Thanks for all good words.I'm really glad yoo like it
The copper is painted with thin layer of lacqer.The better RCA's sure,but these were the best I had at hand that fited right.
Rotate RCA's-no way,I love this way when interconnects cables stand up.
As to the schematics.A ladder type (as you know) is when there is always ,regardless of position only one resistor in series in signal path and one to the ground.One needs 4 deck attenuator for RCA and 8 deck for XLR.I think this is quite ideal approach.
There are many ladder type attenuators calculator.You can find it.The problem is you never find the resistor values that you ideally calculate.So my idea was to use two parallel resistors instead of the one (it's still better than two in series,and lots better than 24 in series in series type attenuator).
The copper is painted with thin layer of lacqer.The better RCA's sure,but these were the best I had at hand that fited right.
Rotate RCA's-no way,I love this way when interconnects cables stand up.
As to the schematics.A ladder type (as you know) is when there is always ,regardless of position only one resistor in series in signal path and one to the ground.One needs 4 deck attenuator for RCA and 8 deck for XLR.I think this is quite ideal approach.
There are many ladder type attenuators calculator.You can find it.The problem is you never find the resistor values that you ideally calculate.So my idea was to use two parallel resistors instead of the one (it's still better than two in series,and lots better than 24 in series in series type attenuator).
Attachments
For other values of resistors.
One would have to:
1.Find some switch,let's say 24 position.
2.Calculate the values of resistors for number of steps and
attenuation he wants (like 40db or 50db) in the step he wants.
3.Find teh resistors wants to use and write down all the values that can be obtained (bought).
4.Than put all that values of to that Exel file.
5.Find the combinations values that fit to calculated values.
I attach the ladder type calculator for 24 pos. switch.
I found it somewhere on the net some time ago.It is not my property.It was free to download (but I don't remember who's it was,sorry for that)
Bartek
One would have to:
1.Find some switch,let's say 24 position.
2.Calculate the values of resistors for number of steps and
attenuation he wants (like 40db or 50db) in the step he wants.
3.Find teh resistors wants to use and write down all the values that can be obtained (bought).
4.Than put all that values of to that Exel file.
5.Find the combinations values that fit to calculated values.
I attach the ladder type calculator for 24 pos. switch.
I found it somewhere on the net some time ago.It is not my property.It was free to download (but I don't remember who's it was,sorry for that)
Bartek
Thank you.
Yes ,Elma switches are much better.Judging by the sound this project haven't come that good.Probably the quality of switch isn't very good,or/and resistors (these are quite cheap,1% metal film).Also,maybe putting it in some shielded enclosure might help.
The other thing is I have never had a power amp that sounded better with this kind of passive pre than with good active preamp.But it also can be inserted between the preamp and power amp as separate unit,usually performing much better than potentiometers.
Bartek
I consider this kind of attenuator a part of active preamp,usually as a replacement of pots (replacing the pot with attenuator brings quite an improvement).I don't consider this a stand alone preamp ,couse as I said before I've never had the power amp that benefited with taking the active preamp out and putting passive pre (like this one) in.If I was to put any kind of buffer I wouldn't bother with passive.My comment about the sound was based up on comparisons of this unit not with active preamp (which is not fair) but with other attenuator built of better components.That was Elma (Nelson is right ,these are great sound and build quality) switch and a bit better resistors (Welwyn 0,5% as I recall).And the Elma based attenuator was much better indeed.The only passive preamp I consider to be good is trnsformer based preamp,and I'm planning to try one as soon as I have the money to buy tranies.I spent some 20$ for parts while building this one (I found the attenuator at surplus store for 4$).It's good to have that thing at hand.For example building a new preamp to evaluate I don't have to bother with volume controls as ,just mount inputs-outputs and use this tiny little toy to get a preamp working.
Bartek
Bartek
Not exactly.. I was thinking about something like in this thread http://www.diyaudio.com/forums/showthread.php?threadid=17132&perpage=15&highlight=&pagenumber=1
Eccu said:
There are several ways to do an attenautor. If you look at
the schematic he posted here
http://www.diyaudio.com/forums/showthread.php?postid=256822#post256822
you will see that he needs a 2-pole switch for each channel,
that is, a 4-pole switch is necessary for stereo. In this case,
each level setting has its own pair of two resistors, used only
for that level, so it it possible to get a constant input impedance
over the whole range.
You can use the Elma switch for stereo but you cannot use
the same type of attenaution network.
Eccu said:Sorry, but I’m somekind electronic dumbass so I don’t understand why use 4 deck switch against 2 deck switch in stereo preamp?
Or is this 4 channel passive preamp?
It's a ladder type attenuator which has only two resitors involved with each switch setting. One deck handles the series resistor and the other handles the shunt resistor. So for two channels, you need four decks (assuming one pole per deck).
Here's a little tutorial on Goldpoint's website that explains the various types: Compare Attenuator Types.
Sure. You'd just have to make a series type attenuator where the resistors are all connected in series and the switch switches the nodes between the resistors.
Never apologize for asking a question.
se
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