i hope this one makes someone excited

[ee]

Update - New 12au7's are in and the amp is going strong  . The volume control is pretty touchy. It is useable from 0 degrees to about 45 degrees in very small increments.
I will try adding the 100k resistors from the selector switch to the pot for all of those wires (+ and -)and putting a 20k across the outer two lugs which should be the out and ground.
Thanks for your help. I'll give another update when I get done.
As far as the Stereomour and me making it an amp. Do I put the 100k resistors on wires both the + (red) and - (black) from the rca or just a resistor on the + (red) wires?
thanks
Eric

[Paul Birkeland]

I will try adding the 100k resistors from the selector switch to the pot for all of those wires (+ and -)and putting a 20k across the outer two lugs which should be the out and ground.

The middle lug of the pot is the output.  Nothing connects there except the connection to the 9 pin socket.

Thanks for your help. I'll give another update when I get done.
As far as the Stereomour and me making it an amp. Do I put the 100k resistors on wires both the + (red) and - (black) from the rca or just a resistor on the + (red) wires?

Just turn the volume pot all the way up, then it becomes a pair of 100K resistors.

[ee]

I failed to mention I had already taken out the vol pot and selector out of the Stereomour. But in the process I have learned more about the vol pot functioning as a voltage divider. V out = V in (R2/R1+R2) helped me understand I was putting them in the right place.  It's soldered in and measurements and sound vol are equal to before. Added benefit from the Kiwame carbon film I put in is that it sounds really nice as initial impression. Milky smooth and a bit warm and bass improved. Perhaps the detail quality of the bass seems better.

[corndog71]

The cap at the tube socket is for the DC offset on the AC heaters.  No need to change it or increase it.

As long as we're chatting about this...  Do you know if that cap and voltage divider is necessary if one uses regulated dc for the heaters?

[Grainger49]

The bias is there to keep the cathode to heater voltage within spec.  That is if I remember this correctly from over a decade ago. 

Whether the DC is regulated or not the bias is a good idea.

[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.

[Bill Epstein]

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)

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi.ebayimg.com%2F00%2Fs%2FMTA2NlgxNjAw%2Fz%2FDDkAAOSwkNZUqwuK%2F%24_35.JPG%3Fset_id%3D880000500F&hash=bd2a90254274bb80639a7b13f08e3abba4cf4fec)

[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:g:DDkAAOSwkNZUqwuK

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.