hi guys,
i just finished a pair of Sachiko speakers (fostex FE206E in a BLH) and am going to build an F2 for them. i also need a preamp, and am wondering if the BOZ is a good match? will there be any impedance mismatch?
thanks
mymindinside
i just finished a pair of Sachiko speakers (fostex FE206E in a BLH) and am going to build an F2 for them. i also need a preamp, and am wondering if the BOZ is a good match? will there be any impedance mismatch?
thanks
mymindinside
Hi,
Years ago, I built the BOZ, but with some slight modifications to the power supply. Very nice sounding preamp.
I never used the BOZ PCB I got from AudioXpress.com and right now I've almost got a cascode version of the preamp working using the stock PCB. It uses 4 BF862 JFETs cascoded with an IRF510 Mosfet per channel.
I accidentally adjusted the bias potentiometers wrong which put too much voltage across BF862 JFETs and fried all of them. 🙁
It's kind of a G.Rollins SSTART preamp, but biased differently with different JFETs and it uses voltage feedback. Measures nicely in SPICE ... should sound good, but we'll see.
I'll post the schematic later, when I have time if you like?
Years ago, I built the BOZ, but with some slight modifications to the power supply. Very nice sounding preamp.
I never used the BOZ PCB I got from AudioXpress.com and right now I've almost got a cascode version of the preamp working using the stock PCB. It uses 4 BF862 JFETs cascoded with an IRF510 Mosfet per channel.
I accidentally adjusted the bias potentiometers wrong which put too much voltage across BF862 JFETs and fried all of them. 🙁
It's kind of a G.Rollins SSTART preamp, but biased differently with different JFETs and it uses voltage feedback. Measures nicely in SPICE ... should sound good, but we'll see.
I'll post the schematic later, when I have time if you like?
Have you considered the DoZ pre? I am using it and is quite a great sounding preamp for class-a designs. One drawback, it does not have comlementary inputs, only non inverting. It's a current feedback pre so is exceptionally fast too! it's made from cheapest parts available... see if u can give it a try. Simulations shows flat response up to about 300MHz.
The dual supply version is here-> Minimalist Discrete Hi-Fi Preamp
The dual supply version is here-> Minimalist Discrete Hi-Fi Preamp
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hey shaan,
you are based in india aren't you?did you source the semiconductors for this locally?how much did the project cost you? did you do it p2p or on a pcb?
what poweramp are you driving with this?
i just need a basic pre for my F2.
cheers
mymindinside
you are based in india aren't you?did you source the semiconductors for this locally?how much did the project cost you? did you do it p2p or on a pcb?
what poweramp are you driving with this?
i just need a basic pre for my F2.
cheers
mymindinside
Yes ALL semiconductors shown in the circuits are commonly available, sourced locally. Two of the preamps cost me about Rs.300(quite cheap isn't it?). I made them on dot board. I am driving a pair of MOSFET follower with them. But the preamp can be used for any kind of amp/power followers.
And if you really need a "basic" preamp for your F2 then this is the exact thing you are looking for. Plus, its performance is on par with other exotic preamps. Highly recommended!
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Hi,
Here's the circuit, as modeled using the Linear Systems LSK170C, though I'm actually using the BF862. I've haven't got it working again yet since I fried my JFETs last time. So, this is an untested and not listened to circuit. I plan on getting it wired up again soon maybe this week.
That DoZ looks nice and is simpler and easier to wire up. I might also try that. Thanks Shaan.
Here's the circuit, as modeled using the Linear Systems LSK170C, though I'm actually using the BF862. I've haven't got it working again yet since I fried my JFETs last time. So, this is an untested and not listened to circuit. I plan on getting it wired up again soon maybe this week.
That DoZ looks nice and is simpler and easier to wire up. I might also try that. Thanks Shaan.
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Hey mymindinside,
The highgain BOZ is totally wrong as F2 has a sensitivity of below 1,5Vrms.
What is the output of your source?
It might be enough with a volumepot at the input, if you only run a CDP.
The highgain BOZ is totally wrong as F2 has a sensitivity of below 1,5Vrms.
What is the output of your source?
It might be enough with a volumepot at the input, if you only run a CDP.
For my soon to be born F2 I'm going to build the DCB1 with a Lightspeed attenuator, maybe this could also be an option for you if matching some LED strings, matching (or buying matched) optocouplers and 2SK170s with similar ldss requirements do not put you off.
Hi,
If you are using efficient speakers (as you do) and with the gain of F2, you need nothing more than just a buffer. Just B1. Simple.
If you are using efficient speakers (as you do) and with the gain of F2, you need nothing more than just a buffer. Just B1. Simple.
this is what i was wondering...i am using efficient speakers (FE206E in Sachiko BLH) but will be using the system with an ipod source. i thought that the ipod line out might need some gain from the preamp to be loud enough
what do you think?
cheers
mymindinside
what do you think?
cheers
mymindinside
I think a buffer is where you want to be with such sensitive speakers. I think the buffer will also help even out the output of the ipod a bit better for the amp.
Naah...don't use Ipod...
Get yourself a decent DAC (doesn't have to be too expensive)and a laptop...much better...
Get yourself a decent DAC (doesn't have to be too expensive)and a laptop...much better...
You can absolutely use your iPod if you use Wave-files. It also have a low-Z directly from the DAC so no external buffer should be needed. But do not use the headphone output it sucks, you must go via a docking adapter get direct out from the DAC. Unfortunately the newer iPods have a less good DAC.
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If this is the case then go with DoZ. One advise, as you are using efficient drivers you might not need too much gain from the preamp. The default 10Kohm resistor in the feedback path of the DoZ circuit sets the gain at 3.2(10dB nominal). I think this will be enough for your setup. I replaced that resistor with 3K3 for my follower and the lowest recommended is 2K7.
As noticedd by a few of us in this thread, the F2 has high sensitity of ca 1,5V. An iPod dock has a LowZ output of 0,7V(headphone 0,9V).
The preamp needs to have a gain of 3.
The preamp needs to have a gain of 3.
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In this case I think DoZ preamp in its default gain of 3.2 is just about right. What do ya say?
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