,
Very interesting read, might have to try it some time.
Looks very interesting if I could just get the pot wired up right
Need to go to bed now, like i said exhausting day physicaly and mentally. I guess most of us here on this fourm are lucky enough to live in stable democracies where this crap is extremely rare. Still my worse day since living in london these last 10 years. Mustn't grumble though too many poor sods wont have a tomorrow to look foward too.
Fil
Very interesting read, might have to try it some time.
Looks very interesting if I could just get the pot wired up right
Need to go to bed now, like i said exhausting day physicaly and mentally. I guess most of us here on this fourm are lucky enough to live in stable democracies where this crap is extremely rare. Still my worse day since living in london these last 10 years. Mustn't grumble though too many poor sods wont have a tomorrow to look foward too.
Fil
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