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Loud Community designed 9v battery powered amplifier.

Started by No6h, June 18, 2015, 02:46:19 AM

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J M Fahey

Quote from: LateDev on June 29, 2015, 07:41:37 AM
The circuit shown claims 40mW into the 800 ohm Load.

I hate saying "I told you so""  but can't avoid it:
QuoteThat 12V tube amp will be happy to deliver > 0.1W`(not a typo, 1/10th of a watt)  .... if that much.
:-X

Any commercial transformer maker will probably charge, say, U$50 for the transformer itself ... PLUS U$200/800 on setup fees (no kidding) , depending on whether you supply the blueprints or they have to design their own.

Now if you order 1000 units, they may cost as little as U$ 15 each.

And in China they can cost as little as U$5 each, in 50000 unit orders.

But on a single, custom unit, starting costs are murderous.

LateDev

#16
I was merely giving added data, so find your comment quite extraordinary.
I also supply everyone with data and a circuit to show that a typical amp gives 40mW.

Quote from: J M Fahey on June 30, 2015, 01:17:42 AM
I hate saying "I told you so""  but can't avoid it:
:duh
How is showing people you are correct via a good example, worthy of that comment.

You could at least show that your assumption of less than 100mW was justified.

I find it quite strange that some people come out with blind statements and don't give out information to others, to help further their knowledge.

People do not learn anything if you expect them to rely on blind faith.

As far as the transformers are concerned, a lot of manufacturers do keep back stock of audio transformers as they are still extensively used, and I think you will find that the cost is not in the order you want to assume it is.
Do a search on the net http://comingsoon.radioshack.com/radioshack-audio-output-transformer/2731380.html#.VZJdvkZTsQo

J M Fahey

Quote from: LateDev on June 30, 2015, 05:08:55 AM
I was merely giving added data, so find your comment quite extraordinary.
I also supply everyone with data and a circuit to show that a typical amp gives 40mW.

Quote from: J M Fahey on June 30, 2015, 01:17:42 AM
I hate saying "I told you so"  but can't avoid it:
In a multiple people conversation, sometimes one thinks generic "you" is addressed to him, while it's addressed to someone else, so let's clarify, although it will sound klunky.
The original conversation was with No6h (so "you" refers to No6h), who intends to:
QuoteIm currently building a small 386 amp, and just want to move up in quality of output and volume, really.
So what is his reference point? ... a 500mW(9V)/1W(12V) amp.
No6h then posts a 12V tube amp schematic.
I warn No6h he's going down in "quality of output and volume" which is true and as a reference I state:
QuoteThat 12V tube amp will be happy to deliver > 0.1W`(not a typo, 1/10th of a watt)  .... if that much.
.... which ius true, by the way, and shows it's not the right path for what No6h wants.
Quote:duh
How is showing people you are correct via a good example, worthy of that comment.
I did in the very next line:
Quoteif you have 12V available, the very best amps are those designed for car radios and such
which I later expanded into:
Quotea $2 LM383/TDA2003
being a "10W CAR RADIO AUDIO AMPLIFIER"  as the datasheet states, I *guess*  it's a better choice than the 12V tube amp, any time of the day.
Do we agree so far?

QuoteYou could at least show that your assumption of less than 100mW was justified.
1) I was right after all.
2) I have what's called "experience" and know the limitations of tubes fed such low voltages, specially delivering *power* .
Should I pull the datasheets to show that it's a poor choice for a >1W amplifier?

QuoteI find it quite strange that some people come out with blind statements and don't give out information to others, to help further their knowledge.
Why would LateDev call it a blind statement?
Does everything posted here require a full page filled up with formulas?
Think again.
Quote
People do not learn anything if you expect them to rely on blind faith.
Knowing such a tube and supply combination is a poor choice for No6h goals is not blind faith but experience.
If anything, stating the opposite would require a lot of blind faith.
To boot, new member LateDev has backed my statement, so I guess I'm in good company :)

QuoteAs far as the transformers are concerned, a lot of manufacturers do keep back stock of audio transformers as they are still extensively used, and I think you will find that the cost is not in the order you want to assume it is.
Do a search on the net http://comingsoon.radioshack.com/radioshack-audio-output-transformer/2731380.html#.VZJdvkZTsQo
Now LateDev is attempting to change the rules in the middle of a game by introducing the back/old stock card ... but his original suggestion was, and I hate having to quote his own words:
QuoteAs far as the transformers are concerned, if you got to Hammond or Sowter, or indeed any company that produces quality transformers for audio, they will be able to supply whatever you want.
I warmly suggest LateDev asks for a single 1k/8r single ended output transformer , custom wound to his specifications, and posts price here.
Whatever they charge, will be way more expensive than a TDA2003 (is this also a blind statement?) , to boot that tube must still be fed clean 12V (single ended outputs do not reject hum and happily inject it into the speaker) plus whatever filaments take.

And we'd still end up with a 40mW amp when the goal was surpassing 1W .

Am I missing something?

LateDev

Ignores most of that as rhetoric. Whenever someone replies to any forum post, they are answering either the main topic or the post immediately in front of the one they are posting.
I think people who read this thread will be able to tell the difference.
Quote
Does everything posted here require a full page filled up with formulas?
Not at all, just a simple line with a small explanation, to help those who find this a little over their heads, would help clarify, otherwise statements like it will only give > .1W sounds condescending

Quote from: J M Fahey on June 30, 2015, 06:58:24 AM
Now LateDev is attempting to change the rules in the middle of a game by introducing the back/old stock card ... but his original suggestion was, and I hate having to quote his own words:
QuoteAs far as the transformers are concerned, if you got to Hammond or Sowter, or indeed any company that produces quality transformers for audio, they will be able to supply whatever you want.
Am I missing something?
[/quote]

Again the pointless dig. I have used Sowter in the past and they have provided a transformer to the common specifications that they have used millions of times before.
What you decided to state was that if you went to a transformer manufacturer and specified a bespoke/custom transformer then it would cost a lot, which is not untrue, however a Valve output transformer with the parameters you specified is not bespoke, and the link I gave everyone, shows this to be true.

I am an Engineer with over 40 years experience and merely wished to help or possibly educate, so I will bow out here as it serves no purpose.


J M Fahey

Quotea Valve output transformer with the parameters you specified is not bespoke, and the link I gave everyone, shows this to be true.
Unfortunately the link you gave is NOT a valve OT but a transistor OT , 1000 ohms center tapped.
Besides, it's meant for push pull use, as its specs show.
Which also means it will saturate with important DC current through it (Class Asingle ended tube)  and behave very poorly.
So I guess you'll have to order a custom transformer after all, and pay whatever makers charge.
Sowter, like any other transformer manufacturer, may charge less for a transformer IF it still is in their catalog , if/because they still keep the specs and details, but if not, they'll have to design it for you.
That's not cheap, and this is an understatement.
By the way, even if the transformer is free, the 40mW amp will not meet the OP's requirements.
Quote
I am an Engineer with over 40 years experience and merely wished to help or possibly educate, so I will bow out here as it serves no purpose.
Sorry you take it that way.
Experience is always welcome, of course, but I suggest you read a few posts first to get acquainted on how the Forum works and stop behaving like an elephant in a crystal shop, or stomping over everybody .

And don't turn it into a pissing contest, you might get surprised at the over 200 man-years experience (not a typo) amassed around here.

Take care.

Edit: as of the "every answer is directed to the post immediately above", think again.
While a response is being written, which often can take up to one hour or more, because a responsible guy may search for schematics or datasheets, draw a schematic, etc. , one or ten  answers by other Forum Members may appear in the interim, so it's prudent to check who might be the true recipient of an answer before feeling despised or angry.

Nobody is getting a cent as salary here, we are all doing it for fun and love of Musical Electronics (and it shows) 

Joe

I have a broken Line6 15W combo ready to be converted into a portable :)



J M Fahey

You mean a line or a 12V battery powered one?

If the former, maybe you can reuse the power amp section or at least the power transformer; now for battery operation you can only reuse cabinet, chassis, and speaker.

LateDev


Joe

This Line6 15W was a perfect amp to gut for this purpose. It's empty except the power transformer, which I could add back in later for line power, but battery is the first goal.

Now it's just a matter of the circuit. I would personally skip tubes for this, and just try to make a nice simple clean amp that is safe/easy to build. Maybe an opamp preamp/chipamp power amp? (The original Line6 used a little 5-pin TO-220 sized chipamp.)


J M Fahey

#24
IF battery powered is the main parameter, then you are stuck to a car radio type chipamp.

I have used TDA2005 since forever, still have a few left, but they seem to be obsolete.

A popular one is TDA7240, also a bridged type amp, some 15/20W into 4 ohms with 12V supply.

Here's the Pignose Hog 20, using a datasheet example of TDA7240 chipamp and a very simple 1 transistor preamp.


Just ignore the "squeal" section, a couple diodes, a pot and a switch intended as a poor excuse for distortion, you use just the clean preamp or cook your own.


J M Fahey


Joe


J M Fahey

Very sorry but it has a couple problems:
1) +/-m 15V rails are hard to implement in a battery powered amplifier
2) the output transistors are unbiased and will add a lot of crossover distortion
3) "normal" Op Amps such as these do no swing rail to rail , typically get not closer than 2 or 3 V from them so you have a power waste there.
4) nor have enough drive current available, tops 5mA, not sure if enough to drive those non Darlington TIP31/32
5) *if* they could be fully driven, current into load would be 15V/4 ohms=~4A peaks ; they are rated 3A maximum and because of Hfe drop at high currebnt, in practice are not used above 1A  for good efficiency.
That said, the amp shown will (somewhat) work if fed a guitar signal and loaded with a guitar speaker, only it will not be very efficient or clean.

No6h

I think a LM383 would be my best bet. According to generalguitargadgets.com, A LM383 produces around 8 watts at 12v. I like this one, (Len Galasso's Practice Man) but it only produces about three watts and it works on 6v. I like the fact it has a full three band eq and two channels. You can also download just the eq section schematic though, but I guess it only works on the 6v power supply.