Hello, I've been thinking about having a go at DIY project for some time and I really appreciate some advice. I don't have any technical knowledge but I have been able to solder a couple of simple passive crossovers together as well as make my own cables.
The BOSOZ balanced line stage has caught my interest as it looks simple enough and I really need a balanced preamp! Commercially available balanced preamps are quite thin on the ground and pricey too
My amplifier is a balanced SAC KT88 Glowmaster and I have two balanced sources (a Audiolab MDAC and a PS Audio GCHP). .
Would the BOSOZ be a good match for my equipment and suitable for a beginner to build?
I was also wondering if the BOSOZ could be made in two half width boxes as this would suit my rack space?
The BOSOZ balanced line stage has caught my interest as it looks simple enough and I really need a balanced preamp! Commercially available balanced preamps are quite thin on the ground and pricey too
My amplifier is a balanced SAC KT88 Glowmaster and I have two balanced sources (a Audiolab MDAC and a PS Audio GCHP). .
Would the BOSOZ be a good match for my equipment and suitable for a beginner to build?
I was also wondering if the BOSOZ could be made in two half width boxes as this would suit my rack space?
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I see that you can string two sentences together and describe your ability
to solder components. Therefore you are qualified to build BOSOZ and
most other projects.
😎
to solder components. Therefore you are qualified to build BOSOZ and
most other projects.
😎
Thanks for the vote of confidence and thanks for your design article. I'm looking forward to giving this project a go and hopefully learning something on the way!
Hi everyone,
I'd really appreciate some advice please!
I'm trying to get my parts order together, but as I am hoping to get everything I need from RS Components here in the UK rather than importing from Digikey I need to make some parts substitutions.
1. Can I use a 2x55V transformer for the power supply? I think this should be enough for the 60VDC output but I may have missed something.
2. Are wire wound resistors suitable for R1 to R6?
3. Can I use 221ohm 0.6W Vishay MRS metal alloy resistors instead of the 0.25W metal film on the parts list? The 0.25W they sell are 10x the price of these Vishays.
4. I already have some 10uF film capacitors that may be suitable for the blocking caps C1 and C2, but they are huge (90x40mm) Obbligato film and oil types with the leads at one end. Assuming I can fit them in the case, would these be a worthwhile improvement over standard MKT/MKP types?
I'm going to wire everything point to point, so PCB size isn't an issue...
Cheers,
Patrick
I'd really appreciate some advice please!
I'm trying to get my parts order together, but as I am hoping to get everything I need from RS Components here in the UK rather than importing from Digikey I need to make some parts substitutions.
1. Can I use a 2x55V transformer for the power supply? I think this should be enough for the 60VDC output but I may have missed something.
2. Are wire wound resistors suitable for R1 to R6?
3. Can I use 221ohm 0.6W Vishay MRS metal alloy resistors instead of the 0.25W metal film on the parts list? The 0.25W they sell are 10x the price of these Vishays.
4. I already have some 10uF film capacitors that may be suitable for the blocking caps C1 and C2, but they are huge (90x40mm) Obbligato film and oil types with the leads at one end. Assuming I can fit them in the case, would these be a worthwhile improvement over standard MKT/MKP types?
I'm going to wire everything point to point, so PCB size isn't an issue...
Cheers,
Patrick
Thanks Merlin, but I need balanced inputs and outputs...
I have read through the Balance Zen Line Stage article a few times and I'm beginning to understand what does what and I'm pretty sure I can put it all together.. But, I obviously have a long way to go before I fully understand!
I was wondering if things like the inductance of resistors makes a difference to this design (as I read this can be a problem with wire-wounds in some circuits)? If my calculation for the diode bridge AC to DC conversion are correct (55VAC * 1.414 - 1.1Vf = 76.67VDC) and if this is still an "adequate margin from the unregulated supply" compared to the original design?
Sorry if I'm asking dumb questions, I am trying to learn for myself, but I want to get started building and not get too bogged down on the technical stuff for now.
I have read through the Balance Zen Line Stage article a few times and I'm beginning to understand what does what and I'm pretty sure I can put it all together.. But, I obviously have a long way to go before I fully understand!
I was wondering if things like the inductance of resistors makes a difference to this design (as I read this can be a problem with wire-wounds in some circuits)? If my calculation for the diode bridge AC to DC conversion are correct (55VAC * 1.414 - 1.1Vf = 76.67VDC) and if this is still an "adequate margin from the unregulated supply" compared to the original design?
Sorry if I'm asking dumb questions, I am trying to learn for myself, but I want to get started building and not get too bogged down on the technical stuff for now.
I've got another beginner question...
Do I need to have 10uF DC blocking capacitors if my power amp has an input impedance of 200Kohm (XLR) / 100Kohm (RCA) or can I just use (say) 1uF caps.?
According to Coupling Capacitor Calculator by V-Cap
If this is right, would it have any effect on the cap. value if I choose to use potentiometers P3 and P4 on the output?
Do I need to have 10uF DC blocking capacitors if my power amp has an input impedance of 200Kohm (XLR) / 100Kohm (RCA) or can I just use (say) 1uF caps.?
According to Coupling Capacitor Calculator by V-Cap
If this is right, would it have any effect on the cap. value if I choose to use potentiometers P3 and P4 on the output?
What voltage does Bosoz use?
Is it a single polarity supply or a dual polarity supply?
Does it have a DC blocking capacitor on the output?
Is Boz the same or different from Bosoz?
Is it a single polarity supply or a dual polarity supply?
Does it have a DC blocking capacitor on the output?
Is Boz the same or different from Bosoz?
Hi Andrew, the details of the BOSOZ are on the Pass DIY website, it's proper name is Balanced Zen Line Stage. It is different from the BOZ. I think (but bare in mind I'm just learning) that it uses a 60VDC dual polarity supply (in that the PS has a regulated 60V output and supplies both positive and negative). The DC blocking caps are on the output but before the optional output volume control.
Am I right to think that blocking caps and coupling caps are the same thing? Also, that the volume pots will effect the impedance seen by the preamps output?
Am I right to think that blocking caps and coupling caps are the same thing? Also, that the volume pots will effect the impedance seen by the preamps output?
The Pass pre-amps are already in my Pass Folder.
But I can't remember which is what off the top of my head.
Do I have to open the file to check you have read it correctly?
But I can't remember which is what off the top of my head.
Do I have to open the file to check you have read it correctly?
Us DIYers can even make the big Obbligatos fit.
Here is the Pass B1 with Obbligato PIOs.
Attachments
I'm pretty sure the info I've given is correct Andrew, does it make sense? The recommended pot value is 5Kohm and the cap value is 10uF.
fig2 & fig3 show what you need.
Yes, +-60Vdc for the BalZen
That +-60Vdc comes from the regulators. They need ~60Vac+60Vac from the transformer. Your 55Vac+55Vac will almost certainly do the job.
Attenuating pots on the inputs and outputs will ruin the balanced impedance of this BalZen.
Balanced impedance connections require very tight tolerances of impedances. Both resistors and capacitors must be very accurately matched.
Yes, +-60Vdc for the BalZen
That +-60Vdc comes from the regulators. They need ~60Vac+60Vac from the transformer. Your 55Vac+55Vac will almost certainly do the job.
Attenuating pots on the inputs and outputs will ruin the balanced impedance of this BalZen.
Balanced impedance connections require very tight tolerances of impedances. Both resistors and capacitors must be very accurately matched.
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I see, you were on about the transformer, I thought you were answering my question about the coupling caps! Thanks for that all the same.
It seems the more I try to learn, the more I'm confused !
It seems the more I try to learn, the more I'm confused !
re fig2 & fig3.
What are your specific questions?
10uF and a load of 5k//100k//receiver impedance will roll off the very low bass very slightly.
If I were doing this I would follow Rane's (or maybe it's Jensen) advice: A far too big non-polarised Panasonic electro//good film cap, to ensure that the whole audio signal can get out. You still need to match these component values between the Hot and Cold (what Pins 2 & 3 see).
What are your specific questions?
10uF and a load of 5k//100k//receiver impedance will roll off the very low bass very slightly.
If I were doing this I would follow Rane's (or maybe it's Jensen) advice: A far too big non-polarised Panasonic electro//good film cap, to ensure that the whole audio signal can get out. You still need to match these component values between the Hot and Cold (what Pins 2 & 3 see).
Most of the Pass Pre-Amps use a 1uF input cap, the B1 certainly does. Increasing its value simply decreases the low frequency roll-off point.
10uF is the normally specifed output cap. Again, you can increase this at extra cost.
It is the quality of the caps that really matter in this instance.
WIMA MKPs are good for the input cap and whatever you can afford for the output. 10uF MKPs will do but there are much better caps around for a good deal.
If you look at my post #11. The original had MKS 1uF at the input and Polydrops at the output. The final version had Siemens MKP's at the input and Obbligato PIOs at the ouput.
The FINAL, FINAL version had a Salas Shunt Reg PSU which did make a big difference.
10uF is the normally specifed output cap. Again, you can increase this at extra cost.
It is the quality of the caps that really matter in this instance.
WIMA MKPs are good for the input cap and whatever you can afford for the output. 10uF MKPs will do but there are much better caps around for a good deal.
If you look at my post #11. The original had MKS 1uF at the input and Polydrops at the output. The final version had Siemens MKP's at the input and Obbligato PIOs at the ouput.
The FINAL, FINAL version had a Salas Shunt Reg PSU which did make a big difference.
Attachments
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PassDiy do the B1 PCB at a good price. Its also easy to DIY.
The B1 will work up to about +/- 15V or a single 30V supply.
This is well outside of your traffo. Although it doesn't need it, it does work well with a regulated PSU.
The B1 will work up to about +/- 15V or a single 30V supply.
This is well outside of your traffo. Although it doesn't need it, it does work well with a regulated PSU.
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I have been giving this some thought. One alternative, switched attenuators look ideal, but are expensive and look tricky to make. Another option I have been trying to get my head around, but not having much luck, is a balanced "shunt" type (U-pad) volume control, such as: http://www.diyaudio.com/forums/soli...control-using-single-attenuator-possible.html or http://www.diyaudio.com/forums/pass-labs/166635-aleph-p-balanced-shunt-attenuator.html. Looks cheap and easy to make, but will it work with the BOSOZ and if so, what value resistors and pots would I need (or better still where can I find this info for myself)?
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