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Millett "Starving Student" hybrid amp - Page 457

post #6841 of 6853

For the 3.5mm input, look here.

You don't need a switched jack.

You can use a DPDT switch or just make sure

no to have both inputs connected at the same time...
 

post #6842 of 6853

One more thing:  I cannot find anywhere a complete BOM for the 12au7 version of the SSMH.  Every link points to the 19J6 BOM (http://www.diyforums.org/SSMH/bom/SSMH.htm).  Surely there's a complete 12au7 version for the BOM..?  

post #6843 of 6853
Quote:
Originally Posted by Dean N. View Post
 

One more thing:  I cannot find anywhere a complete BOM for the 12au7 version of the SSMH.  Every link points to the 19J6 BOM (http://www.diyforums.org/SSMH/bom/SSMH.htm).  Surely there's a complete 12au7 version for the BOM..?  


This is DIY.  A little effort is expected on your part. ;)

 

Compare this:

http://www.diyforums.org/SSMH/schematic/SSMH-origPCB.gif

 

To this:

http://www.diyforums.org/SSMH/variants/SSMH-12AU7.gif

(found under the "Variations" menu selection on the SSMH website).

 

A separate BOM would be a bit of overkill to simply list new values for R2 and R8. ;)

post #6844 of 6853

Ha.  Point taken.  Impatience + DIY = frustration for me.    I guess I have some homework to do.  Thanks for all your patience with us noobs.

post #6845 of 6853
Quote:
Originally Posted by tomb View Post
 

A new run of SSMH PCB kits is close to becoming a reality.  PCB's have been ordered and Hammond Mfg is fabricating the cases.  There will be 50 kits, period.  No substitutions, no modifications, and no extra PCB's or other parts. BOM is the same as it's always been on the SSMH PCB website (with the exception of price).  You'll get two tested 19J6 tubes with each kit, but if they are microphonic or go bad soon after, you may be on your own.  I will have a handful of spares, if any.  However, onesie-twosie's have always been available through reputable tube dealers and on ebay, although a bit expensive (typically $10 ea). I'm still acquiring parts, so I'm not sure of the final kit price, yet - perhaps $30 more than last time.  Remember that the last time we sold these was around 2009!  I will have the BOM corrected within the next week or two, so you'll be able to see.

 

They may go on-sale on Beezar in mid-November/Thanksgiving, I'm hoping.

Hello Tomb,

 

Any updates on this run? I checked the Beezar website and didn't see the full kit available for sale.

post #6846 of 6853
Quote:
Originally Posted by nbkgudx View Post
 
Quote:
Originally Posted by tomb View Post
 

A new run of SSMH PCB kits is close to becoming a reality.  PCB's have been ordered and Hammond Mfg is fabricating the cases.  There will be 50 kits, period.  No substitutions, no modifications, and no extra PCB's or other parts. BOM is the same as it's always been on the SSMH PCB website (with the exception of price).  You'll get two tested 19J6 tubes with each kit, but if they are microphonic or go bad soon after, you may be on your own.  I will have a handful of spares, if any.  However, onesie-twosie's have always been available through reputable tube dealers and on ebay, although a bit expensive (typically $10 ea). I'm still acquiring parts, so I'm not sure of the final kit price, yet - perhaps $30 more than last time.  Remember that the last time we sold these was around 2009!  I will have the BOM corrected within the next week or two, so you'll be able to see.

 

They may go on-sale on Beezar in mid-November/Thanksgiving, I'm hoping.

Hello Tomb,

 

Any updates on this run? I checked the Beezar website and didn't see the full kit available for sale.


Any time now, maybe tomorrow ...

post #6847 of 6853

Well, it turned out that I'm still lacking some parts.  I have them ordered, but it will be a few more days ...

post #6848 of 6853
Quote:
Originally Posted by tomb View Post
 

Well, it turned out that I'm still lacking some parts.  I have them ordered, but it will be a few more days ...

I may jump on this deal myself!

post #6849 of 6853

This is a sneak preview of what I'm currently working on. It's a proof-of-concept prototype to test out some of my ideas in real life. I tried to keep the look, feel and sound as close as possible to the original amplifier by Mr. Millett. This means point-to-point wiring, a simple metal box and using two cheap & cheerful 6J6 tubes. ($2 a pop at Beezar)

 

Concept:

 

 

Outside (front, back, idling tubes):

 

         

 

Inside (front, back):

 

    

 

Main circuit (overview, tube details):

 

         

 

Stay tuned,

GlowGale

post #6850 of 6853

I was in awe of your dead-bug soldering until I noticed you're using the steel case as a ground return for both power and signal. Heresy! D=

post #6851 of 6853
Quote:
Originally Posted by KimLaroux View Post
 

I was in awe of your dead-bug soldering until I noticed you're using the steel case as a ground return for both power and signal. Heresy! D=


In what way can that give problems? Please explain, I'd like to know more about it.

post #6852 of 6853
Quote:
Originally Posted by GlowGale View Post
 


In what way can that give problems? Please explain, I'd like to know more about it.

 

http://www.valvewizard.co.uk/Grounding.pdf

post #6853 of 6853
Quote:
Originally Posted by KimLaroux View Post
 

 

http://www.valvewizard.co.uk/Grounding.pdf


Thanks for the reference, but what page precisely? That's a whole chapter from Merlin's book. Anyway, just checked section 15.6 and now I'm left wondering why I don't have any problems.

 

My first guess is we're running in class-A, so the current taken by the output stage is rather constant. This probably means I have a lot less interference than with a class-AB amplifier. Secondly, the impedance between the input and output ground are immeasurably low. Just went and measured 0.2 ohms, which is by coincidence also the lead resistance from my multimeter. Maybe I'll check for DC-offset between the two grounds when the amp is running, that should be more precise than a quick-n-dirty resistance test.

 

Anyway, thanks for the heads up, I'll look into it if I'm running into any trouble. If you want some more heresy, forget about the thumb tacks and search for the hex wrenches. :D 

 

PS: I'm looking to make some isolated islands on the ground plane, e.g. for a signal ground. I'm looking for some kind of dirty version of terminal strips or turrets. I don't like drilling or glueing, since soldering is a lot faster when prototyping things like this.


Edited by GlowGale - 12/13/14 at 2:44pm
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