porkchop61 said:
Thanks for the reply Sherman.
I thought the KT88 cathode was the 47 Ohm 25 watt resistor?
I'm asking about the 470k ohm resistor that's joined with the 0.22uF
coupling capacitor going to ground, isn't that the grid (g)?
Glenn
That's what I get for not reading carefully enough. A 1/2 watt would be fine for the 470K. The only resistors carrying enough current to be rated higher are the plate resistor on the 6N1P and the cathode resistors of both tubes. Everything else can be 1/2W.
I did use the 450V Auricaps. I think they sound very, very good and the price is not too bad.
I considered all the usual suspects but the Auris were easily available and have a good reputation. At the time I didn't remember PE having the Kimbers available but if I were building today I might well use them.
I considered all the usual suspects but the Auris were easily available and have a good reputation. At the time I didn't remember PE having the Kimbers available but if I were building today I might well use them.
OT wiring question (Hammond 128SE)
Thanks Sherman. I only have to buy 2, so price isn't that much of an issue.
On another topic, I'm looking at the wiring diagram for the Hammond 1628SE OT's. On the primary side they list the the blue lead as common, then there is a red lead and a blue/yellow lead for the 40% screen tap. My question is, does the B+ go to the black lead, and the plate of the KT88 go to the red lead, or the other way around? I assume the screen (pin #4) of the KT88 goes to the 40% screen tap.
This is my first SE amp, I'm used of PP designs so this is a little different.
Thanks for all your help!
Glenn
BTW: I'll be posting pix of my progress as I go along. I just got my 1/8" thick aluminum chassis plate from UPS today. I'm going to work on the red oak base this week.
Sherman said:
Thanks Sherman. I only have to buy 2, so price isn't that much of an issue
.On another topic, I'm looking at the wiring diagram for the Hammond 1628SE OT's. On the primary side they list the the blue lead as common, then there is a red lead and a blue/yellow lead for the 40% screen tap. My question is, does the B+ go to the black lead, and the plate of the KT88 go to the red lead, or the other way around? I assume the screen (pin #4) of the KT88 goes to the 40% screen tap.
This is my first SE amp, I'm used of PP designs so this is a little different.
Thanks for all your help!
Glenn
BTW: I'll be posting pix of my progress as I go along. I just got my 1/8" thick aluminum chassis plate from UPS today. I'm going to work on the red oak base this week.
hi sorry to jump in but ive been watching this thread with some interest since it first started - the only thing that has prevented me from taking the project on has been the thought of getting new speakers - im currently using spendor s3/5's and my ella kit which is a el34 pp powers it up quite nicely.
so the question is, what speakers are you folks using to hook up the amp to? im leaning in the direction of an open baffle design - only because its easy
so the question is, what speakers are you folks using to hook up the amp to? im leaning in the direction of an open baffle design - only because its easy
mikey115 said:...- im currently using spendor s3/5's and my ella kit which is a el34 pp powers it up quite nicely.
so the question is, what speakers are you folks using to hook up the amp to? im leaning in the direction of an open baffle design - only because its easy
I've used this amp with Advent/1 (not the original large Advents but still a 10" 2 way of about 88dB/1W/1M, Dynaco A25, three different DIY pairs with efficiencies of 90-96dB/1W/1M and a pair of JBLs that I didn't even get the model number of.
I've had the amps (I built monoblocks) in three rooms, one of 10 feet by 12 feet, on of 12 x 14 feet and currently in my family room of 13 x 17 feet. Room filling volume was possible in all of them but window-rattling is probably out except with 96dB speakers.
My monoblocks built with this schematic make about 7.5 watts and I seldom listen at rock concert volumes any more. I can turn up "Who's Next" enough to bother everyone else in the house though.
Bottom line I guess is how big your room is and the type of music and volume you like? I'm betting you'd be happy with this amp and your current speakersfor virtually any acoustic music (except maybe full orchestra), and maybe for any music if you don't like to crank it up to ear-bleeding volume.
I have been building amps similar to this design. Information and a link to the schematic is here:
http://www.tubelab.com/SimpleSE.htm
Full construction details and PC boards will be posted within the next few weeks.
I have a pair of Yamaha NS-10M studio monitor speakers (86db) which work well with this amp as near field monitors. They are sufficiently loud in my lab, but the sound is not loud in the next room.
On the other hand, I built a pair of speakers by puting some modern Silver Iris 15 inch drivers into a pair of 65 year old Zenith console radios. These drivers are designed for open baffle mounting. They are about 96db efficient, the bass does literally shake the walls. With my KT88 amp in triode mode they sound really nice for anything from Norah Jones to Metallica. When I run it in UL mode with CFB (14 watts), It can be plainly heard in the living room of the house across the street!
The amp is shown in the foreground, with one of the speaker cabinets behind it.
To triode wire a KT88, yes put a 100 ohm resistor (1 watt or more) from the plate to the screen grid (G2). I have had 1/2 watt resistors fail.
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