| dw8083 |
Thanks again for everyone's help in a prior thread selecting the BOSOZ preamp to tackle as a first hifi DIY project.
I'm new to DIY hifi, but have an ancient background in digital circuits and can fabricate, solder, and assemble very well.
As a foundation, I already have Kristijan's BOSOZ preamp board, w/2 PSU boards http://web.vip.hr/pcb-design.vip/ to get started.
3 Questions:
1) Are there well established or obvious parts substitutions to consider from the start?
2) What are some of the key "newbie" pit falls or traps folks fall into?
3) For attuenation, I'm considering either the APOX relay http://www.apoxcontrols.com/apox2.htm or take the Resister ladder approach as used in the DIY Taiwan site http://babelfish.altavista.com/babe...lp=zh_en&tt=url
Any thoughts here would be appreciated as well.
If possible I'd like to leverage as much collective wisdom here as possible, and avoid the common mistakes and gain the obivious sonic improvements with the right parts.
I appreciate any and all suggetions, ideas, or experiences anyone is willing to share.
Thanks again!!!
-David |
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| moe29 |
i built the BZLS using the parts as described in the article, and it
sounds great... so you don't need to substitute stock parts with
"better" exotic parts for excellent sound.
the stock pots are fine, just a little cumbersome when adjusting
the volume. Balanced pots for each channel would be nice. If you
can swing the Apox setup - that would be pretty sweet.
have fun! good luck - you won't be dissapointed. |
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| sianturi |
How bout using this as the attenuator (DACT)? It has 4 ganged of potentio suitable for balance preamp. Saves you lots of trouble synchronizing Left & Right channel volume.
Now the question:
Which potentio works best as Volume control?
P1& P2 or P3&P4 ?
Also, if I were to choose P3&P4 as volume control, is it better for me to use high quality *fixed value* resistor for the P1&P2? I don't want some cheap potentio getting into the way of signal path, so how do you guys deal with it?
I know Mr. Pass wrote these in his article:
"Once you have obtained the optimal gain and input level, adjusting the output level with P3 and P4 will give you an effective volume control which attenuates circuit noise as well as level," but I'd like to hear other people experiences. |
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| Peter Daniel |
| quote: | Originally posted by Nelson Pass
Pardon me for barging in at this point, not having read most
of the previous posts, but the general recommendation is
that you use both input and output attenuators on both the
BOZ and SBOZ. Inputs of 25-50 Kohm pots and outputs of 5
-10 Kohm are typical. In actual practice, this has worked quite
well for the vast majority of systems.
Forgive me also for repeating for the 100th time:
With the output pots all the way up, set the input pots for the
highest level you are likely to want. Then use the output pots
for day-to-day volume controls.
You don't have to do it this way, of course, but it's a good start.
:cool: |
Sianturi,
I posted this quote from the other thread as it explains a lot. After setting the input pots, I would replaced them with fixed resistors and this would be the end.
The Elma switchers seem to be a good choice, but pretty expensive too. Why not try this guy instead? http://www.diyaudio.com/forums/show...0652#post270652 |
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| cowanrg |
| im building a bosoz, and thats what i will use (see peter's post) |
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| sianturi |
Helo Peter Daniel,
Thanks a lot! That answers my question. :)
Cheers, |
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| Mad_K |
| I am VERY happy with DACT CT2-10K*4 as input attenuator in my XBOSOZ (No outputatt. in this design) ;) |
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| sianturi |
| quote: | Originally posted by Mad_K
I am VERY happy with DACT CT2-10K*4 as input attenuator in my XBOSOZ (No outputatt. in this design) ;) |
hello Mad_K,
How do you connect your DACT attenuator to your circuit? Did you use CT-conn1 (Connector unit for CT1/2/4/5, incl. 3 x 300mm (3 x 12") wires) ? Or did you make custom footprints for the attenuator in your PCB (solder directly to PCB)?
Thanks! |
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| Mad_K |
| quote: | Originally posted by sianturi
hello Mad_K,
How do you connect your DACT attenuator to your circuit? Did you use CT-conn1 (Connector unit for CT1/2/4/5, incl. 3 x 300mm (3 x 12") wires) ? Or did you make custom footprints for the attenuator in your PCB (solder directly to PCB)?
Thanks! |
They are mounted like this;
http://www.diyaudio.com/forums/show...&highlight=bzls
but I have since done lots of mods to it, the most significant was x-ing it.. (and a lot of tidying up wiring etc) ;) |
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| kevyjo |
| Are you doing the BOSOZ or x-BOSOZ? |
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| till |
| quote: | | 2) What are some of the key "newbie" pit falls or traps folks fall into? |
My only problem was heatsinks got to hot. Use large enough heatsinks.
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| Variac |
| Since we are substituting fixed resistors for the input pot, one could put the resistors before the input selector switch.That way each input could have a different vaue to compensate for different outputs of source components. |
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| gchrist |
Why not use the sfrenice p11, cermet pot. It is cheap compared to other pots and sounds good.?
George |
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| kevyjo |
| I wanted to ask, Mr Pass said he's seen many of these preamps tweaked with different pots/caps/resistors, but none with upgraded transistors, and he'd be interested to see that. I'm having a hard time locating much of any info on appropriate transistors, let alone "impoved" ones, any thoughts? |
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| dw8083 |
I decided to go ahead with the Taiwan attenuators, http://www.diyaudio.com/forums/show...0652#post270652 from this thread. It's a 10K resister network for both input and output.
Question is: Should both the input and output sides be attenuated the same and synced concurrently, or should the input side be fixed like suggested in Peter's quote of Mr. Pass above?
Which is preferred if both options are as easily feasiable?
kevyjo's question on which transistors to consider upgrading and with what type is also of interest.
Thank you,
-David |
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| dw8083 |
Hi kevyjo, The BOSOZ based on Kristijan's preamp board.
-David |
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| sianturi |
| quote: | Originally posted by dw8083
Question is: Should both the input and output sides be attenuated the same and synced concurrently, or should the input side be fixed like suggested in Peter's quote of Mr. Pass above?
Which is preferred if both options are as easily feasiable?
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I vote for Peter's suggestion.
Attenuating and sychronizing both input and output requires 4 ganged pot for mono, meaning 8 ganged pot for (balanced) stereo. This makes a high economy solution for a poor guy like me. Besides synchronizing 8 pots (ie: 2 piece of 4 ganged pots sync) involves elaborate mechanical construction. Just have a look at Stefano's Blue BoSoZ (I forgot the thread... Search for Blue Bosoz)
Cheers, |
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| moe29 |
the thing about the transistors was tongue-in-cheek... of all the
things in a circuit, the transistors have the most effect on sound
quality, and we're using the best available right now.
attenuate as Mr. Pass suggests and you will get the most out of
the circuit... he designed it that way for a reason. ;) |
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| dw8083 |
Thanks Moe29,
I kindof assumed that selecting a Ladder resister network with 10K value was a decent choice, or is 25K better?
85% of my listening is sourced from a CD and the remaining 15% from an FM tuner for background music.
What values have others selected to atuenate the BOSOZ's output?
Thanks,
-David |
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| kevyjo |
| silly me :innocent: |
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| gchrist |
What are you guys using for the input selector. Any suggestions other than DACT?
George |
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| gchrist |
Digikey holds some Grayhill switches series 44,56 and 71. For the bosoz how many decks and poles per deck do I need?
Thank you
George |
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| till |
| quote: | | What are you guys using for the input selector. |
relays controled by PIC microcontroler |
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| eLarson |
| quote: | Originally posted by gchrist
Digikey holds some Grayhill switches series 44,56 and 71. For the bosoz how many decks and poles per deck do I need?
Thank you
George |
That depends on how many items you'll be wanting to switch.
If you only have one item, you wouldn't need the switch. Two
and you could perhaps get by with some type of toggle switch
(ON-OFF-ON).
It also would depend on whether any of them would be balanced
inputs.
Mine is based on a Greyhill switch, I think. It was a surplus Sonic
Frontiers part that I had picked up at one of their "Garage Sales".
(Works okay.)
Erik |
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| amo |
| What about the IRL510 instead of the IRF510 (which is supposed to be better then the IRF610)? |
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| SGregory |
For my x-bosoz I used a cheap 12 step switch wich controlled decent relays for the attenuator. Same for the input selector.
P.S. After reading this thread, perhaps a new input selector is in order with individual attenuation, I think so!
Scott |
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| amo |
| I have been thinking quite a bit about attenuation, and feel like a "switched relay" solution may be good. I am thinking about using a single-wafer switch of maybe 12 or more positions, that would drive four sets of relays from each position - in parallel. This way the switch would not have to be of signal quality, just good enough to turn on a relay. Also synchronising four sets of resistors will be easy, because they are relay driven. This can be repeated for P3 and P4, while P5 can be implemented using a set of only two relays from each position. Another benefit is that all the resistors can be placed on a board, instead of jerry-riged to the switch. What do you guys think? Also, what is the difference between BOSOZ and x-BOSOZ? |
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| sianturi |
| quote: | Originally posted by amo
Also, what is the difference between BOSOZ and x-BOSOZ? |
x-BoSoZ is basically a BoSoZ, BUT.... with X-feedback employed to the original Bosoz circuit. X-feedback was patented and invented by Mr. Pass, and it basically feeding + output to - input... more or less like that.
If you want to see the x-Bosoz, try Henrik's X-Bosoz:
http://www.diyaudio.com/forums/show...67322#post67322
Mad_K has also tried Henrik's circuit, and he seemed well satisfied with the modification.
Cheers, |
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| amo |
| quote: | Originally posted by sianturi
x-BoSoZ is basically a BoSoZ, BUT.... with X-feedback employed to the original Bosoz circuit. X-feedback was patented and invented by Mr. Pass, and it basically feeding + output to - input... more or less like that.
If you want to see the x-Bosoz, try Henrik's X-Bosoz:
http://www.diyaudio.com/forums/show...67322#post67322
Mad_K has also tried Henrik's circuit, and he seemed well satisfied with the modification.
Cheers, |
Thank you for that. I promise I will search more from now on.:smash: |
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| gchrist |
I was searching for a good input selector other then the DACT CT4. I have found at digikey a Grayhill selector GH7104-ND. This selector has 2 poles, 2 decks and 6 positions per pole. Does this mean that it is an equivalent selector as a single deck 4 pole?
Can I use this selector for the BOSOZ. The first deck with 2 poles will change the +In and -In and the second deck will change the same for the other channel.
Other suggestions?
George |
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| gchrist |
I meant the DACT CT3.
George |
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| dw8083 |
Hi Folks,
What is the best choice and a source for wire selection for internal connections between the PCB, external connectors, attuenator, and selector switch?
Is there an advantage of pure or high silver content over copper?
Appreciate the help,
-David |
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| kevyjo |
| I have no answer to youre quest. above, but wanted to add, what would be considered a transformer "upgrade"? I've searched and read various things about higher current transformers sounding better, ect. forgive my ignorance on this, im learning alot, but am totally confused about the transformers. |
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| lgreen |
I've been reading up on this topic for quite a while. Here are my thoghts on parts. I've got the BOSOZ working, but have not listened to it seriously, I'm still fitting everything into the case and trying to find some switches.
The standard 750 ohm resistors get hot. Its not a problem, but you could spend extra money and use TO-220 style thick film resistors with heat sinks. These weill take up more room on the board than the standard resistors, and are much more expensive.
http://dkc3.digikey.com/PDF/T033/0812.pdf
I used MUR820 high speed rectifier diodes in the power supply (cheap but good). Am using 2 power supplies instead of one, separate power supplies for each channel.
I used two Plitron transformers, one for each channel. This could be considered a transformer upgrade. (See www.plitron.com). Plitron just raised their prices.
I used solid silver wiring for the signal path, some silver plated wiring in other areas; copper for the power supply.
I am doing relay switching of inputs using NAIS DS series relays.
http://www.naisweb.com/e/relaye/mec...ech_eng_ds.html
People talk about upgrading the DC blocking capacitors. If you are going to to this (I have not tried it yet) realize that substitute capacitors are very large physically, so save room.
For volume, I am using an stereo ALPs blue volume POT (really a switched attenuator) on each channel. I don't think that these are made in 5k so I'm still trying to tweak the ouput circuit using a 50K ALPs instead of 5K as instructed in the article. I kept the other 3 conductive plastic pots in the circuit. |
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| amo |
| quote: | Originally posted by kevyjo
I have no answer to youre quest. above, but wanted to add, what would be considered a transformer "upgrade"? I've searched and read various things about higher current transformers sounding better, ect. forgive my ignorance on this, im learning alot, but am totally confused about the transformers. |
I am also new to this, so here is my very limited understanding of the transformer issue: You need to match the voltage of the transformer to what is specified to make it easier on yourself. The current rating, I think, indicates UP TO how many amps you can draw at the voltage specified. I think the problem with using one that is too small by trying to draw too much current, is that it will start physically vibrating causing the dreaded transformer hum (not to mention not providing enough current when needed). Not sure if there is a problem with using one that is too big, aside from it being a huge waist of money. By having two separate power supplies (4 transformers total), your are, besides many other things, lowering the load on each of the transformers...... I think a really cool upgrade is getting one that is encapsulated in a metal can. Besides looking very good, this prevents stray magnetic field from interfering with other components that are sensitive to this kind of thing. If you will put everything in one chassis, then this is highly recommended. |
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| kevyjo |
| I read about someone using two 160VA transformers and a 16000mf bank of capacitors, and saying the sound was more "effortless", I have no idea. Would any of the surplus transformers from apexjr. work? www.apexjr.com |
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| Variac |
It was mentioned in some BSOZ thread that if you use a hugely oversized transformer, it's better to spec it at lower than 60 volts, cause with such a low load there is no voltage drop.
I got the impression that 55 volts would work. The advantge of Plitron is that they make a transformer of this output so you don't have to use 2 Avel transformers per channel (the way NP does it- actually he powers both channels from one supply in his write up) |
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| kevyjo |
| Which Piltron transformers did you use? |
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| amo |
| quote: | Originally posted by Variac
It was mentioned in some BSOZ thread that if you use a hugely oversized transformer, it's better to spec it at lower than 60 volts, cause with such a low load there is no voltage drop.
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Better in terms of cost or sound quality? |
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| Peter Daniel |
Better in providing specified AC voltage.
Each transformer has a regulation factor, which means that without load, the AC voltage is higher than under the load. The bigger the transformer, the bigger the difference. |
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| kevyjo |
| Honestly, I really pretty confused about all the transformer specifications and terminology, and which specifications are critical and which arent. If someone who knows alot more than me would explain them, I would be most grateful! |
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| amo |
| quote: | Originally posted by kevyjo
Honestly, I really pretty confused about all the transformer specifications and terminology, and which specifications are critical and which arent. If someone who knows alot more than me would explain them, I would be most grateful! |
Check out www.plitron.com, under "tech notes" on the right side of the screen. Tells you what you need to know about transformers on one page. |
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| wuffwaff |
| quote: | Originally posted by Peter Daniel
Better in providing specified AC voltage.
Each transformer has a regulation factor, which means that without load, the AC voltage is higher than under the load. The bigger the transformer, the bigger the difference. |
Hi Peter,
I´m shure you meant "the smaller the transformer, the bigger the difference";)
william |
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| kevyjo |
I hope this is all ok dw8308, thought you might have transformer questions also, dont mean to hijack youre thread. What do you guys think of these guys, is there any reason these wouldnt work?
http://www.coilws.com/Toroidal%20Po...roid_Pwr_PN.php
By the way, thank you for the help, I understand the specifications now |
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| amo |
| quote: | Originally posted by Variac
I got the impression that 55 volts would work. The advantge of Plitron is that they make a transformer of this output so you don't have to use 2 Avel transformers per channel ... |
So you are saying that, instead of using 2 transformers rated at 30 + 30 volts at .5 amps for one channel (from Avel), to use one transformer rated at 55 volts at (for example) 2 or more amps.... Just want to make sure I understand. |
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| Variac |
Yes, my understanding from Nelson's text is that he used the two 30 volt transformers because a transformer rated around 60 volts wasn't available. Since Plitron has 55 and 60 volt transformers, you only need one. I believe that Nelson uses the same transformer source for both channels. So, you could use only one 55 volt transformer for the whole stereo preamp, or use one per channel if you want to be super high end. As far as whether you want 60 volts or 55 or 50, I don't know. All I remember from a members post was that his circuit was getting really hot burning off extra power while regulating it.
Personally, since a single transformer is a lot cheaper generally than using 2, and since a transformer with double the power is only a little bit more expensive, I am tempted to use a more powerful unit than Nelson mentions. So, I'll probably use the 55 volt model. |
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| kevyjo |
SOOOO, Let me see if I have this right. I'll just talk about the piltron transformers for clarity. If one went the "standard" route, they would use two 30VA toroids with 30v output, and a current rating of .5A a piece. This is expensive though, for the same money one could buy one gigantic 500VA transformer at 55v output, and a current rating of 4.55A (#87052201). More practical price wise would be a single 300VA 55V output, and a 2.73A rating (#077042201). A "high end" route would be two 160VA at 30v output, with a huge combined current rating of 5.34A (57041201).
I dont know what the best route to go is. The one 300VA is cheaper than two 30VAs, so if it works just as well if not better, it seems it would be the way to go if one was trying to save money. For the high end route, two 160VAs is not really much more expensive than the standard route, and I don't know if one could use a 500VA one, would this fry other parts??
I don't know about other questions. Others have talked about metal cans, as far as i can see, the piltron ones dont have metal cans. I'm not overly concerned with asthetics INSIDE the preamp, but if it helped with noise then I would do it. |
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| Variac |
Righto I believe. I'm sure that others will correct me if I'm wrong.
A huge transformer will of course not "force" too much power into the circuit, EXCEPT for that somewhat higher voltage thing due to the lack of voltage sag that I mentioned before. (because the transformer it's so lightly loaded.) Which pretty much DOES "force" more power into the circuit. You can compensate for this by using slightly lower voltage. HOw much lower I don't know, but I am guessing the 55 volts
There seems to be general agreement that big transformers are good , even in preamps.
Personally, I'd be tempted by one 160 VA transformer per channel which are each twice what Nelson speced. Also he said two channels would run from what he speced, so you are in effect using 4 times the size.
| quote: | | A "high end" route would be two 160VA at 30v output, with a huge combined current rating of 5.34A (57041201). |
Well, this is what I wouldn't do it I understand you correctly.
For high end I would use two 160 VA at 55 volts each. One for each channel. The question is: Does Plitron make a 55v 160 VA transformer? Using 2 per channel has no advantage to my knowledge
EDIT: Plitron seems to have dual 55 volt output 160VA transformers. The next size up is somewhat bigger jump in price.
Since 160VA is huge in this context, I'd use one of these for each channel (or one total for both channnels combined which should fine and half price) |
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| kevyjo |
Yes, if we are talking there standard transformers, Piltron offers 160VA 55v output, along with pretty much every other specification. I'm a little confused agan however, does the "standard" parts list include one or two 30VA transformers per side? If it is one, then it doesnt make sense to replace a 30VA, 30v output one with a 160VA, 55v output one, but if it is 2, then youre talking a total of 4 30VA, 30v output transformers, VERY expensive.
So if I'm understanding you correctly, you can use 4 30vas, which would have a total current rating of 2A, or 2 160vas 55w output, which would have a total current rating of 2.9A, or one 300va, 55v (or 50v??) output with a current rating of 2.73A. Is this right? Or could you possibly use the one 500VA, 50v output at a 5A rating? |
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| kevyjo |
| P.S., using one 160VA transformer for both channels would actually give you a substantially lower current rating than 4 30VA ones, which given my paltry understanding of this issue, would concern me. |
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| amo |
| quote: | Originally posted by Variac
Yes, my understanding from Nelson's text is that he used the two 30 volt transformers because a transformer rated around 60 volts wasn't available. Since Plitron has 55 and 60 volt transformers, you only need one. I believe that Nelson uses the same transformer source for both channels. So, you could use only one 55 volt transformer for the whole stereo preamp, or use one per channel if you want to be super high end. As far as whether you want 60 volts or 55 or 50, I don't know. All I remember from a members post was that his circuit was getting really hot burning off extra power while regulating it.
Personally, since a single transformer is a lot cheaper generally than using 2, and since a transformer with double the power is only a little bit more expensive, I am tempted to use a more powerful unit than Nelson mentions. So, I'll probably use the 55 volt model. |
A couple of points/questions:
1) Variac - I think you meant 30 VA instead of 30 volts - got me confused for a sec.
2) Why does a Plitron 30 VA trans cost twice as much as an almost identical Avel 30 VA trans? Is this a rip-off, or is there something I am missing?
3) If we want to increase the capacitance bank of the bosoz, do we just increase the caps (C101 and C102), or is there some other part that has to be changed accordingly? Does the same hold true for the AC filter cap? Is it a good idea to add a bigger AC filter cap? When adding a large capacitance bank, is it better to do so using a large number of smaller caps or a smaller number of larger caps? (I remember seeing something on this around the forum). Thanks. |
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| kevyjo |
| I can't seem to find a price list for avel toroids except for audioexpress, but there you have to go up to 800VA to get a 50-55v toroid, although it is cheap for under $70. The piltron ones do seem quite pricey in comparison, though the bigger ones seem to be a better value. |
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| dw8083 |
Hi kevyjo,
You are very considerate. And yes, I find the transformer discussion very interesting. There is not enough discussion about the various transformer options and sonic quality differences between the manufacturers.
Wire question:
Could anyone comment on their thoughts for internal wire selection, both gauge, type, and possible brand?
Component question:
I'm looking for suggestions on resisters or capacitors as well to upgrade.
Thanks!
-David |
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| amo |
| quote: | Originally posted by dw8083
Hi kevyjo,
You are very considerate. And yes, I find the transformer discussion very interesting. There is not enough discussion about the various transformer options and sonic quality differences between the manufacturers.
Wire question:
Could anyone comment on their thoughts for internal wire selection, both gauge, type, and possible brand?
Component question:
I'm looking for suggestions on resisters or capacitors as well to upgrade.
Thanks!
-David |
I have asked a similar wire question somewhere, and from responces I understand the following:
Small guages rule out stranded, so solid only (probably will sound a little better too). Pure silver is great and will give a colder/brighter/more analytical sound, while copper and gold are on the worm side. I do not have tests to prove anything, but my guess is that the coldness of silver will complement the overall wormness of PASS designs... It should be a nice balance. The guage, contrary to my intuitions, should be as small as possible, but not so small that you are using jewler's tools to solder a piece of wire :smash: . To me that means not the smallest available, but defenantly not the thickest. As far as insulation, many prefer bare wire. Teflon, I guess, would be the next best thing. To me, a little extra insulation can not hurt, and will probably keep me from frying a part or two. I have not looked too much, but the source that I have found so far is:
http://www.a-msystems.com/physiolog.../silvertef.aspx
Hope this helps. |
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| sianturi |
| quote: | Originally posted by kevyjo
I don't know if one could use a 500VA one, would this fry other parts?? |
No, using 500VA, even 1000VA for the correct voltage ratings would not fry the parts. Toroid transformer is just a voltage source. An ideal voltage source will provide a constant voltage regardless of the load impedance. So, assuming you are using 100VAC from the transformer secondary tap, with 10 Ohm load, then the current passing the load will be 100VAC/10 Ohm = 10A (AC)
| quote: | Originally posted by Variac
A huge transformer will of course not "force" too much power into the circuit, EXCEPT for that somewhat higher voltage thing due to the lack of voltage sag that I mentioned before. (because the transformer it's so lightly loaded.) Which pretty much DOES "force" more power into the circuit. You can compensate for this by using slightly lower voltage. HOw much lower I don't know, but I am guessing the 55 volts
There seems to be general agreement that big transformers are good , even in preamps.
|
I think the correct terminology for huge transformers is not "force too much power into the circuit", but as you said, bigger transformers have a good regulating factor. In plain english, it goes like this: the bigger (VA ratings) the transformer, the secondary voltage will tend to output the same (not changing) voltage over a wide range of load impedance.
So, I think there is no need to compensate the power that goes into the circuit. The power that goes into the circuit will only depend on the trafo (secondary tap) load and the output voltage of the trafo (sencondary).
What you need to anticipate though, is the voltage drop at the rectifier (diodes, filters, etc) and how much the DC voltage (after the rectification) will drop due to the load impedance and/or the regulating FET.
So the question:
Does the 55VAC secondary voltage will do the job? I think so.
Here's the reasoning:
Supposed that you use MUR860 as your diodes (high speed, soft recovery diodes) for the bridge rectifier. The max forward voltage drop is 1.5V. For half cycle, the current will pass 2 diodes, so the Voltage drop at diodes (Vdd) = 2 x 1.5V = 3V.
VDC (after rectification) = 1.41 x (55V - Vdd) = 73.32 Volt.
So, in our Bosoz, we have a margin of 73.32 - (7 x 9.1V, zenner drops) = 9.62 Vdc, which will be dropped at the FET acting as regulator.
For the preamp, I got the feeling that 1 big trafo is better than 2 medium size trafo. Using 2 trafo will create EM radiation affecting each trafos. But again, this subject is a never ending discussion. I guess you better try both and listen. In my case, WAF plays an important consideration, so I cannot try both ;)
Hope this helps, |
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| Variac |
OK I think there is still some confusion.
Here is a quote are from Nelson Pass's instructions: "Because the voltages required by this project are higher than delivered by off the shelf transformers, I have chosen to use two transformers T101 and T 102 with secondary circuits in series...."
So the point is that Mr. Pass would be happy to run both channels together off of one transformer, but he couldn't find a small one that put out 60 volts on each leg of the supply so he puts two 30 volt transformer outputs in series to create 60 volts.
BUT, what we figured out was that if you buy a large transformer, they DO come in 60 watt + and 60 watt - configuration. AND it's often cheaper to get a single large transformer than two smaller ones.
Then I mentioned that a possible problem with the oversized transformer is that because it is under such a relatively small load, the voltage doesn't drop as much as it would with smaller transformers. A possible alternate explanation is that Plitron are pretty high quality so they don't drop their voltage much under load. Someone on this forum mentioned that he got a big Plitron and the volts ended up a little bit too high, so I thought I'd pass this warning along.
Plitron just raised their prices, so there are probably better deals out there. An Avel or Toroid or Victoria Magnetics with two 60v
outputs will work fine.
NOW: another subject:
If you make the supply with two transformers as Nelson mentions, AND you want a separate supply for each channel, THEN you WOULD end up buying 4 transformers. IF you do as I suggest and get a transformers with two 60 volt outputs then you need two transformers total- one for each channel power supply.
Whew, I need a beer.... |
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| sianturi |
| quote: | Originally posted by Variac
OK I think there is still some confusion.
BUT, what we figured out was that if you buy a large transformer, they DO come in 60 watt + and 60 watt - configuration. AND it's often cheaper to get a single large transformer than two smaller ones.
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You mean 2 x 60 VOLT Taps ;) Not 60 Watts.
Cheers, |
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| amo |
| quote: | Originally posted by Variac
OK I think there is still some confusion.
Here is a quote are from Nelson Pass's instructions: "Because the voltages required by this project are higher than delivered by off the shelf transformers, I have chosen to use two transformers T101 and T 102 with secondary circuits in series...."
So the point is that Mr. Pass would be happy to run both channels together off of one transformer, but he couldn't find a small one that put out 60 volts on each leg of the supply so he puts two 30 volt transformer outputs in series to create 60 volts.
BUT, what we figured out was that if you buy a large transformer, they DO come in 60 watt + and 60 watt - configuration. AND it's often cheaper to get a single large transformer than two smaller ones.
Then I mentioned that a possible problem with the oversized transformer is that because it is under such a relatively small load, the voltage doesn't drop as much as it would with smaller transformers. A possible alternate explanation is that Plitron are pretty high quality so they don't drop their voltage much under load. Someone on this forum mentioned that he got a big Plitron and the volts ended up a little bit too high, so I thought I'd pass this warning along.
Plitron just raised their prices, so there are probably better deals out there. An Avel or Toroid or Victoria Magnetics with two 60v
outputs will work fine.
NOW: another subject:
If you make the supply with two transformers as Nelson mentions, AND you want a separate supply for each channel, THEN you WOULD end up buying 4 transformers. IF you do as I suggest and get a transformers with two 60 volt outputs then you need two transformers total- one for each channel power supply.
Whew, I need a beer.... |
I think we are all on the same page now... |
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| Nelson Pass |
The quality of the Plitron product is appreciated for its
mechanical quietness under the increasingly difficult
conditions that AC line sources offer. This makes them
more expensive.
Other brands of transformer deliver power very nicely, and the
reason that Plitron is used is that we find customers who
complain if they can hear anything when they put their
ear on the amplifier. :cool:
If you can put up with a little bit of mechanical hum under full
power conditions, then save yourself some money and don't
worry about it. |
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| kevyjo |
| As far as I see it, I might as well go the Avel route and get the 800VA toroid for $69, I believe I read in previous threads about current inrush issues, and that I'd have to install a circut to slow the inrush down, Ill look back. Given the voltage sag issue, would I get closer to the optimal output v if I went with the 50+50 or the 55+55 toroid? |
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| sianturi |
| quote: | Originally posted by kevyjo
Given the voltage sag issue, would I get closer to the optimal output v if I went with the 50+50 or the 55+55 toroid? |
Hello Kevyjo,
If I were you, I played it safely. I would pick 55+55 trafo. The zeners should have an adequate amount of reverse current in order to operate at their specified voltage rating.
Btw, I'm designing my own pcb for BoSoZ. I have a question about the size of the caps. I plan to use WIMA MKP4 10uF for C1 and C2, and I see on their spec sheet that this cap's size is 41.5mm x 19 mm x 37.5mm (Width x Length x Lead spacing). Is the specs correct? I don't have the caps at the moment so I cannot measure the actual size. I don't know, but it seems to big in my PCB....
Thx! |
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| Variac |
| quote: | | You mean 2 x 60 VOLT Taps Not 60 Watts. |
Yes Yes Yes > I can't believe I screwed this up....while trying to clarify things...
:smash:
:xeye: |
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| dw8083 |
Does anyone have a Web URL for Audioexpress?
I'm still a litle confused about which transformer to use to power the BOSOZ. I'd like to use only one transformer if possible for both power circuits. Any recommendations?
Thanks,
-David |
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| dw8083 |
Couple of questions:
-Does anyone have the URL for AudioExpress?
-Will this Avel transformer work for the BOSOZ if I want to use a single transformer to power 2 powersuple boards?
Part #122-715
Power: 800VA
Sec: 55V + 55V
Thanks!
-David |
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| kevyjo |
| As far as I understand it now dw, one transformer will work. I was looking at the Avel 800va 55x55 transformer because, if there is anything to the sonic benefits of overkill on current capacity of a torioid, the 800va has a massive 7.37A rating, and is no more expensive than the specified toroids. It's huge and heavy though, 14lbs, that doesnt bother me at all, but might bother some. It might be silly, but I feel like a big, heavy pre-amp will feel more "high end", but hey, it's my preamp, or will be hopefully, I might as well have fun with it. |
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| SteveA |
Why not buy from Avel Lindberg directly? They have several in the D series which could be used in the BOSOZ.
SteveA |
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| Variac |
I guess we weren't aware that you can buy from A-L directly.
On the Avel info sheet, at Parts Express they list much smaller 55 or 60 volt/leg transformers which I assume would be available from A-L. A 250 VA is still waaaaaay overkill, and even if their prices are higher than PE, would be the cheapest solution yet. |
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| SteveA |
I bought two D4007s (if I remember correctly) from them. I can't remember the price but it was probably in the $40 range. These are the 30 VA 30-0-30 units (which I believe some people believe is underkill).
They have been quite willing to sell me a few pieces at a time. And I'm sure my purchases have not exactly "made their day".
SteveA |
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| dw8083 |
Thanks guys for the pointers.
It sounds like a smaller transformer is in order. Perhaps the Avel Y series?
Power Secs Model
160VA 55 + 55 Y236506
250VA 50 + 50 Y236657
330VA 55 + 55 Y236755
I'm leaning towards the 250VA model. Any thoughts here would be helpful.
Just want to make sure I don't make a mistake.
Thanks,
-David |
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| dw8083 |
Actually thinking about this a little more... The Avel 120VA and 160VA both seem like a major overkill compared to two 30VA in series as originally specified.
Perhaps the 120VA model Y236457? I'll go with the 120VA or the 160VA depending on what's in stock.... Unless someone jumps in and stops me from doing something dumb.
-David |
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| dw8083 |
More Info....
I just spoke with a VERY friendly sales women at Avel and she said they are happy to ship directly to DIYer's. She asked how I heard of Avel, and I mentioned DIYAudio.com. Their number is +1(860) 355 4711.
The 120VA model Y236457 is $31.74USD and the 160VA model Y236506 is $35.26. Both are instock and ready to ship.
Thanks for everyone's help!
-David |
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| tomchaoda |
For my BZLS, I use Plitron one 120VA, 60Vx2. It is well built and not expensive!
I have also one from Avel for BZLS. The quality is not close to Plitron, in my opion! |
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| dw8083 |
Newbie question: :rolleyes:
Does the BOSOZ input selector need to have 4 decks to properly switch XLR inputs?
-David |
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| Mad_K |
| quote: | Originally posted by dw8083
Newbie question: :rolleyes:
Does the BOSOZ input selector need to have 4 decks to properly switch XLR inputs?
-David |
yes ;) |
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| tomchaoda |
If you mean the Input VR, yes, you need 4 DACT or using Stereo VR to seperate R & L.
If you mean the Input Selector (using Selector board), then you need 2 Pole, 6 positions selector like the ELMA Type 04 (they have silver plated version and gold version). For wiring sample, check this one in Korean's DIYMANIA.net
http://www.diymania.net/pass/projec...e/pass-wire.gif
(Note: But beware, their XLR wiring is different than NP's) |
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| Magura |
I did a search, but somehow failed to find the diagram and values of the resistors for a 10K ladder attenuator for the BOSOZ. Anybody remember which thread its in (its gotta be somewhere) ??
Or anybody care to explain it once more??
Magura:) |
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| Magura |
Thanks Thomas
What im missing now is a general explanation.
....where is Peter Daniel when you need him....did i mention Peter daniel....i guess thats one for Peter Daniel.
Cheers
Magura:) |
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| Magura |
Thanks David.
Exactly what i was looking for.
Magura:) |
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| Slash |
I can't find genuine article for BOSOZ preamplifier. Can anyone help me?
slash_irk@aport.ru |
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| tomchaoda |
| quote: | | I can't find genuine article for BOSOZ preamplifier. Can anyone help me? |
You can find it here in passdiy.com
http://www.passdiy.com/legacy.htm
There is also many DIY reports in the Gallery section. A wonderful preamp I have!
Thomas |
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| Slash |
Tomchaoda,
Sorry for stupid question, but is it the "Balanced Zen Line Stage" article?
One more question: I'm planning to build Zen Penultimate (v4) and I heard that bosoz is very good couple for it. But can I simply use variable stereo resistor to control the volume or it is necessary to use preamp? |
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| gchrist |
I was wondering which resistors and capacitors are the most crucial for the sonic signature of this circuit. So if someone whants to use better parts in the construction of this project then what components need to be upgraded? As a first build I wish to use the best parts only where necessary.
Thanks
George |
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| gchrist |
Ok, I got it! There is no need for tweaking.
George |
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| dw8083 |
Hi George,
The circuit as designed sounds fabulous! I'd recommend building as designed to set a baseline, and from there tweak it further from there. Some biuld tips...
Transformer:
Lots of guys have used a 55-0-55 at 120va the Avel-Lindberg #Y236457 http://avellindberg.com/transformers/y23_range.htm
I used one transformer to drive two power supplies for the BOSOZ.
Wire:
Upgrade the chasis wire from standard hook-up wire to pure copper with silver coating, with Teflon insulation. 20ga Wonder Wire from Micheal Percy audio works great. Get enough of it since it seems to magically disappear inside the case. :7)
Solder:
Try a high quality solder that's not too exotic with a standard melting point like Wonder "Ultraclear" available from http://www.percyaudio.com a 1/4 pound is enough.
Connectors:
Consider Cardas connectors like Vampire or XLO.
Next steps:
Listen to the circuit for while and experiment with the attuenation device you are using; perhaps upgrade it first, and then try the exotic resistors and caps that are in the signal path.
Also money spent on a balanced signal source like your CD player makes a bigger improvement than the exotic components. I was surprised at the improvement when I added an ADCOM GDA 700 balanced DAC to my Marantz CD-63SE.
Just FYI.... Good luck,
-David |
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| jh6you |
For my BOSOZ, I use electrolytic output caps of 47uF/100V with no bypass film cap. I don't know who is the maker for the caps. I bought them cheap. The sound from them is, however, very good for me.
:) |
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| ampsarus |
I have been considering building a P2P wired BOSOZ for way too long. So far all I have done is design/layout the perfboards for the seperate PS & pre.
I am rather confused about something on the passdiy site: In the pdf. text it says we use transformers with 40+40 secondaries, which we pad down to 60V for the fets, right? But in the parts list for the PS a 30+30 transformer is listed. What have you guys done? Are the R values critical between 60V and 60V rails?
Please help a weary potential DIYer! Thanks, Andy Bacon |
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| dw8083 |
| quote: | Originally posted by ampsarus
I am rather confused about something on the passdiy site: In the pdf. text it says we use transformers with 40+40 secondaries, which we pad down to 60V for the fets, right? But in the parts list for the PS a 30+30 transformer is listed. What have you guys done? Are the R values critical between 60V and 60V rails?
Please help a weary potential DIYer! Thanks, Andy Bacon |
Hello ampsarus,
Nelson originally spec'd two transformers, since a cost effective 60VAC was not readily available for DIYer's. Under the original parts specified, a person needs four transformers for true dual power supplies. I just used the one 55+55 AvelLindberg listed above to drive two powersupplies with excellent results. The rail voltages for me are +60.1 and -60.2 using this transformer. I would hazzard to guess that a single powersupply would sound the about same, and simplifies the P2P wiring to use one supply. I'm going to experiment with a single supply myself to see if I can hear any difference.
BTW, There is HUGE sonic difference when I went to a balanced DAC as a source with the BOSOZ.
Good luck,
-David |
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| ampsarus |
Gentelemen,
Thanks you for your responses. And thanks to raincheck for the power supply spec article- A great resource which I have saved.
dw8083: My CDP has balanced outs (meridian 588) which now feeds a classe cp60 through balanced lines. My hope is that the bosoz will outperform the classe to a point where I can dismiss it's convienence and sell it.
(this is where it might get wierd)
Further, what I'd really like to do, if possible is build 4 or 6 independent L/R preamps so I can quad-amp my 4-way JBL's and have an extra L/R channel for external subs. Then I will have level control over each driver, desireable IMO when using 116dB sensitivity compression drivers with 99dB sensitive woofers! (I despise using resistors in my crossovers, even the good ones stink)
Could I feed my source signals to 1 bosoz, (or to my classe pre) and then use that signal to drive 4 or 6 more bosoz inputs in parallel? I imagine I would build 2 large power supplies, 1 for right and 1 for left. Seems like a better idea than sourcing a couple dozen transformers. I'm wondering if the regulator fets would be up to supplying that much, of if I'm stuck building 4 or 6 independent power supplies to realize this idea.
Thanks again for your help guys, please let me know if this half-baked idea would even work.
-Andy Bacon |
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