I'm back 
I've managed to finish the operational part of my amp (which means it only needs a case and proper connectors now).
Improvement from bi-amping configuration over ordinary stereo is, honestly, quite small. In fact, I've been doing so many alterations in my system recently that I can't be sure if there was any improvement at all But I feel that dynamics improved and music flows with more freedom, without strain (if there was any before ). Also I think that there is less compression at very large volume levels.
The bottom line is that a simple removal of muting transistors from my Marantz CD-52 SE had much more influence on system's overall sonics. Which is not to say that I regret building a bi-amped setup - even if the improvement is not striking now, it leaves lot of potential for further tweaks (ie active crossovering).
The amp works fine, without DC block caps. I also (as advised by Peter) removed 220R resistors from its inputs. I still has no fuses neither, in case you ask
However, after connecting the other two channels, the speakers startet to emit this, kind of, "hum". It is not loud, but definitely audible; and it was definitely not present before. I wonder if it can be occuring because I left every ground connecton floating (i.e. not connected to earth, not even tied channels together). Or maybe I should use separate power supply for the other pair of channels (for now, I just paralell-connected the second rectifier bridge along with the first to the same trafo)?
PS. Did I mention that GCs are the best thing since handkerchiefs?
I've managed to finish the operational part of my amp (which means it only needs a case and proper connectors now).
Improvement from bi-amping configuration over ordinary stereo is, honestly, quite small. In fact, I've been doing so many alterations in my system recently that I can't be sure if there was any improvement at all
But I feel that dynamics improved and music flows with more freedom, without strain (if there was any before ). Also I think that there is less compression at very large volume levels.The bottom line is that a simple removal of muting transistors from my Marantz CD-52 SE had much more influence on system's overall sonics. Which is not to say that I regret building a bi-amped setup - even if the improvement is not striking now, it leaves lot of potential for further tweaks (ie active crossovering).
The amp works fine, without DC block caps. I also (as advised by Peter) removed 220R resistors from its inputs. I still has no fuses neither, in case you ask
However, after connecting the other two channels, the speakers startet to emit this, kind of, "hum". It is not loud, but definitely audible; and it was definitely not present before. I wonder if it can be occuring because I left every ground connecton floating (i.e. not connected to earth, not even tied channels together). Or maybe I should use separate power supply for the other pair of channels (for now, I just paralell-connected the second rectifier bridge along with the first to the same trafo)?
PS. Did I mention that GCs are the best thing since handkerchiefs?
Hi Uncle_Leon,
Looks like you got ground loop problem, lifting chassis ground is not recommended for safety reason and it's not allowed in this forum to give such recommendation. for other place other than chassis it's possible to re-route the grounding or lift it on some point, but the circuit itself should still be grounded to the mains ground at some point, again for safety reason. you could try tying the chassis ground to the RCA input ground, and see if there's any difference.
active bi-amp give big difference, passive bi-amp is easier to implement if you already got passive x-over in the speaker, I also only get very little audible benefit(difference really)from passive bi-amping in the past.
Hartono
Looks like you got ground loop problem, lifting chassis ground is not recommended for safety reason and it's not allowed in this forum to give such recommendation. for other place other than chassis it's possible to re-route the grounding or lift it on some point, but the circuit itself should still be grounded to the mains ground at some point, again for safety reason. you could try tying the chassis ground to the RCA input ground, and see if there's any difference.
active bi-amp give big difference, passive bi-amp is easier to implement if you already got passive x-over in the speaker, I also only get very little audible benefit(difference really)from passive bi-amping in the past.
Hartono
Thanks for the reply, Hartono. I tried connecting earth to different ground points, but the amp was always picking up terrible noise whenever earthed. It didn't matter if I made connection with just plain wire or through a 10R resistor, the noise was always there. I might connect metal parts of case to ground to make it safe, but there's no way I'm going to earth the amp itself, this noise is just too much - and I'm talking about serious interferences here, not just a bit of white noise somewhere in the background.
I suspect that this hum may be some source-side related thing, because when I just stop the music and crank up the volume pot on the amp, the hum audibly changes (gets louder in the first place).
So what I'm thinking is: if there is a ground loop, it goes from input ground of pair1 (the 'tweeter pair') to input ground of pair2 (the 'bass-mids pair'), through the signal-spliting point. But I have no clue how to deal with it in an elegant way... At first, I thought that putting a resistor across one of the input grounds might solve the hum, but it would also effectively attenuate the signal for this one pair of amps, right?
So I came up with this other idea - would it be safe to link one pair's ground with the other's? I mean simply putting a cable from each InputGround (or each OutputGround) and soldering them all together in the middle?
I suspect that this hum may be some source-side related thing, because when I just stop the music and crank up the volume pot on the amp, the hum audibly changes (gets louder in the first place).
So what I'm thinking is: if there is a ground loop, it goes from input ground of pair1 (the 'tweeter pair') to input ground of pair2 (the 'bass-mids pair'), through the signal-spliting point. But I have no clue how to deal with it in an elegant way... At first, I thought that putting a resistor across one of the input grounds might solve the hum, but it would also effectively attenuate the signal for this one pair of amps, right?
So I came up with this other idea - would it be safe to link one pair's ground with the other's? I mean simply putting a cable from each InputGround (or each OutputGround) and soldering them all together in the middle?
Hi Uncle_Leon,
"because when I just stop the music and crank up the volume pot on the amp, the hum audibly changes (gets louder in the first place)."
so you're using passive pre-amp ? this could happen, the input of the amplifier is picking up noise because it sees high source impedance, try shorting the input of the amp, with no source connected, see if it still hums/noisy.
Hartono
"because when I just stop the music and crank up the volume pot on the amp, the hum audibly changes (gets louder in the first place)."
so you're using passive pre-amp ? this could happen, the input of the amplifier is picking up noise because it sees high source impedance, try shorting the input of the amp, with no source connected, see if it still hums/noisy.
Hartono
Anyone else tried Sikorel capacitors in their GC yet?
I now have 10000uF on each rail and 940uF at the chip, with 100V 47uF BG standard sitting between the V+ and V- pins.
This betters my BG N GC by a long way! No comparison!
Sorry to repeat my recommendation for Sikorels - I've still got tons of 470uF 35V caps spare if anyone wants to try these (I'll even mail them for free as I bought 100!)
Let me know if anyone is interested..... I'd love someone else to see what they think
I now have 10000uF on each rail and 940uF at the chip, with 100V 47uF BG standard sitting between the V+ and V- pins.
This betters my BG N GC by a long way! No comparison!
Sorry to repeat my recommendation for Sikorels - I've still got tons of 470uF 35V caps spare if anyone wants to try these (I'll even mail them for free as I bought 100!)
Let me know if anyone is interested..... I'd love someone else to see what they think
Wait a minute, there's two separate things:Hartono said:
- noise, when any of amp grounds is connected to mains earth
- hum, which is present always
I can get rid of noise in a very simple way, which is NOT connecting amp ground to earth.
As to the hum, I can short inputs all the way I like and it's still present. Besides, it was not present with a standard 2 channel setup, which again leads to a conclusion that there is ground loop between each pair of amps.
Oh, and yes, the so-called 'preamp section' of my amp is passive. Very passive, actually, it's a simple pot at the moment
You know that saying: "Play by the rules or fry the rules"?AndrewT said:
Of course I have a choice, and you can't convince me that I must earth the amp circuit. The chassis will be made mostly of an insulating material anyway, so what's the difference.AndrewT said:
It is a bi-amp stereo (or classic quadro) setup with each two amp channels being fed via pot from a single RCA input.
Hey, why not, I'd gladly try some of them if you price them reasonablysharpi31 said:Anyone else tried Sikorel capacitors in their GC yet?
I now have 10000uF on each rail and 940uF at the chip, with 100V 47uF BG standard sitting between the V+ and V- pins.
This betters my BG N GC by a long way! No comparison!
Sorry to repeat my recommendation for Sikorels - I've still got tons of 470uF 35V caps spare if anyone wants to try these (I'll even mail them for free as I bought 100!)
Let me know if anyone is interested..... I'd love someone else to see what they think
Only thing is, they would be working under voltage almost as high as their rated voltage... Don't you happen to have some 50V or 63V ones?that is not what the rules say.
You must earth all exposed conductive parts.
If you use shrouded connectors where the signal and earth pins are NOT exposed to prying fingers AND use an insulating case, then you are entering ClassII territory. Try finding the regulations that apply and tell us how one can make an amplifier comply and presumably the regulations will demand proof of compliance.
uncle_leon,
I have got some higher voltage sikorels - email me your address to james.r.sharp@gmail.com and I'll post some out (no charge :-D)
I use a transformer with 18VAC secondaries so the 35V caps are fine for me - I have either 63V or 75V 470uF caps at home too, so these might be better for you...
I have got some higher voltage sikorels - email me your address to james.r.sharp@gmail.com and I'll post some out (no charge :-D)
I use a transformer with 18VAC secondaries so the 35V caps are fine for me - I have either 63V or 75V 470uF caps at home too, so these might be better for you...
Hi Uncle_Leon,
"As to the hum, I can short inputs all the way I like and it's still present. Besides, it was not present with a standard 2 channel setup, which again leads to a conclusion that there is ground loop between each pair of amps."
yes... I was only asking you to ground the input so that we can see what's the real problem. how about your power supply ? so now you got new set of power supply as well ?
Hartono
"As to the hum, I can short inputs all the way I like and it's still present. Besides, it was not present with a standard 2 channel setup, which again leads to a conclusion that there is ground loop between each pair of amps."
yes... I was only asking you to ground the input so that we can see what's the real problem. how about your power supply ? so now you got new set of power supply as well ?
Hartono
That was obvious to me from the very beginning
I was only arguing because I thought you were telling me to earth the amp circuit never minding the noise it would introduce.As for now, both pairs of channels run on the same trafo. But I have separate rectifier bridges for each pair.
As to the hum, cross-connecting all input grounds solved the problem.
Hey, I would really rather pay (at least some symbolic price). The reason is that I never sell anything that I got for free - and I want to sell (cheaply, but still) my next amp to a friend.
As to caps and voltages, I'm using a 18V trafo too at the moment, but I might try swapping it against some other in the future. And I like the thought that my caps have a good voltage margin, and hence long lifespan
So I'd still rather go with 63V ones.
It may be harder, but I made it
Back to the topic of 'upgrades' - considering transformers.
Are there any sonical advantages/disadvantages of using encapsulated transformers as opposed to non-encapsulated ones? I know, of course, that encapsulated radiate out less magnetic interferferences (and tend to be more silent, in general), but what about sonical side?
Back to the topic of 'upgrades' - considering transformers.
Are there any sonical advantages/disadvantages of using encapsulated transformers as opposed to non-encapsulated ones? I know, of course, that encapsulated radiate out less magnetic interferferences (and tend to be more silent, in general), but what about sonical side?
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