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Hi All,
This is my first post of a SE Triode Strapped amp I built.
Almost complete, need's tidying up and a few aesthetic add ons.
It was primarily built for KT88's, KT77's and 6550's. I used some EL34's for testing.
I designed it for sound quality more than power.
The ocilloscope shows over 5 watts.
KT88's
Plate Voltage to ground is 486V
Plate to Cathode is 426V
70ma dissipation current
EL34's and 6l6gc's plate to ground 500V
Plate to Cathode is 450V
60mA
6F5's are the pre-tubes.
290 Plate
1mA
6K5GT can also be used...but the plate is pin 3 rather than 6F5's pin 4.
6DE4 single rectifier tubes used for the bridge rectifier...
1-460V 250VA industrial transformer
1-25Vct 2A Filament transformer for the bridge
1 -12.6Vct 3A Filament transformers
The Output transformers are 7K going to 6ohm speakers 90db sensitivity.
Don't have distortion specs.
I changed the coupling caps from 0.50 MFD to 10nf. I want to increase the grid load resistors to increase base...but the almost owner doesn't want me changing the sound as he loves it.
I lifted the top of the amp on washers to allow for better ventilation.
All Comments welcome
Normality frightens me- its what they use to lure you into the cookie cutter.
Roger
Follow Ups:
Nice build...please cover those plate conductors....It's a nice conversation piece but a bit risky especially for strangers, kids and pets ;> )
How does the strapped KTs sound?
Stuben
Thanks Stuben,
As already mentioned, The top caps are for the grids.
I designed this circuit...so I will be as unbiased as I can.
The sound from the KT88's are transparent, deep with a balanced frequency response and good texture rendering.
An audiophile that Owne's some 211 Cary's loved it and felt that it sounded very detailed without being etched...however this is with the EL34's. I feel the KT88's do even better. This was played through cheap 4" DBX bookshelf speakers I use for smoke testing.
The owner loves it. With the higher value coupling caps, it has good strong bass without sacrificing too many highs.
I like the KT88's more than the EL34's...but not as much as the 6L6gc's.
The 6L6gc's sing at the top end...and are firm in the bottom.
Normality frightens me- its what they use to lure you into the cookie cutter.
Roger
I have a similar set up myself except-
LCLC filters for each channel
Choke loaded 6P5 driver tube
Output tube grid chokes
Another one to try is the Genalex KT66.
I use Tungsol 6L6G Coke Bottles too.
And SED KT88s are in the mix too.
KT66 is more in your face, like
front center at a concert.
6L6G is more like a intimate club setting.
KT88s are when I want to rock the house.
DanL
The top cap is g1 (-:
I assume you don't need bass.
The 10nFd cap will give you
an F3 of 72Hz.
If so then the 6F5 bypass cap
can be much smaller -
1.3uFd for F3 of 72Hz.
And the KT88 bypass cap
can be 4.7uFd.
DanL
Thanks for the math.
I'm going to try to get him more bass...it's there...I just have to let it through.
Normality frightens me- its what they use to lure you into the cookie cutter.
Roger
I found your build interesting since I also use wood with roughly the same dimensions, and also washers between the top deck and the sides.
Could you post a photo of how you attached your RCA jacks.
ray
A simple Pre-made board from Radio Shack. 4 pair RCA pre-mounted.
http://www.radioshack.com/board-with-eight-standard-type-phono-jacks/2740370.html
Normality frightens me- its what they use to lure you into the cookie cutter.
Roger
The schematic shows the control grid connected to the plate. I assume it's actually the screen grid. How does it sound?
--------------------------
Buy Chinese. Bury freedom.
Triode Kingdom,
You are correct...my apologies.
Normality frightens me- its what they use to lure you into the cookie cutter.
Roger
The bridge is drawn upside down, isn't it?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Yes...
I hereby promise to never draw a schematic until I have had 5 cups of coffee...
How embarrassing..
Sorry about that... i'll fix it
Normality frightens me- its what they use to lure you into the cookie cutter.
Roger
"How embarrassing.. "
Don't be, it happens to all of us.
When I built my CCS feed VR tube shunt regulated power supply for my phono preamp I mis-wired it.
Months later I was looking at a bottom side picture I had taken and realized that I took the B+ off the wrong side of the CCS and it wasn't regulated at all.
How embarrassing..
You only drew yours wrong, I wired mine wrong!!! and then listened to it that way for months???!!!
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
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