Building a 45 SET
First of all sorry about the Noob questions, This is my 1st SET. I have built many SE, UL, and PP amps, HiFi and Guitar, but this is my first with regulated fil and thought best to ask questions here first.
I have been gathering components togather for this build.
List as follows...
2- matched NOS Kenrad 45 st's
OPT James JS-6113HS
2-matched NOS RCA 27 st's
What would you recomend for a driver?:confused:
I intend on regulating the filaments for graveyard quiet transients, but still working on that.
I still have to order the power tranfo yet any Ideas? preferably James for matching appearance. and chokes...
Yes, this is still a little vague,:rolleyes: but I will fill in the blanks as build continues.
I and a good many of us around here have found the 27 to be somewhat unreliable, and inconsistent in terms of sound quality - some are very good, and some surprisingly are rather the reverse.
You could consider a single 6SN7 which has enough gain to drive a pair of 45s if you are contemplating cd level signals - the purist in me would use a 270H plate choke from Lundahl such as the LL1667 configured for SE operation with the 6SN7 biased for 10mA or so.. B+ of about 200V.
A combination I particularly like is the 5842/417A with 100H choke load and this provides about 7dB more gain than the 6SN7 option described previously. Run this at around 15mA and B+ of about 125V..
I like fixed bias on my 45s as well, and found an operating point of 250V/38mA pretty nice.. A 5K primary Z will give you roughly 2Wrms out at < 5% thd. Grid bias would be somewhere around -45V (pot range approximately -40V to -50V) or so depending on the specific tubes. Fixed bias gets rid of the inevitable colorations introduced by a cathode bypass cap and gives you a lot of flexibility to optimize the operating point. The down side of course is that a very simple but well filtered bias supply is required. Measure cathode current with a single 1 - 10 ohm resistor in the "cathode" circuit. (I usually use center tapped filament transformers)
I have found the 45 to be extremely quiet even with AC heating, but a simple DC supply with a CCS will eliminate IM sidebands due to the AC heating and result in better measured performance. (Which in some cases may also be audible - George of Tubelab can elaborate on this further.) Antek makes inexpensive toroids that are suitable for powering a CCS based heater set up..
The 45 is a GREAT tube to cut your SE teeth on.. I have loaned my original prototype recently to a friend, but it remains one of my favorites. IMHO It is one of the best sounding power triodes out there period.. (I also like the 300B and GM70)
Link here: 45 S.E Stereo Amplifier
I think you could do even better than this design, and hopefully my suggestions are helpful.. And yes I do like regulated B+.
Here's an option:
Before I decide on the 27's, I will breadboard out the amp for a good listen.
I do have many 6sn7's of sorts and a half dozen of the CCCP 6H8S t plate.
I guess I will be bread boarding for a few days to find out what may sound the best.
My list of tubes on hand is over 2500 strong, yes been at it for a few years.:p
Too many choices, and I haven't tried all the options yet.
I was hoping to stick with ST's, just for looks.
My other options:(many each)
I was looking into the 27 because a local friend considered it his "holy grail input".
Back to (fun) work again:D
Ty, thank you
That is another nice version, I will give it some thought.
Back to the bench, much work to do for today.
Yes... the 76 is so nice I have many, but not a pair that match.
While digging for parts, to my suprise I found a nice filament tansformer.
I think it is manufactured by Thordoson, but not in a box the part number is T16F09 stamped on one side and 2.5V 10A on the other. This should be adequate for the 45's it is center tapped.:) Now to dig through the half ton of power transformers...:rolleyes:
Just another possible brain fart of mine, How about an srpp 6sl7 in first then a 6ah4 driver for the 45 output? Just throwing some ideas around, what do you think? Could be very transparent.
I have many of the 6ah4, 6bl7, 6bx7's on hand also that I wasn't thinking about at the time of starting this thread.
The reason for all this is to figure out what will give the best solid frequency response across the board. We listen to all types of music styles from classical to modern hip hop (kids). I prefer instrumentals though...
I have a supply of 6an4's, 6t4's, 12a4's, 12b4's ect. I have basicaly whatever type that are favorites on the net. and then some.
I ask for help on frequency response, because I do not have a o-scope at hand yet. I did have, but it was pushed off bench by kids (accident).
I promise when this get's started it will become interesting, indulge me for a few days, some components are in transit still so pics at this time won't show enough.
Found a NOS Mullard GZ34 for rectification...!
With the 45 set, it will be powering a pair of vintage RCA speakers that rock with even 1.4w se 6an5. They originally were powered by 6v6 UL amp out of an early 1940's tall boy record player and complimenting them with 4" Audiophile full range and pair of super tweets. Quite a home-brew mix, but sounds fantastic.
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