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Old 1st July 2004, 05:06 PM   #1
Klax is offline Klax  United States
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Default Multiple projects

Let me preface my post by providing some background.

My first electronics course was taken in 1972. From there I joined the military. In actuality I joined twice. The first time was the USAF as an avaiation electronics technician. My second brush with the military was the Navy. I attended nearly two years solid of basic and advanced electronics surrounding communications and cryptographic maintenance. After the Navy, I began working in the medical imaging industry. I began repairing medical x-ray equipment and moved on to MRI about 12 years ago. I build gaming computers (that rival and/or surpass Alienware, Falcon NW, etc) for friends, as a hobby. I play guitar (instrumental rock) and modify and maintain my own equipment including tube amps. I also work as a sound technician for the church I attend. Living in Nashville, TN. I work with and for pros. In other words, I'm adept enough to understand the difference between "good", "great", and "exceptional" sound. I also modify and maintain my lovely 2000 RC51 (it's a v-twin sportbike - 130hp at the tire, weighing under 400 lbs). After riding on a track, I don't enjoy street riding much anymore.

Suffice it to say, that I feel that my experience provides me with the background to build or fabricate any level of electronics involved in building a Tube amplifier. Other than my guitar amp, my experience with tubes has been 10KW - 15KW radio transmitters (42mHz - 63mHz respectively) used in MRI equipment.

Finally to the questions:

What is the highest quality audiophile grade tube amp DIY kit or project (schematics/instructions) that is available?

Are there any tube designs and/or kits for an amp strong enough to drive a PA system that would be comparable to a 400W transistor based amp?

Are there any tube designs and/or kits for a power amplifier used in automotive applications?

Many thanks in advance for your help.
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Old 1st July 2004, 06:17 PM   #2
benny is offline benny  Australia
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Quote:
What is the highest quality audiophile grade tube amp DIY kit or project (schematics/instructions) that is available?
different strokes for different blokes... y' know what i mean??? it's going to be a subjective thing this, but i'm sure people will recomend some good amps... which one is the highest quality will be personal opinions.

Quote:
Are there any tube designs and/or kits for an amp strong enough to drive a PA system that would be comparable to a 400W transistor based amp?
400W per side or 400W total so therefore 200W per side?

400W per side, i really don't know what you'd do... this would need a HUGE output tranny, or two BIG trannies paralled...

i am not familiar with otl amps so i can't say wether one of these would be possible at this power.

200W per side seems like a pretty reasonable ask though... you could do this with a BIG trannie and two pushpull paralel sets of something like KT88's...

mind you, this is going to be one very expensive amp, especially with the cost of the hefty power tranny factored in too. and with all that iron, you won't want to be moving it around too much.

Quote:
Are there any tube designs and/or kits for a power amplifier used in automotive applications?
http://members.aol.com/sbench101/Bat...s/BattAmp.gif/

this is not necesarily a car amp, but it is a 12V batery powered amp.
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Old 1st July 2004, 08:12 PM   #3
EC8010 is offline EC8010  United Kingdom
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You could make a 400W valve amplifier. To keep it vaguely sensible, it would have to be push-pull. To keep the HT down to a sensible voltage, you could parallel four, or more, pairs of KT88 running in Class AB1 configured in ultra-linear mode. But you wanted highest quality, so I suppose you want pure Class A. You'd probably need about ten pairs of KT88 to give 400W. The output transformer would have a low turns ratio, so it should be possible to make a very good component. If you really wanted super quality, you would use triodes, but they're less efficient, so you'd probably need fourteen pairs of triode-strapped KT88.

Alternatively, you could use some big transmitter triodes. You wouldn't need many 4212E to get 400W. The HT would be a lot higher (and more expensive), and the output transformer ratio would be higher.

If you've worked on small transmitters, you probably know where to get the power supply bits to go the triode route, and could search out a pair of triodes (833?) that could operate in push-pull Class A to give 400W. They would take a lot of driving, but I'm sure everybody here would love to see such a thing.
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Old 1st July 2004, 08:45 PM   #4
SY is offline SY  United States
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Quote:
To keep it vaguely sensible
No 400 watt tube amp is sensible!

Going the class A route is a difficult choice- you'd need to dissipate over a kilowatt per channel from the plates at idle (that's 30 tubes per side for KT88s!), and then there's a few hundred more for the heaters. A stereo pair would require some humongous amounts of air conditioning or location in the Arctic.

Now, three pairs of EL509s run in screen-drive class B will get you the 400 watts (actually, a bit more like 500 watts), but I know how skeptical you and many others are of such goings-on.
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Old 1st July 2004, 09:18 PM   #5
Klax is offline Klax  United States
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Perhaps Varian makes a triode that is usable for that range. I don't know how a metal triode (made for RF), would sound in an audio application. I'm not an engineer so I'm uncertain if the f0 of the tube would have any discernable effect.

6L6s operate in the 450-500 volt range and output around 25W. A 50W push pull amp could fit inside a shoe box, PS and all.

YU-204 has a plate voltage of 10K and an output of 10KW. The Housing for the YU-204 is 19x19x19 (blower vent cooling). And, the power supply for the unit was about half as large (4x as heavy though).

So for 400W, maybe I could get away with something the size of and weight about twice the size of a 400W semiconductor unit eh?

Thanks for the replys. I've been digging for weeks on this. I seem to be able to find 300B et al in kits. But then I see these $5K to $50K amps. However, there appears to be no kits, or even schematics, for those.
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Old 1st July 2004, 10:33 PM   #6
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ARC sells a 200+ WPC amp. It uses 20 6550s; 16 are signal and 4 are regulators. The Pres. of the club I belong to uses the "beast" to drive his "Maggies".

How about PPP AB1 813s in pentode mode with regulated screen grid B+?
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Old 2nd July 2004, 12:36 AM   #7
Klax is offline Klax  United States
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I was thinking of something like this:

http://www.manleylabs.com/containerpages/500_99.html
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Old 2nd July 2004, 12:42 AM   #8
G is offline G  United States
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Default Re: Multiple projects

Quote:
Originally posted by Klax
Let me preface my post by providing some background.

My first electronics course was taken in 1972. From there I joined the military. In actuality I joined twice. The first time was the USAF as an avaiation electronics technician. My second brush with the military was the Navy. I attended nearly two years solid of basic and advanced electronics surrounding communications and cryptographic maintenance. After the Navy, I began working in the medical imaging industry. I began repairing medical x-ray equipment and moved on to MRI about 12 years ago. I build gaming computers (that rival and/or surpass Alienware, Falcon NW, etc) for friends, as a hobby. I play guitar (instrumental rock) and modify and maintain my own equipment including tube amps. I also work as a sound technician for the church I attend. Living in Nashville, TN. I work with and for pros. In other words, I'm adept enough to understand the difference between "good", "great", and "exceptional" sound. I also modify and maintain my lovely 2000 RC51 (it's a v-twin sportbike - 130hp at the tire, weighing under 400 lbs). After riding on a track, I don't enjoy street riding much anymore.

Suffice it to say, that I feel that my experience provides me with the background to build or fabricate any level of electronics involved in building a Tube amplifier. Other than my guitar amp, my experience with tubes has been 10KW - 15KW radio transmitters (42mHz - 63mHz respectively) used in MRI equipment.

Finally to the questions:

What is the highest quality audiophile grade tube amp DIY kit or project (schematics/instructions) that is available?

Are there any tube designs and/or kits for an amp strong enough to drive a PA system that would be comparable to a 400W transistor based amp?

Are there any tube designs and/or kits for a power amplifier used in automotive applications?

Many thanks in advance for your help.
Since most SS amplifiers are rated at peak power you would probably only need a 100 - 150 watt tube amp to get the same sound pressure level you get with a 400 watt SS amp. Something with say four EL34s or 6550s per side in a PP arrangement would get you close I think. I'm not sure where you would get the output transformers or the power transformers though. They would cost a considerable amount of bucks. I would recommend a pair of Paramours from Bottlehead for home "audiophile" type listening though. That or a Zen amp from Decware. Both are kits that are highly thought of by a lot of people that are reasonably priced. Your miles may vary. You will also need highly efficient speakers with either kit. About 96dB 1w/1m should do it.
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Old 2nd July 2004, 01:50 AM   #9
Klax is offline Klax  United States
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Thanks for the input Gavin. The 400 watt project is for a PA system. I doubt that the efficiency of the cabs is to the level of 96dB 1w/1m.

While browsing the Manley site, I noticed that they also are selling a 300B monoblock. Are these specs typical of any kit monoblocks? Because the Manleys are $2500 each. Most of the kits that I've seen range between $300 and $600.

Vacuum Tubes: 2 x 300B (Output), 1 x 6SN7 (Driver), 1 x 6SL7 (Input), 2 x 5U4 (Rectifier)

Output Power @ 1Khz with 5 dB FeedBack in SINGLE-ENDED: 11 Watts @ 3% THD
Output Power @ 1Khz with 5 dB FeedBack in PUSH-PULL: 24 Watts @ 1.5% THD.

Frequency Response with 5 dB FB in SINGLE-ENDED: 15 Hz - 15 Khz +/- 0.5 dB (measured at 5 watts)
Frequency Response with 5 dB FB in PUSH-PULL: 10 Hz - 20 Khz +/- 0.5 dB

GAIN: 20db w/10dB FB setting; 30dB w/0dB FB setting in SE mode

Input Sensitivity with 5db FB SINGLE ENDED: 700mV
Input Sensitivity with 5db FB PUSH-PULL: 450mV

S/N Ratio: SINGLE ENDED: 83.5dB Ref. 1W; 2.83v//8 ohms,20KHz BW; 5dB FB.
PUSH-PULL: 85.4dB Ref. 1W; 2.83v//8 ohms; 20KHz BW; 5dB FB.

Dynamic Range: SINGLE ENDED: 94dB Ref. 3% THD; 20KHz BW; 5dB FB.
PUSH-PULL: 99.5dB Ref. 1.5% THD; 20KHz BW; 5dB FB.

Input Impedance: 100Kohm, direct coupled.

Load Impedance (switchable): 4 to 12 Ohms appropriate for 4 & 8 ohm speakers
12 to 20 Ohms appropriate for 16 ohm speakers


Power Consumption: 240 Watts max.

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Vacuum Tubes: 2 x 300B (Output), 1 x 6SN7 (Driver), 1 x 6SL7 (Input), 2 x 5U4 (Rectifier)
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Old 2nd July 2004, 02:58 AM   #10
G is offline G  United States
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Manley is one of the more expensive manufacturers of tube amps so I would say no that is not typical. It's not that unusual though. There are a lot of companies out there that specialize in highway robbery. Some don't though. When I recommended efficient speakers it was for home speakers to match up with one of the low powered kits I recommended for your personal use. Both of the kits are reasonably priced and sound good. A good way to get your feet wet without too much risk. You also might be surprised at how efficient those PA speakers are. A 100 watt tube PA amp would drive them. I've just never seen one. I'm sure someone makes one though. Cheers.
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