SR45 amplifier

[johnsonad]

You mean the Brainiac Plate Choke? I wish Mikey would make a run of them.

 

[Grainger49]

YUP! 

 

[Paul Joppa]

Haha! I acquired that nickname back in the old VALVE days when I would work out operating points in my head. I don't think anybody has used it in the last 10 years though. :^)

 

[Doc B]

Nowadays we call Peej "I'llbebackwithananswerafterathoroughanalysisiac", and the products have improved vastly because of it. But it's kind of a crappy name for a choke.

 

[howardnair]

well!-it being a choke it is a form of audio-erotica

 

[howardnair]

ok bad puns put aside-i have just breadboarded my power supply for the SR45--i have 121v ac in
334v ac out and my dc voltage is 454v dc---the schematic shows 300v ac and  rectified voltage at 372v dc--how concerned should i be at this point-- with nothing else in circuit--thanks howie

 

[vetmed]

From what you have described it sounds like you have no load on your circuit. If that is the case then your voltages are about what you should expect. You can approximate the load using a high wattage resistor of appropriate value; you'll have to figure that out yourself since I don't know how much current your circuit draws.

Robert Lees

 

[howardnair]

robert -thank you-that is correct no load--howie

 

[najo49]

Robert, The resistors should be two 10w ,10ohm ww in parallel thats a 5 ohm load and they will never overheat.

 

[braubeat]

If you are testing the high voltage supply with a resister you need 6000 ohms and at least 25 watts.

Michael

 

[howardnair]

now my next question--i am using the paramount softstart which is for a a 5670 tube - i am using a 6cm7-so there is a pinout difference for starters--using the softstart schematic and comparing that to the sr45 schematic -on section 1 of the 5670 on the softstart-pin 4 is plate-pin3 is grid and pin2 is cathode-the connection to the board are as follows-OB to plate -rca input to grid via 220r -KregA to cathode-so my connections on section1 of the 6cm7 will be OB to pin 6 which is the  plate-rca to pin7 the grid and KregA to pin3 the cathode- and  the same thoughts to section 2 --is this correct-here are links to 5670 and 6cm7
http://www.classiccmp.org/rtellason/tubedata/6CM7.PDF
http://www.mif.pg.gda.pl/homepages/frank/sheets/093/5/5670.pdf

 

[vetmed]

6K and 25 watts sounds right ;D When you say 5 ohm 20 watt you are undoubtedly thinking of a dummy load for the output transformer

Robert Lees

 

[Paul Birkeland]

As long as you are aware that the 6CM7 has two very different triodes, you should be OK.  Triode 2 is the beefcake that regulates the power supply, and triode 1 is the driver triode for the 45.

I'd use a much, much larger heatsink on the "top" MJE5731 than comes with the Paramount soft start.

 

[howardnair]

--as for the larger heatsink ,what size --a link would be best if you have one- i actually did not get one with my softstart kit-is there another tube that would be optimal--thanks howie

 

[Paul Birkeland]

could i use the 5670 with the SR45?

No.

as for the larger heatsink ,what size --a link would be best if you have one

There were some supplied with the SR-45 kit, though I don't have the part number handy.

 

[howardnair]

here is a link to digikey-stocked heatsinks
http://www.digikey.com/product-search/en?pv623=6&FV=fff40012%2Cfff80068%2Cfffc003b%2C1880002%2C5940002&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25
having never chosen a heatsink before slightly mystified-the hs300 looks to be the  best choice
ii would need 1 each total 4 -howie

 

[debk]

Deb,

The 0.47uF KK Teflon is big enough.  I would get by with 0.1uF or 0.22uF.

How many hours does the KK Teflon have on it?  If less than 100 it would sound bad by itself.  If less than 400 it isn't completely broken in.

Found a bypass capacitor I really like!
I put in a 0.1uf Obbligato Teflon Tin foil capacitor.  They are not quite broken in yet but even new they sounded great. Liked them enough that I soldered them in this morning.
Smoothed out any rough edges left and not quite sure how to describe it but the amp sounds "faster" music just seems to flow.

Deb

 

[najo49]

Ya, I bought a few of those caps just to try them. I put a pair of .47 in my eros  phono and I was really surprised to see how good they sounded. very poor mans v cap!

 

[Paul Joppa]

The good heat sinks are large, like 1x2x2 inches, extruded aluminum not bent sheet aluminum. They are too large to fit on the "soft-start" board.

 

[johnsonad]

Hi Paul. How about an update on the project sir?