I am looking to build an F-5 to go with Markaudio 10P Pensil speakers, and I would like to make the F-5 into an integrated amplifier. My source is Mac Mini/Macbook Air through a Micromega MyDAC.
I have seen the build that includes the Mesmerize buffer preamp in the same chassis as an F-5, and I was wondering what other options/alternatives folks have successfully built or designed to make an Integrated Amp using the F-5 curicuit boards as the amplifier stage. I would be interested in both active or passive/bufffer options.
Thanks in advance for your time and consideration.
I have seen the build that includes the Mesmerize buffer preamp in the same chassis as an F-5, and I was wondering what other options/alternatives folks have successfully built or designed to make an Integrated Amp using the F-5 curicuit boards as the amplifier stage. I would be interested in both active or passive/bufffer options.
Thanks in advance for your time and consideration.
i had tryed
a b1, bosoz and a aleph P 1.7. (all clones) with my F5 (a clone too).
-i think the b1 could be the best choice -easy to build only unbalanced like the f5
-second best because also easy to build bosoz
possibilitys i had not tryed
The jfet boz, lsk pre from BA2013 and the BA3 as pre could also be good.
a b1, bosoz and a aleph P 1.7. (all clones) with my F5 (a clone too).
-i think the b1 could be the best choice -easy to build only unbalanced like the f5
-second best because also easy to build bosoz
possibilitys i had not tryed
The jfet boz, lsk pre from BA2013 and the BA3 as pre could also be good.
It depends on if you need additional gain or not... what are the output levels of your DAC?
The Mesmerize and B1 are buffers with no gain, so that won't do the trick in your F5.
BA-3 as a pre has 20 - 30 dB gain, a bit too much.... though it's easy to lower it.
I have build it recently and it sounds terribly good!
Maybe you should try this: http://www.diyaudio.com/forums/pass-labs/176723-mezmerize-dcb1-building-thread-112.html#post3778938
The Mesmerize and B1 are buffers with no gain, so that won't do the trick in your F5.
BA-3 as a pre has 20 - 30 dB gain, a bit too much.... though it's easy to lower it.
I have build it recently and it sounds terribly good!
Maybe you should try this: http://www.diyaudio.com/forums/pass-labs/176723-mezmerize-dcb1-building-thread-112.html#post3778938
and you could also think about build an aleph j with an aleph p as pre.
If i had to choose an integrated amp at the moment i would do this way
If i had to choose an integrated amp at the moment i would do this way
http://www.diyaudio.com/forums/pass-labs/125893-preamp-ideas-f5-6.html
post #53... Could not be simpler.
post #53... Could not be simpler.
If I had to do the integrated F5 now, the preamp part would look like this (see attachment).
It gives a wide and linear response with about 9 dB of gain and Zout=1k (which is fine for F5's Zin of 100k).
It's simple to build, doesn't require hard-to-find/expensive parts and it sounds beautiful.
Id through BF862 is 10mA. Max. clean Vout is about 8V_peak. ELKOs should be high quality type, low ESR.
For use outside the amp's box a buffer stage should be added (so we could drive cable capacitance).
It gives a wide and linear response with about 9 dB of gain and Zout=1k (which is fine for F5's Zin of 100k).
It's simple to build, doesn't require hard-to-find/expensive parts and it sounds beautiful.
Id through BF862 is 10mA. Max. clean Vout is about 8V_peak. ELKOs should be high quality type, low ESR.
For use outside the amp's box a buffer stage should be added (so we could drive cable capacitance).
Attachments
Sure, but it wouldn't be very practical since ACA is a single rail supplied amp and this gain stage needs two power rails. Also, the third coupling cap would be needed.
Here it is.
Now the input cap is needed - that's the point of using two rails.
If you intend to use this with ACA (19V power rail) the following changes are needed:
C12 = 10 uF
R2 = 240 R
R5 = 820 R
Now the input cap is needed - that's the point of using two rails.
If you intend to use this with ACA (19V power rail) the following changes are needed:
C12 = 10 uF
R2 = 240 R
R5 = 820 R
Attachments
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Juma,
I decided to try your proposal from post #6. I would like to try it with both an F5 and also with an ACA; for the latter the preamp will need an output buffer.
can I just copy the output buffer from your LSK-pre? Do i just take the output from the drain of the first BF862 to the gate of the other BF862 and copy and paste the rest? (the PS I believe was the same +-24Vdc as for the rest. btw I am hooking up everything to the same F5 amp PS so I hope up to an extra volt is no problem for the preamp? (unless the PS sags a little under load which is also possible; I am using the regulated PS from Zen v5 article).
Thanks a lot!!!
I decided to try your proposal from post #6. I would like to try it with both an F5 and also with an ACA; for the latter the preamp will need an output buffer.
can I just copy the output buffer from your LSK-pre? Do i just take the output from the drain of the first BF862 to the gate of the other BF862 and copy and paste the rest? (the PS I believe was the same +-24Vdc as for the rest. btw I am hooking up everything to the same F5 amp PS so I hope up to an extra volt is no problem for the preamp? (unless the PS sags a little under load which is also possible; I am using the regulated PS from Zen v5 article).
Thanks a lot!!!
Yes, but you have to use a coupling cap between the gain stage and the buffer
Yes, with the coupling cap between them.
Not a problem at all
and of course i forgot another question:
I may have to compensate for a little difference in gain b/ween F5 and ACA in a bi-amped system. How can the gain be calculated/adjusted for this bf862 pre?
p.s. re: the coupling cap: as usual: the best film cap and as big as possible?
Thanks again!!
I may have to compensate for a little difference in gain b/ween F5 and ACA in a bi-amped system. How can the gain be calculated/adjusted for this bf862 pre?
p.s. re: the coupling cap: as usual: the best film cap and as big as possible?
Thanks again!!
The gain is calculated as a ratio of Drain resistor's value and total resistance in Source circuit (Rs + 1/gm). Of course, we have to take care to provide for optimal swing at the preamp's output (Drain at about 1/2 Vcc) by calculating the value of Rd at given Id. Also, we want to use this JFET in its most linear transfer curve region (Id close to Idss). Id is set by voltage between Gate and the Source.
I'm happy with Wima MKP10 and MKC4 (value as low as possible). IME, expensive boutique caps are nothing more than Dumbo's magic feather - if you believe in it, it will work for you...
Juma ,
would you please glance at the schematic to see if I hooked up the bf862 preamp with bf862 buffer properly. i only used a 0.1uF cap in between. i was not sure if i still needed a resistor in series as well as one to ground (like those 470R and 2M2 in your LSK pre + the same buffer)?
also in the buffer (in my C10 position), the schematic calls for a non-polar i.e. film cap. for size and cost restrictions I was thinking of using an electrolytic one (Elna) plus a small film bypass. is this doable with the polarity as shown?
sorry if these questions are not quite to the level. I am about to route a pcb for it so i would like to make sure the schematic is correct.
Thanks a lot.
S.
would you please glance at the schematic to see if I hooked up the bf862 preamp with bf862 buffer properly. i only used a 0.1uF cap in between. i was not sure if i still needed a resistor in series as well as one to ground (like those 470R and 2M2 in your LSK pre + the same buffer)?
also in the buffer (in my C10 position), the schematic calls for a non-polar i.e. film cap. for size and cost restrictions I was thinking of using an electrolytic one (Elna) plus a small film bypass. is this doable with the polarity as shown?
sorry if these questions are not quite to the level. I am about to route a pcb for it so i would like to make sure the schematic is correct.
Thanks a lot.
S.
Attachments
It's OK except for Q4 not having a dc reference at the Gate. You need a 1Meg resistor between the Q4's Gate and GND. You also need the gate stopper resistor (220R - 1k).
The same goes for BF862 in gain stage.
The same goes for BF862 in gain stage.
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