new attenuaotors

[gkantermd]

I just received the glassman shinkoh 24 stepped attenuator to switch out the "sweet whispers" attenuators in my Foreplay III pre amp.  However, the shipping did not include any schematic and I am new at this so I am not sure which leads to place where for the glassman attenuator.  Thanks for any help.

[Grainger49]

I would need a picture to even start.  A meter set on ohms and a few minutes will answer your questions if you have a good idea of what they do.

[dmannnnn]

Here is a link to the Shinkoh layout from HiFi Collective.

http://www.hificollective.co.uk/kits/pdf/shinkoh_fig7.pdf

'Signal in' comes from the selector switch.  'Signal out' goes to the amplifier.  'Signal earth' goes to ground.   It shouldn't matter where the ground wire is attached to the wire that rings the non-switch side of the resistors.  I like to scrape the wires with an x-acto knife and use a little flux to ensure a good clean joint on connections like this.  Just wrap the one wire around the other with your needlenose pliers and trim the excess. 

I may be wrong, but this looks like the same configuration as Voltsecond's S5 attenuator.  If the switch ever breaks contact there will be no attenuation at all, save for the input resistor.  I like this configuration, but if you get contact bounce or the switch starts failing you will get loud pops when switching.

Here is a link to the product page.  The layout linked above is found along the left side of the page.

http://www.hificollective.co.uk/components/shinkoh_stepped_attenuator.html

Let us know how it works out.

[Grainger49]

Here is a link to the Shinkoh layout from HiFi Collective.

http://www.hificollective.co.uk/kits/pdf/shinkoh_fig7.pdf

.   .   .    I may be wrong, but this looks like the same configuration as Voltsecond's S5 attenuator.  If the switch ever breaks contact there will be no attenuation at all, save for the input resistor.  I like this configuration, but if you get contact bounce or the switch starts failing you will get loud pops when switching.

Here is a link to the product page.  The layout linked above is found along the left side of the page.

http://www.hificollective.co.uk/components/shinkoh_stepped_attenuator.html

Let us know how it works out.

Those are good links.  You are spot on, that is the same as VoltSecond's S5 attenuator.  If I get crazy I'll get a surplus USSR switch and build two for my FP 2.

Those are beautiful switches I hope there is no contact bounce.  That would really be disappointing.  If it were to happen would a parallel high value resistor keep the volume from going wide open?  IIRC that was a quick fix for similar problems on the old forum.

Do you have the resistors, or at least know what you are looking for?  If not VoltSecond's site has a spread sheet (about 1/2 way down on the page) you can use:

VOltSecond S5 Attenuator Page

[Bribase]

Hi GKantermd

I was thinking about getting the Glasshouse Takmans from hifi collective and was wondering what resistance you chose. I've tried the stock 100k and some 50k nobles but haven't decided which I prefer. And what generally do you think of hifi collective's attenuators? I'm only going for the

[debk]

What value attenuator do you suggest if you are going to replace the one included in the kit?  What value are the attenuators included with the kit?

Debra

[Paul Joppa]

The kit has Sweetest Whispers, which are 15K 12-step attenuators, made to be affordable and still provide the virtues of fixed resistors rather than a wiper contact. The connection is a bit unusual but fairly easy to understand. I generally recommend 10K if you can't find 15K in higher-price options, unless you have a real shortage of gain in the system - in that case, go for 20K which will add 6dB or so.

My white paper on system gain budgets is linked on the Bottlehead > Community page.

[debk]

So what sort of gain would you consider a shortage?  The amp I have has a 27 dB gain structure.  Is this the number I should be looking at or we talking apples and oranges?

I know this a little side track from my original question, but I'm trying to understand this.  my amp with the 27 dB gain will have a better SNR than say an amp with 32 dB gain structure?  Is the Foreplay III considered fairly high gain?  It is rated at 10V RMS before clipping.  This seems higher than most preamp spec I have looked at.  They seem to be in the range of 6-9V RMS.  Does the fact that the Foreplay is a tube preamp and the other were solid state?  Am i correct in concluding that the Foreplay III and the 27 dB gain structure amp should work fairly well together.  I find this very interesting, and would like to learn more.

So back to the attenuator question.  since the 20K attenuator will add about 6 dB of gain to the system, would this also lower the SNR? So the 20K attenuator may let you achieve higher volume, but it would trade it for a worse SNR?   In the situation of the Foreplay III with the 27 dB gain amp would you be better off with the 10K or 20K attenuator?

I know lots of question but I really want to undertand this

Thanks
Debra

[Bribase]

Hey guys

I just finished fitting some glasshouse takmans on the elma switch, I went for the mono 10k version and have a few comments.

- The hole in the aluminium plate is slightly small on the foreplay, about 1mm too small. Use of a metal rasp and a hacksaw to fit the tab properly sorts this out.

-I opted to build the elmas myself. The instructions on the website are a long way from the straightforward instructions for the foreplay! Luckily the guy from hificollective is happy to talk you through it.

-The shaft on the elmas are taller than on the whispers, also it's very stiff at first. I'm going to pick up some new knobs to see if this helps.

- Make sure that your cables running to the selector switch are nice and neat, the switches are quite a bit larger than the whispers and may get in the way. They fit pretty easily for me but I was worried initially.

I actually swapped these out from a pair of 50k nobles that I've been running for a few months. The nobles proved the be a bit of a mistake, the sound became pretty fatigued and much of the dynamics was lost. I gave the elmas a quiet audition as I finished them at 2am and didn't want to bother my neighbours. Without a proper burn in I'm very pleased with them, things sound much more controlled, the soundstage is lovely and wide and the harshness of the nobles is gone. Tomorrow I'm going to let them out and see how they work with non 2am music.

Hope this helps

B

[Bribase]

Just a little update on the elmas after about 20hrs of listening. I'm really happy with how they are turning out. The sound is deffinately more controlled, the soundstage is wider as I wrote before and overall things seem more balanced than with the nobles.

The really great news though, is that I had a slight hum on the right channel, it's a common problem on the foreplay and I figured it was a problem with the dual power supplies on the extended kit or on the selector switch (probably to be my next upgrade). Somehow fitting the elmas solved the problem, maybe it's because I ran the silver wire that connects the resistors together on the switch straight to the ground terminals with a little loose PTFE around them, now my background is inkier than ever!

At the moment I'm only listening to this on nearfield monitors from my office. My kef RDM2s are being repaired at the moment. I can't wait to hear what they'll be like once they've been fixed!

B