Stepped attenuators

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karatestu
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Re: Stepped attenuators

Unread post by karatestu » Mon Mar 12, 2018 9:42 am

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
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Dr Bunsen Honeydew
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Re: Stepped attenuators

Unread post by Dr Bunsen Honeydew » 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.
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karatestu
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Re: Stepped attenuators

Unread post by karatestu » Mon Mar 12, 2018 11:27 am

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
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valvesRus
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Re: Stepped attenuators

Unread post by valvesRus » 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

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Dr Bunsen Honeydew
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Re: Stepped attenuators

Unread post by Dr Bunsen Honeydew » Mon Mar 12, 2018 11:41 am

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.
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_D_S_J_R_
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Re: Stepped attenuators

Unread post by _D_S_J_R_ » Mon Mar 12, 2018 11:41 am

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:

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SteveTheShadow
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Re: Stepped attenuators

Unread post by SteveTheShadow » Mon Mar 12, 2018 12:00 pm

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.
DIY NVA amplification ( roughly equivalent to NVA A60) BTE Designs passive preamp, BTE Designs Lenco L75 turntable, Rega R200 arm, Goldring E3 cartridge, NVA Phono 1
Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, ripped CDs streamed via WD MyCloud Home Duo NAS, with PLEX media server.
Speakers - Large sealed cabs, with Fane 12-250-TC 12" full range drivers.

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karatestu
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Re: Stepped attenuators

Unread post by karatestu » Mon Mar 12, 2018 12:12 pm

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:
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Lurcher300b
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Re: Stepped attenuators

Unread post by Lurcher300b » Mon Mar 12, 2018 1:11 pm

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?

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karatestu
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Re: Stepped attenuators

Unread post by karatestu » Mon Mar 12, 2018 3:32 pm

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:
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