Hi Chris,
design is absolutely fine. Look up IOTA-CD amplifier by Dr. Borivoje Jagodic.
Ofcourse DC relay connects speakers after everything is stabilized, and it takes just about 15 seconds. Amplifier uses DC servo.
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Cool , drivers are current sourced ... which keeps OP bias stable until
the valve stabilizes.
One step beyond -
Vzaichenko's hybrid-http://www.diyaudio.com/forums/solid-state/262450-ultra-high-performance-yet-rather-simple-hybrid-more.html
... uses 3 stages with the valve on the 1'st. red led
Vf keeps VAS current stable here (until the valve stabilizes).
Just the old Sansui 3-stage with a Valve instead of Jfet's.
ALL of Dr. Borivoje Jagodic's designs are rock stable with solid engineering
behind them. My studies involved his designs to gain my present level of
understanding.
He's "the man" (for amp design).
OS
the valve stabilizes.
One step beyond -
Vzaichenko's hybrid-http://www.diyaudio.com/forums/solid-state/262450-ultra-high-performance-yet-rather-simple-hybrid-more.html
... uses 3 stages with the valve on the 1'st. red led
Vf keeps VAS current stable here (until the valve stabilizes).
Just the old Sansui 3-stage with a Valve instead of Jfet's.
ALL of Dr. Borivoje Jagodic's designs are rock stable with solid engineering
behind them. My studies involved his designs to gain my present level of
understanding.
He's "the man" (for amp design).OS
I wasn't suggesting that Andrew was 'wrong', just that, like many topics and solutions within these forums there are often contradictory solutions. Separating the wheat from the chaff is often difficult - depending upon whom you choose to believe.
There has to be a practical solution for DIY'ers without having to build an external box just to contain a buffer - especially when no other preamp is used and only a single source is used.
Where do you then place the volume control? As any number of our wonderful forums exhibit, I've seen hundreds, if not thousands of DIY amps with and without volume controls.
I'm still trying to reconcile Andrew's statement:
"Because it forces you to place the Source close to the Receiver.
That in turn places the volume control next to the speakers, or excessively long speaker cables."
What does he mean, 'places the volume control next to the speakers'? And why does that necessarily imply long speaker runs? If my scenario is described as below;
SOURCE > (short interconnects) > BUFFER > (very short interconnects <6") > AMP > (short speaker cables) > SPEAKERS.
If I have very short <6" interconnects from the BUFFER(w/VC) to the AMP, why would it matter (practical sense), where the BUFFER physically resides?
Simply put: What is audio's 'best practice' here, especially when so many commercial integrated amps get it wrong!
Rick
I wasn't suggesting that Andrew was 'wrong', just that, like many topics and solutions within these forums there are often contradictory solutions. Separating the wheat from the chaff is often difficult - depending upon whom you choose to believe.
There has to be a practical solution for DIY'ers without having to build an external box just to contain a buffer - especially when no other preamp is used and only a single source is used.
Where do you then place the volume control? As any number of our wonderful forums exhibit, I've seen hundreds, if not thousands of DIY amps with and without volume controls.
I'm still trying to reconcile Andrew's statement:
"Because it forces you to place the Source close to the Receiver.
That in turn places the volume control next to the speakers, or excessively long speaker cables."
What does he mean, 'places the volume control next to the speakers'? And why does that necessarily imply long speaker runs? If my scenario is described as below;
SOURCE > (short interconnects) > BUFFER > (very short interconnects <6") > AMP > (short speaker cables) > SPEAKERS.
If I have very short <6" interconnects from the BUFFER(w/VC) to the AMP, why would it matter (practical sense), where the BUFFER physically resides?
Simply put: What is audio's 'best practice' here, especially when so many commercial integrated amps get it wrong!
Rick
I think AndrewT's point was the source, buffer and volume control are all sensitive to EMI and other noise produced heavily by the amplifiers and speaker cabling. It's best to keep them as far apart as reasonably possible.
without a an output stage that can drive long cables we are all consigned to using short cables.
That puts the source near the vol pot.
And puts the vol pot near the amplifier.
and puts the amplifier near the speaker.
That restricts operability.
We need longer cables somewhere.
The easiest is longer interconnects between the Buffer and the amplifier.
Then we can locate the source near the switcher, near the vol pot, near the Buffer. Then longer interconnects from the Buffer to the amplifiers which are near the speakers.
That uses just one stereo buffer at the output of the vol pot. The vol pot in this situation is the Source. The vol pot is the Source that cannot drive long cables.
That puts the source near the vol pot.
And puts the vol pot near the amplifier.
and puts the amplifier near the speaker.
That restricts operability.
We need longer cables somewhere.
The easiest is longer interconnects between the Buffer and the amplifier.
Then we can locate the source near the switcher, near the vol pot, near the Buffer. Then longer interconnects from the Buffer to the amplifiers which are near the speakers.
That uses just one stereo buffer at the output of the vol pot. The vol pot in this situation is the Source. The vol pot is the Source that cannot drive long cables.
My "pitchfork" preamp will have the line buffer included (below).
With -200db PSRR and 1ppm THD20 , I would never throw it in
with my "slewmaster" power amp.
It would not take much EMI or inductive coupling to degrade those specs.
Plus , the 10 ohm output impedance will assure even poor interconnects
will perform.
OEM "integrated amps" often include a pre-buffer to accommodate the wide
array of inputs - but this is a separate "pro" system - not OEM consumer fare.
OS
Hi OS,
Any plans on balanced design? PCB group buy?
Thanks
Do
As with "all good things" , they must be built , debugged , refined.
It took days to just find the right low noise solution (on mars) ...
mars probe "wenzel" tech. To create a piece of fine instrumentation
requires researching the "commonplace" , to set higher goals.
The Badger was a 2008 - 2011 ongoing project before it became DIYA's
amp.
PS - the "pitchfork" won't take 3 years , but I'm being real "anal" with it.
OS
It took days to just find the right low noise solution (on mars
) ...mars probe "wenzel" tech. To create a piece of fine instrumentation
requires researching the "commonplace" , to set higher goals.
The Badger was a 2008 - 2011 ongoing project before it became DIYA's
amp.
PS - the "pitchfork" won't take 3 years , but I'm being real "anal" with it.
OS
So.... Is it fair to say (or not), that a well-designed active preamp (by definition) will include a buffer stage suitable enough to drive long interconnects to the amp? Or, is that just an assumption on my part as to what a preamp does? Maybe it would help to define what is 'long' in our context here. 6' or 18'?
I want to drive 12' quality cables. 10R Z should do it. Some digital sources
also might need a bit more gain. My CD will drive my big amp (all the way).
My sound card won't. It helps to have more than 1:1 gain in a buffer to
equalize different sources.
I can keep my DAC/buffers/attenuation away from anything else , shield
the trafo .... even build a partial faraday cage around it. Super shielded
and dead quiet. Real hard to do this in the "big amp" - all that industrial
AC wiring , relays .... huge trafo's !
The buffer (being discrete), can also easily drive headphones and
12' cables , driving the big amp all the time (all the way) might get the cops called !
OS
SONIC Amp Photos by oscillator2 | Photobucket
To investigate further and not spam the topic, click the photobucket link for more photo's
Started it yesterday and did hurt my back by lifting it off the ground to the table, completely silent if Laptop is turned off while RCA's are connected.
Biased to 30mA each channel, @ 25C room temperature without cables attached to amp. Sound wise, it has potential
To investigate further and not spam the topic, click the photobucket link for more photo's
Started it yesterday and did hurt my back by lifting it off the ground to the table, completely silent if Laptop is turned off while RCA's are connected.
Biased to 30mA each channel, @ 25C room temperature without cables attached to amp. Sound wise, it has potential
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8 Channel APEX A-14 amp finished, sound awesome.
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RIAA phono preamplifier from scrap parts
A communications device metal box, and a tape head amplifier board (from an old cassette player) plus some paint work and an acrylic front plate, repurposed as a nice RIAA phono pramplifier...
A communications device metal box, and a tape head amplifier board (from an old cassette player) plus some paint work and an acrylic front plate, repurposed as a nice RIAA phono pramplifier...
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