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Old 29th December 2003, 09:33 PM   #1
Ysabban is offline Ysabban  Israel
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Question Help me choose a Tube Amp. Project

Hi

As i wrote on pervious threa
i want to build a tube amplifier to use with my
87dB/w/m 6oh 50w speakers (sherwood)
my room is about 3meters on 4.5 meter
and the music i hear is mainly Rock and Alternative rock
my sources are (Sanyo L60 turntable, and a CD player)
most of the amplifiers schemes and project i saw was 14-8 watt (WPC for stereo amplifiers)

I read some info and reviews and i found the the 300b SE
is the most preffered amplifier but i dont know if 8-10wpc output is enough
can you help me choose a tube amp. that will give me the best preformance from my speakers

as you can see there are many schemes and project over the internet
but i still dont know what will be the best for me
please help me
maybe i am looking on the wrong tube type?

i have add below links to the amplifier projects i read and liked so that you could give me recommendations

Thank you
yehonatan sabban


Derek Walton 300b page
http://indigo.ie/~walton/300b.html

Andrea Ciuffoli
http://www.audiodesignguide.com/my/pse.html

This 18Wpc 300b amplifier
http://www.enjoythemusic.com/tubelust/thorsten300b.jpg
http://www.enjoythemusic.com/tubelust/300bschem1.gif
http://www.enjoythemusic.com/tubelust/300bschem2.gif

another 300b
http://members.home.nl/deckersmoll/grand_olivier_en.htm

and there is also Dave Ewing's #00b amplifier
http://www.geocities.com/k4de/

this is 329b amplifier
http://www.pmillett.addr.com/829b_amplifier.htm
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Old 29th December 2003, 09:55 PM   #2
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6L6 PP (UL or pentode).

Tim
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Old 29th December 2003, 10:16 PM   #3
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I have used an 8W amp on 87dB speakers (though my room is bigger than yours). I too mostly listen to rock. I don't think a 300B SE will produce satisfying sound. I currently listen to 96dB speakers on 3.5W amps (1/2 the power, 8 times the sensitivity), and I still wish sometimes that I had a more powerful amp (or higher sensitivity speakers).
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Old 29th December 2003, 10:18 PM   #4
Previously: Kuei Yang Wang
 
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Default Re: Help me choose a Tube Amp. Project

Konnichiwa,

First, from experience, with 87db/W/m you need as much power as you can get hold of. With 300B's this means PSE, BUT PSE Sounds MUCh, MUCH worse than SE and in fact, at that point you are better off going Push Pull (I am listening to Push-Pull 45's with 96db/1W/m sensitive open baffle speakers right now - sounds as great as anything i had in my system).

I remember this Amp well. It drove some Watt/Puppy Inspired Speakers (93db/1W/1m 4 Ohm) and mamanged a credible job, but tended to run out of steam when I had really big stuff (Mahler, Ravel/Mussorsky, St Saen) playing.

I think you would be better off with a well designed 2A3 PP Amp (which will cost a lot less than a decent 300B PSE Amp) using "any old EL34 PP Output transformer" and Sovtek 2A3's while spending your money on better (and thus invariably more sensitive) speakers.

If you must have loads of power, consider the 6S33, look here:

http://diyaudio.com/forums/showthrea...822#post285822

Sayonara
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Old 29th December 2003, 10:28 PM   #5
Ysabban is offline Ysabban  Israel
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Thanks

if i remember correct

my target is to produce sound level 0f 100dB (which is very loud i guess (120db - jetplane)
and as i saw on other threads

87db - 1w
90db - 2w
93db - 4w
96db - 8w
99db - 16w

so getting a amplifier with 16w output is enough? and i right?

but i realy dont know what the 6 ohm means?
i saw amplifier with 4 ohm and 8 ohm,
if i connect my 6ohm speakers to an 8 ohm amplifier output' is it o.k?

and as for the 6l6pp do u have any source for schematics
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Old 29th December 2003, 11:32 PM   #6
Ysabban is offline Ysabban  Israel
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Default Re: Re: Help me choose a Tube Amp. Project

Quote:
I think you would be better off with a well designed 2A3 PP Amp (which will cost a lot less than a decent 300B PSE Amp) using "any old EL34 PP Output transformer" and Sovtek 2A3's while spending your money on better (and thus invariably more sensitive) speakers.


for all the 2a3 Amplifiers i saw their output is between 3-6.5w
this is less then the 300b,

if you can direct me to a better schematics, it will be great!!

and for the 6L6 PP , what schematic you suggest?
i have found one schematics on

http://babelfish.altavista.com/babel...p=fr_en&tt=url

(sorry for the long url but i translated from french to english using babelfish)

Thank you
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Old 29th December 2003, 11:52 PM   #7
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Search for some... thousands to chose from...

Tim
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Old 30th December 2003, 12:40 AM   #8
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Hi,

Quote:
I think you would be better off with a well designed 2A3 PP Amp
Couldn't agree more...more than ample for my bedroom two way 88dB/W speakers.

Cheers,
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Old 30th December 2003, 05:48 AM   #9
arnoldc is offline arnoldc  Philippines
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may i ask about your experiences between PSE 2A3 vs. PP 2A3?
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Old 30th December 2003, 09:32 AM   #10
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Default Re: Re: Re: Help me choose a Tube Amp. Project

Konnichiwa,

Quote:
Originally posted by Ysabban

if i remember correct

my target is to produce sound level 0f 100dB (which is very loud i guess)
Hmmm. 100db WHAT?

100db short peaks or 100db sustained average SPL? At 1m Distance or where you are sitting? The Milkfloat Driver calculation you present is mathematically correct, but irelevant to the topic.

At a classic concert with large scale music I measured a highest AVERAGE Sound Level of around 90 - 92db on the climaxes. Knowing the ballistics of the meter used AND the dynamics of live music I expect at least 10db higher peaks. In recorded music I usually find a crest factor (peak to average ratio) of around 10db.

Further, each time you double the distance to the speaker you loose 6db SPL in normal free field conditions. Using a stereo pair of speakers in a room reduces the drop in SPL and boosts SPL, but it remains that with around 3m listening distance you need a 1m/SPL at least 6db higher than that desired at the listening position.

So, let's calculate what is needed for 100db at the listening position with a 10db crestfactor. First, peak power is 3db higher than the RMS power, so we need to reproduce 110db peaks but only 107db "RMS" at the listening position. In addition we need to account for the drop in SPL with Distance, so we add another 6db to give us an SPL requirement per stereo Speaker of 113db/1m at rated amplifier power. Assuming a 20W RMS Amplifier (or 13dbw) we require a Speaker pair with 100db/W/m sensitivity.

A Speaker with 87db/W/m would require an amplifier with 26dbw output power or 400 W RMS, assuming the speaker could handle this kind of power and/or would not alrady heavily compress.

If we relax our requirement to 92db at the listening position with 10db crest factor we still need 99db "RMS" at the listening position and around 105db/1m. This can be achieved by using for example a 95db/W/m Speaker and an amplifier with 10dbw Power (eg. 10W RMS) or an 87db Speaker with with 18dbw Power (eg. 65W RMS).

Quote:
Originally posted by Ysabban

so getting a amplifier with 16w output is enough?
MOST LIKELY, NO.

Quote:
Originally posted by Ysabban

but i realy dont know what the 6 ohm means?
i saw amplifier with 4 ohm and 8 ohm,
Would you feel it a good idea to put a 120W Lightbulb into a fitting rated at 80W? A Speaker with a nominal 6 Ohm Imepdance usually has impedance drops to below 4 Ohm and belongs really onto the 4 ohm Tap.

That said, sometimes the subjective percieved effect is better with a lower impedance speaker on the higher impedance tap. In most cases Valve Amplifiers are tolerant of even short circuited outputs and thus you cannot easily damage things by connecting the speaker with the wrong impedance, but the sound may not be good.

Are you sure that you should attempt to build a Valve Amplifier, with lethal voltages inside from scratch (as opposed to a kit) if you do not know the basics of electronics? I would advise against it. It may be better (and safer to you and your loved ones) to start with a kit.

Given your speakers, how about the DIY HiFiSupply "Ella" Amplifier? This will give 40W in Ultralinear mode and maybe 15 - 20W in triode connection and at a later stage, when you have more experience, you could convert the Amplifer to use 300B's in Push-Pull and hardwire the entire circuit for better performance.

http://www.diyhifisupply.com/diy_kits/the_ella.html

If you where to purchase better Speaker (better automatically means higher sensitivity, if you accept that lower distortion and compression mean "better") you might be able to use the "Joplin" 2A3 PP Amp from DIY HiFisupply, I use a modified version of this myself, currently with 45's but I can fit 2A3's and 300B's also.

http://www.diyhifisupply.com/diy_kits/the_joplin.html

My Joplin through the times and mods....

http://www.diyhifisupply.com/KYWJoplin/KYW.htm

Quote:
Originally posted by Ysabban
for all the 2a3 Amplifiers i saw their output is between 3-6.5w
this is less then the 300b,
With my own Joplin Amp I get around 10W RMS if fitted with 2A3's, 12W RMS if fitted with 300B's and around 6W RMS if fitted with 45's. Please also note that I recommended to use the 2A3 PP Amplifier in conjunction with better speakers. A 2A3 PP Amplifier is much cheaper to build than a 300B SE Amp and can sound very good.

Quote:
Originally posted by arnoldc
may i ask about your experiences between PSE 2A3 vs. PP 2A3?
I have compared 300B PSE vs. SE (in the same Amp - I literally removed one valve and connected the 4 Ohm Speakers to the 2 Ohm Tap) and various SE vs PP (2A3, 45, 10/VT25, 300B, 845, 813).

Most PP Amplifier literally suck, not sure why. I found that certain direct and transformer coupled PP designs (like the Amity from Lynn Olson) have most of the positive attributes of SE Amp's with non or very little of the negative attributes of PP Amp's.

PSE Amp's can sound okay on some recordings, on others the loss of resolution and transparency is not small. Comparing the Audio Note Japan Baransu (300B SE) to the more expensive Kegon (300B PSE) on suitable speakers (like Avant garde Duo's) illustrates exactly what I mean.

I hope this helps.

Sayonara
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