O.K., is that a .01uf or .1uf coupling cap in the schematic?? Also, am I really loooking at a 1k ohm 50W resistor in the p.s.?? The reason I'm asking is because the online schematics are fuzzy and hard to read. Anybody??
cadaverdog said:
The schema i was reading yesterday said 0.1 uF -- it really doesn't need to be that big. (0.1 uF x 330k = 0.033 Hz?).
dave
BTW: a bogus ZEN (ie ZENclone) is called a Mulligan 🙂
icebear said:
Still gives a 0.33 Hz LF cutoff... if your OPT is small, even smaller would likely be better.
dave
planet10 said:
Dave,
Feel free to correct me if I'm wrong, but doesn't a 0.01uF coupling cap into a 330K grid resistor create a pole at:
1/(2*pi*0.01uF*330K) = 48Hz?
audiousername said:
In my 1st post with a cutoff i put a question mark because i wasn't sure of the formula and being away couldn't look it up... you could well be right...
dave
Dave,
I checked Steve Bench's "Frequency Response Synthesis" article: http://members.aol.com/sbench/freqresp.html
The coupling cap/grid resistor combination does create a zero at DC and pole at 48Hz (for 0.01uF / 330K) - meaning the freqency response will be 3dB down at 48Hz (neglecting the OPT).
Of course, this may be a good thing if the amplifier is used as a tweeter amp, or the OPTs are small and saturation is to be avoided.
Icebear,
Do you find your amp lacking in low bass?
I checked Steve Bench's "Frequency Response Synthesis" article: http://members.aol.com/sbench/freqresp.html
The coupling cap/grid resistor combination does create a zero at DC and pole at 48Hz (for 0.01uF / 330K) - meaning the freqency response will be 3dB down at 48Hz (neglecting the OPT).
Of course, this may be a good thing if the amplifier is used as a tweeter amp, or the OPTs are small and saturation is to be avoided.
Icebear,
Do you find your amp lacking in low bass?
I run the amp on Prometheus dipoles, and have active subs from 100Hz and down so I can not say I'm lacking any bass. I got it up and running yesterday, so I'm not familar with is yet 🙂
But I think I'll change the cap to the correct value anyway.
b
But I think I'll change the cap to the correct value anyway.
b
because the human ear naturally lacks bass response, and the -3dB point provided by the equation 1/(2*pi*C*R) for this case is 48Hz, you may not notice that much of a lack in bass seeing as from -3dB down point there is a -6dB rolloff per octave. this means by the time you get to 24Hz (1 octave lower than 48Hz) you are only down -9dB, and while this attenuation is noticeable at higher frequencies, considering the ears natural bass response you may not notice that much difference, unless this amp powers the sub, then you will definately 'feel' the difference, but you already said you have active subs.
cheers
by the way... it does not generally hurt to use a larger value cap in a coupling position unless it was placed there specifically to give a particular frequency response. HF response may suffer a little by using a larger value, but this can be overcome by placing another cap of 5% of the other caps value in parallel.
cheers
by the way... it does not generally hurt to use a larger value cap in a coupling position unless it was placed there specifically to give a particular frequency response. HF response may suffer a little by using a larger value, but this can be overcome by placing another cap of 5% of the other caps value in parallel.
Icebear,
I assume you mean the Prometheus speakers available from DIY Hi Fi Supply? If you are driving the active sub from the speaker level inputs, it is almost certain that there will be an improvement found by increasing the coupling cap. However, if the active subs are driven by line level inputs from the source/preamp (a much better solution), it is probably better to leave the tube amp rolled off in the bass. The Zen amp doesn't need to make bass in this setup, so there's no need to get the OPT to pass low frequencies (which risks satuation if your OPT is small, which in turn results in distortion at all frequencies). Oh, and small-value high quality coupling caps are cheaper and generally have better performance than larger value ones 🙂
Benny,
Granted, the 1st order highpass created by the coupling cap/grid resistor isn't as significant as many other factors in affecting bass production (OPT size, speakers, etc...), but adding another mechanism by which bass is attenuated only makes things worse unless bass is not required (such as in a bi-amped arrangement, or with an active sub)
EDIT: By the way, I read in your DiyAudio profile that you are a high school student in Melbourne? VCE exams over! 😀 unless of course you do a language...
I assume you mean the Prometheus speakers available from DIY Hi Fi Supply? If you are driving the active sub from the speaker level inputs, it is almost certain that there will be an improvement found by increasing the coupling cap. However, if the active subs are driven by line level inputs from the source/preamp (a much better solution), it is probably better to leave the tube amp rolled off in the bass. The Zen amp doesn't need to make bass in this setup, so there's no need to get the OPT to pass low frequencies (which risks satuation if your OPT is small, which in turn results in distortion at all frequencies). Oh, and small-value high quality coupling caps are cheaper and generally have better performance than larger value ones 🙂
Benny,
Granted, the 1st order highpass created by the coupling cap/grid resistor isn't as significant as many other factors in affecting bass production (OPT size, speakers, etc...), but adding another mechanism by which bass is attenuated only makes things worse unless bass is not required (such as in a bi-amped arrangement, or with an active sub)
EDIT: By the way, I read in your DiyAudio profile that you are a high school student in Melbourne? VCE exams over! 😀 unless of course you do a language...
Thanks
I run the sub's from linelevel yes. What you say is making sense, so I'll go with the small cap, and enjoy the nice HF 🙂
Thanks for your help.
Bjørn
I run the sub's from linelevel yes. What you say is making sense, so I'll go with the small cap, and enjoy the nice HF 🙂
Thanks for your help.
Bjørn
yeah, all over - media on monday was the last... i wasn't really stressing though coz i haven't really taken school very seriously this year... i've been more focused on my music which is better and more fun... like about a month ago my band played a gig up at dizzys (maybe you know it?) and we were asked to come back and play regularly next year... so we were pretty stoked and all got paralytic and didn't get home till 4am... 9am i had a Physics SAC i hadn't studdied for, and i didn't care... it's kinda disapointin now schools over coz now i have to think about doing something with my life.
sorry, that was off topic
benny said:
Yeah it was, but I brought it up... Anyway, good luck for results on Dec 13th!
er... I think I should end this off topic stuff now...
Mating the zen with a sub..........
If I decide to run the zen using an active sub, how would I route the low frequencies to the sub. I am capable of building a buffer of some sort if it is necessary- (high speed op-amps, etc.) What do you think???
If I decide to run the zen using an active sub, how would I route the low frequencies to the sub. I am capable of building a buffer of some sort if it is necessary- (high speed op-amps, etc.) What do you think???
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