Another conversion

[jeff]

Hi guys, I got a another tube stereo off of Craigslist.
I want to use the transformers from this to build another 5E3.
The amp origanaly uses EL84 but I would like to use 6V6's if possible.
I don't want to damage anything.
Is there anything you can tell by looking at the schematic if this will or won't work?

 Thanks
   Jeff

[LooseChange]

Go for it!  You can make a stereo 5E3 with this one.
Does the stereo work?  Do you own a tube stereo?

[jeff]

Stereo would be cool but I don't use stereo effects and I'll save the other OT for something else. Fate will send me a PT down the road.
Don't know if it works, Don't have any EL84s, it was sold without tubes.
That's why I want to build something with 6V6s. Got lots of those. No problem using 6V6s with an EL84 transformer?

I did get a tube stereo as a gift but I haven't got a chance to check it out yet. Probaly should get on that instead of building another guitar amp out of this one.

[jjasilli]

This is a candidate for a hi-fi restoration/upgrade.  See:  http://www.angelfire.com/vt/audio/  If you don't already have vacuum tube hi-fi  you might want to check it out.

[DummyLoad]

that is much too nice of a piece of hi-fi gear to gut into a guitar amp. respectfully, you should reconsider, unless it's a total basket case.

--DL

[jeff]

 You know, you're right. I check it out and get some tubes for it. Got enough guitar amps anyway.
Someone cut the cord off so I hope it's not damaged beyond repair. I checked the windings for continuity and they seem OK. Hopefully someone needed a lamp cord and robbed it and theres no major problems.
I think I should get my hands on some cap cans. I'll test the values of the resistors for any that have drifted or opened. What else should I do/check for before powering it up?

  Thanks for talking me out of butchering it.
                   Jeff

I've never actually heard a tube stereo.  With a stereo you want to cleanly and accurately reproduce the sound not alter and distort sound. The reason tubes are great for guitar amps is how they sound when we push them. Is there a big difference between a tube and a SS stereo?

[LooseChange]

Yeah, good thinking. Tube it and fix it up. I've got a Radio Shack all tube Stereo amp in my shop. Got it hooked up to two Dynaco speakers from the same era. I plug my iPod in and it sounds great! Always an inspiration for better tone when I'm working in my shop.

[DummyLoad]

I think I should get my hands on some cap cans. I'll test the values of the resistors for any that have drifted or opened. What else should I do/check for before powering it up?

coupling caps, fresh electrolytics, check PS chain resistors, replace CC resistors that have drifted. install some fresh tubes. bring he up on a lamp limiter. bet she'll go another 40 yrs +.

tube amps clip smoother than SS amps, to me they sound much more mellow than SS because of that. if you decide that you don't care for the "tube" sound, then flip it to some hi-fi folk who do.

--DL

[jeff]

When you say coupling caps are you suggest replacing all the coupling caps or testing them? Check for DC on the other side of the cap and if there is none keep em? Do CCs deteriorate in quality or is it a matter of if they're leaky or not?

tube amps clip smoother than SS amps, to me they sound much more mellow than SS because of that. if you decide that you don't care for the "tube" sound, then flip it to some hi-fi folk who do.

Do you want to run your stereo to the point of clipping??

[firemedic]

I rehabbed a 1962 victor console stereo a couple months ago- it didn't need much besides a grounded power cord and new electrolytic caps. But, it did have leaky coupling caps to the power tubes, causing them to redplate. They were yellow waxy caps that looked pretty good visually.
It also had a few carbon comp plate & B+ resistors that had drifted WAY up in value, choking off some of the FM tubes.
The net result was that the stereo didn't work anymore & was unsafe. Once those issues were addressed, using stuff I had laying around, it sounded fantastic. It's not a hifi but I love the sound. Once you play records (or radio) with tubes, you'll never go back.

[DummyLoad]

Do you want to run your stereo to the point of clipping??

no! modern program material is very dynamic. even at "normal" listening levels, occasionally, things will peak/clip. when clipping does occur, to me the tube amp is easier on the ears. this just an opinion.

When you say coupling caps are you suggest replacing all the coupling caps or testing them?

i was suggesting that you replace them. modern caps are made much better than anything made 50 years ago. to me they sound better. your opinion is the only one that matters in this case; i'm merely making suggestions.

--DL



   

[jeff]

See your point about clipping now.

 Should I replace the ceramic disk caps with c.d. or something else? Any suggestions for what caps sounds best in a stereo?

I think this amp has tone "packages". A combination of caps and resistors. If you look at the schematic the caps and resistors within the dotted lines(tone stack) are all contained in one part with many leads not individual caps and resistors. Wierd.

  Thanks
   Jeff

[Frankenamp]

Not wierd if it saves money in production. I found one of those in a tape recorder amp I converted; think of it as the grand uncle of the integrated circuit. If it ain't broke, don't fix it. You might want to leave the ceramic disc caps alone, they rarely if ever go bad. Leave the paper in oil rooskie caps for the real audiophiles :)

[jjasilli]

Different schools of thought.  Angela (www.angela.com) belives that vintage ceramic caps are desirable.  Many hi-fi guys believe that all vintage paper or plastic caps are substandard, and likely to be or to become leaky.  Hence they replace them automatically.  If desirable specimens like Bumblebees or Black Beauties for example, they re-sell them to us guitar guys!  Replace them with what?  Opinions abound and the the sky's the limit; you can spend over $100 for ea Jensen paper & oil signal cap. 

One approach is to go step-by-step.  First restore the amp at reasonable cost. Once you hear it you'll probably be hooked.  Then think about upgrades to boutique components.