Rebuilt Quickie: "The Bonze"
- Thread starter Bonzo
- Start date
aragorn723
New member
Paul Joppa said:
Definitely agree Paul, I couldn't think about changing the Quickie to something else (though i'm sure the other bottlehead pres are a step up!). I'm temped to play with it some times more than others (though there's probably not much more that could be modded-already changed the coupling caps to Russian PIOs and bypass caps to black gates-which leaves maybe changing the volume pot, and a teflon bypass for the coupling caps).
Dave
aragorn723
New member
Bonzo,
How do you like the teflon? The PIOs are really nice, but I wonder what the teflon would do to the sound (PIO seemed to take some of the bass out, which the black gates brought back, but not completely).
Dave
How do you like the teflon? The PIOs are really nice, but I wonder what the teflon would do to the sound (PIO seemed to take some of the bass out, which the black gates brought back, but not completely).
Dave
aragorn723 said:
Ciao Dave,
Sorry if I wasn't clear: I have the Teflon caps but I cannot fit them in my quickie due to lack of space (but I promise I'll do my best to fit them). Bypassing a PIO with a Teflon cap could, IMHO, restore both a bit of bass and a bit of high, it's the same improvement I heard on my phono pre (where I was able to fit both PIO and Teflon) and also reported here: http://www.enjoythemusic.com/diy/0411/capacitor3.htm
aragorn723
New member
Sounds like that might be the answer! How about placing another box below the Quickie to make room for the teflons?
8)
Dave
8)
Dave
mcandmar
New member
If were talking Russian Teflons the K72's are fairly compact and should be easy to fit. e.g. here is a 2.2uf K75-10 with a .022 K72-6 i used in one of my amps. I found with the K75's on their own to be dark sounding, adding the K72's brought back the high end detail. I'm usually not a fan of bypassing caps but in this case it worked rather well.
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aragorn723
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i'm curious to see if the teflons would change the bass too.. That's the main thing i'd like to see come back a little more. The black gate bypass caps aren't burnt in yet (I feel funny about using up battery power to burn in caps; they only have 30 hours on them out of ~400).. Probably should let those burn in !
Dave
Dave
mcandmar
New member
Going to say no. The small capacity .022uf will only pass high frequencies and do little to nothing for the low end. To me the K75's roll off both ends of the spectrum, their strong point being the rich mid range tone. It was because of that lack of low end i removed them.
I would suspect a basic Mundorf or Solen MKP would perform better overall. I tried a bunch of 2.2uf caps in my Quickie and ended up staying with the ClarityCap ESA, and for $8 each they are reasonably priced too. Then again the Mundorfs and Solens are half that price and almost as good. Any of them will have better low end than the K75's IMO.
I would suspect a basic Mundorf or Solen MKP would perform better overall. I tried a bunch of 2.2uf caps in my Quickie and ended up staying with the ClarityCap ESA, and for $8 each they are reasonably priced too. Then again the Mundorfs and Solens are half that price and almost as good. Any of them will have better low end than the K75's IMO.
Just a question: the resistance across the output rca of the quickie (if I remember correctly) is 220kohm, so with a 0.022uf cap the cutoff frequency of the rc filter would be 33hz. It seems, by my calculation, that the teflon bypass cap could pass also some bass frequencies, or did I completely miss the point?mcandmar said:
I haven't considered amp's input impedance, assuming it was pretty high like all Bottlehead's kit (with a low input impedance amp, the cutoff frequency would rise a lot).
Ciao!
That is certainly worth considering. It isn't uncommon to see an amp with a 10K input impedance.Bonzo said:
Paul Joppa
Moderator
Bonzo said:
That is technically true, assuming a similarly high input impedance for the following amplifier. However, the impedance to ground of the "hot" lead is very high, making it sensitive to electric and electromagnetic fields - also known as hum and noise.
Now I lost the track! :-[Paul Joppa said:
Paul, do you mean the design of the quickie is likely to be sensitive to hum, period, or that is better to use a low impedance amp with it to reduce hum (and so is better to use bigger teflon caps to hear their contribution even to bass frequencies)?
Sorry for the dumb question!
aragorn723
New member
Caucasian Blackplate said:
Interestingly, I have an amp with 10k input impedance.. So does that mean the rolloff frequency would be lower with that? The bass isn't bad, I just wish there was a little more sometimes.. Maybe a subwoofer would fix this (got a few laying around).
Dave
Paul Joppa
Moderator
Hah - I'm sorry for the unclear post, so we're even :^)Bonzo said:Now I lost the track! :-[
Paul, do you mean the design of the quickie is likely to be sensitive to hum, period, or that is better to use a low impedance amp with it to reduce hum (and so is better to use bigger teflon caps to hear their contribution even to bass frequencies)?
Sorry for the dumb question!
For the best noise sensitivity, the coupling cap impedance should be less than the source impedance of the preamp (about 2K ohms for the stock Quickie, 4K with the PJCCS), at the lowest frequency of interest for noises. That places the "hot" interconnect line at the lowest possible impedance to ground, enabling it to minimize electric field (capacitive) coupling.
My usual rule is to make the cap impedance less than the source resistance at 120Hz. I also check that the response corner for the lowest rated load impedance is 5Hz or lower. These are two different and independent criteria, and are occasionally over-ridden by listening tests - I love science but it is not everything.
aragorn723 said:
If you have a tiny cap at the output of the Quickie and a 10K input impedance on your power amp, you'll get bass rolloff.
The output impedance of the Quickie is also a tad high for a 10K load, but this is more about distortion rather than frequency response.
aragorn723
New member
Caucasian Blackplate said:
The output caps are 2uf Russian K75-10s, shouldn't be an issue with rolloff, right? (Except the inherent k75 bass rolloff).
Dave
