Newbie needs help

[starlite2991]

I have a LOT of questions. I am the type of guy that does stuff and experimentationa a lot on stuff and then learns . I am a very hands on person. I am hoping someone can not only guide me but counsel me in building this dream amp of mine and problem the only amp i will ever build.

I was never good at math. I am the grunt worker at work.. so to speak.

I am glad to be here and any guideness would be very helpful. OK some things i am unsure about., and in my experiences with these forums is i recv an answer in about 3 weeks from now. Are others not willing to help or they don't want to be bothered? We come on these sites to learn and grow. Well now i am asking for some help so i don't lose a eyeball!! :p

I am Etempting to build a class A amp out of 2 12au7's and 4 6L6Gc coke bottle tubes. B+ is 305 volts dc. And a separate 12.6 ct transformer for the filimates. So if i run my 260v - 260v trans thought a full wave bridge rec i get WAY over my intended voltage.

and yes i cant spell i am dislectic. I don't read well either. But i try and tri again. So i get sparks on my 500 v 100uf cap. I don't do anything to do this but it arcs on it's own. So i called up a buddy and he said i have to use the center tap on my trans. Which i did not before i started this. He said nooooo don't do that. you will burn up the power trans.

Make instead a full wave with a 2 diodes and tie the anodes together and use the center tap as your ground connection. So i did that now i have 380 volts rectified and filtered DC. Which is what i need. I now notice that i might have messed up my filter cap as ealyer said. It looks to have vented. I am not sure. Also i am using cheap tools and a $6.00 multiplier. I live on a single check a month. A fixed income. I can across this schematic from Light House Electric. It does not help i am wrting this is the dark.

Our electric here is 120 volts a/c.

The transformer is a 260v - 260v 90ma Stancor. So now i have made a full wave and hooked the diodes with the anodes together and i am waiting for it to smoke and pop. Maybe blow a breaker!

Ok in my experimentation i come across this. Arcs when using a full wave birgded rectifier. Arcs and sparks. And the cap got VERY warm very quick.

So what em i doing right and what em i doing wrong. Am i going to lose a eyeball or not?

http://www.lh-electric.net/projects/17gita.html

thanks
Gday
Vince

[Cantplay]

It the cap shows damage, it is probably best to replace it.

Any particular reason you chose that schematic? Have you heard it play?

Your schematic is for an amp with 2 power tubes, and you want to use 4.

Will your power transformer have enough current to supply the extra heaters, and B+ current for twice as many tubes?

Is this amp to play at home, or on stage? 4 6L6 will play quite loud. Way too loud for a small apartment or home.

John

[surfsup]

It the cap shows damage, it is probably best to replace it.

Agreed. Sounds like your cap was rated at a voltage below what you threw at it initially. What voltage does it read on the side of C1? THe 100U cap next to the rectification diodes?

Your schematic is for an amp with 2 power tubes, and you want to use 4.

Your OT will have to change to match the impedance of the parallel tubes, as well. (if you plan to continue with 4 tubes and didn't buy the OT yet). I assume you have the OT since you're powering up the circuit so what OT did you use?

Will your power transformer have enough current to supply the extra heaters, and B+ current for twice as many tubes?

He did say he has a separate tx for the filaments. What tx are you using for the heaters?

You also say you're using TWO 12AU7s and the schemo calls for ONE 12AT7...so the gain structure will be different as well as biasing, as well as, well....everything!

[Jana]

You are not going to be able to run 4 - 6L6 tubes in class A with a PT that supplies 90ma.

[Structo]

One of the first things you should build is a light bulb current limiter.

You seem to be the type that is unsure about what you are doing, so this may protect you as well as your new amp.

Start with a 25 watt bulb which will limit the current to around .25 watts.

https://tubeamparchive.com/viewtopic.php?t=20341

[starlite2991]

Thanks for chiming in Cantplay

No for apt use. I just wanted a dual use amplifier for both listing to music and playing electric guitar. One of my goals this year is to learn how to play rock guitar and build a loud amp. (to hell with my neighbors) hehe

OK i'll do that, get another cap. I did not know where to look for a schematic. So i did a search for 6l6 tube amp and his came up. No i did not listen to it. I am not in a hurry with this project. And why did i choose these tubes. Well i bought a chassis off fleabay and was going to put together an EL84 8 watt amp. But when the chassis arrived it had 4 8 pin sockets and one inch gaping holes in it. So i decided to use the 8 pin sockets and ordered parts to get this going. yes it has 4 8 pin tube sockets...
i am using a separate filly xtans for those 6 filaments . It is a 2.5 amp 12.6 center tap new Triad.

Well i don't know. If it does not have enuff current i will have to get another different tube transformer. But with 380 volts rectified at 100 ma i think it should be plenty. If not i can get a 275 - 275 volt 120 ma pretty quick

I am aware of the difficulty of the OT's for this amp.

I want it loud and grungy

Thank you Gday

It the cap shows damage, it is probably best to replace it.

Any particular reason you chose that schematic? Have you heard it play?

Your schematic is for an amp with 2 power tubes, and you want to use 4.

Will your power transformer have enough current to supply the extra heaters, and B+ current for twice as many tubes?

Is this amp to play at home, or on stage? 4 6L6 will play quite loud. Way too loud for a small apartment or home.

John

[starlite2991]

Thank you surfsup

Yea but i really don't have a way to properly test a power supply above 500 volts, My muitimeter is a 6.00 harbor fright unit! OMG!

No i don't have a OT yet. I am well aware of what OT to use. OT 's are 40 bucks a pop for the one's i want to use, Remember this is going to be a dual usage amp hehe.

yes i will be using separate filament Xtrans for those 6 tubes.

i miss spoke. I will be using 2 12AT7's not 12au7's, sorry.

umm i am reading 384 dc volts at my probably blown cap. As far as how many ma's i don't know

Thank you Gday

It the cap shows damage, it is probably best to replace it.

Agreed. Sounds like your cap was rated at a voltage below what you threw at it initially. What voltage does it read on the side of C1? THe 100U cap next to the rectification diodes?

Your schematic is for an amp with 2 power tubes, and you want to use 4.

Your OT will have to change to match the impedance of the parallel tubes, as well. (if you plan to continue with 4 tubes and didn't buy the OT yet). I assume you have the OT since you're powering up the circuit so what OT did you use?

Will your power transformer have enough current to supply the extra heaters, and B+ current for twice as many tubes?

He did say he has a separate tx for the filaments. What tx are you using for the heaters?

You also say you're using TWO 12AU7s and the schemo calls for ONE 12AT7...so the gain structure will be different as well as biasing, as well as, well....everything!

[starlite2991]

Thank you Jana

What ma's do you and the other guys recommend? I am open ears at this point?

also i am tieing the outside legs together and using the center tap as ground. so shouldent the Ma's double up?

Thank you Gday

You are not going to be able to run 4 - 6L6 tubes in class A with a PT that supplies 90ma.

[starlite2991]

Thanks for chiming in Structo


Well if i lose an eyeball or a few fingers i will learn. Nobody's teaching me to do this. I don't have a single tungsten bulb in the house. I have plenty of fuses to use although.

OK i'll get myself a 25 watt bulb to start. And for safety

Thank you for the link, it's appreciated.

Gday

One of the first things you should build is a light bulb current limiter.

You seem to be the type that is unsure about what you are doing, so this may protect you as well as your new amp.

Start with a 25 watt bulb which will limit the current to around .25 watts.

https://tubeamparchive.com/viewtopic.php?t=20341

[xtian]

I just wanted a dual use amplifier for both listing to music and playing electric guitar.

Oy, mate! You're in for disappointment right here. These are two separate projects!

[Jana]

If you are going to use the power transformer you have, I would suggest building a champ with 1 6V6 tube.

I really don't think a 4 - 6L6 Class A amp is the right choice for a beginner. But, if you're set on that, you are going to need a big power transformer. Something on the order of about 400 to 500 ma. for the high voltage winding with a full wave rectifier. You are also going to need about 6 amps or so for the heaters.

That is a big chunk of iron.

Seriously, build a Champ. You don't need volume to learn how to play guitar.

http://www.webphix.com/schematic%20heav ... _schem.pdf

[starlite2991]

Hello mate

Thanks Jana

Ok i'll start looking for a 500ma trans asap. What voltage??

My budget is V E R Y limited. I got this original trans from Fleabay.

Enybdy interested in a good used 260 - 260 volt 90Ma transfmr? Make an offer. Shipping is included! Only in the lower 48 states of usa please. Pictures on req please...

As far as a Champ amp, na i would rather spend my money and go all
out. :") Thank you Jana!

Gday matey

If you are going to use the power transformer you have, I would suggest building a champ with 1 6V6 tube.

I really don't think a 4 - 6L6 Class A amp is the right choice for a beginner. But, if you're set on that, you are going to need a big power transformer. Something on the order of about 400 to 500 ma. for the high voltage winding with a full wave rectifier. You are also going to need about 6 amps or so for the heaters.

That is a big chunk of iron.

Seriously, build a Champ. You don't need volume to learn how to play guitar.

http://www.webphix.com/schematic%20heav ... _schem.pdf

[Jana]

You say your budget is very limited yet you want to build an amp with 4 large bottle power tubes. Let me be honest with you--you are way in over your head.

I'm trying to be as polite as possible. But, I usually wind up stepping on toes. So, here goes. Go to a pawn shop and find a 200 to 300 dollar amp. You can probably get a Peavey or similar amp that is 50 to 100 watts. That will be plenty of power--more than enough to give you permanent hearing damage. That 200 to 300 dollars is what you are going to have to spend on transformers alone if you are going to build this amp you *think* you need.

Have you ever played through a 100 watt tube amp? Do you have any idea how loud they are? Do you know what tinnitus is? I have played many gigs through 100 watt amps and I know all too well what tinnitus is.

If you don't know how to play guitar yet, you can't possibly know what you want/need in an amp.

[tribi9]

Building an amp gets expensive. Shipping, especially if you have to use different suppliers, adds up quick.

I'd suggest you take Jana's advice.

Build something simple first or buy a:

Fender Champ 600 (Around a $100 used)

A 1X15 (I got a Traynor with a 70's Eminence Speaker for $100

A Boost, or Distortion pedal. You can buy a BOSS DS-1 any day for about $25 bucks.

You'll be shocked at how loud you'll be.

[Leo_Gnardo]

As Jana said, in way way over your head. The parts you have will never add up to a 100W amp. Find a kit to build a Champ type kit amp, with cookbook directions. Like cut 4 inches of red wire, trim quarter inch insulation off each end, put one end to tube socket 1, pin 4 and other end at circuit point C, solder each end. etc etc etc. You'll have to get your soldering skills together, nuttin' & boltin', and most important following directions. That last one will be a skill which should improve your life dramatically.

And although a Champ only delivers a couple of watts, it's surprisingly good sounding for music. I listened to the radio thru my Champ test bench amp for decades. Good tone, loud enough to fill the room, no complaints.