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In Reply to: RE: schematic for 60watt per side posted by jpirroni3@comcast.net on March 18, 2012 at 18:30:05
The frequency response is 40-10,000
These are what UTC calls "Commercial Grade" parts.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Follow Ups:
Dont write off the "Commercial Grade" parts. My current home amps (I'm always changing) are a pair of Bogen MO100 monoblocks.
Definitely Commercial Grade. Rated at 100W ea, measured 70W at clipping. Dual 5AR4 rectifiers, dual 6550 finals, separate screen supply, etc.
Haven't measured freq. response, I don't want to be disappinted. But they sound fine in my system with high efficiency speakers.
I inherited these parts from my dad who was a tube guru (I should have listen to him closer)
I have many vintage tube parts and want to build an amp in tribute to him
So its a very personal project
and Ive got my heart set on using the cvp-3s as my output trans
I appreciate everyone's input
While we can derate power handling to 15 W. and get decent bass extension via GNFB, I wonder how much the top end can be helped.
Guitar amp service, not HIFI, is the obvious place for that "commercial" grade stuff.
Eli D.
this a utc schematic but it seems that it uses other utc transformers
The UTC data sheet Tre' linked indicates that 30 WPC can be tried. Don't expect miracles, as NFB will be used to squeeze bandwidth out of the questionable "iron". However, an OK sounding 1st project should be the end result.
I propose you build an "El Cheapo Grande". You will use the same small signal topology as the low powered "El Cheapo" (schematic uploaded), but 7591 O/P tubes will be employed. While a PP pair of 7591s can easily make 30 W., they are as easy to drive as low powered tubes. ;> ) Highly respected manufacturers, including Fisher and Scott, took advantage of that fact. We will follow, to a degree, in their footsteps.
I've linked the 7591 data sheet below. Suggestions for full pentode operating conditions from other "inmates" are welcome. It is a given that screen grid (g2) B+ will be regulated. Combination bias will be employed to finesse the grid to ground resistance limit. Current production 7591s are intolerant of the sort of liberties the old time manufacturers took there.
Now info. on that power trafo is needed. Maybe it can be used.
Look into dad's stuff. See what sort of filter chokes are there. Then, report your findings.
Oh yeah, the UTC "iron" will be wired for 7 KOhm primaries and 8 Ω secondaries.
Eli D.
I came up with an old Stancor catalog. The PC8414 might be usable, but it will be difficult. A 5R4 rectifier working into a choke I/P filter could provide both a reasonable B+ rail voltage and sufficient B+ current. The chokes needed to pull this off will be both HEAVY and EXPENSIVE. Of course, dad's legacy might save the day.
From an expenditure perspective, buying new power "iron" may be the smart thing to do.
Eli D.
THANKS ELI
I did see some filter chokes I will look again tomorrow
I will try to send you that info via email tomorrow
HiJoe,go ahead and build that one and get your feet wet.If you like what you hear then try different transformers when you want to. Plan Plan Plan is the key word here.
thanks for the encouragement
how close do I need to be with the capacitor values
what do you think about my power transformer
page 14 section C (stancor catalog)
http://www.clarisonus.com/Archives/Trans/Stancor61.pdf
The pc8414 has a 1200 volt center tapped HV winding rated at 200ma.
With a choke input filter you will get about 460vdc.
60 watts per channel usually means 6550 output tubes.
The 6550s will draw the 200ma. and you won't have any left for the front end.
The pc8414 has 2 6.3 volt filament windings.
The 6550 draws 1.6amps each.
I think if you had 2 of those power transformers you could make a killer pair of 60 watt mono block amplifiers.
You could do a stereo 6L6GC amplifier but it won't make 60watts.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
could I just add another filament transformer and use the pc-8414 for the hv
I know I have other filament trans
.
Have Fun and Enjoy the Music
"Still Working the Problem"
I have done some homework and found some chokes and filament transformers
1- CHICARGO CHOKE FILTER REACTOR
HENRIES MAX CURRENT DC MA DC OHMS TEST INSULATION
8 250Ma 90 2500RMS
1-UTC S-37 FILTER CHOKE
HENRIES MAX CURRENT DC MA DC OHMS TEST INSULATION
8 500Ma 60 5000V
1- TRIAD FILAMENT TRANSFORMER F-17U
6.3VOTS @ 15AMPS
Wich choke is best with attached circuit
looks like I will be using 4-6550 tubes heater current 1.6 each
will the triad work for all the filament requirements
thanks JOE P.
I have done some homework and found some chokes and filament transformers
1- CHICARGO CHOKE FILTER REACTOR
HENRIES---------MAX CURRENT DC MA-------- DC OHMS----- TEST INSULATION
8------------------- 250Ma----------------- 90------------- 2500RMS
1-UTC S-37 FILTER CHOKE
HENRIES----------- MAX CURRENT-------- DC MA DC OHMS ------TEST INSULATION
8--------- 500Ma -----------------60------------------ 5000V
1- TRIAD FILAMENT TRANSFORMER F-17U
6.3VOTS @ 15AMPS
Wich choke is best with attached circuit
looks like I will be using 4-6550 tubes heater current 1.6 each
will the triad work for all the filament requirements
thanks JOE P.
That 200 mA. is probably with cap. I/P filtration. Half again plus rates to be OK with choke I/P filtration. 4X 7591s and 2X 12AT7s is (IMO) within the realm of possibility.
Eli D.
.
Have Fun and Enjoy the Music
"Still Working the Problem"
hoping I can reach you tomorrow when I will have more options to pick from
if not by this forum by your personal email
The data sheet says "outputs for P.A."
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
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