# TRU Technology C 7.4T Tube amp



## kappa546 (Apr 11, 2005)

Not necessarily a "deal" (forget what they sold for new) but certainly a very unique and allegedly excellent sounding amplifier. RARE Tru Technology C 7 4T Tube Car Amplifier Milbert Butler Old School 4CH | eBay


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## Victor_inox (Apr 27, 2012)

Technically speaking it`s not true tube amp but hybrid. 
Tube pre/driver and solid state power amplifier. Nice one nonetheless.
I can achieve the same with any high quality solid state amp and tube preamp I made. Sounds freaking great with D class. Silky smooth tube highs and mid bass solid state punch, best of both worlds.


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## piyush7243 (Sep 9, 2009)

Victor_inox said:


> Technically speaking it`s not true tube amp but hybrid.
> Tube pre/driver and solid state power amplifier. Nice one nonetheless.
> I can achieve the same with any high quality solid state amp and tube preamp I made. Sounds freaking great with D class. Silky smooth tube highs and mid bass solid state punch, best of both worlds.


i hope you remember i wanted that preamp


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## PPI_GUY (Dec 20, 2007)

Beautiful amp that Tru. 
Could the same hybrid design be attained with the Panasonic bottlehead and a solid state amp?


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## Victor_inox (Apr 27, 2012)

piyush7243 said:


> i hope you remember i wanted that preamp


 Not ready for prime time yet, it works and very stable, noise is minimal ( there is no completely quiet tubes exist). Finding an enclosure for it is another story. it`s about 10"x7"x2 1/2" no active cooling required.
I`ll have 2 and 4 tube versions in stereo.
As soon as it ready I`ll send couple for reviewing And only after that look for customers. I will not sell incomplete product. Failure is not an option. 
I might consider selling kits for self assembly and whatever enclosure you might find yourself but I don`t think it`s a good idea.
250Volts on tube grid is liability waiting to happened


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## Victor_inox (Apr 27, 2012)

PPI_GUY said:


> Beautiful amp that Tru.
> Could the same hybrid design be attained with the Panasonic bottlehead and a solid state amp?


 Single double triode tube don`t do much in bottlehead HU but that`s is exactly what it does, inserting harmonics and distortion typical for tube amplification. Digital files sounds more or less "vinyl like" without crackling of course. that`s typical for hybrid amps. Unlike buttler where tubes not in the sound path, if removed nothing changes. they exist for looks only despite all that ******** buttler saying on his website.


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## thehatedguy (May 4, 2007)

I want a tube preamp for my car.

I always thought the earth would implode if you used a tube pre on class D amps though


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## kappa546 (Apr 11, 2005)

I also looked into a tube preamp last year, thought about copying a design some guy overseas built for his car. Ultimately I got a little intimidated by the project and never made it. That and finding a practical place to install it while keeping things simple and out off sight shelved the idea.


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## Victor_inox (Apr 27, 2012)

kappa546 said:


> I also looked into a tube preamp last year, thought about copying a design some guy overseas built for his car. Ultimately I got a little intimidated by the project and never made it. That and finding a practical place to install it while keeping things simple and out off sight shelved the idea.


Do you have a link to that project you talking about?


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## kappa546 (Apr 11, 2005)

I'll have to look for it. I think it was on diyaudio.com


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## Victor_inox (Apr 27, 2012)

kappa546 said:


> I'll have to look for it. I think it was on diyaudio.com


I tried few designs, chosen 2, conrad johnson and maranz . maranz is smaller, conrad johnson sounds better IMO, more natural. building power supplies for in car use is a *****. design stable and dead quiet.
Getting ready for in car testing, making them sing on the bench is 1 thing, car environment will be more difficult. Ideally I'd like tubes exposed and amp mounted to be visible. hiding that amber glow is retarded. using blue leds for illumination cheesy.
Making picture in the dark is difficult, sorry for shaky hands.
pictures made on top of Phoenix gold SD 500 amp, class D amp with tube pre, is the way to go.
Pre is not required bias adjusted. US or russian military grade NOS tubes needed replacement every 5000 hours of so. current production chinese made tubes last even longer but IMO don't sound as good. I never tried to burn them in for a 100 hours as all tubes suppose to, I compared new to new. 
Imagine and FR is astonishing. I can't bring myself to switch it off.


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## Sprocket3 (Mar 16, 2014)

Ground Zero make a tube amp for anyone who wants to know.


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## Victor_inox (Apr 27, 2012)

Sprocket3 said:


> Ground Zero make a tube amp for anyone who wants to know.


Hybrid as well 
"The best of two worlds are brought together in the Ground Zero GZPA Reference 2T by combining a tube pre-amplifier with a solid state power output stage. Vacuum tubes in the signal path give the sound that famous warmth, while the output stage offers high power for which modern solid state circuitry is so well known."

EUROPEAN IN-CAR HIGH-END COMPONENT 2013-2014 - Ground Zero GZPA Reference 2T on Vimeo


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## WestCo (Aug 19, 2012)

I would love to demo one of these in person.


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## Victor_inox (Apr 27, 2012)

WestCo said:


> I would love to demo one of these in person.


which one?


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## thehatedguy (May 4, 2007)

The power supply thing is what has stopped me from making a tube preamp.

The only one that I've found that could run on anything close to what I could make would be something like the Bottlehead Quicky preamp.

There was a power supply floating around on the web that was a high voltage car design for tubes, but I don't know anything about it.

Switch mode power supply for car vacuum tube amplifier


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## thehatedguy (May 4, 2007)

12AX7 stereo tube preamp only 12 volts - YouTube

Might be worth building.


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## Victor_inox (Apr 27, 2012)

THank you, I`ll check it out.


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## Victor_inox (Apr 27, 2012)

thehatedguy said:


> 12AX7 stereo tube preamp only 12 volts - YouTube
> 
> Might be worth building.


As a first project it`s ok but matching impedance and HU sensitivity will required more sophisticated circuitry. 20DB of amplification that tube provide must be controlled. 12AX7 is great dual triode tube used in very good designs but channel separation will suffer, channels should not use common parts in both channels. As cheap headphones preamp it`s ok though..
12V for plate voltage is not enough, I use 12 to 250VDC conversion.


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## thehatedguy (May 4, 2007)

I don't know enough on how to make 250 volts from 12.

I have seen talk of people using an invertor and taping into it to get the high voltage...don't remember exactly where I saw that at though, or the details of it.

You would know more about that stuff than I do.


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## Victor_inox (Apr 27, 2012)

thehatedguy said:


> I don't know enough on how to make 250 volts from 12.
> 
> I have seen talk of people using an invertor and taping into it to get the high voltage...don't remember exactly where I saw that at though, or the details of it.
> 
> You would know more about that stuff than I do.


Using invertor is backwards, I won`t do that. 
12ax 7 plate heater voltage is 12.6, grid voltage as high as 300.
regulating grig voltage is another way of adjusting sound character. 
obviously tube conducts at 12V grid voltage as demonstrated by that video.
Is that what that tube was designed for- far from it.


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## Victor_inox (Apr 27, 2012)

i will start separate thread for preamps I do but here is a teaser for now:
I have 4 channel version ready to go. 
First version will be fully enclosed to prevent physical damage to tubes.
case is extruded aluminum 5.75"x2.75"x7,75".
http://www.diymobileaudio.com/forum/technical-advanced-car-audio-discussion/161717-tube-preamps-mobile-installations.html#post2075670


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## Victor_inox (Apr 27, 2012)

Sprocket3 said:


> Ground Zero make a tube amp for anyone who wants to know.


I bought one.


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## Carlton8000 (Feb 5, 2011)

Tube pre in a Car! Definitely on my want to try list. Please let me know if this becomes something for sale once you get it all sorted out. As info here is a link to a power supply for Tube use in a car.

In


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## piyush7243 (Sep 9, 2009)

Victor_inox said:


> i will start separate thread for preamps I do but here is a teaser for now:
> I have 4 channel version ready to go.
> First version will be fully enclosed to prevent physical damage to tubes.
> case is extruded aluminum 5.75"x2.75"x7,75".
> http://www.diymobileaudio.com/forum/technical-advanced-car-audio-discussion/161717-tube-preamps-mobile-installations.html#post2075670


Which tubes and i will be on the interested list surely


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## Victor_inox (Apr 27, 2012)

piyush7243 said:


> Which tubes and i will be on the interested list surely


12AX7 go to that thread I started, more info available there.


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## starboy869 (Dec 16, 2006)

i want this, but the price wow....


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## Victor_inox (Apr 27, 2012)

starboy869 said:


> i want this, but the price wow....


Today is your lucky day!http://www.diymobileaudio.com/forum/technical-advanced-car-audio-discussion/161717-tube-preamps-mobile-installations.html#post2075670


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## Victor_inox (Apr 27, 2012)

wrong tread


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