Tube amp for my car

[lnx64]

This is going to be an odd request.. But I love the sound of tubes.. Even the headphone amp on my Mac is tube powered, and in the livingroom when watching movies and stuff on the Apple TV, we use an amp that is tube powered.. Love it, LOVE it. Especially when people think tubes aren't that good, and they hear a gun shot or explosions in some action movie with regular 8 ohms speakers, and they are like "wow, and there's no subwoofer?!"

Now I want it for my car. Someone I work with, has a Fisher 500c receiver, that is pretty banged up. Electrically it works and had the caps replaced, but it has no casing, and is just a bare chassis.. I was thinking, if I replaced the speakers in my car with a higher impedance other than 4 ohms, perhaps 6 or 8 ohms, I could use this amp, and even use an inverter to provide it the AC power it needs.

Now, that should be easy to do. My car is already wired up for an amp, which has bit the dust, and it needs to be replaced, so this is why I am thinking of doing this.

Can that wonderful old amp be retrofitted into a car? It would be mounted in the trunk of the car, but on my Caprice, the trunk actually doesn't get hot at all, even in hot weather, it's rather nice in there, so heat won't be as much of a concern.. Though I would install fans anyway just to play it safe.

Is it a crazy idea, or an interesting idea? Should I do it, or is there a better solution for tube sound in the car?

My commute to work is an hour, so good tunes is very important for me.

[bob91343]

It takes all kinds, and if doing this pleases you, by all means go ahead. You can build or buy an inverter. Just the heaters in the tubes draw so much current that it might be wise to take them off the filament winding of the power transformer and run them directly from the battery instead. That would improve the efficiency of the setup, which will be pretty grim in any case.

So you like to wait for tubes to warm up, and you like the distortion many tube amplifiers provide. I prefer clean amplifiers, something solid state is much better at providing than even the best tube amplifiers.

[lnx64]

I don't mind warmup time. I'm not in a rush.. And even when tubes provide distortion, it's much more graceful to the ears than a transistor distorting. I don't hear that distortion. Not even in the livingroom amp.

[CoogarXR]

I suggest trying it with an inverter first, then see if you want a permanent mod. You might want to come up with some kind of shock-absorbing mount too. I am not sure if tubes would like all that road vibration.

[rpm1200]

You should get a Panasonic CQ-TX5500D - Japanese-market car stereo with tube drivers! There's one on the 'bay for $645 BIN right now.

If you do go with the Fisher, like CoogarXR said, you should put in some kind of isolation to preserve the tubes (and cut down on microphonics when going over bumps).

[lnx64]

Originally Posted by rpm1200

You should get a Panasonic CQ-TX5500D - Japanese-market car stereo with tube drivers! There's one on the 'bay for $645 BIN right now.

If you do go with the Fisher, like CoogarXR said, you should put in some kind of isolation to preserve the tubes (and cut down on microphonics when going over bumps).

Problem with this one, is that the 94 caprice's radio is not a double DIN spot.. It's close, but not quite. I already have a custom radio in there anyway, that's hybrid digital on FM and AM (I refuse to call it HD radio as it's not high definition), and has a USB port so I can just plug in my flash drives for music.


As far as microphonic, i'll definitely find a way to make it shock absorbed so the tubes fare well.

[N2IXK]

Ran a modified Dynaco Stereo 70 in a '71 Plymouth Duster many years ago.

Rewired the heater circuitry for direct operation from 12VDC. Pulled out the stock power transformer and the 5AR4, and obtained B+ from an old surplus dynamotor from a 50s era mobile 2-way radio setup. Negative bias supply came from a little DC-DC converter circuit I cobbled together.

Soon discovered that EL34s and 7199s don't like vibration very much. Tubes developed loose internals and microphonics very quickly, even with the entire amp shock mounted on rubber isolators. If I were to try something like this again, I would strongly consider the use of highly ruggedized mil-spec tubes. Bendix Red Bank 6384s would be great for the output tubes, but they are getting harder to find and go for $$$ if you can find them.

[Jeffhs]

Originally Posted by CoogarXR

I suggest trying it with an inverter first, then see if you want a permanent mod. You might want to come up with some kind of shock-absorbing mount too. I am not sure if tubes would like all that road vibration.

The idea of tube-type amplifiers in car radios is not new. Years ago, car radios used miniature tubes and they worked quite well; no microphonics unless the output tube had loose elements, and the radios themselves were built to withstand road shakes, bumps, and other things that would shake a standard radio's tubes apart. However, the old automobile radio reverberation systems with actual metal spring delay lines were prone to noise problems if the car in which they were installed went over a bump in the road. The springs would bounce against each other or against the unit's housing, resulting in a loud "BONG!" sound from the radio's speakers (the main one in the dashboard and the second one in the back of the car, near the rear seat). My dad had one of these reverb units in his 1963 Chevy BelAir; the reverb worked very well, no problems with the springs causing the noises I mentioned -- at least none I can remember.

BTW, Cadillac car radios probably had reverb as standard equipment, as these were luxury cars with all the bells and whistles (and a price to match). My mother had a '57 Caddy with an AM radio that had a signal-seeking tuner and preset buttons for favorite stations. I wouldn't have been surprised if that car had a reverb system as well.

[old_coot88]

You should definitely do it with an inverter first, to be sure you're gonna be happy with the results (IMHO). Sort of a 'proof of concept' run.

[rpm1200]

Should be an interesting project. As long as you have fun doing it... I actually put 8-track players in two of my previous cars just for the heck of it. (Link)

If you don't like iBiquity's marketing term "HD Radio" you can always call it "IBOC" (the engineering name, in-band on-channel)...

[mstaton]

Cadillacs DID NOT come with reverb units. They had the standard AM signal seeking radio. AM/FM mono was optional by '63 and did not have the signal seeking feature. They were tube with solid state outputs(hybrid). As far as that Fisher is concerned, you will most likely need to replace the electrolytics. They dry up and short. More than likely will have very dirty tube sockets. I've worked on tons of Fishers and they always have some issues. I suggest that you install brand new 7591's.

[ctc17]

I can just hear the buzzing from the crappy stepped signwave out of the inverter. The power transformer in the receiver would not like the stepped sign wave either and would be very inefficient.

Also speakers used with tube equipment are usually very efficient, over 100db 1 watt 1 meter. Automotive speaker are usually horrible, around 85db.

Also, if the amp uses 200 watts thats 20 amps at 12v, then factor in all the inefficiency of the inverter it would be 30+amps continuous on the cars electrical system and the alternator wont support that. If you factor in fuel pump, headlights, blower fan, compressor clutch, engine management, etc it wont do it. Maybe if the engine is always at 2000rpm but not through a regular driving range.

When guys a thousand watts of solid state power its very low duty cycle, Tubes dont do that, they draw a fairly consistent current from a whisper to a scream.

I always wanted to convert one of those old tube motorola police radios to a ham rig for my truck but its just way to impractical

[Electronic M]

If you are keeping it in the trunk and using your cars existent solid state tuner then removing the tubes associated with the radio would be a wise move to save power. If you wire the tubes to take the car's 12V mains directly then why not go a step further and add a DC to DC converter for the B+(you can get them pre-made or design and build your own).

I have a home made car headphone amp designed with sub-miniture hearing aid tubes that has been partially dismantled by me for tubes for a project that I got sidetracked on. Even when I do part it out I intend to draw a schematic so I can duplicate it someday if I desire.

I prefer tube sound to SS as well. If you like vinyl and 78's like me you will find tubes to be substantially more forgiving of record scratch. I can really demonstrate this by taking a worn 78 and playing it through a tube amp followed by a solid state one(my 65 Zenith SS console sounds GREAT on a good LP, but put a 78 on and the record noise overpowers the music).
Also I find the highs on my tube gear to be sharper and more melodic than those of mt better SS gear which makes them feel a bit jagged.

[wa2ise]

As mentioned above, another approach for getting some tube sound in the car would be to use a tube buffer stage ahead of a SS amp. And the tube buffer built using say subminiature tubes intended for fighter jets or guided missile service. Say a pair of triodes in cathode follower connections. And you may be able to take apart an inverter to get at the high voltage DC before it's chopped into square wave AC, to get the B+ for the tubes.

[ctc17]

Originally Posted by wa2ise

As mentioned above, another approach for getting some tube sound in the car would be to use a tube buffer stage ahead of a SS amp. And the tube buffer built using say subminiature tubes intended for fighter jets or guided missile service. Say a pair of triodes in cathode follower connections. And you may be able to take apart an inverter to get at the high voltage DC before it's chopped into square wave AC, to get the B+ for the tubes.

I was thinking of that but with a 12AX7 type tube. I had not though of opening the inverter and removing the chopper fets. Brilliant!
All you need to do is ad the 2nd and 4th order harmonics to give it the tube sound.
I saw an ipod docking station with a 12AX7 preamp with the same intention.