[ThermalAlchemy]

They are Wilma film caps

 

[tomb]

This lazy schematic drafter says the film caps don't belong to Fred Flintstone's wife. They're WIMA film caps, not Wilma's.

 

[Nathan P]

Note that the films in my BOM are mkp2 as there's not room for the mkp10 on Fred's boards. I believe Tomb's boards use the mkp10 which is probably a better cap. I'd argue that in this application the difference is going to be small though.

If stock of the WIMAs is ever out, Kemet PHE426 are a nice series as well, and for a polypropylene film they tend to be on the smaller side physically.

 

[DrivenKeys]

Hi everybody! My amp has been sitting incomplete in a box, and I finally got it together

I swear, I didn't originally intend for the robot face, but couldn't be happier it happened.

Overall, it sounds amazing, but I need to tweak volume control. When driving my 250 ohm Beyers, I have to provide an overpowered source. After combing through whatever I could find on this and the Starving Student thread, I think it's because I combined a 100k pot with 47k resistors at the source.

I'm great at following directions, slow on theory, so perhaps someone here can help me out before I dig in again: The pot is an Alps blue, I splurged after I damaged my cheap Alpha. So, I've got an awesome pot, can I simply remove the resistors before it?

It's said the resistors attenuate the signal so it stays in the upper range of the Alpha pot, as its lower range is unreliable. The goal being comfortable listening around 12 o'clock. Since this Alps is reliable down to zero, that shouldn't be needed, right?

My first guess is to just remove the resistors. Will this have the desired effect of raising volume without negatives? Do I just need a lower impedance pot?

 

[tomb]

amazing ...

​

 

[fuens]

@DrivenKeys

Hello mate.
I recommend as drawings said R16 and R17 50k (47k resistor) and pot 50KAx2 dual 50K Log.

I builded three and are exellents.
Move perfectlly my beyers 250ohm and Hifiman HE-500
The only upgrade I made was increasse to 1000uF C3 and C5 (nichicon muse fg 1000uf 63v) but with the original design of 470uF is enough.
Enjoy

 

[Darkblade48]

Just wondering if anyone still had these PCBs kicking around (or if Fred has a couple left?)

 

[IKillPCParts]

Got the same question as Darkblade, do PCBs for this still exist? Or hell, even a GERBER file if paid for?

 

[Darkblade48]

Eh, worst case scenario is that I design the PCB myself. Was just trying to save a bit of work.

I can try my hand at PCB design and then post up the schematics for anyone that's interested; only problem is I haven't done PCB design work for about 15 years now, so I'm a bit rusty and will need someone to double check my work

 

[jekjek]

I still have 1 pcb

 

[Darkblade48]

I still have 1 pcb

I'd be interested in it, if postage and all isn't too bad. Shoot me a PM!

 

[Shakydog]

Hi Fred_Fred2004

As others, are these boards still on sale? Anyone done a design yet?

 

[IKillPCParts]

Hi Fred_Fred2004

As others, are these boards still on sale? Anyone done a design yet?

I've made a PCB using the schematic made for using 12AU7 tubes, I've already ordered it with oshpark so I hope it's fine already. I'm expecting a lot of criticisms though and already I've spotted a mistake! Just left in a GND-GND trace on the board, it's fine but it's going to bug me forever.

Spoiler

EDIT: Forgot to add that my schematic basically just takes Dsavitsk's schematic and doesn't do much other than "cleaning it up" I guess, in my eyes.

 

[Darkblade48]

Hi Fred_Fred2004

As others, are these boards still on sale? Anyone done a design yet?

I have re-traced the schematic and am working on PCB design, but with slightly different components (such as using WIMA MKP series film caps). However, I am running into some trouble with connecting up all the nets in the PCB design!

 

[Darkblade48]

I am pleased to report that the PCB I designed following Dsavitsk's updated schematic for using 12AU7 is functional. Please try to ignore the mess of wires

Now to find an enclosure!