Should I bother? Beginner tube amp question...

[jtnfoley]

Should I bother? There's a Stromberg-Carlson console nearby that I think I can have for a song, but its' not of the really-cool desirable Stromberg line (i.e. its' NOT an ASR 333/433/444 amp.)

Instead, its' an entry-level turntable-only stereo console with not even a proper pre-amp (just a couple of rheostats for volume, bass, and treble.)

The amp is a stand-alone sheet metal box type with one 7199 and one 7408/6V6 for each channel.

It was apparently little used, and the tubes are all original Stromberg-branded parts.

Should I even bother? Is this thing worth the effort to destroy and dispose of the carcass? My application would be cornwall/la scala, BTW.

The output transformers are running off to some tiny little 6x9 and a smaller mid/high.

This is the bottom of the volume/bass/treble plate, with the "multiplex input" shown on the schematic shot visible adjascent to the L&R inputs form the TT.

[mike stehr]

I would think it would be a nice sounding little single-ended 6V6 stand alone power amplifier. A friend of mine has one, IIRC.

It's entirely up to you. If it's a entry level console stereo, and the console is trashed, then it's easy to not feel guilty about tossing the console. Or if you want to deal with the trouble of converting a stereo console amp into a stand alone power amp. It's not difficult to do. Or making sure all the parts are up to snuff.

But if the console is in good condition, then it's more of a guilt trip....

[jtnfoley]

No guilt trip... the console is moderately unattractive and certainly not something that should be restored in its' own right.

I'm actually leaning toward picking this up as a totally sacrificial "practice exercise" before jumping into more sophisticated restoration efforts... I've got some Dynaco goodness that a friend is asking me to assist with...

[billybob]

This(vintage systems) is what I have been contemplating doing also, to get into tubes, as a learning adventure. For next to a song, my curiosity will prevail.

[jtnfoley]

Kinda what I was thinking... Cheaper than a SET kit even so what the hey ya know?

[Erik Mandaville]

"Cheaper than a SET kit even so what the hey ya know?"

It's true, some of the SET kits available are expensive. There are alternatives, however -- good for beginners, and has gotten some good reviews considering the cost. Probably the least expensive tube kit available, or at least that I've seen.

Go to: www.tubesandmore.com

See the menu on the left, and scroll to 'Audio' Click 'Audio'. See the stereo amplifier kit for $185.00 complete with all parts and instructions. There is also a monoblock version.

Parts are installed on a wooden base, very much like old radios from the 1920s. With some minor modifications, the circuit could be installed in a simple chassis for greater safety, with short screws into the bottom of the base. Wood won't conduct, so it's insulated.

The vintage stuff is always cool, and can sometimes turn into something pretty involved. Line voltages are higher now than what they used to be, which means filament supplies (the things that make tubes glow) can run on the high side (not so good as far as tube-life goes); filter capacitors usually need to be replaced or reconditioned; resistors replaced that have drifted in value which can throw off correct operation. They or neat though! If you have a variac, that would be good as you begin to check it out. Something like this was how I got zapped a long time ago. An old 6V6 pp amp, with no fuse and an un-earthed line cord. I was able to let go by throwing it -- all the way across the room. Those kinds of shocks are hard to forget.

Have fun but be careful

Erik

edit: Correction: Go to the website, and first click on 'Kits' on the menu. From there scroll down to 'Audio' as mentioned above.

[billybob]

"Cheaper than a SET kit even so what the hey ya know?"

It's true, some of the SET kits available are expensive. There are alternatives, however -- good for beginners, and has gotten some good reviews considering the cost. Probably the least expensive tube kit available, or at least that I've seen.

Go to: www.tubesandmore.com

See the menu on the left, and scroll to 'Audio' Click 'Audio'. See the stereo amplifier kit for $185.00 complete with all parts and instructions. There is also a monoblock version.

Parts are installed on a wooden base, very much like old radios from the 1920s. With some minor modifications, the circuit could be installed in a simple chassis for greater safety, with short screws into the bottom of the base. Wood won't conduct, so it's insulated.

The vintage stuff is always cool, and can sometimes turn into something pretty involved. Line voltages are higher now than what they used to be, which means filament supplies (the things that make tubes glow) can run on the high side (not so good as far as tube-life goes); filter capacitors usually need to be replaced or reconditioned; resistors replaced that have drifted in value which can throw off correct operation. They or neat though! If you have a variac, that would be good as you begin to check it out. Something like this was how I got zapped a long time ago. An old 6V6 pp amp, with no fuse and an un-earthed line cord. I was able to let go by throwing it -- all the way across the room. Those kinds of shocks are hard to forget.

Have fun but be careful

Erik

edit: Correction: Go to the website, and first click on 'Kits' on the menu. From there scroll down to 'Audio' as mentioned above.

Now that is very cool! Thanks!

*jtnfoley, for a song, and a dance, you can have old and new!

[synthfreek]

I see the Baby Sophia for $300 all the time and I've always thought that would be a great piece for the tube curious.

[oldtimer]

LOL synth, "tube curious" sounds a little deviant eh?

[Erik Mandaville]

Whether vintage or modern: Keep in mind that filter capacitors can store strong electrical charges for days. Not all power supplies are complete with bleeder resistors, and you have to be careful. Don't assume the component is safe just because it's been turned off and unplugged. There are several places inside the amp and tube sockets that, if you touch them, will drain the filter capacitors very quickly -- into you, and that's not a good thing. This is a fun hobby, but you just have to remember (and respect) the fact that these things make music through the use of dangerously high voltages.

Erik

[mike stehr]

No guilt trip... the console is moderately unattractive and certainly not something that should be restored in its' own right. I'm actually leaning toward picking this up as a totally sacrificial "practice exercise" before jumping into more sophisticated restoration efforts... I've got some Dynaco goodness that a friend is asking me to assist with...

If you want cut your teeth in DIY with tube circuits and practice, then that Stromberg Carlson SE 6V6 console amplifier would be a excellent start. Something simple.

It will probably only be around 3-4 watts per side.

Find a schematic, check the R's and the C's. Test the tubes....I wouldn't doubt those original tubes are probably still ok. Are the output tubes Stromberg Carlson labeled 7408's? That's a little more robust tube than a 6V6.

Yeah, I wouldn't be the least bit concerned taking a claw hammer to that console......That old record changer maybe worth keeping.....but most the cheap console stereos used junk for TT's.

[jtnfoley]

Rather than quoting multiple responses, I'm just going to kinda reply in general.

Regarding safety... I play with CRT projectors with 35kV anodes. I'm good! Thanks for the concern, tho! []

Mains voltage: The paper label states 117Vac / 60 cps, but I'll keep an eye on the filiment voltage. 6.3VDC, right?

I've got a Variac, and am One with Ohms Law and Borgs' Law ("Resistance is futile, if less than or equal to one ohm!")

The power tubes are difinately Stromberg-branded 7408s... All the tubes bear the Military numbers.

I guess my ultimate question was/is... is THIS specific amp a good learner. Looks like it will be: I think I'm going to do it. At the very least I'll be able to turn
it into a desktop amp for my PC speakers [] That'll be a conversation
starter in my office if I'm able to re-set the gain to line-level...

[billybob]

What the hay! You sound like a "tube" guy! I'll be looking at your project with interest!

[jtnfoley]

What the hay! You sound like a "tube" guy! I'll be looking at your project with interest!

Yep.... I'm definately One with Analog. Its' in my blood... Granddad (still vertical) was Massachusetts TV Repair Man #10, and I'll be rifiling his basement looking for tubes in the near future. [] I know most won't be of interest to us, but I'll keep my eyes open.

Several years ago, before I became interested, he sold his GE armoir (GE used to put big freestanding armoirs in service shops) FULL of a thousand or more tubes... IIRC he was asking $200, the buyer (first respondent) insisted on giving him something like $750.

[billybob]

What the hay! You sound like a "tube" guy! I'll be looking at your project with interest!

Yep.... I'm definately One with Analog. Its' in my blood... Granddad (still vertical) was Massachusetts TV Repair Man #10, and I'll be rifiling his basement looking for tubes in the near future. I know most won't be of interest to us, but I'll keep my eyes open.

Several years ago, before I became interested, he sold his GE armoir (GE used to put big freestanding armoirs in service shops) FULL of a thousand or more tubes... IIRC he was asking $200, the buyer (first respondent) insisted on giving him something like $750.

Nice to have a stash to look at! Yes, it's definitely a blood thing! Granddad no doubt, could tell a tale or so! Good Fortune!

[Erik Mandaville]

"Regarding safety... I play with CRT projectors with 35kV anodes. I'm good! Thanks for the concern, tho!"

Sure. It's intended for anyone reading this, (which may be many) who are interested in the same thing yet may not have experience working around high voltages -- which you certainly do.

There have been a number of occasions in the past where even long time forum members with solder slinging skills have reported very bad shock experiences in working with these components. Others have talked about working on and soldering in energized equipment, which is not good anyway one looks at it.

'Yes' on the 6.3 volt filaments supply. It may be fine, although one way to lower that, as well as provide some in-rush current suppression is to use an in rush current limiter as part of the AC input into the amplifier.

For a stand alone power amp, it could be as simple as replacing the volume controls (which might be in the range of .5 megohms or so) with a fixed grid leak resistor (from the grid of the input tube to ground) in each channel. If you can find a shematic, the location will be easy to see.

Have fun,

Erik

[mike stehr]

"Others have talked about working on and soldering in energized equipment, which is not good anyway one looks at it."

Does this have to with the time I was visiting my EE friend and almost soldered on a energized circuit, when the friend told me he should turn the variac before I soldered on the circuit. To which I replied, that might be a good idea, and then he called me chicken?

One, he was just kidding.

Two, I would NEVER advise anyone to solder on live chassis, and NEVER would my retired EE friend.

It seems to me as of late that you have a beef with everyone around here.....what's the problem, Erik? I could be wrong, but it's the impression I get.

If you think I give folks improper advice about tube amplfiiers just say so, don't just take some comment out of context.

Maybe you should have the Administrator make a big sticky pinned up at the top of the 2 channel forum regarding DIY tube amplifier rebuilding and electrical safety. You can host it, since it seems you're the man when it comes to the topic.

I not trying to slam you for being particular when it comes to others safety with respect to high voltages and tube circuits, you can never be TOO safe. And I do my best to keep from getting electrocuted......The ol' EE did show me the safe way to go about these things, regardless of what you think.......

But you have to kinda quit assuming that everyone is totally ingnorant to the subject.

No offense.......

[jtnfoley]

"Regarding safety... I play with CRT projectors with 35kV anodes. I'm good! Thanks for the concern, tho!"

Sure. It's intended for anyone reading this, (which may be many) who are interested in the same thing yet may not have experience working around high voltages -- which you certainly do.

Good point on the "posterity" aspect of these posts... Words are tenacious things on this ol' Internet []

Have fun,

Erik

I think I will!

Now I just have to resist the urge to collect consoles for the sake of their contents, as disposing of the carcass is kind of a drag in my neighborhood (transfer station silliness WRT "construction debris.")

[Erik Mandaville]

"But you have to kinda quit assuming that everyone is totally ingnorant to the subject."

The title of this thread is "Should I bother? Beginner Tube amp Question"

Based on that, would it be correct in your estimation to assume the person involved has a comprehensive understanding of high voltage charges in storage capacitors? If that's an assumption you would like to make, that is your business; however I will pass on a warning simply to remind about safety regardless of what others think about it. For me, based on the knowledge I have and experience with being shocked in the past, it would be a serious professional compromise to not mention it to someone who, by the nature of the title of the thread, seemed uncertain and was a self-described tube amp beginner.

He pointed out his experience with working at very high plate voltages, which I acknowledged, and then explained that the safety warning was intended for anyone else who might be interested in getting started in electronic DIYing. I have had a number of non-posting members ask me questions about things like this.

If you would rather make the assumption that people ARE aware of very real safety issues concerning potentially fatal shock hazards, that's your business. I would rather make my error on the side of preventing that from happening to anyone. I have friends who are pros at this who have admitted becoming so familiar with the work at times that they forget to be afraid -- and gotten zapped by a careless mistake, such as forgetting to turn a component off before soldering.

I think we sometimes forget that our conversations about such things as this, where people can be very seriously injured or worse, are viewed only by the small handfull of participants within a given thread. The fact of the matter is that it's global, and we simply CAN'T know who is following along, and possibly ready to jump in and have a hand at whatever is being discussed without being warned of the potential dangers.

You can expect me to continue to make some of those concerns public where I think appropriate. It was not meant as an insult, and the author of this thread seems to recognize that.

No offense taken,

Erik

[Erik Mandaville]

Now I just have to resist the urge to collect consoles for the sake of their contents, as disposing of the carcass is kind of a drag in my neighborhood (transfer station silliness WRT "construction debris.")

I totally understand that, same problem here. My wife got so tired of seeing an old beatup but nevertheless really cool Sears console from the W II era that she stripped the nasty green paint off it (I helped), and turned it into a nice display shelf for her hand-made teddy bear collection. I saved some of the tubes and transformers, and dumped the rest.

There is something so captivating to me about those old things. I've gone the smaller or at least more portable route from two decades or so earlier.