New Soul Sister preamp build

[Mike F1]

Hello,

When Doc posted the Valve issues many months ago I saw the Soul Sister preamp schematic and was intrigued.

Few weeks later I ordered some B7's from Mike LaFevre (MagneQuest) and the installed remaining parts I had from other projects.
Here is the finished project.

The goodies:
- 2x5670 tube (GE JAN 5670)
- MagneQuest B7 (Parafeed Output Transformers) 15k/500
- Goldpoint 100k Stepped Attenuator
- AuriCap 1ufx400v High Resolution Capacitor
- Metal film, Carbon comp and Vishay Dale 1% metal film resistors
- Power supply similar to Seduction & Foreplay 2 with RRSF
- DC Heater circuit.
- Rack mount chassis.
- DIY Knobs

Listening impression...WOW! I think this circuit does sound better than my Foreplay 2 (with the Anticipation mods)
Even my wife noticed right away.
I can't really put my finger on it but it appears to have a greater/smoother bandwidth, more clarity and sparkling highs than what I was prevoiuly used to with my other preamps.


Future mods:
- Regulation with the unused triode section
- Headphone jack
- Regulated heater circuit.


Thanks Doc for making the Valve issues available!

Mike

 

[HF9]

Very nice build with a neat internal layout. Great work! Any build cost estimate if you don't mind my asking?

 

[Mike F1]

Thank you.
I still have to re-route a few wires. This was bit of a prototype layout. I always seem to have issues with grounding! lol
It's pretty good as it is. I almost nailed this one!

As it sits I'm into to it for around $500.00
The Goldpoint Attenuator and Transformers (PT & OT) being the bulk of the cost.

M

 

[balancedtriode]

Beautiful Build! what did you use as a PT?

 

[Mike F1]

The PT is a Hammond 269EX - 380VCT @ 65ma; 6.3V @ 2.5A.

I mounted it on it's side and it seems to be far enough away from the OT's to not create any issues.
However, I may end up installing some rubber isolators on the mounting bolts for the PT to help stop any vibrations.

M

 

[4krow]

Good work indeed. I am new here, but I can readily see that this forum will help me greatly. I have a question about the power supply caps. What value are they and do you think that it matters what brand is used?

    chow

 

[Mike F1]

Thank you.

Out of all the forums I've belonged to over the years I've found that I've learned the most from Bottlehead.

In my PSU I used "Atom" 220ufd @ 400v
Does it matter what you use, I suppose. (I'm sure others will chime in here)
I tend to use more band name caps than the "no-name" caps. I believe you get what you pay for.

M

 

[Grainger49]

My opinion is that the capacitor(s) nearest the audio circuit are the most important.  You can upgrade to a lower ESR electrolytic, go with a film which will be enormous, or bypass with a film which is a great and more reasonable idea.  Even if you go with the lower ESR cap bypass with a film.

 

[mchurch]

Mike;

Nice clean looking work. Like you say I have learned a lot form this forum and I get more confident every time I build a new kit. I am thinking that I will try to build something from the ground up this year as well. But first,, another pair of Paramounts!!.


Cheers;

Mike C

 

[Hank Murrow]

Dear Mike; Wonderful job of implementing Doc's original 'Sister' schematic. I saw the article in VALVE when it first came out, and began sourcing components, including Mikey's Cobalt B7's, Horace Atkinson's Transformer Volume Controls and turret boards, 6C45Pi tubes, etc. By VSAC 2008, I realized that the iron was never going to make blue smoke and Doc introduced me to Paul Birkeland, who was conducting the amp-building class there. I had a confab with him and months later we were underway. He leaned on Paul Joppa for the PS(separate shunt reg with current sources) and added some pretty Front Panel Express casework to house it all. A last minute addition was a padded-down fan and V-Caps, and the result can be seen here:  http://www.bottlehead.com/smf/index.php/topic,64.0.html

Dead quiet, lots of drive, the HD600's love it, as do I. Congratulations on joining the "Sisterhood"!

 

[balancedtriode]

I've been contemplating building one of these for a while, do you still have the layout you used for the power supply? I would be interested in looking at it, I'm still deciding how to configure it if I do build one.
thanks,
coltrane.

 

[Mike F1]

I'm still enjoying this preamp... and it also makes a great headphone amp (with AKG K240 - 600ohm)

The power supply layout is pretty simple/standard. It's similar to the Foreplay 1 but with RRSF like the Seduction PS.
I think Voltsecond's website has a schematic of that.

I'm sure the PS could be improved on but it's quiet and works for my ears.

The CCS also helps for ripple reduction so I'm not sure all that capacitance in the PS is really required in this circuit. YMMV

Thx

Mike

 

[4krow]

When/if you cease to enjoy this pre-amp,  let me know.