Millett "Starving Student" hybrid amp
Nov 20, 2014 at 9:59 AM Post #6,841 of 7,258

Avro_Arrow

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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...
 
 
Nov 22, 2014 at 12:50 AM Post #6,842 of 7,258

Dean N.

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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..?  
 
Nov 22, 2014 at 9:39 AM Post #6,843 of 7,258

tomb

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  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.
wink.gif

 
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.
wink.gif

 
Nov 29, 2014 at 4:50 PM Post #6,845 of 7,258

nbkgudx

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  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.
 
Nov 29, 2014 at 7:44 PM Post #6,846 of 7,258

tomb

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  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 ...
 
Dec 13, 2014 at 2:02 PM Post #6,849 of 7,258

GlowGale

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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
 
Dec 13, 2014 at 5:37 PM Post #6,853 of 7,258

GlowGale

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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.
biggrin.gif
 
 
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.
 
Dec 25, 2014 at 7:27 PM Post #6,854 of 7,258

Amatsu

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Quick question. On the_equalizer's mod, are the tube's pins 4 and 5 connected together? I have 5 to ground now but I'm not sure if I need to connect 5 to 4.  Thanks.
 

 
Dec 25, 2014 at 10:39 PM Post #6,855 of 7,258

tomb

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  Quick question. On the_equalizer's mod, are the tube's pins 4 and 5 connected together? I have 5 to ground now but I'm not sure if I need to connect 5 to 4.  Thanks.
 

 
Pin 4 must be connected to the voltage source in each case.  The heaters are connected within the tube, but you must have 18-19V going through them.  If pin 5 is connected to ground (correct), the only way that will happen is if you connect pin 4 to the voltage source.
 

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