Stepped attenuators

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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 3:35 pm

Lurcher300b wrote:
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?
I meant that they're across the load shunting unwanted level away, not directly in series with it where I assumed that if one can hear any difference, you'd notice it with this one resistor in series.

Somewhere and I forget where (it could be HiFi Collective, or Goldpoint), there's a suggested list of resistors to use for each 'step' and in the different configurations.

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Dr Bunsen Honeydew
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Re: Stepped attenuators

Unread post by Dr Bunsen Honeydew » Mon Mar 12, 2018 3:46 pm

I think you are forgetting it is AC Dave the shunt resistors are as much in the signal path as the load resistor.

_D_S_J_R_
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Re: Stepped attenuators

Unread post by _D_S_J_R_ » Mon Mar 12, 2018 3:47 pm

OK. Thanks for the info.

I'll back off while I'm still behind ;)

valvesRus
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Re: Stepped attenuators

Unread post by valvesRus » Mon Mar 12, 2018 3:51 pm

How to wire a potentiometer in shunt mode, and why.

http://www.world-designs.co.uk/forum/sh ... php?t=6885

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Dr Bunsen Honeydew
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Re: Stepped attenuators

Unread post by Dr Bunsen Honeydew » Mon Mar 12, 2018 3:54 pm

Done it worn the tshirt. Not worth the faff.

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karatestu
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Re: Stepped attenuators

Unread post by karatestu » Mon Mar 12, 2018 4:09 pm

I have not swapped the resistors over yet as I am enjoying this too much.

It's fecking awesome, I can't believe how much the window to the music has been cleaned to :dance: :dance: :dance: I am sat here in a trance. It is a bloody revelation :guiness; I am not sure I have any credibility left as almost every change I have made since joining this forum has been a result musically.

I am listening to some very familiar Blue Note jazz at the moment and the volume is slightly lower than I would like but the noise floor is low around here at the moment so I can hear everything with ease. I am going to put another CD on which is always louder than this BN one- bloody modern recordings :roll:

I will see what that is like and then try and estimate if 604R in the shunt position is going to be too much. If it is then two 604R in parallel might be worth a go.

This really is a no brainer. Less in the way of the signal (music), one double power rail psu taken out of the equation. Wish I had done it sooner .

Back soon......... :epopc:
Naim, Linn & Harbeth fanboy

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Dr Bunsen Honeydew
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Re: Stepped attenuators

Unread post by Dr Bunsen Honeydew » Mon Mar 12, 2018 4:29 pm

I told you so months ago, I never do nutting for nought reason (never listens to me mutter mutter)

The number of times it seems I ave to say *NVA amplifiers are designed to be used with a passive pre / control unit*

All you are doing is creating a SA of one position and no switch contacts.

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karatestu
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Re: Stepped attenuators

Unread post by karatestu » Mon Mar 12, 2018 4:46 pm

Dr Bunsen Honeydew wrote:
Mon Mar 12, 2018 4:29 pm
I told you so months ago, I never do nutting for nought reason (never listens to me mutter mutter)

The number of times it seems I ave to say *NVA amplifiers are designed to be used with a passive pre / control unit.*

All you are doing is creating a SA of one position and no switch contacts.
Yeah, sorry Doc. I do listen to you honest ..... :liar: .....I wouldn't be where I am now if I hadn't. I know your power amps are designed for passive pre but I have only had your boards up and running since Thursday, before that it was Avondale only. I think I have been quite quick to try it out. Wanted to make sure the nva based amps were ok before commencing with this.

Yes no switch contacts and I can't alter the volume without getting the soldering iron out :lol: This exercise has allowed me to listen before I order the bits for a proper SA though - being the impatient sort. It will be interesting to find out by how much the switch contacts degrade the signal.

Goodbye active pre .......it was good while it lasted . I have noticed DC offset on the output of the nva amp boards has risen slightly but nothing to be worried about. Still running cool as well. :dance:

Stu
Naim, Linn & Harbeth fanboy

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Dr Bunsen Honeydew
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Re: Stepped attenuators

Unread post by Dr Bunsen Honeydew » Mon Mar 12, 2018 5:06 pm

OK I forgive you, but you could have tried it on the old Avondale boards, I think that is what I advised you to do.

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karatestu
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Re: Stepped attenuators

Unread post by karatestu » Mon Mar 12, 2018 5:24 pm

Yeah I should have done it years ago really but I listened to too many forum nay sayers who said it would be no good. I know better than to listen to such people now.

Stu
Naim, Linn & Harbeth fanboy

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