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PostPosted: 11 Aug 2011, 06:49 
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I'm no expert but can assume that the noise is due to the chemical reaction occurring inside the battery . All the batteries I have tried have shown some low level hash when on load when observing the power line on an oscilloscope . Lead acid batteries are particularly poor in this respect , when powering an 845 this way I had to use an additional 2mH laminated choke in series with the filament . I have also noticed when using battery directly heated types , that powering the filament by batteries can sometimes make for a slightly harsh sound . Adding a film bypass cap at the load helps matters somewhat , try adding a cap around 1uF . Better still add more batteries in series for the filament supply and implement a CCS

BDA


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PostPosted: 11 Aug 2011, 09:59 
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Hi.
booangler wrote:
How do batteries create noise?


Batteries, like anything else electrical/electronic, get noise. This is physics.
(1) Johnson noise,
(2) shot noise (thermal noise)
(3) voltage noise
(4) current noise.

To cut the very long story short, according to a 1995 IEEE paper on "measurement of voltage noise in chemical batteries",

Ni-Cd battery gets the lowest noise - -195dBV/Hz at 1Hz & -204dBV/Hz at 6.5KHz :o , (measaured spectrum 1Hz - 75KHz),
followed by D alkaline, then AA alkaline, then AA lithium...

I don't know why NiMH battery was not included in the test :confused: Otherwise, I expect its noise level would have beaten NiCd.

In the paper, it recommended NiCd batteries to replace "noisy capacitor/resistor chains" used in biasing networks.

Something else may surprise you too:- resistor noise vs battery noise.

In a paper: "Measurement of battery noise & resistor-current noise at subaudio frequencies":-
It was found carbon resistors are most noisy - 10,000,000 times of its thermal noise ast 3Hz ! :hot: Standard (Zinc-carbon) dry batteries & wire-wound resistors "exhibit no measureable excess noise".

Though the internal resistance of a battery is low low well less than 1R, its inductance & capacitance may affect the passage of audio signal. So when used as HV for a SE classs A tube amp, & filament heating, like yr linestage, I'd use bypass caps for the audio signals to pass thru.

c-J

PS: That's why I use battery as cathode bias to replace the "noisy capacitor/resistor chain". :up:

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PostPosted: 11 Aug 2011, 20:14 
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cheap-Jack wrote:
... Standard (Zinc-carbon) dry batteries & wire-wound resistors "exhibit no measureable excess noise".

C-j, doesn't the above quote contradict everything you stated earlier in your reply?

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PostPosted: 12 Aug 2011, 08:41 
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Hi.
booangler wrote:
contradict everything you stated earlier in your reply?

Please don't take it out of context.

Those were 2 test reports on diffferent objects. 1st one was on batteries noise levels in term of -167dBV/Hz & lower levels. The 2nd paper was on noise levels of "dry batteries vs resistors" without stating any reference noise levels measured.

I don't see any contradiction at all.

c-J

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PostPosted: 12 Aug 2011, 16:43 
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I still feel that the statements are contradictory. If the battery has no measurable excess noise, then it has no excess noise regardless.

I addition your noise numbers from the 1995 report, as they were explained to me, are irrelevant when it comes to the amount of noise a battery actually makes. In the explanation I was given I used the numbers you quoted. Here is how it was explained to me using the Quickie as reference.

"... take the -204dBV/Hz at 6.5KHz value. (It's actually square-root Hz, incidentally.) Over a 20000Hz band, that's 43dB more than -204, or -161dBV. (That translates to 8.9 nanovolts.) Assuming that the signal level at the output of the Quickie is 1 volt (0.0dBV), and the Quickie in stock form has about 6dB rejection of power supply noise, the signal to noise ratio is about 167dB, which is about 23dB better than a perfect 24-bit digital stream with no dithering. I think you can safely ignore it."


Sounds to me, and to the person who explained this to me, that these "noise" numbers are insignificant.

Alan

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PostPosted: 17 Aug 2011, 13:24 
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Hi.
booangler wrote:
noise numbers from the 1995 report, as they were explained to me, are irrelevant when it comes to the amount of noise a battery actually makes

To save yr arguement..

The IEEE paper was done for ultra low noise requirement by measurement equipment & other specific LN applications, NOT for home-brew stuffs like yours. OK?

I bought up this paper is to give you a choice of batteries to be used in yr linestage project. Given choice, why not go for batteries of lower noise. If you don't appreciate this goodwill, who care?

FYI, I built a very simple 2-stage MM stereo phonostage using 2 bipolars each channel in a discrete dual monoral format (from phono I/P jack to O/P jack). It's powered by 2x9V alkaline batteries for each channel. NO no chip please!

The idea was to find out how good can a very simple design/built SS phonostage could sound. I installed battery voltage monitoring point to check out the 18VDC voltage from time to time. Let me tell you, it is a pain to replace batteries considering I built it in a small Hammond black plastic box (only 6"x3"x2") 100% aluminum liner shielded inside.

c-J

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PostPosted: 30 Aug 2011, 19:57 
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cheap-Jack wrote:
... The IEEE paper was done for ultra low noise requirement by measurement equipment & other specific LN applications, NOT for home-brew stuffs like yours. OK? ...

Then why use it in application to Audio? So you are basically applying the paper in away it was not meant to be applied. :confused:

cheap-Jack wrote:
... I bought up this paper is to give you a choice of batteries to be used in yr linestage project. Given choice, why not go for batteries of lower noise. If you don't appreciate this goodwill, who care? ...

That may be what you meant but it is not what you said. You never asked what batteries I was using, you implied that batteries were to noisy, and to tedious to work with, and I would have been better off with AC to DC chip system. Do you really now with I would have been better off with? :down:

cheap-Jack wrote:
... Let me tell you, it is a pain to replace batteries considering I built it in a small Hammond black plastic box (only 6"x3"x2") 100% aluminum liner shielded inside. ...

Did you even look at the Quickie? It was designed to be used with batteries, comes with the necessary hardware, and all batteries are mounted on the top plate for easy access. This design is anything but tedious. If you want to be helpful be helpful, but please don't be spiteful and, or patronizing. :up:

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PostPosted: 24 Mar 2013, 03:26 
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Suncalc wrote:
rparsh wrote:
Can anyone post a schematic of the "Quickie?" It would be fun to fabricate one. Thanks, Robert P
Well, as indicated above, the design for the "Quickie" from Bottlehead is not in the public domain so even if someone had the schematic, it wouldn't be right to just publish it without permission.

However, that does not mean that you can't implement a similar amp with your own design. For example, I took a look at the data sheets for the 3S4 and saw what it would take to get a battery powered preamp out of it. Just doing a basic load line design will work. After looking at the data sheets I decided that a 45v B+ was more appropriate. Here is my version.
Attachment:
Load line.jpg

This load line results in the following simple 1 channel circuit.
Attachment:
One Channel Schematic.png

Now the gain is low, only about 3, so it is just a simple preamp but the distortion numbers look good. The current draw is only about 1mA per channel so the nine volt batteries should last a good long time. The 1.5v cells are another matter. The filament current is about 50mA per tube so 100mA per pair. If you use Duracell brand alkaline "D" cells, they rate their batteries at 15 Ah (@150mA load) to 0.8v per cell. SInce you'll probably need to keep the filaments above at least 2v, from their constant load graphs it look s like you'll get maybe 30hours off a pair of D cells. Rechargeables may be a good idea here but their voltages are different, so design accordingly.

So here we have a battery powered 3S4 basic stage design which is NOT the "Quickie" but is based on the same principle. After doing this much design, I'm not sure I'm sold. Don't get me wrong, it would make a great conversation piece. But not quite sure of the utility. I guess to each his own.

Good morning to everybody,
I'm about to experiment this scheme to try a "quickie-like" preamp: I've already build the Oatley tube headphones amp and I'm very satisfied with battery-power hifi gear.
Only one question: I red that original quickie has 4kohm plate resistor, how this change can affect the sound of the scheme above?
Can I also change the input load with 470k resistor?
As told before by other members I don't want to disclosure any industrial secret, nor beeing unpolite, so admin feel free to correct or delete my post.


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PostPosted: 24 Mar 2013, 12:05 
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bonzo15011978 wrote:
I red that original quickie has 4kohm plate resistor, how this change can affect the sound of the scheme above? Can I also change the input load with 470k resistor?
Well, if by "above" you mean the 3S4 design I posted, then I can answer your questions.

Firstly, in my opinion, 4kΩ for the plate load on the 3S4 is far too low. From the load line design, you'll see I calculated the plate resistance at this bias point as about 6.4kΩ. So I started with a 12.7kΩ load for the initial calculation (not shown in this post but it is still in my design notebook). What I found was that the gain was far too low and the distortion was too high. I finally settled on the 22.5kΩ load as the performance sweet spot for this bias level. As I said, I did a traditional load line design process given the B+ constraints of the problem. I would not change the load or bias point with out further analysis.

As for the input grid resistor, you should be able to go as low as you want. I would not however go muck below 100kΩ (this is just my gut feel for the tube).

Please keep us informed as to how your build turns out.

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PostPosted: 24 Mar 2013, 12:57 
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Thank you for your reply Matt.
I'm an absolute newbie in electronic, and I'm still in the middle between the two implementations, but I think I'll build both versions and then... Testing, testing and testing again 8-)
The main problems with your implementation are the value of the components...a bit hard to find!

However I'll keep you posted!


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