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Old 28th February 2013, 05:29 PM   #21
6L6 is offline 6L6  United States
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That sounds very interesting!

Any schematics you can point towards? Datasheet perhaps?
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Old 28th February 2013, 06:36 PM   #22
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Datasheet is great. Here is what Juma drew for gainclone type setup. The opa549 can be replaced with F4. Maybe even consider naked F4 as the opa1632 can drive it no problem. You'll have to tinkle with gain setting to meet your needs. GC SuperSymmetry
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Old 1st March 2013, 01:51 AM   #23
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Quote:
Originally Posted by chuckd View Post
Crossover Points: 340Hz & 2.5kHz

Impedance: Nominally 4 ohms
I think you should take advantage of using an active xo for the bass and using a class AB high power amp there. Then you could prob get away with a standard F5 for the tweeter and mid.
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Old 1st March 2013, 04:06 PM   #24
chuckd is offline chuckd  United States
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Originally Posted by 6L6 View Post
Running single-ended stereo, yes.

I wrote that. I'm working on one for the F4 as we speak.

Well, if you have a balanced preamp with about a 20v output swing, you can drive a pair (as monoblocks) of F4 to 100WPC. The disadvantage is that you are basically building a preamp specific to the needs of those power amps. The advantage is that you then have F4's, which practically everybody says are completely transparent sonically.

Anyway, F4's aside, have you started collecting parts for your F5T build?
Well thanks for starting that F5 thread!!! It has been a great source of information.

So you're onto the F4's now...that's very interesting what you say about them. I'm not locked into an F5 by any stretch. So far I have been adding to my shopping cart on Mouser but I don't have any parts in hand as yet.

I've actually spent the last couple of days trying to find a replacement for BJT pair 2SC4793/2SA1837 since they are no longer made. Also the 1st replacement pair 2SC5171/2SA1930 are finished or finishing. I actually found 2SC5200N/2SA1943N which seemed to be the latest design from Toshiba so was going to use them. I'm still looking for the latest Toshiba JFETs and MOSFETs. Or I might just use the IRFP240/IRFP9240 for the MOSFETS.

But I could build the F4 except AudioSan stated the F4 wasn't suitable for 4 ohm speakers. Any thougts on that??
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Old 1st March 2013, 04:27 PM   #25
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Old 1st March 2013, 05:19 PM   #26
koja is offline koja  Canada
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Default some pointers

you seem to be all over the map.
you should start by understanding your source, your speakers and your needs.
source: SE or XLR?, output voltage and impedance?
speakers: sensitivity, impedance (minimum) and how reactive (impedance and current-to-voltage phase differences): some speakers like B&W for examples will have a highly negative phase and low impedance combined in say upper bass/low mid range (100-200Hz) which makes delivering power to the speakers really hard. these curves however are generally not available for commercial speakers but somebody on the net may have measured them and/or commented.

re: your question: balanced signals btw only have the advantage if you run very long cables (for lower susceptibility to induced noise), otherwise SE is fine. balanced sources and amps however have typically more gain (6dB) than one half run SEnded.

the advertised power limits for speakers are useless. the question is how much power and at what combination of current and voltage do they need to play to your needs (i.e. to your listening levels and in your room).

F5 is very good for comparatively lower heat dissipation into smaller impedances than alephs, and for its ability to deliver very high currents into low impedances. it has however lower gain and may need a preamp to drive it to its limits if your source does not have enough volts out to begin with. it also has a higher input impedance if the previous stage (volume attenuator or other) is at a higherZ. f5 schematic is simple but still requires some tuning.

AlephX and anything symmetry based will depend on everything being perfectly matched including thermal conditions etc. or else the noise will be in. these are praised for their midrange quality(on high sensitivity, mainly FR speakers). similarly F5s are regarded as wide bandwidth, good for top and bottom frequences, but may be too revealing especially with fairchild fets, so many are substituting Toshibas to try to get them to be less brutal to less-than-perfect sources.
I hope this helps.
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Old 1st March 2013, 06:46 PM   #27
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re: your question: balanced signals btw only have the advantage if you run very long cables (for lower susceptibility to induced noise), otherwise SE is fine.
There are no other advanatges?
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Old 4th March 2013, 05:32 PM   #28
chuckd is offline chuckd  United States
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Short and to the point. Thanks.
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Old 4th March 2013, 07:19 PM   #29
chuckd is offline chuckd  United States
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Quote:
Originally Posted by koja View Post
you seem to be all over the map.
you should start by understanding your source, your speakers and your needs.
source: SE or XLR?, output voltage and impedance?
speakers: sensitivity, impedance (minimum) and how reactive (impedance and current-to-voltage phase differences): some speakers like B&W for examples will have a highly negative phase and low impedance combined in say upper bass/low mid range (100-200Hz) which makes delivering power to the speakers really hard. these curves however are generally not available for commercial speakers but somebody on the net may have measured them and/or commented.

You are correct. I am a little bit over the map. I'm just trying to work out differences between amps and get people's opinions on the nuances of the different types.

The sensitivity and impedance I understand but the 'reactive-ness' of my speakers as described is getting a bit beyond the scope of my research. I think you can get too carried away with trying to find the 'perfect' amp. At the end of the day you just have to make a decision and start building one and find out for yourself and that's the point I think I'm at.


Quote:
Originally Posted by koja View Post
the advertised power limits for speakers are useless. the question is how much power and at what combination of current and voltage do they need to play to your needs (i.e. to your listening levels and in your room).
I don't have a room yet and when I do it may change. So I figure I'll just build an amp and if it has excess power that I dont every use, then I'm ok with that. At least it's there if I need it.


Quote:
Originally Posted by koja View Post
F5 is very good for comparatively lower heat dissipation into smaller impedances than alephs, and for its ability to deliver very high currents into low impedances. it has however lower gain and may need a preamp to drive it to its limits if your source does not have enough volts out to begin with. it also has a higher input impedance if the previous stage (volume attenuator or other) is at a higherZ. f5 schematic is simple but still requires some tuning.

AlephX and anything symmetry based will depend on everything being perfectly matched including thermal conditions etc. or else the noise will be in. these are praised for their midrange quality(on high sensitivity, mainly FR speakers). similarly F5s are regarded as wide bandwidth, good for top and bottom frequences, but may be too revealing especially with fairchild fets, so many are substituting Toshibas to try to get them to be less brutal to less-than-perfect sources.
I hope this helps.


I have decided on the F5 but since a couple of people have mentioned the F4, I'm going to look into that a bit. The Aleph X, I think I'll leave for now. I will have a processor/pre-amp for the volume control too.

Thank you very much for the response. Every bit of feedback, information, knowledge really helps and I really appreciate it.
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Old 4th March 2013, 07:48 PM   #30
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I just built an F5 and couldn't be happier, with the exception of needing a bit more gain with low-output sources.

F5 / Mezmerize Integrated
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