• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

My first preamp with tubes

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#305
Horowitz and Hill.

Max Martin said:
I wrote/gave a link also earlier in the thread what caps i was using, voltage and so on if i don't remember completly wrong, so strange that nobody didn't say anything.
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We can't be expected to double-check every contribution for circuit errors or inadequate components. It would take far too much time, so we have to assume that people roughly know what they are doing. We spot some problems; the rest are a matter of DIY!
 
#306
I will change around little and put my 10uF "only 250VDC" to bypass cathode and order some 400VDC to PSU then so I also have some safety at home 😉

Also have some WIMA MKP4 over (rated 1000V DC!) that i can paralell right behind rectifier.

And gridstopper going back.

Meanwhile i'm lowering b+ below 250V just to be safe(r)

Plus to Arcotronics then not to overrate their specs. I guess if it would be some crap it would have blown already.
 
#307
DF96 said:
Horowitz and Hill.


We can't be expected to double-check every contribution for circuit errors or inadequate components. It would take far too much time, so we have to assume that people roughly know what they are doing. We spot some problems; the rest are a matter of DIY!
Click to expand...

Ok. Fair enough. I've learned my lesson not to think "speaker crossover" in my head anymore when it comes to B+ voltages 😀

Thx for the tip

EDIT: Yes i have done alot with this preamp (and other stuff recently) without blowing anything up yet so far so good. Just good i asked that stupid question(s)
 
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#309
Max Martin said:
I will change around little and put my 10uF "only 250VDC" to bypass cathode and order some 400VDC to PSU then so I also have some safety at home 😉
Click to expand...

You can try to bypass cathode resistors, but also you will have more distortion and more gain, which is already high.

If you still decide to do it, 10uF is very low and you will lose bass, try between 100uF and 470uF, or a cheap red LED instead of the resistor, is a better solution.

A very good reference about SRPP here

http://valvewizard2.webs.com/SRPP_Blencowe.pdf

Max Martin said:
Meanwhile i'm lowering b+ below 250V just to be safe(r)
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You must use capacitors rated at about 450V, your circuit would work better at about 300V.
 
#310
popilin said:
You can try to bypass cathode resistors, but also you will have more distortion and more gain, which is already high.

If you still decide to do it, 10uF is very low and you will lose bass, try between 100uF and 470uF, or a cheap red LED instead of the resistor, is a better solution.

A very good reference about SRPP here

http://valvewizard2.webs.com/SRPP_Blencowe.pdf



You must use capacitors rated at about 450V, your circuit would work better at about 300V.
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Thank you. Actually i saw that link on valvewizards page so i was just done reding it wheni saw you posted this here 🙂

I have tried it and like it. Cap is 47uF now. I was thinking 4x10uF MKP but i'll guess i have to go up in value
 
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#318
popilin said:
I did not mean to offend you, but I feel you don't like my advice. 🙄

As I said before, bypassed version of SRPP gives more distortion, and the dominant noise source is the volume pot, with higher gain you also have more noise, even when bypassed SRPP has less noise than unbypassed version. 🙂
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No, no i really do. I like your advice (remember gridstopper)

I think you have alot of knowledge.

Best way is to test out. Tomorrow i will remove bypassing again and see. Today i changed couple of other things so i can maybe have an other opinion tomorrow... (did some mod on my dac home, caprolling 😛😀)

The only negative i heard today with bypassed cathode was a bit smearing/laidback sound. Fits some songs. No, little hum/noise is still there. No change.
I don't know what a better cap will do though.
 
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