John Curl's Blowtorch preamplifier part II

Status
Not open for further replies.
and a bad passive design would have AC in the BOX John? I have not seen such a device ... are you expecting a significant piezoelectric effect from such an expensive switch? if not what other effect might a small amount of vibration cause in a large passive control? and how exactly does selected areas of damping material on some of the flat surfaces alone, prevent this effect?

you must have different meanings for the words clean and direct over there in the USA? how else would you wire up a control of this type? apart from, more directly...

as discussed, the fact they are not bundled means there is more likelyhood of ground loops because it makes a more effective aerial and coax/foil will do nothing to avoid EMI

John Curl said:
IF I can get a constructive word in to this discussion: Let's see what is GOOD about this passive design.
First: No AC in the Box
Second: Thick walls with added damping.
Third, Clean, direct design with first class volume control and pretty good looking switch.
Four:Wires are separated and not bundled.
If I had not worked on the Blowtorch project, I would have prefered a passive preamp much like this one.
 
Last edited:
Another "toy":
 

Attachments

  • passive2.JPG
    passive2.JPG
    153.5 KB · Views: 232
A passive attenuator done right

Looks nice. I'm afraid to ask the price...

But let's not lose the forest for the trees- all the units we're talking about here are unity gain, which is correct for modern sources. Line stages with gain are an accretion from the '60s. Steve's circuit has some gain from the input transformer because of some oddball headphones' requirements, but for line-stage-only use, one could certainly use a 1:1 input transformer.
 
...
Steve, perfect right angles without round or angle are also not strictly recommended for manufacture either, probably not as bad these days, or at this scale, but they were/are a no-no because they trap the developer/acid and PCB software will usually put a small bevel on the corner. not picking there, i'd say its not a problem, but my concern if any would not be about frequency content, much more basic than that.
....

Strictly speaking right angle traces produce an impedance dip as there is more copper area going around the corner. One can chamfer the outside corner to compensate (of course its only important if you are trying to control the impedance). And yes angles less than 90 were problematic for over etching.

Thanks
-Antonio
 
Last edited:
AX tech editor
Joined 2002
Paid Member
Jan,

I've been told by the Italian importer of Weiss that the ATT202 was born as a custom design made for a single customer that was willing to pay an outrageous - even by high end standards - amount of money just for the convenience of the remote in a passive setup. The custom made device then became a standard product but it soon became discontinued - or, at least, it looks like as it is no longer listed on the website product page. I guess that the passive attenuator was somewhat overlapping to the other product in the line and maybe too expensive for mere mortals.

Cheers

Giorgio
 
you could at least post a decent example for us to discuss, several better ones have since been posted over this somewhat inept version which has only shiny parts going for it. I can only find fault with that one and weve all had our say, now its simply boring and dare I say; trolling... to post it again. what possible positive outcome is there to post it again, you dont like this person? hes a competitor?

I think its a pretty bland comment and does not speak in favor of you at all, you sometimes disagree with yourself.. since when do a bunch of opinionated people agree totally about everything? can you really have so little experience with the human race that this amuses you and makes you feel somehow better than when this occurs? then again I suppose the thread has moved on a few pages overnight and it could use being reaffirmed.

I thought we all (except for you) had pretty consistently come down against it for pretty similar reasons, what is it we didnt agree about? many see that a well executed passive preamp has its place in some systems, myself I dont use any analogue sources these days so it has no place for me, but the Weiss is a nice use of technology and is rather pretty without enough extra wire to make another 9 of them. the other examples are orders of magnitude more sophisticated than this one above

perhaps it surprises you that one person likes the relays and another doesnt? really?
 
Last edited:
Status
Not open for further replies.