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Old 11th January 2006, 05:41 PM   #1
sopapo is offline sopapo  Spain
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Default which discrete preamp ?

I am in the process of building a boz pre,I would like to build another designs of preamps too,especially discrete.....(opamp too)

What design you'd advice me?

The issue with the bride of zen of pass is that the output impedance isn´t that low....and the volume control is in the output......what do you think of this?

I am interested in the dis pre of pavel macura,any of you have experience with it? it have a low impedance, its look good

another design of pass?

advices welcome

Thanks to all
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Old 11th January 2006, 07:06 PM   #2
00940 is offline 00940  Belgium
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http://headwize.com/projects/showfil...lmore3_prj.htm

this one makes a very, very good preamp.
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Old 12th January 2006, 01:20 PM   #3
sopapo is offline sopapo  Spain
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Thanks 00940,this design looks good,its for a headphone amp but I think its nt difficult to use for line preamp.....

do you have experience with preamp pass design?

Someone have compared the doz preamp of rod elliot to the bride of zen?

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Old 12th January 2006, 01:29 PM   #4
lineup is offline lineup  Sweden
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Hi!
sopapo

There is a guy in Pass Labs
that is about to build a preamp.

I tried to give him some small hints.
You probably know this already,
but anyway .... you can have a look
and somebody new reading this may catch a thing or two

http://www.diyaudio.com/forums/showt...731#post813731

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Old 12th January 2006, 03:08 PM   #5
sopapo is offline sopapo  Spain
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thanks lineup,yes to me the discrete design is more appealing to me,in fact I am building a bride of zen preamp,the thing I wanted with this topic is to make a "summary" of discrete line preamp designs for diy

I only know of this:

-bride of zen
-bosoz (or x variations)
-doz preamp of rod elliot

I dont know if there are others design of nelson pass availables (x series) I there are I would like to know...

The only negative issue that I see with discrete designs is that the output impedance isn't that low as with opamp designs...... (in the realm of less than 200 ohm)

although I have see tube designs,for example the famous messenger preamp, that have an output impedance of 30 ohm (read in the specs)

if you know more designs your help will be very apreciated

Thanks for all
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Old 12th January 2006, 03:43 PM   #6
00940 is offline 00940  Belgium
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The headphone amp I pointed to can be used as such, without any modification as a preamp. Output impedance is 0.3 ohms. Gain is 11.

I've no experience with the pass preamps. I can only compare it to opamps based preamps and they're really no match for this design.
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Old 12th January 2006, 04:19 PM   #7
Decker is offline Decker  United States
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I built the BOZ without the volume controls on the output. I'm using a 100k stepped attenuator on the input. This is a great sounding preamp, and very quiet. I originally built it as a backup for when my tube preamp was on the bench, but it has stayed in the rack for 2 years now. I think the plans show the volume pots on the output because it was intended to mate with the Zen amp. If you have an amp with an input impedance over 25k or so, just build it like an ordinary preamp, and enjoy.
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Old 12th January 2006, 07:53 PM   #8
thalis is offline thalis  Greece
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I didn’t know about this doz kind of thing, I searched for it and had a look.
I would not consider doz or doz preamp, or anything named as ‘death of...’ as valuable options. Some (special) times, it is attainable to determine qualities of products by just looking at the constructor’s prepositions. If someone takes a known design....ignores its various virtues (an amplifier isn’t just a low or high THD producer)....measures its THD....finds it is ‘high’....says -in other words- that this thing isn’t for music....ads stages and transistors....measures better THD....has no real good speaker to hear it, doesn’t bother to tell it as well....designs something completely different in topology....declares that he manufactured the grave of the original design and names his own as the ‘death of the original’, then he can’t be a serious man, he is rather offensive to others contributions, and so should be it as well with his constructions – constructions are as serious as their constructors are ;-)
Since we can’t know everything, we can’t know the quality of work in various fields, we can’t determine if a doctor is good since we are not doctors, but we can conjecture about his work judging by his character and his manners, we can see if he is serious enough for his job to –possibly- produce good results.
And I really can’t understand why this monomania with THD figures exists. I thought that after all this tube-based circuitry come-back, people would unstuck from it ;-))
Reproduction of music depends on dynamics, compression, staging, detail, immediacy, and less on distortions, as I believe.

Sorry for possible offends, I just presented a way of thinking to which I’m accustomed to, that rarely proved to be ineffective in my experience. With so many schematics out there, perhaps someone who can’t make something of his own should have such criterions to save time and energy :-)

I would suggest: stick to your single ended one stage pre, put the volume pot in its input - the relatively high output imp is adequate for all usual loads, as I believe (don't forget that zen was a very difficult load), and, in the end, give to you construction this name: 'death of doz':-)))

Regards,
Thalis
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Old 12th January 2006, 08:08 PM   #9
thalis is offline thalis  Greece
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In a second thought, perhaps ‘’Death of zen’’ is only a humoristic title, and perhaps his designer had no prepositions as I first considered . Now that I think of it as such, as a good possibility, I regret my certainties expressed above and apologize.
In any case, I think you can do your job with your existent construction though.
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Old 13th January 2006, 02:48 PM   #10
sopapo is offline sopapo  Spain
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yes thalis I think the same as you in respect to the issue of death name......and the same I think about thd specs...is not the most determinant parameter....

although this,many people think that this preamplifier and amplifier sound good and this is what has put me on track on this....

I have to add the dis pre of pavel macura and the ALEPH P to the list,have someone of you had experience with it?

How is the aleph p compared to bride of zen?

where are the schematics of aleph P?

Thanks
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