Why do you need a preamplifier
FastEddy
I was trying to fit in with the INITIAL general thrust of this topic.The mods were briefy mentioned to illustrate only that the audible results in this test may not have been quite so dramatic with a standard Oppo Player. In another small Forum that I am a member of, those small mods are generally known. I expect to take delivery of the Oppo later today.Obviously, for use in this manner ,you would not need a preamplifier, if your primary uses were watching DVD movies and listening to CDs. Many people (not me) would'nt bother with their audio setup to watch TV.
SandyK
FastEddy
I was trying to fit in with the INITIAL general thrust of this topic.The mods were briefy mentioned to illustrate only that the audible results in this test may not have been quite so dramatic with a standard Oppo Player. In another small Forum that I am a member of, those small mods are generally known. I expect to take delivery of the Oppo later today.Obviously, for use in this manner ,you would not need a preamplifier, if your primary uses were watching DVD movies and listening to CDs. Many people (not me) would'nt bother with their audio setup to watch TV.
SandyK
" ... In another small Forum that I am a member of, those small mods are generally known. ..."
?? Another Forum?? Like who? AudioAsylum.com ? Other? = me too, & several others, but not regularily.
" ... expect to take delivery of the Oppo later ..."
Super. If you decide to make some mods, lert us know [on another topic / arena of your choice]. (All I did was add some plastic caps to snubb down the +/-9 VDC power at the DAC analog board connector.)
I have the tube pre-amp in the daisy chain string to have a quiet source switcher (FM tuner, Oppo DVD player and of course my iTunes / Mac Internet radio feed) and an impedence matcher ... and to take the edge off and mellow out any clipped signals ...
?? Another Forum?? Like who? AudioAsylum.com ? Other? = me too, & several others, but not regularily.
" ... expect to take delivery of the Oppo later ..."
Super. If you decide to make some mods, lert us know [on another topic / arena of your choice]. (All I did was add some plastic caps to snubb down the +/-9 VDC power at the DAC analog board connector.)
I have the tube pre-amp in the daisy chain string to have a quiet source switcher (FM tuner, Oppo DVD player and of course my iTunes / Mac Internet radio feed) and an impedence matcher ... and to take the edge off and mellow out any clipped signals ...
Why do you need a preamplifier
Fast Eddy
The small forum is "Rock Grotto Audio Forum"
Since a few days ago you have to register to view. It is mainly devoted to Headphones and their amplifiers, DACs , Valve gear in general , and general chit chat/discussions.If you need further information email me.
SandyK
alexkethel@optusnet.com.au
Fast Eddy
The small forum is "Rock Grotto Audio Forum"
Since a few days ago you have to register to view. It is mainly devoted to Headphones and their amplifiers, DACs , Valve gear in general , and general chit chat/discussions.If you need further information email me.
SandyK
alexkethel@optusnet.com.au
" ... amplifiers, DACs , Valve gear ..." = My meat ... 
(As I write: Listening to Apple MacBook <<>> Radio Skipper (iTunes internet radio feed @ 128k) <<>> 2 channel, 24 bit/96K Echo Digital AudioFire4 DAC <<>> ForePlay III tube pre-amp <<>> DIY 150 Watt X 2 MOSFET amp <<>> Maggie MMG planar speakers ...
)
(As I write: Listening to Apple MacBook <<>> Radio Skipper (iTunes internet radio feed @ 128k) <<>> 2 channel, 24 bit/96K Echo Digital AudioFire4 DAC <<>> ForePlay III tube pre-amp <<>> DIY 150 Watt X 2 MOSFET amp <<>> Maggie MMG planar speakers ...
)Attachments
Why do you need a preamplifier
Seems like the small >400 member Rock Grotto forum should be of interest to you. It may be small, but it has members globally, although some of the equipment mentioned is from British
"boutique" manufacturers. You will even see a thread by me on Extreme Modifications to the Musical Fidelity X-DAC V3.
It is a very informal group and very helpful.
However, for the sheer breadth of information, as well as some very clued up people.(some major designers and gurus too)
This forum is undoubtedly the premier forum. I prefer Class A solid state,preamp and power amplifiers, and enjoy trying the latest devices (LM4562 etc-overhyped? I am "burning in" a couple of LM4562 at present) and new circuit techniques.Most of my gear, however, doesn't stay stock standard very long, though.
SandyK
Seems like the small >400 member Rock Grotto forum should be of interest to you. It may be small, but it has members globally, although some of the equipment mentioned is from British
"boutique" manufacturers. You will even see a thread by me on Extreme Modifications to the Musical Fidelity X-DAC V3.
It is a very informal group and very helpful.
However, for the sheer breadth of information, as well as some very clued up people.(some major designers and gurus too)
This forum is undoubtedly the premier forum. I prefer Class A solid state,preamp and power amplifiers, and enjoy trying the latest devices (LM4562 etc-overhyped? I am "burning in" a couple of LM4562 at present) and new circuit techniques.Most of my gear, however, doesn't stay stock standard very long, though.
SandyK
Pre-Amp: Here is one way to do it
http://www.national.com/pf/LM/LM4562.html =
* Ultra high quality audio amplification
• High fidelity preamplifiers
• High fidelity multimedia
• State of the art phono pre amps
• High performance professional audio
• High fidelity equalization and crossover networks
• High performance line drivers
• High performance line receivers
• High fidelity active filters ...
...
THD+N (AV = 1, VOUT = 3VRMS, fIN = 1kHz)
?RL = 2k? 0.00003% (typ)
?RL = 600? 0.00003% (typ)
? ?Input Noise Density 2.7nV/ ? ^Hz (typ) ===
One could imbed this chip in a small switching box (for selecting sources) and have a tidy little stereo pre-amp, two for 4 channels, three for db 5.1 surround ...
http://www.national.com/pf/LM/LM4562.html =
* Ultra high quality audio amplification
• High fidelity preamplifiers
• High fidelity multimedia
• State of the art phono pre amps
• High performance professional audio
• High fidelity equalization and crossover networks
• High performance line drivers
• High performance line receivers
• High fidelity active filters ...
...
THD+N (AV = 1, VOUT = 3VRMS, fIN = 1kHz)
?RL = 2k? 0.00003% (typ)
?RL = 600? 0.00003% (typ)
? ?Input Noise Density 2.7nV/ ? ^Hz (typ) ===
One could imbed this chip in a small switching box (for selecting sources) and have a tidy little stereo pre-amp, two for 4 channels, three for db 5.1 surround ...
Why do you need a preamplifier
I am presently trialling the LM4562 in a preamplifier designed by Silicon Chip magazine, and which used OPA2134s.Initially, I was impressed by the big soundstage and the wealth of detail, but hoping that the "brashness" would improve as the chips burned in. A friend and I, both felt that in this particular application, the LM4562 didn't handle complex stuff as well as the OPA2134.
Overall, my existing Class A home brewed preamp is noticeably better. I offered my friend a couple of LM4562 to try in his preamp, but he declined the offer ! My preamp is still switched on,
and I will leave it on for another couple of days.
Thanks for the info.
SandyK
I am presently trialling the LM4562 in a preamplifier designed by Silicon Chip magazine, and which used OPA2134s.Initially, I was impressed by the big soundstage and the wealth of detail, but hoping that the "brashness" would improve as the chips burned in. A friend and I, both felt that in this particular application, the LM4562 didn't handle complex stuff as well as the OPA2134.
Overall, my existing Class A home brewed preamp is noticeably better. I offered my friend a couple of LM4562 to try in his preamp, but he declined the offer ! My preamp is still switched on,
and I will leave it on for another couple of days.
Thanks for the info.
SandyK
Eval Board of the LM4562
The Evaluation board probably does not have the connectors, but would offer the evaluator these specs, at least:
"¥ Easily drives 600½ loads
¥ Optimized for superior audio signal fidelity
¥ Output short circuit protection
¥ PSRR and CMRR exceed 120dB (typ) ... "
... and use this partial circuit plus provisions for adding PS filtration / connections: http://www.national.com/images/pf/LM4562/201572k5.pdf
The Evaluation board probably does not have the connectors, but would offer the evaluator these specs, at least:
"¥ Easily drives 600½ loads
¥ Optimized for superior audio signal fidelity
¥ Output short circuit protection
¥ PSRR and CMRR exceed 120dB (typ) ... "
... and use this partial circuit plus provisions for adding PS filtration / connections: http://www.national.com/images/pf/LM4562/201572k5.pdf
Attenuator technical
Hi I have a basic question about the attenuator and I would need only some techical advice on this please.
I have found a wonderful rotary military switch from a local military surplus for only $15. The switch is porcelain with golden contacts and plastic domes to prevent the dust going on the contacts. More superior in my oppinion to the classic high quality golden pins pcb chip resistors pontentiometers and far more supperior to the $20 plastic ladder attenuators sold on ebay.
I am thinking of making a very high quality attenuator using caddock resistors with it.
Note that I am going to use it with a PSE 2A3 tube amplifier.
My first question is:
The switch is 26 positions but because of the flange configuration I can use only 13 positions. What a nomimal maximum value in KOhms will be suitable for my passive preamplifier?
This 13 position switch will be suitable for the preamplifier or the steps will be so far appart? (i.e. big difference from the lower music level to the next higher)
My second question is:
I have seen almost all good quality passive preamps on the web using stepped ladder attenuator with this signal divider (or composer) approach where the output signal is composed of a portion of the input signal + the rest from the GND (earth). In a simple not ladder pontentiometer this is, connecting the input signal in the left pin of the pontentiometer, the output in the middle pin and the GND in the right pin.
Now, why this is done? Why can't I just ignore the GND and connect the pontentiometer as a reostat, like a single variable resistor between the signal input and the output? Or can I?
And my third question continues the previous one:
If I do have to use this GND approach can I just use the pontentiometer as a reostat (variable resistor) and having the GND resistor to be the one that is used in the grid of the tube in the next stage? Note this grid resistor is connected from the input signal of the amplifier to the GND and there is no capacitor in the imput of the amplifier.
Thank you very much!
Hi I have a basic question about the attenuator and I would need only some techical advice on this please.
I have found a wonderful rotary military switch from a local military surplus for only $15. The switch is porcelain with golden contacts and plastic domes to prevent the dust going on the contacts. More superior in my oppinion to the classic high quality golden pins pcb chip resistors pontentiometers and far more supperior to the $20 plastic ladder attenuators sold on ebay.
I am thinking of making a very high quality attenuator using caddock resistors with it.
Note that I am going to use it with a PSE 2A3 tube amplifier.
My first question is:
The switch is 26 positions but because of the flange configuration I can use only 13 positions. What a nomimal maximum value in KOhms will be suitable for my passive preamplifier?
This 13 position switch will be suitable for the preamplifier or the steps will be so far appart? (i.e. big difference from the lower music level to the next higher)
My second question is:
I have seen almost all good quality passive preamps on the web using stepped ladder attenuator with this signal divider (or composer) approach where the output signal is composed of a portion of the input signal + the rest from the GND (earth). In a simple not ladder pontentiometer this is, connecting the input signal in the left pin of the pontentiometer, the output in the middle pin and the GND in the right pin.
Now, why this is done? Why can't I just ignore the GND and connect the pontentiometer as a reostat, like a single variable resistor between the signal input and the output? Or can I?
And my third question continues the previous one:
If I do have to use this GND approach can I just use the pontentiometer as a reostat (variable resistor) and having the GND resistor to be the one that is used in the grid of the tube in the next stage? Note this grid resistor is connected from the input signal of the amplifier to the GND and there is no capacitor in the imput of the amplifier.
Thank you very much!
Re: Attenuator technical
If each step is 2db then you can get 0db to -24db using your 13 steps.
Why can't you get to the other 13 steps?
if you can arrange for the zero attenuation of the switched volume control to match your maximum output you will ever listen to (by adjusting the gains of both the pre-amp and power amp), then you can sometimes find that -20db to -30db covers a range of volume that you are happy with.neazoi said:
If each step is 2db then you can get 0db to -24db using your 13 steps.
Why can't you get to the other 13 steps?
Thank you,
I cannot because the flange of the switch has holes that correspond to every two switch positions. i.e. each "klick" corresponds to two positions of the switch.
There is also another thing, using caddock resistors a 26 position will greatly double the cost to high levels for my budget..
How about these PRECISION MULTITURN pontentiometers? Why couls not I use them? are they noisy compared to a stepped ladder? Very inductive, or what?
I cannot because the flange of the switch has holes that correspond to every two switch positions. i.e. each "klick" corresponds to two positions of the switch.
There is also another thing, using caddock resistors a 26 position will greatly double the cost to high levels for my budget..
How about these PRECISION MULTITURN pontentiometers? Why couls not I use them? are they noisy compared to a stepped ladder? Very inductive, or what?
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