Preamp discussion

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Folsom

Re: Preamp discussion
« Reply #60 on: 6 Dec 2015, 12:26 am »
While running a test signal through it, of course, that is at the preamps highest impedance and voltage.

I'm not sure what you're saying exactly, but you can use a multi-meter with ampere function in place of a fuse to measure. There's no reason you'd leave the fuse in.

But here's a question, if there's a fuse in your preamp what size is it? That'll give us a rough idea of the amperes.

Jonathon Janusz

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Re: Preamp discussion
« Reply #61 on: 6 Dec 2015, 12:50 am »
Jonathon, if you had actually read my previous posts on this string, you would have seen that the 11A has been listening tested for years. In fact I mentioned using speakers up to 28 grand. (Interesting you would not quote me.) In fact I have not mentioned measurements once in my posts on this string, so why the claim that I stated the exact opposite of what I actually posted.   :roll:

And what is your opinion of no perfection based on? Amateurs/diyers claiming to be industry participants? Dodd made a good move by using batteries as he eliminates the mistakes of almost all designers in building a power supply.

It is a little irritating that a few claim since they cannot obtain their goal, no one else can either. 

Our purpose here is to help the public, not mislead.

Cheers
Steve

Steve, I am sorry that I did not make my point as clearly as I intended.  I did not intend to imply anything regarding your mentioning of measurements, or lack thereof.  I also read very clearly that you made note that the 11A had been listening tested, along with by way of the cost figures listed a wide variety of speakers.

Your second to last sentence maybe underscores my point and maybe clears up some confusion between yourself and Folsom earlier.  With your preamp, you achieved your goal, and that of many others in the pursuit of the sound they are after.  Great!  Congratulations!  I hope to find my way to my ideal someday as well.

What I believe Folsom took issue with, and the point I was trying to make, is that "perfection" and "achieving your goals" are two completely different things.  Further, it seems in the pursuit of audio, everyone's definition of "perfection" varies and likely none of them truly are perfection in the most literal sense, which seemed to me to be the definitive tone you took in the exchange.  No amount of measuring (my insertion) or listening (yours) will likely ever be able to result to all parties' satisfaction in the literally flawlessly ideal widget.  To believe that in no way, ever, by anyone can a thing be improved beyond where it currently is no matter how difficult or how little improvement that may ever be is really a hard argument to make.  Tomorrow we may all wake up with some newly discovered revelation that changes all of what we know, making everything before it something less than we thought the night before.  If we as a species ever get to the end of the road in discovery, I think the world will be a far less interesting place.

Again, my apologies if I was in error, but reading the thread just now, I was also commenting on a different version of your reply to Folsom than I see currently which I unfortunately could not quote in my reply, as the quote would only place the current version in my text; we must have been writing very close to the same time with the message system hiccuping.

Considering this is The Lab, and although I very much respect the idea that a professional - who is good at something - not do a paying job for free, if an idea for a power supply to address Charlie's problem starts floating to the top and gets some wheels under it, I hope that you are able to offer some constructive input to solve the originally posted problem and avoid a critical flaw in design that would defeat the purpose of the effort.  I'm sure no one is asking that you design and build one from scratch for nothing, but as someone who has demonstrated exceptional results with a non-battery power supply, the opportunity to take advantage of your guidance and insight as a professional to the DIY community here is one of the things that makes a forum like this a great place for a dedicated hobbyist.

Davey

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Re: Preamp discussion
« Reply #62 on: 6 Dec 2015, 12:53 am »
While running a test signal through it, of course, that is at the preamps highest impedance and voltage.
I'm not sure what you're saying exactly, but you can use a multi-meter with ampere function in place of a fuse to measure. There's no reason you'd leave the fuse in.
But here's a question, if there's a fuse in your preamp what size is it? That'll give us a rough idea of the amperes.

Whether there's a signal present or not won't make any appreciable difference.  This is a preamp and signal current requirements for the power amp load are way less than current requirements for the circuitry itself.

Prying up one side of the fuse allows an easy test while the preamp is powered up.  You could remove the fuse too.  They'll both work.

The fuse rating would not be indicative of the quiescent current requirement of the preamp.  It's in there for safety purposes and also it has to tolerate the in-rush when powering up the unit.

Dave.

Steve

Re: Preamp discussion
« Reply #63 on: 6 Dec 2015, 01:00 am »
While running a test signal through it, of course, that is at the preamps highest impedance and voltage.

I'm not sure what you're saying exactly, but you can use a multi-meter with ampere function in place of a fuse to measure. There's no reason you'd leave the fuse in.

But here's a question, if there's a fuse in your preamp what size is it? That'll give us a rough idea of the amperes.

First of all, running a signal through into the preamplifier would make no difference as the preamplifier's operation is class A (unless overloaded) with a battery power supply. In class A operation, the average plate current of the tube is constant. The resistance of the multimeter is neglible, so no sweat.

Next, I would trust Davey's method as much much more accurate than simple looking at the fuse method. Check the availability of fuses and one would almost certainly need to order a fuse of 0,1 amp and smaller, maybe even 0,25 amps thorough the catalog or manufacturer. However, all four sections of the typical tube used in the Dodd would typically draw 0,06 amps or less. One would be off by nearly double just checking the fuse.

As I said, Davey's suggested method  is much more accurate.

Cheers
Steve

ps. Radio Shack certainly will not have such a small fuse in stock or by order.

Steve

Re: Preamp discussion
« Reply #64 on: 6 Dec 2015, 01:07 am »
Steve, I am sorry that I did not make my point as clearly as I intended.  I did not intend to imply anything regarding your mentioning of measurements, or lack thereof.  I also read very clearly that you made note that the 11A had been listening tested, along with by way of the cost figures listed a wide variety of speakers.

Your second to last sentence maybe underscores my point and maybe clears up some confusion between yourself and Folsom earlier.  With your preamp, you achieved your goal, and that of many others in the pursuit of the sound they are after.  Great!  Congratulations!  I hope to find my way to my ideal someday as well.

What I believe Folsom took issue with, and the point I was trying to make, is that "perfection" and "achieving your goals" are two completely different things.  Further, it seems in the pursuit of audio, everyone's definition of "perfection" varies and likely none of them truly are perfection in the most literal sense, which seemed to me to be the definitive tone you took in the exchange.  No amount of measuring (my insertion) or listening (yours) will likely ever be able to result to all parties' satisfaction in the literally flawlessly ideal widget.  To believe that in no way, ever, by anyone can a thing be improved beyond where it currently is no matter how difficult or how little improvement that may ever be is really a hard argument to make.  Tomorrow we may all wake up with some newly discovered revelation that changes all of what we know, making everything before it something less than we thought the night before.  If we as a species ever get to the end of the road in discovery, I think the world will be a far less interesting place.

Again, my apologies if I was in error, but reading the thread just now, I was also commenting on a different version of your reply to Folsom than I see currently which I unfortunately could not quote in my reply, as the quote would only place the current version in my text; we must have been writing very close to the same time with the message system hiccuping.


I have to divide your comments into apology and not correct. I will accept your apology. I Agree there is a difference between "achieve my goals" and "perfect"

If you check the bulk of my posts, you will see that I stated at least twice that the preamplifier is "perfect", and explained that the preamplifier did not alter the signal in any way. It faithfully, accurately/naturally reproduced the dynamics, clarity, image, depth, width, etc so the output was exactly the same as the input. The audio system sounded the same with or without the 11A connected. This was performed with listening tests over years and years and with individuals at the store etc.

I hope I am more clear, more understandable Jonathon.

Cheers
Steve

 

Jonathon Janusz

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Re: Preamp discussion
« Reply #65 on: 6 Dec 2015, 02:08 am »
Davey, Folsom, I think you guys are trying to figure out the same number from different ends of the equation?

Davey, you're asking how much current the preamp draws, outlining a way of measuring it.  Folsom is thinking by way of the current rating on a fuse at the power input that we can in a quick and dirty fashion know the maximum current that the device could draw regardless of its actual current draw (or just below it, as that value or more would blow the fuse).  This would get us in the ballpark of determining what to build for in a power supply knowing at most what we could possibly need.

A quick google search through pictures of Dodd preamps, and knowing what the last generation of them looks like, leads me to believe that it is a 2A fuse.  If Danny or Rich are reading this, they've replaced blown fuses in these units and could likely confirm that for sure.

Whether it goes without saying or not - I don't know because I don't design power supplies - polarity of the battery supply matters when connecting the battery to the Dodd preamp.  There are sacrificial parts at the power inlet should you get it reversed, but the magic blue smoke will escape if positive and negative get reversed, so please do be careful not to damage the preamp when testing the power supply alternatives.

Hope this helps get the conversation back on track. :)

Danny Richie

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Re: Preamp discussion
« Reply #66 on: 6 Dec 2015, 03:41 am »
Hey Steve, Does that 11A pre-amp use an output coupling cap?

And what type of RCA connectors are used on it?

Folsom

Re: Preamp discussion
« Reply #67 on: 6 Dec 2015, 10:55 pm »
Depending on how the preamp works as a buffer, regulation may provide no benefit by itself. Some buffers act to correct the signal changes, so whatever voltage goes in, comes out. If the parts used aren't overly sensitive to sounding different from biasing, then you only need as high of working voltage as the parts require or the music plays.

But they so often provide better filtration that it's worth it. Just like the Teddy I linked you to, it provides wonderful low noise power.

G Georgopoulos

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Re: Preamp discussion
« Reply #68 on: 6 Dec 2015, 11:37 pm »
Depending on how the preamp works as a buffer, regulation may provide no benefit by itself. Some buffers act to correct the signal changes, so whatever voltage goes in, comes out. If the parts used aren't overly sensitive to sounding different from biasing, then you only need as high of working voltage as the parts require or the music plays.

But they so often provide better filtration that it's worth it. Just like the Teddy I linked you to, it provides wonderful low noise power.

in an unregulated ps,the choke part of pi filter also acts as a passive regulator it stores and releases energy thus the load sees constant energy,this can work with large loads as well but the choke gets too big,so smaller and cheaper active regulators win... :green:

Folsom

Re: Preamp discussion
« Reply #69 on: 7 Dec 2015, 12:02 am »
George, have you seen my Antipole? That's how I prefer to do unregulated.

G Georgopoulos

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Re: Preamp discussion
« Reply #70 on: 7 Dec 2015, 01:28 am »
George, have you seen my Antipole? That's how I prefer to do unregulated.

Hi Folsom

first time i see it,i have no doubt it's working well for you
,in regard to tube buffers i agree with you.

cheers mate... :green:

G Georgopoulos

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Re: Preamp discussion
« Reply #71 on: 7 Dec 2015, 02:14 am »
Steve, what he was trying to say was a variation in power supply voltage would make no much of a difference in tube transconductance... :)

Danny Richie

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Re: Preamp discussion
« Reply #72 on: 7 Dec 2015, 02:46 am »
So Steve, Does that 11A pre-amp use an output coupling cap?

And what type of RCA connectors are used on it?

sfox7076

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Re: Preamp discussion
« Reply #73 on: 7 Dec 2015, 02:03 pm »
I said this sincerely.  I would love to hear a 11A one day.  I know it isn't made anymore, but it is on my list of potential preamps to hear.  I currently use a Concert Fidelity preamp.

Shawn

adminRH

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Re: Preamp discussion
« Reply #74 on: 8 Dec 2015, 07:42 pm »
This is the thread split off from the 'Dodd Battery Powered Preamps' thread.

Some posts have been moved to IGWB for containing negative personal comments.

I did my best to walk the line between good and bad posts over 6 pages. If you don't want admin deciding what is good and bad, then keep the bad out of your posts:

1. Stick to the topic
2. don't make negative personal comments
3. ignore existing negative personal comments

Thank you

Steve

Re: Preamp discussion
« Reply #75 on: 8 Dec 2015, 10:27 pm »
Steve, what he was trying to say was a variation in power supply voltage would make no much of a difference in tube transconductance... :)






I think the data from a 417A/5842 tube will help us to understand a tube more fully. Gm is the Transconductance, Rp is the plate resistance of the tube, and Mu is the amplication factor of the tube.

The relationship between the amplification factor, transconductance, and plate resistance of a tube is given as: Mu = GmRp, or Gm = Mu/Rp, or Rp = Mu/Gm.

The top graph shows the plate resistance varies with the grid voltage, plate voltage, and a change in plate current as a result since a change in grid voltage for a given plate voltage will alter the plate current.

Next graph shows the Gm changing with respect to grid voltage, plate voltage. There will also be a change in plate current.

The 3rd graph shows the change in amplification factor with changes in grid voltage, plate voltage. Again, there will also be a change in transconductance and plate current.

The bottom graph shows the change in plate current with changes in grid voltage and plate voltage. Of course the plate resistance and transconductance  changes.

The second graph from the top is the easiest to shows the effects of plate voltage on transconductance.

Everything is related. As the plate voltage, grid voltage, plate current varies, the transconductance varies, the gain of the stage varies. It only takes a few tenths of a db change of gain in one channel to alter the imaging of a stereo signal.

Cheers
Steve


« Last Edit: 9 Dec 2015, 01:51 am by Steve »

Folsom

Re: Preamp discussion
« Reply #76 on: 9 Dec 2015, 12:00 am »
So Steve, Does that 11A pre-amp use an output coupling cap?

And what type of RCA connectors are used on it?

Steve

Re: Preamp discussion
« Reply #77 on: 9 Dec 2015, 01:22 am »
Classified. 

Cheers
Steve

sts9fan

Re: Preamp discussion
« Reply #78 on: 9 Dec 2015, 01:27 am »


Carrying Danny's Troll water? If you have nothing to contribute then don't post.

Folsom

Re: Preamp discussion
« Reply #79 on: 9 Dec 2015, 02:19 am »
Classified is a fine answer.