i hope this one makes someone excited

[ee]

The tune up is coming along pretty good. I did place new 100k resistors across in/out of vol pot. Vol pot is now single Valab series stepped attenuator. I really like it. Vol is not twitchy like it was before.
My mental state is being messed with by cap 1 and cap 2 of power supply though. I ordered 220uf as the original value spec'd. The new ones showed up measuring 190uf each. Should I let this bother me and replace them or parallel some, or it's fine and no performance issue. I mean it is foreplay but i don't want a performance issue. haha
Thanks
Eric

 

[Paul Joppa]

Electrolytic caps are VERY imprecise, often +50%/-20% or worse - no worries in the power supply.

If they are new they may change after the first few hours as the surface forms itself.

 

[amioutaline?]

I'm very happy with my Foreplay 2.1, the .1 is because I made the power supply CLC with a pair of 220uF Nichicons and a Hammond 156J. I had one of those Valab series attenuators in there but thought it sounded kinda ...I dunno...muffled...so I replaced it with the newer Valab Ladder type that has solder ports(?). Big difference! It now has outstanding clarity and sounds fabulous driving my latest and very first push-pull amps that I just have to show off. (The Foreplay Pic shows the older Valab)

 

[Strikkflypilot]

Beautiful work!

 

[Grainger49]

Bill,

Did I say welcome back?  If not, welcome back!

Wow, I like the star ground and the new stand offs/terminal strips.  You make me want to clean up my FP 2.

I have a pair of 110uF Oilers hanging off the back looking like empty beer cans.  I added a fourth stage to the power supply in a VoltSecond PDMPS.  The 1k Ohm resistors only drop a little voltage.  It is inconsequential.

I have that choke, it is time to choke my power supply.

Now, after rolling in the rack you need 8" spikes you can drop and lift it off of the rollers.  That is an insane suggestion, I know.  I doubt it would make any difference but you know how we audio guys are.  My Eros is on spikes on a Creek isolation device like the "cloud." 

Is this the kind of stepped attenuator you bought?

http://www.ebay.com/itm/Valab-23-Step-Ladder-Type-Attenuator-Potentiometer-100K-Log-Stereo-/121765537138?hash=item1c59caa572:gDkAAOSwkNZUqwuK

It might be time for me to play with one. 

 

[mcandmar]

I prefer this version as it uses Dale resistors, but you don't get the nice PCB's on either end.

http://www.ebay.co.uk/itm/assembled-dale-24-step-copper-axis-attenuator-volume-control-100k/281664997434?hash=item41948ac83a

 

[Grainger49]

That is more than twice the price.  That is a lot for $0.17 resistors.

An old Bottlehead, I wish I remembered who, suggested to decide what steps are used most often then put in designer resistors in only those steps.  I could buy a few pairs of $4 resistors for the $27 one when I make the decision.

 

[RPMac]

I've been looking along these same lines and it brings up something I don't fully understand...impedance.

If no other changes were made except for a 50K, 100K or 250K attenuator, what would be the differences?

I know it is previous stage dependent which in my case would be BH-DAC and BeePre for my amps.

These things vary in price from a little over $20 to a little under $200.
What are the factors to determine the best value?

 

[mcandmar]

That is more than twice the price.  That is a lot for $0.17 resistors.

An old Bottlehead, I wish I remembered who, suggested to decide what steps are used most often then put in designer resistors in only those steps.  I could buy a few pairs of $4 resistors for the $27 one when I make the decision.

Didn't notice that, they never used to be that expensive.  If your a sucker for punishment you can buy a blank switch and populate it yourself, and as you say cherry pick resistors for the range you will use.  I did exactly that with the last Goldpoint i built by using .1% resistors in the usable range, and regular 1% everywhere else. In for a penny, in for a pound...

 

[Grainger49]

Ok, impedance is what happens when AC meets a reactive load.  If the resistors are only resistive (none really are) then you can just say resistance.

Resistance us more properly used for DC.  But for an input attenuator it is an easier concept.

The importance here is that the input resistance can't be too low or your CD player's output chip might go into current limit.  A 1K load, maybe even a 5k load would sound awful.  Input resistances between 20k and 100k are pretty safe for almost anything. 

If you get over 100k you can get noise sneaking into the signal. 

Oh, BTW, changing the resistance value doesn't make your listening position on the volume control change.  The whole thing is a proportional voltage divider. 

I'm not up for making my own ladder attenuator.  But I'm not adverse to changing out 6 or 8 resistors with something nicer. 

 

[amioutaline?]

"Now, after rolling in the rack you need 8" spikes you can drop and lift it off of the rollers."

I'll have you know that's a $60 Ikea TV stand! When I complete the JEL 76 Line Stage maybe I'll spring for something that will hold it and the two amps. Right after the brake job, 4 new tires and a power steering pump 

The last of the parts arrived today and I'm looking forward to it after hearing Steve's but truthfully, I've just come from listening to Count Basie and the Kansas City Seven, the one with Freddie Hubbard, Lockjaw Davis and JJ Johnson and I'm blown away, Foreplay and all.

I did indeed use the Valab you linked and had a look recently at McandMar's Dale version. Dales are nice but It's very true that there are about 4 positions that get all the use and upgrading those Xicon Rs would make more sense. Not Dales, tho'. I'd go for AN Tantalums or nude Vishays.

 

[2wo]

The way the volume control is drawn. Sure that is correct?...John 

 

[amioutaline?]

The way the volume control is drawn. Sure that is correct?...John

LOL...I just caught the wrong way arrow. Thanks for pointing that out.

 

[Paul Birkeland]

LOL...I just caught the wrong way arrow. Thanks for pointing that out.

What wrong way arrow?  That's a fairly normal diagram for a pot.

 

[Paul Joppa]

The input has an "out" arrow. Makes sense if the arrow is labelled "to input RCA jack"  but not if you see it as an indication of signal direction. That's the only thing I see.

 

[ee]

The tune up is coming along pretty good. I did place new 100k resistors across in/out of vol pot. Vol pot is now single Valab series stepped attenuator. I really like it. Vol is not twitchy like it was before.
My mental state is being messed with by cap 1 and cap 2 of power supply though. I ordered 220uf as the original value spec'd. The new ones showed up measuring 190uf each. Should I let this bother me and replace them or parallel some, or it's fine and no performance issue. I mean it is foreplay but i don't want a performance issue. haha
Thanks
Eric

Hey guys just some additional clarification about the resistor that goes from the selector to vol pot input from previous message I wrote. When I received the foreplay it had the the 100k resistor going from the selector to the input of the pot and across to the output lug also. This is how I have done mine just copying the previous setup. No manual.
Is that the correct wiring? It sounds good just wondering if I should really just have the 100k resistor going from selector to volume pot input only. Does it being soldered to both lugs input and output do anything because the input and output is continuous within the pot anyway? I would then place 20k resistors to ground if I think it needs it for volume control as Grainger suggested. I would mess around with it but it's in place, works, and the solder ports on the valab won't take much abuse of soldering and unsoldering under my hand. I can easily remove what is essentially a jumper wire from the valab input to output if that's what needs to happen.
I attached a photo of the original build with one of the channels going from selector to vol pot showing it soldered to the input lug and then going across to output lug if the pic helps.
Second photo is with valab in. In the photo-  input with vishay resistor is furthest away, ground middle with black wire, output is closest in pic showing the jumper going from input to output.
Thanks all
Eric

 

[Paul Birkeland]

When I received the foreplay it had the the 100k resistor going from the selector to the input of the pot and across to the output lug also.

A 100K resistor between selector and the input of the pot would be a good way to pad the preamp down.  When you say "and across the output lug also", I didn't see that in your photos, but making that connection would turn the pot into a shunt element, which would offer finer control at very low volumes.

 

[ee]

Ok sounds good. I tried to fix the picture a bit to show the resistor connecting from selector to outer lug (input) and then middle lug (output). Thank you for your explanation.
Eric