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Old 27th June 2012, 06:42 AM   #1
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Default First Amp Build, (But not complete beginner to electronics)

Hey this is my first post here...so, hello!

I tried to find help on the ampgarage.com and they sent me here..... so here it goes

I was fumbling around the web for some simple diy stereo tube amplifiers and came across this schematic

http://www.specimenproducts.com/wp-c...atic-photo.jpg

Its looks really simple, and I have the time and money to make it......also a good friend of mine has A LOT of experience with amps so he would be able to help me if I ran into trouble..

My major questions are
Is it easy to make something like this/good for a beginner?
Any ideas if it would even sound good/be worth making in the first place?
OR should I just go with a kit of some sort?

Thanks in advance for all and any advise, Anthony
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Old 27th June 2012, 09:41 AM   #2
DF96 is offline DF96  England
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Low power directly-heated triode SE is not a good place to start, IMHO. You would need a very small room or very high efficiency speakers. Better to start with something cheaper, make your mistakes, learn to debug valve circuits, then try something a bit bigger.

I must admit to bias: I would not want an SE amp anyway, except in a wireless set where fidelity is a secondary issue.
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Old 27th June 2012, 12:25 PM   #3
Fenris is offline Fenris  United States
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One of Tubelab's kits is a pretty good place to start. Or an EL84 type amp - there's lots of different designs, the tubes are fairly inexpensive, and there are less "gotcha"s.
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Old 27th June 2012, 03:11 PM   #4
rmyauck is offline rmyauck  Canada
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Welcome!

The 17W/CH Simple PP EL84 amp from George @ tubelab.com can be had for $100 for a board & kit of parts less tubes and transformers or $35 for the board only. It could be built for under $400 with quality Output Transformers.

You can't beat the sound quality of EL84 tubes as a first amp if that's enough power, and if you research nobody dislikes their sonics. That was my first tube amp( vintage Eico HF-12's) , if you don't count a 1949 RCA AM/FM table radio with an RCA input that got me hooked on the Tube sound.

Up to 17W/ CH will power more speakers than the SE your looking @ with 3W/CH. George's non DHT SE amp boards will give up to around 10W/CH though and uses more affordable non DHT tubes.

He does have a DHT board too for the 45, 2A3, & 300B tubes.


It all depends on your speakers. Sometimes more power reserve is nice to have.

Tubelab Home

Tubes & Transformers

Lots of support on his boards & board kits.

Tubelab - diyAudio

Lots of support on his boards & board kits.

Some people like the sound of SE, but as stated you need very efficient, usually big and $ speakers. PP is more efficient so came out back in the day for more affordable power. With 2 or more pairs of Output Tubes per channel the design cancels out most distortion so gives a different sound than SE. Most are class AB amps for maximum power.

If you want or need more power perhaps a good compromise is to run a PP amp in class A for an almost SET (Single Ended Triode usually using DHT tubes) sound quality. Even better with DHT output tubes , but more pricy. Non DHT tubes can be strapped for Triode operation for a low cost alternative, but are usually not quite as good sonically as DHT tubes.

Anyway google class SE, PP, class A & AB amps.


Output transformers are what make a tube amp so really research them before spending $. The more expensive ones usually have more mass and more interleaving in the windings adding to the cost. The are EI cores, C cores, and Toroidal designs, with the vintage style EI being usually the most affordable and popular in NA anyway.

Hope that helps!

Randy

Last edited by rmyauck; 27th June 2012 at 03:23 PM.
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Old 27th June 2012, 03:24 PM   #5
Merlinb is offline Merlinb  United Kingdom
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You might like to look at the 'Harmless' amp, which was designed specially for beginners (possibly with some interest in guitar- since you've been spotted at ampgarage!), and has good support via the ax84 forum:

Build document:
http://ax84.com/static/harmless/harmless_r0.pdf
Original site and explanation:
CopperAmps - "Harmless" Stereo Amplifier Project
Forum:
AX84.com - The Cooperative Tube Guitar Amp Project
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Old 27th June 2012, 10:30 PM   #6
tomchr is offline tomchr  United States
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I don't see anything grossly wrong with the schematic posted in Post #1. It's a pretty straight-forward SE DHT design.

Yeah.... Single-ended directly heated triode amps don't offer much output power. My 300B amp maxes out around 8 W. But then, I'm using it with 87 dB efficient speakers (not all that efficient, actually) in a small-ish living room (16 sq meters or so). And I'm not looking to rock the house off its foundation. My setup is plenty loud. Loud enough to make my ears ring (100+ dB(A) SPL).

I second looking at Tubelab's SSE design. It's a good amp.

~Tom
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Old 27th June 2012, 11:39 PM   #7
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Let us not forget this kit - cheap, easy to build, sounds nice as it is but can be better with better capacitor and trannies.

K-502 kit
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Old 28th June 2012, 01:46 AM   #8
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I have to agree with rmyauck . el84 pp is a great place to start. As you can see on the site you get a great pc board with the bug all shook out and teck help who can get you up and running .This allowes you the chance to tube role then cap changes . Learning about the hobby with a strong mule to work with . Besides tubelab a good guy.
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Old 29th June 2012, 03:25 AM   #9
garbage is offline garbage  Singapore
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Quote:
Originally Posted by agreco1489 View Post
Its looks really simple, and I have the time and money to make it......also a good friend of mine has A LOT of experience with amps so he would be able to help me if I ran into trouble..

My major questions are
Is it easy to make something like this/good for a beginner?
Any ideas if it would even sound good/be worth making in the first place?
OR should I just go with a kit of some sort?
Hi Anthony

Welcome to the forum!

The 2A3 is a popular amp, but you will need reasonably sensitive speakers to go with it. So, the choice of amp is really dependent on the speakers you intend to use.

It's definitely worth the build. With a lower B+ requirement, you can use nice PIO capacitors for the power supply, film/oil caps in the cathodes, etc. Supply should be cheaper to build than a design with a higher B+.

Regarding a kit or DIY, well... both allows you to learn, but DIY may take longer to build as you will need to get all the parts, layout, etc.

Since you have a friend to help, I guess DIY may be better. There are also improvements that can be made to the circuit, such as have a constant current at the driver. The schematic does not show the power supply portion, but it should not be difficult to come up with one. You can download psud2 to simulate different supply arrangements. While there, check out the 6c6 datasheet. It appears to be in a triode strapped mode as a driver to the 2A3 in the schematic that you posted.

Main thing is to have fun while building the amp! Cheers!
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Old 29th June 2012, 03:37 AM   #10
tomchr is offline tomchr  United States
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I'd probably go with an ECC99 for the driver. They're current production tubes made by JJ.

~Tom
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