Senior Member
Location: Much Wenlock
Posts: 1,523
I'm Gary.
Attenuator
Hi guys,
I want to make some 10dB attenuators, I'm told I need 1/4w metal film resistors in 6.9k and 4.7k.
Are there metal film resistors and metal film resistors i.e. Is there a quality or sound issue, if so watts (sorry) best to use.
Where's best to get them (long live Maplin), or will somebody throw me some.
I know it's not a complete scenario, but let's just assume I'm right in these values.
Gary
It is easier to seek forgiveness than to ask permission
Rules are meant for the obedience of fools and the guidance of wise men
Just get accurate values and make sure the match per channel. Simples
I'll have a look at what I've got.
Trade: LDR
Location: North Island New Zealand
Posts: 1,757
I'm Chris.
Hi Gary
Resistor values easily available are 6k8 and 4k7 , but if you need a 6k9 you could use formula R1xR2 / R1+ R2 to
arrive at 6k9 with two parallels - 6k8 is probably close enough for the purpose.
For any attenuator there are known Pad types the L pad being very common, comprised of a series and shunt resistor
for each channel.
Metal film is good for the purpose., but would be remiss of me not to mention a LDR being much better.... which is variable
Fount Master & Moderator
Location: Essex
Posts: 31,967
I'm openingabottleofwine.
What do you want the attenuator for? What are the source and load impedances? 0.25W rated resistors will be fine.
Barry
Senior Member
Location: Much Wenlock
Posts: 1,523
I'm Gary.
Sorry, I knew someone would ask but I don't have that info. not ideal I know but let's assume as I said above that these values are true, it's just a test.Originally Posted by Barry
Gary
It is easier to seek forgiveness than to ask permission
Rules are meant for the obedience of fools and the guidance of wise men
Fount Master & Moderator
Location: Essex
Posts: 31,967
I'm openingabottleofwine.
Where will the attenuator be used - between which two items will it be placed? For example between a CD player and a preamp?
Barry
Senior Member
Location: Much Wenlock
Posts: 1,523
I'm Gary.
Yes source and preamp
It is easier to seek forgiveness than to ask permission
Rules are meant for the obedience of fools and the guidance of wise men
Fount Master & Moderator
Location: Essex
Posts: 31,967
I'm openingabottleofwine.
What is the source: pick up or CDP?
Barry
Senior Member
Location: Much Wenlock
Posts: 1,523
I'm Gary.
CD
It is easier to seek forgiveness than to ask permission
Rules are meant for the obedience of fools and the guidance of wise men
Fount Master & Moderator
Location: Essex
Posts: 31,967
I'm openingabottleofwine.
Well assuming the CD player has a low source impedance (most likely to be < 100R), and the line-level input of your preamp presents a typical load impedance of 10k, then with a 6k8 series resistor and 4k7 shunt resistor your L-pad attenuator will offer an attenuation of 9.9dB, so the values suggested are quite correct.
Barry
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