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Posts posted by Blueman2

  1. 1 minute ago, starcat said:

    Hey guys, very nice builds here!.

    Are the srx6rev2.zip and srxshunt3.zip for the PSU the latest gerber versions? Thanks a lot. 

    I think so.  However, I am not sure that the shunt PSU was ever finalized.  I recommend going with one of the GRHV variants for the power supply.  But the SRX itself remains a great, simple to build amp.    

    • Like 1
  2. 1 hour ago, JoaMat said:

    Today I made a couple of “adapter” boards with small smd transistor 2sc3324and replaced ksc2690 Q8 and Q11. So far it seems to work…

    Whaaat?  Did you hack apart a TO-247 casing to put that SMD into it?  Insane.  😄

  3. 7 hours ago, JoaMat said:

    @Blueman2 Have you tried any of the alternative devices to C2M000170D in a Carbon amplifier?

    I have successfully used the ROHM version (3rd column in the list above) for over a year in the Carbon amp with no issues, but I think that part is also out of stock?  Used the one if the first column (which has good availability now) in a GRHV with no issues, but not on a Carbon.  But from the specs, it should work as well as the other two.  

  4. I applaud this thread!!! 

    On 2/20/2021 at 12:59 AM, jamesmking said:

    1. part of the headcase experience is trawling a massive number of posts in one thread e.g. the carbon to find out about the grhv. Having a dedicated thread is seen as cheating. 🙂

    2. to build a grhv you need C2M1000170D which are out of stock just about everywhere with little hope of being back in stock anytime soon... this is one of the issues delaying my megatron build.

    On point 1 that James made, I am very guilty of helping cause this issue.  I have mixed comments on the GRHV across threads for Blue Hawaii BJT, Carbon, and a few others as well.  Just to make sure that it is almost impossible for anyone to learn from what I did.  😁

    On point 2, I have tested 2 alternatives to the C2M1000170D, and both appear to work fine.  One of them is pretty new and usually in stock:


    Item on left is the one that is in stock.  Item to the right is the alternative that I successfully used as well, but often not in stock.  Middle is the standard part which appears to be quite elusive.  



    • Like 4
  5. 6 hours ago, Rodeodave said:

     Not sure if I'll go up to 20mA, this amp is a furnace at 17mA already.

    Yes, this baby will keep you warm in the winter.  I ended up doing the same, starting with 17mA and then increasing to 20mA after it was running for a couple days.  Not sure it really made much difference in either sound or heat production, but just wanted to push the envelope. 

  6. Pars, there is a replacement/alternative for the C2M that I found and used successfully in my build.  Let me find that part number.  


    Here is a link to my post:

    Here is the part:


    Unfortunately, it also appears out of stock, but it is an alternative that worked for me in my Blue Hawaii and is still going strong, if you can find it elsewhere.    


    I just checked my supply of parts and have none of the SiCs.  Sorry.  

    EDIT3: TTI appears to have some of the ones I used:



  7. @simmconn

    First, that is a great looking build.  Can you share pictures of the internals?  Curious how you crammed all that into such a small space. 

    As for the hum,  a few thoughts:

    1. You are using separate transformer windings for the 6SN7s and the 12AT7s, right?  

    2. Have you tried to elevate the filament heaters as described in the thread?  That eliminated my hum


    Nice build!!!

  8. Just now, waltzingbear said:


    In the process of gathering parts and am down to psu and transformer choices. Blueman2, have you gotten your transformers or are they just ordered. I was wondering what the actual performance is (voltage with and without load)



    I did this build about a year ago.  I have used Antec for all 4 of my builds so far and have been very happy with them.  Antec is very conservative with their VA rating, so I would not worry so much about that.  As for the voltage, I think they spec their voltage at 115, but not sure.  It will say on their site for each transformer.  You then have to look at your normal line voltage.  For me, I typically am at 122 to 124 volts AC here in San Francisco area with PGE.  So my 300V transformers typically give me 320VAC under load.  But YMMV depending on local AC voltages.  

  9. On 9/6/2020 at 10:58 AM, Pars said:

    Getting ready to order the PSU parts and transformers for the Carbon I'm building. These are the transformers I was thinking about:

    AS-0515 - 50VA 15V Transformer

    AS-3T325 - 300VA 325V Transformer

    Let me know if these are appropriate or not.

    I know the 50VA 15V is big for the requirements, but it is shielded whereas the 25VA are not. It will be going in a separate PSU enclosure, so probably doesn't make much difference, but I prefer the shielded, particularly if it were to be reused for something else.

    I also don't know if going with the 300VA HV transformer is massive overkill or not. It looks like some use the 200VA, but those are only $1.50 cheaper, are 350V instead of 325V, and are out of stock. The 325V should theoretically give me a raw 459Vdc to work with.

    I had the same thoughts come up when I ordered mine.  I ended up going with smaller (in voltage and in VA) simply because that is what would fit in my case.  If space is not an issue, I think your choices are good.  

  10. @mwl168, I found exactly the same thing.  Once I elevated the heaters, the hum was eliminated completely.   12AT7s are at 60V (voltage divider off B+ rail) , and 6SN7s are at -340V (tied directly to B- rail).  In all, I did 4 things to make mine totally silent:


    •  Used voltage divider to elevation the filament voltages.  +60V for 12AT7s and -315V (or in my case, I just tied it to B- so -340V) for the 6SN7s
    • I switched to different set of tubes.  The ones I started with just hummed.  After switching, much less hum
    • More careful grounding of components
    • Finally, to get rid of slight hum when volume control was at 11:00 to 5:00 position, I switched from a 50K pot to a 10K pot, which totally eliminated any hum when the volume control was in the mid/high region.  


    • Like 3
  11. Nice!  Congratulations!!  I am loving the perspex case.  Though for heat dissipation, making the sides of the case heat sinks and using perspex for top, bottom, front, and back would seem better.  You must have a CNC to do all of those drill  holes so perfectly?  

    • Like 1
  12. I recall some threads on people upgrading the trafos on SRD-7s, but not sure how much of a difference it made.  But wow, I am amazed to see how much these SRD-7s are going for on eBay these days.  I bought 4 of them a couple years ago for $100 each.  Now going for 3x that or more.  

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