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i want to build a stereo 60 watts a side tube amp I'm looking for a schematic
i have 2-utc cvp-3 output transformers (6o watts each)
I also have a stancor pc8414 power transformer
many caps resistors and 8 pin tube sockets
what type of tubes do I need
Follow Ups:
I cut my teeth on rusty Dynaco Mk2's and the upgrade boards from Triode Electronics; a complete tear down and rebuild. I had zero electronics experience, and having a "kit" to build taught me a LOT.
Not sure I would attempt a pentode amp scratch build until I had at least a kit/rebuild AND a simple triode amp or two under my belt.
Where output stages go beyond what can be done with nice triodes like the 300b, 2a3 etc (or 845, 813 etc if you like high voltages), I think it's time to look at a hybrid. There's the Moskido thread over on DIY Audio which gives you all the info to build one. And a possibly more interesting route still is the "hypex hybrid" thread there. You buy a fairly cheap digital output stage and bypass the opamp input. You then replace it with a high quality tube circuit. Best option - DHT input tubes like 26 to 4P1L finishing in a push pull transformer like the LL1689 in 4.5:1 stepdown. But any kind of tube stage that will drive 1.8K inputs will work.
I have no more patience for huge boatanchor tube amps - just seems a wasteful and very expensive way of doing something which can be done in a cheaper and simpler way. The quality is in the input tubes and circuitry anyway.
Andy
" What type of tubes do I need? " This appears to be a first time project or early in the DIY life of jpirroni3. Correct? I know it sounds BORING. But, a reliable DIY amp maybe more important and one of the best things to happen, early in any DIY "career." IMHO, at least. Try not to make your unit's endpoint too reliant on one specific tube make and model.
I like to print the possible schematic to be used. And setup a few, clearly reasonable goals. Try to relate how the sections of the amp will help meet some of the goals. Yeah, a GREAT goal is a stable amp.
Arrange the layout in a logical fashion. So maintenance is not an ordeal. It's nice when circuits and layouts are so practical--- that you can figure possible problem areas with a bench of basic tools and meters.
Tone met and consistent.
I'd choose tubes which are available from several sources. Reasonably priced. Easy to find information on modifying operating parameters, showing benefits and drawbacks.
Few bells-&-whistles in the circuits. A rock steady platform, with a nice & stable power supply.
It would great if this ended up a positive experience. With most of your goals met or very close. WITHOUT the need to babysit the unit.
Good luck with your project!
Hi,
I noticed all or most of all suggest filter chokes in his build. I know they make for a better power supply but are they really "the bang" in power supplies?
I have seen or heard many, many really good sounding amps and preamps that aren't choke coupled. They are cap coupled with maybe a choke after the cap. As a matter of fact I have on occasion, taken out the choke from either the Dynaco MK III's or an ST-70 and it sounded better to my ears. For decoupling I put in a resistor(forget the value) but I liked it better.
As for my tastes I like the Heathkit W-7's with the Tubes4hifi front end and it sounded great. Put out almost 60 Watts RMS when measured biased at 45MA per tube. No choke in there either. Maybe using a cap on the rectifier might be a better idea as well as a SS rectifier to get the B+ higher.
As for what Tre' said about the filament. He might have to get additional filament trannys but that's whole other story.
My opinion on going to a Dynaco ST-70 or a pair of MK III's all depends on what you pay for them. From what I've seen they cost just to buy them, and let alone modify them is not cost feasible because even after they are modified they still have the Dynaco shtick attached to them making the enire build way over the top.
In case nobody has seen what MK III's are going for:
lowest I've seen them is $800 and the highest I've seen them is about $1200. Yes they have been cleaned up, new parts, maybe a new front end, but they are still Dynaco.
He might be better off with a full kit from someone that might have something to his liking, and I do agree with that.
I agree on not buying old units. The prices demanded are too high considering:
1) Complete sets of new manufactured iron to the original Dynaco specs are available from Triode Electronics. Stock Hammond iron can also be easily substituted in a MK3 design.
2) There are quite a few third party driver boards from simple and low cost up to "audiophile" grade parts boards with prices to match.
3) I believe there are even new chassis available. I know there are for a Stereo 70.
4) Even if you want the legacy Dynaco circuit, almost all the parts in an old unit will need replacement. Also those old wax impregnated Phenolic PC boards become somewhat conductive with age.
I have one in my KT66 music system amp. McIntosh used one in their re-issue KT88 amps.Another benefit is that since the Gyrator uses a MOSFET pass device, delayed HV turn-on is easy to implement. That what I did.
Edits: 03/19/12
The original poster wants a stereo 60 watts per channel amplifier.The power transformer he wants to use has a high voltage winding rated at 600-0-600 and 200ma.
With a cap input filter he would have too much voltage and too little current.
Cap input filters gives you 1X of the rated current of the winding and 1.4X voltage.
Choke input filters give you 1.45x the rated current of the winding and .9X voltage and much better voltage regulation*.
*To get 60 watts it's likely to be Class A/B circuit and the current draw will vary greatly.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 03/19/12 03/19/12 03/19/12
static induction.
This whole topic is Markedly complex with unknown variables and parameters/goals of the designer to make blanket statements.
However, I still would put a choke {critical inductance addressed} even in a Preamp.
The Mind has No Firewall~ U.S. Army War College.
As I said in the last response, I'm sure that choke input is the way to go but if he needed more voltage then that was the only thing I could think of. If he doesn't need more voltage, as you said, then I would go with choke input as well, if he were confined to using that power transformer.
6550/KT88's KT90's or a pair of Heathkit W-7's that use EL-34's.
As a DIY beginner, your project expectations as a scratch build are too ambitious! You would save yourself a lot of grief by trying to find two used Dynaco Mark III either kits or builds that someone else put together and then modify them. With todays tubes being made in questionable manufacturing circumstances, 60 watts from two push pull tubes is asking a lot. In Class A forget it! That's why you need efficient loudspeakers; 96db/1watt/1meter or greater sensitivity and preferably Class A operation of the output stage. If you meet those two requirements then you won't need 60 watt or of RMS power. A Mark IV would also work. Buying monoblocks like the MK3 or MK4s will allow you to put the amplifier at the loudspeaker with a minimum of cable. Just my two cents and I hope I haven't discouraged you. Good luck, Ray
"The gift of imagination is a gift of the Gods imparted to a few who receive innumerable kicks in the a$$ their entire life." Le Corbusier (Charles-Édouard Jeanneret)
This is the best advice on this board in days.
Consider, if you don't already have some bench tools, a "good" Fluke DMM, adjustable soldering station(Weller, Hakko) and a variac(Powerstat) off fleabay.
Cheers,
W
Hi,
I don't mean to rain down the parade. Base on the questions you ask, sounds like you are probably quite new to diy. If that is the case, to handle a 60W PP from ground up can be quite a challenge. You have the iron but still need chokes and filter caps, coupling caps and a quad of output tubes and spares etc, the whole project is quite a lot of investment. Since the spec of your OPT isn't an ideal candidate, as the family of the diy community, I am quite concern about where it is wise to carry on a project like that.
May be get a beat up dynaco ST70, rebuild it as the starter.
my 2 cents.
This belongs over on the Tube DIY "board".
If you want a circuit that places the O/P trafos inside a NFB loop, come down in your power expectations.
What is the primary impedance of the UTC "iron"?
I ' m a nubie
this is all the info I have from can of trans
UTC CVP-3
PRI. OHMS P- R P JOIN
14,000 1 5 Y 3&4,6&7
10,000 1 5 9 2&4,6&8
8,000 4 5 6
6,000 2 5 8 1&4,6&9
5,000 3 5 7 2&4,6&8
3,000 3 5 7 1&4,6&9
SEC. OHMS CONNECT
(----TO----)
500 10 12
200 10 11
50 11 12
16 A D
8 A C
5 B D
3 A B
1.5 C D
60WATTS MAX PRI. 1750V HIPOT
SEC. 1000V HIPOT
UNITED TRANSFORMER CORPERATION
Thanks for your time
Joe
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"
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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