Im looking to build cheap preamp now. What should preamp output ratings be? What is max the tube can take? I was searching for ECC83`s specifications and found "amplification factor: 100". This is clearly not 1V input signal x 100 = 100v input signal, as I thought it would be.
Mu = 100 could mean 0.5V input gives 40V output. Far more than you will need. Why do you want a preamp? Most systems do not need a preamp.
When I connect it to laptop is loud, I also use VLC player and crank volume to 125% and amp can handle it without any distortion, so I belive that it can handle even more.
If I connect it to mobile phone it`s quiet, it gives out maybe 30% compared to laptop, vlc 125%.
So I need to amplify input signal for about 3 to 4 times.
I don`t have space near PC, if I would want to have it connected to pc I would need 15m of audio cable, sure i could buy it or make it, but than there is still the problem that music is quieter on youtube, than on vlc. I also belive that it could sound even better if sound would be preamplified by hardware, not software - For instance if you take real eq and software eq, you see that software eq is not worth to mention compared to hardware eq (and my eq is 30years old). I belive that this 25% after max volume loudness is the same story.
How can I check that earthed source, like pc is now safe to plug into this amp. Old setup fried my internal sound card, plus gnd traces on front panel. However with old setup I measured 9Vac on input, now I don`t get any voltage no ac, no dc so that looks good so far.
Old setup didn`t have isolation transformer, and there was only 1 diode instead of bridge rectifier, plus live ground.
Thanks
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As long as it is all wired up properly with an isolation transformer now, you should be good to go, especially if your input doesnt show any voltage, although you can add an input capacitor to be extra safe.
Do you want tube, or solid state? If your amplifier chassis has extra room for another socket you could easily add a single tube such as a 6DJ8, 6N1P (6Н1П over there) or 6CG7/6SN7 and rig up a quick and low-distortion pre that runs off of the same supply with just a handful of parts.
Ah yes, but VuMeters with coloured LED back-lighting is quite different from 'bling". It's really a geek toy. There's no gold-plating and you have to be someone into technology to really appreciate it. 🙂
Hello,
yes input capacitor is already there (0,1uF) in series with tube and input, or did you meen to add another? what value in that case?
I have extra room for another socket, it will be tight, but it will fit.
But I`m tight on budget, I would have to buy tube and paint, primer to repaint case again.
So i was thinking to make preamp out of cassete player IC for now. Cassete preamp ICs are low noise and high gain and I think that this would make good preamp.
Some have output as high as 8v. Well i know that there is way too much gain, but after looking at datasheet is see that they have big supply voltage range from 3v to 30v for example, and output voltage depends on supply voltage and ussualy they are supplied with 12v
So if I would supply it with something lower maybe like 6v, I would have just what i need. Or is my theory wrong?
Thank you
I have LA3161 that i removed and saved when I was scrapping old car stereo. It was used as tape head preamp, but in datasheet it`s called "2-channel Preamplifier for Car Stereo"
I am attaching it`s specifications from datasheet:
Output voltage: 1.3
Voltage gain: closed loop=35dB, open loop=78dB
I don`t get what is closed loop and open loop.
To get full power from EL84 in pentode mode you need 4.5V RMS input, the IC you scavenged is rated for 1V output at 9Vcc power supply. To keep things simple, the best approach will be to replace the EL84 with a triode/pentode tube such as ECL86 / PCL86 or PCL85 or PCL805 or PCL82, then rewire the socket to add the extra resistors and capacitor.
Preamp stage: http://www.diyaudio.com/forums/tubes-valves/302531-my-6e5p-amps-spud.html post #5.
NE5532 is 0,56€ - IC NE5532P DIP8 (LOW NOISE AMPLIFIER) | IC ELEKTRONIKA.
You need also dual power supply (+/- 12V-15V).
.
NE5532 is 0,56€ - IC NE5532P DIP8 (LOW NOISE AMPLIFIER) | IC ELEKTRONIKA.
You need also dual power supply (+/- 12V-15V).
.
I see, it's not worth to do anything of this for temporary preamp. I will wait until I buy ecc83 and than I'll do it like I should. Until than I'll use 15m audio cable that I just made and VLC 125% volume 🙂
Poslano z mojega S50 z uporabo Tapatalk
Poslano z mojega S50 z uporabo Tapatalk
I noticed after using different speaker (also 4ohm) and playing different genres of music that on some music specific high frequencies are scratchy, it`s hard to explain but closest sound to it is sound of rustling foil. Oh, and speaker is good, it play`s ok on all other amps that I have. Amp also does that on original speaker, that I first used, but it`s alot quiter, so you don`t notice those sounds if you don`t know that they are there.
I belive that the tube is bad?
I belive that the tube is bad?
I'ts hard to tell without a oscilloscope, but it may be an oscillation. Try to put some distance between the output transformer wires and the tube grid pin. It may also be distortion from a cheap output transformer. When wou will add the ECC83, you may try to add some negative feedback to reduce the distortion.
I will try, but if it can be caused by cheap OT I guess that this is it as original circut was made to cheap.
I must search for 3w or 5w transformer?
thank you
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Oh, and I plugged it into computer and it's all good, nothing fried hehe
Poslano z mojega S50 z uporabo Tapatalk
Poslano z mojega S50 z uporabo Tapatalk
Really?
It's true that 1W parts tend to be sturdier than 1/2W parts, but voltage ratings vary quite a bit. Not sure where this "1W = 200V" rule is coming from.. do you have any citation for that?
Again, this doesn't make any sense. The vast majority of classic tube gear is built with 1/2W by default, and they hold up fine. I built tube gear for many years using 1/2 almost exclusively, and these were mostly Roderstein Resista Mk.III series.. which have very soft, thin copper leads. Yes, you can break those, but you learn how not to, very quickly - it's called gentle touch and strain relief.
Of course vintage amps (and tube radios) mostly use 1/2 W resistors. The context of this thread is a low cost project that a beginner may build with the kind of resistors it could source for the least amount of money from generic distributors or pulls from consumer electronics scrap boards. A modern 1/2 W generic film resistor is flimsy, has very thin wires and may not be rated for tube amp voltages. The manufacturer may be unknown and also the exact specifications. To my knowledge, most kits made from modern standard parts use 1W resistors and I believe that this is a good choice for a novice in the tube amp field. Your point is nevertheless correct, and from a engineering point of view the dissipation rating of any resistor should be chosen according to the circuit function and resistor manufacturing specification. I'ts hard to do for a novice.
According to my experience, quality 1/4W film resistors mostly have a 200V specification, 1/2W 350V and 1W 500V. This is also quoted on the Merlin Blencowe book, so I presume it's a common fact. But the resistor of unknown origin that is sold on ebay or at the spare part store may wery well not be up to this standard. A better statement would have been that "1W resistors are at least 200V". I never found a 1W film resistor with a lesser rating.
According to my experience, quality 1/4W film resistors mostly have a 200V specification, 1/2W 350V and 1W 500V. This is also quoted on the Merlin Blencowe book, so I presume it's a common fact. But the resistor of unknown origin that is sold on ebay or at the spare part store may wery well not be up to this standard. A better statement would have been that "1W resistors are at least 200V". I never found a 1W film resistor with a lesser rating.
I could handle 1/2w resistors fragility as I am not new to whole electronics thing, just tube amps. But I think that it will last longer, as this is point to point wiring, who nows if I will drop it accidentally one day hehe.
What ohm speaker can I connect to this amp, only 4ohm?
What ohm speaker can I connect to this amp, only 4ohm?
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