Tube amplifier

Master Roda

The Jedi
Joined
Feb 1, 2006
Messages
3,227
Location
Scappoose.OR USA
I was told to beg, borrow, or steal a tube amplifier.

I'm opting for the first. Despite popular belief, I don't have alot of money. :sorry:

It's for a side project I'm doing with ribbon speakers.

Can anyone help?
 

scottessex

Sling-Wing Pilot
Joined
Nov 12, 2003
Messages
11,124
Location
central, ga
Aircraft
Dominator 582
Total Flight Time
200+
There has to be some burned out old Grunge bands up there in your neck of the woods that are just dying to sell some equipment cheap to get a fix... :)
 

jcarleto

Aluminum Supporter
Joined
Jun 5, 2007
Messages
3,571
Location
Taylorsville, GA
Aircraft
Beech Bonanza G-35 N4638D/"The Bulldozer" 2-Place Gyroplane N575EE
Total Flight Time
Several
What kind of specs are you looking for?

Pre-amp? Power amp? Guitar amp? PA amp? Stereo amp?

What watt output?
 

RotoPlane

Gold Supporter
Joined
Jan 4, 2008
Messages
3,203
Location
Gilboa, Ohio USA
Replacement tubes are very expensive….if you can find them. I elected to go with discrete components and build my own using the work of Professor Marshall Leach, Georgia Institute of Technology. He is at the School of Electrical and Computer Engineering, and one smart cookie. These amplifiers sound as good and can power anything the tube ones can. I have heard this from several audiophile sources. If you're interested in this stuff, here is the link:

http://users.ece.gatech.edu/~mleach/lowtim/index.html

I designed my own cabinet and two sided channel boards using the Leach circuit. To give you an idea, this what they look like:
 
Last edited:

PW_Plack

Active Member
Joined
Oct 30, 2003
Messages
8,517
Location
West Valley City, Utah, USA
Aircraft
Sport Copter Vortex 582
Total Flight Time
FW: 200 Gyro: 51
Do you happen to know if it can handle low resistance loads? I'm talkin' 1-2 ohms max.
Jon, depending on how long you need it, see what you can rent. Many of the big solid-state amps used these days for sound reinforcement at concerts (ie the huge stacks of speakers on each side of the stage) make their rated output at 2 ohms, and are overload protected.

Some auto amps also have very low-impedance outputs.

A tube audio output stage usually runs at a plate voltage of hundreds of volts, and has an impedance in the thousands of ohms, requiring an output transformer to match a speaker voice coil. If you put a much lower impedance on the transformer's output than its spec, ugly things can happen.
 

Master Roda

The Jedi
Joined
Feb 1, 2006
Messages
3,227
Location
Scappoose.OR USA
I can't use a transformer. I can't use auto amps either. Anything solid state won't work.

The speakers will be characterized, and as such can't have ANY distortion.

I was given my orders by the person that will be characterizing them to get a quality tube amp.

I can't afford one, soooooooo :)
 

choppergabor

Newbie
Joined
Apr 15, 2009
Messages
4,864
Location
Sunshine State
Aircraft
N65GK Behemoth
Total Flight Time
Too few to mention
If you put a much lower impedance on the transformer's output than its spec, ugly things can happen.
Amen to that brother! I have burnt so many speakers in my younger years!!!! And of course the Bass is always more brutal on the cones anyways. But yeah by all means match the impedance Jon!!!
 

Master Roda

The Jedi
Joined
Feb 1, 2006
Messages
3,227
Location
Scappoose.OR USA
I can most likely get the resistance up to 6 ohms maybe higher. Just not counting on it.

I'm shooting for the worst case scenario, and hoping for the best.
 

brett s

Gold Supporter
Joined
May 29, 2004
Messages
2,386
Location
Ball Ground, GA
Aircraft
none currently
Total Flight Time
1300 helicopter
Better qualify what type of tube amp you need - big difference between a guitar amp, PA, or hi-fi stereo amp.

A guitar tube amp should be easy to find anywhere but do a lot of tone shaping which you may not want.

I've got a couple of 50 watt tube combo amps, but they don't ship well at all - both have already been damaged that way unfortunately. They also are both guitar amps that have their own distinctive sound - Marshall JCM 800's :)
 

Master Roda

The Jedi
Joined
Feb 1, 2006
Messages
3,227
Location
Scappoose.OR USA
Brett,

I'm begging for anything, but I would prefer a quality amp. The power required for a test isn't much, but I would like to find the limit of the speaker :)

If someone has what I need I would of course pay for shipping and insurance. I don't have cash, but I might have something for trade if needed.

If I can't find a tube amp, I'll use whatever I can get.
 

RotoPlane

Gold Supporter
Joined
Jan 4, 2008
Messages
3,203
Location
Gilboa, Ohio USA
Thanks Ed!

Do you happen to know if it can handle low resistance loads? I'm talkin' 1-2 ohms max.
This section talks about this amp and ohm loads. At normal 8 ohms loads each amp board is rated at 120w. At 4 ohms this could of course go to 240w, which some people are using successfully. He talks about this and also using 2 ohms. You should go through all sections before deciding whether you want to tackle it.....

http://users.ece.gatech.edu/~mleach/lowtim/bckgrnd.html
 

Master Roda

The Jedi
Joined
Feb 1, 2006
Messages
3,227
Location
Scappoose.OR USA
Quote:
The amplifier will drive a 4 ohm load to full power without current limiting. Depending on the power supply regulation, the output power with a 4 ohm load is as great as twice the power with an 8 ohm load. With loads lower than 2 ohms, the protection circuits limit the maximum output current, and thus the output power, to protect the output transistors. The amplifier is stable with capacitive loads and will drive electrostatic loudspeakers with no problems.

That's what I wanted to know....Thanks!!
 

brett s

Gold Supporter
Joined
May 29, 2004
Messages
2,386
Location
Ball Ground, GA
Aircraft
none currently
Total Flight Time
1300 helicopter
Finding a local amp will be your best bet - renting one for a couple days if you must would also probably be cheaper than shipping one. Larger tube amps weigh a ton, transformers are heavy - mine is near 80 lbs (2x12 combo).
 

Master Roda

The Jedi
Joined
Feb 1, 2006
Messages
3,227
Location
Scappoose.OR USA
Brett,

Your right, I'm just puttin' out all feelers if you know what I mean.

Gabor,

Thanks, but I absolutly HATE borrowing anything. I feel bad if I can't buy it or somehow compensate in some way. If I broke it, well, that would be worse than death...to me anyway.

I really appreciate the help guys. This could be a big thing for me, so I'm trying really hard to get the best and show the best.

The fact of the matter is, I've found a way of making ribbons cheaper and better than ever before. Just need the power....and clarity.

I'm too the point of building EVERYTHING, because I can't find it.

Thanks again for all the help.
 

trl0219

Newbie
Joined
Jan 31, 2010
Messages
67
Location
Wilson, NC
I do a lot with professional audio. Fender makes a small tube amp that has a very clean tone. Pignose also has a small tube amp. They are belt style for street corner playing and they are pretty cheap. Look at Guitar Center's website. Search for tube amp and sort by price lowest to highest. Or you can PM me and I'll give you my number and help you out the best I can.

Good luck,
Tim Langley
 

Master Roda

The Jedi
Joined
Feb 1, 2006
Messages
3,227
Location
Scappoose.OR USA
Thanks Tim.

That was my last resort. I was hoping to find a true audiophile with a pile of stuff to help me.

When my patent pushes a little more, I will divulge the "big deal".

My goal was a ribbon with no distortion and a frequency range of 200hz-30khz. The last thing was powering them with any standard amp in the biz. Before that though, they need to be characterized with something worth a crap.
 

NoWingsAttached

Unobtainium Member
Joined
May 21, 2006
Messages
4,776
Location
Columbia, SC
Aircraft
Air Command Tandem w/ Arrow 100hp; GyroBee w/ Hirth 65hp; Air Command Tandem w/ Yamaha 150hp
Total Flight Time
>350
I just bought a Fender Twin Reverb on Ebay, built in '68.

Now I just gotta get the Gibson pre-1973 Les Paul to go with it. Put in a few bids, but either they are broken necks, too expensive, or ambiguous serial numbers untraceable to pre '73. Or I just miss the bid. Hmm. Yama gyro gots ta come first right now, only so many projects I can support at one time. Gettin old n slow I guess.
 
Last edited:
Top