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Re: Stepped attenuators

Posted: Mon Mar 12, 2018 9:42 am
by karatestu
Yes I have seen your thread Thermio (may I call you Thermio - I don't know your real name ?)

Question for the Doc........

I was going to select a 10K SA but if I am building my own then I could put in any value series/load resistor I liked. Would it be advantageous to go lower than 10k ? Would my phono 1 be happy driving say 5K or nearest value ? Or does it not matter ? Output impedance of my CDP is 10 Ohms.

Thanks Stu

Re: Stepped attenuators

Posted: Mon Mar 12, 2018 10:50 am
by Dr Bunsen Honeydew
Stop feckin around, do a 10k. Again people just don't understand load and matching, when it is important and when it make feck all difference. The latter in this case.

Re: Stepped attenuators

Posted: Mon Mar 12, 2018 11:27 am
by karatestu
Dr Bunsen Honeydew wrote: Mon Mar 12, 2018 10:50 am Stop feckin around, do a 10k. Again people just don't understand load and matching, when it is important and when it make feck all difference. The latter in this case.
Do a 10K - Yes Sir :grin:
Stop feckin around - not sure I can do that (generally) :grin:

I have looked over the Hificollective pages and the Seiden switches are well regarded. My thoughts are 10K charcroft z foil for the series resistors.

Now, this is where the question in my other thread comes in. If I will never use a lot of the steps then why bother to have a switch with lots of steps - save money. I will also save on the buying of lots of fancy resistors for the shunt positions :dance: .

A 23 step, mono seiden switch is £40 + the evil VAT. The 46 step mono seiden is £153 + VAT :shock: . Resistors come in at around £8 to £10 each with the audionote silver tantalum , non-magnetic jobbies being £32 each + VAT :o :o :o There is a better range of values with the charcroft Z foils.

I quite fancy some charcrofts for the shunt resistors as well and if I can narrow down the range that I will use I can leave the later steps unpopulated and save lots of dosh :guiness;

Stu

Re: Stepped attenuators

Posted: Mon Mar 12, 2018 11:34 am
by valvesRus
I'd be inclined to try a Tocos stereo pot with two Z foil shunt resistors.

Have you ever tried a shunted potentiometer ?

EDIT. Seems like HFC no longer stock the stereo version, so mono only.

https://www.hificollective.co.uk/potent ... -mono.html

Re: Stepped attenuators

Posted: Mon Mar 12, 2018 11:41 am
by Dr Bunsen Honeydew
Best value is Takman metal film and what Collective call the 24 step blue. Do that, well under £100. The rest is icing and you being pulled into the bullshit.

Give your self all the steps.

Re: Stepped attenuators

Posted: Mon Mar 12, 2018 11:41 am
by _D_S_J_R_
Chaps, please don't listen with your eyes and wallet.. The switch is just that and modern ones should last a lifetime. The shunt resistors aren't in the signal path as I understand it, so you could probably get away with any good 1% or better film type readily available? If you think you can hear a difference, a top notch type as the *series* resistor may make a difference, but I reckon there are far more important things in a stereo set to bother about to be honest... for the gear we're talking about, a 10k log value seems fine for most sources around out there, apart from Rega CD players and ancient Quad tuners which need to see 50k or so I gather :roll:

Re: Stepped attenuators

Posted: Mon Mar 12, 2018 12:00 pm
by SteveTheShadow
valvesRus wrote: Mon Mar 12, 2018 11:34 am I'd be inclined to try a Tocos stereo pot with two Z foil shunt resistors.

Have you ever tried a shunted potentiometer ?

EDIT. Seems like HFC no longer stock the stereo version, so mono only.

https://www.hificollective.co.uk/potent ... -mono.html
The channel balance was crap on the stereo version, which was a shame as it is a good sounding pot.

Re: Stepped attenuators

Posted: Mon Mar 12, 2018 12:12 pm
by karatestu
Been having a rummage through my parts.

Found some Welwyn RC55y 10K, 200R and 604Rresistors, quite well regarded resistors often used in feedback positions. I am going to try 220R in the shunt position and see what volume I end up with.

This will enable me to get rid of the active pre stage and see what the passive way brings. If it not loud enough then two 604R in parallel and if that not loud enough then just one 604R. A one step attenuator :lol:

Re: Stepped attenuators

Posted: Mon Mar 12, 2018 1:11 pm
by Lurcher300b
The shunt resistors aren't in the signal path as I understand it
So if they are not in the "signal path", just how do they have any effect on the volume?

Re: Stepped attenuators

Posted: Mon Mar 12, 2018 3:32 pm
by karatestu
My one step attenuator using Welwyn RC55Y 10K & 200R resistors is up and running. :grin:

Too bloody quiet though :( Time for a 604R in the shunt I think

I like what I am hearing though :dance: