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Old 30th June 2004, 03:32 PM   #1
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Default diy tube amp

I completely new at this but very interested in building my own amp. Where would be a good place to start? I have a good background in electronics so I'm pretty confident about building the circuit.

I like building from scratch more than building a diy kit. I find that I learn more building doing everything myself. But if there are kits that you would like to recommend, please do so.

My main objective is to hook up 2 bookshelves at the moment, and in the future I may upgrade to more powerful floorstanding speakers. I've noticed most tube amps are mono or stereo, is it possible to make a 5.1 design? And how much harder would it be.

Also, I have not worked out a budget yet so I'll need some kind of rough estimate as to how much I'll need for this project.


Thanks.

Btw, I've posted a similar thread like this about an hour ago, I'm pretty sure it was in this category but I can't find it anymore. I've even searched for it, know where it went?
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Old 30th June 2004, 04:24 PM   #2
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5.1 ? you don't want to build a high power tube subwoofer amp for a first project, it would be expensive.
5 channel tube is possible.. but on one chassis it would be a monster amp, and you can easily get into trouble with hum and other parasitic noises and oscillation.
I suggest you build mono amplifiers, that way you can first power a stereo set with your amps, and later easily make more of them for your multichannel system.
Or you can use tubes for the main channels and sand (transistors) for the effects channels.

Before you can start to make price estimations, you have to decide what you want to build. SE/PP, what power range?

The main cost positions in a tube amp are:
Output transformer
power transformer(s)
filter choke (no must but recommended)
Tubes
Tube sockets
chassis

the other passive parts are much less expensive, the most expensive passive parts are the PS filter caps.

A PP EL34 or EL84 project would likely fit the bill.. with this config you get some power (important if you want to use normal speakers) and manageable cost for the trannies and tubes.

If you want monoblocks (yes!) you need a preamp for source selection and volume control. The cirucitry can be quite simple, so i think additional cost in comparison to an integrated amp will mainly be the box and small power supply. But you gain alot of flexibility! and better sound, too..
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Old 30th June 2004, 04:28 PM   #3
benny is offline benny  Australia
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Quote:
so I'm pretty confident about building the circuit.
this is a good start.. don't be overconfident though... tube amps contain slightly higher voltages than anything you've probably worked with before.

Quote:
Also, I have not worked out a budget yet so I'll need some kind of rough estimate as to how much I'll need for this project.
whatever people recomend to you, be prepared for a nasty surprise... if you're unfamiliar with tubes, you're probably unfamiliar with the cost of a tube amp... a little more expensive than a SS amp!

Quote:
Btw, I've posted a similar thread like this about an hour ago, I'm pretty sure it was in this category but I can't find it anymore. I've even searched for it, know where it went?
i done this before... i posted in one thread accidentaly, and came back the next day and couldn't find it... then i realised i'd acidentally posted in the wrong thread... maybe this your problem.

cheers
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Old 1st July 2004, 01:09 AM   #4
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Default Hmm..

Thanks for the input, but could I get some more info? Those answers really didn't enlighten me too much. (Please don't be offended) Maybe I just phrased the questions wrong. Could you give me some resources to look into? I don't even know what is SE and PP.

Also, I'm looking to build a stereo one, even though it might be much more complicated than a mono, I know I wouldn't be satisfied by a mono one.

I'm not sure how much power I'd be needing, because I'm not sure if tube amp power can be compared directly to those onkyo and denon recievers which go from around 70-100+. I'll need enough to power a pair of bookshelves (a DIY, tweeter and woofer 2way). However, in the future, I'm planning to build a floorstanding which will have 2 woofers, 2 mid, and 1-2 tweeters. I need enough to satisfy both. Not together of course.

Thanks.
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Old 1st July 2004, 07:33 PM   #5
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why wouldn't you be satisified with monoblocks? of course you need two for stereo.. and you can add as many as you need later for a multi channel setup.

about power.. well, the speaker description sounds like a low sensitivity, maybe around 90 dB. It also depends on what level you listen at.
I would target 20-30W. This will probably sound louder than a 70-100W receiver.
For this much power, you want to build a PP amp. PP means push-pull, the output stage uses two tubes working in antiphase.
Use EL34 output tubes.
here's one of many schematics for this topology and tube complement:
http://www.ndh.net/home/kboehm/EL34-S3.htm
here's more:
http://www.bonavolta.ch/hobby/en/audio/el34.htm
here's a kit EL34PP amp:
http://www.diyhifisupply.com/diyhs_ella.htm

if you build everything yourself, i guess you'd be looking at 200-300 USD for a stereo amp.. or sth like 150-250 for each mono block.
this shop:
http://www.tubesandmore.com/
carries about all you need.
A Hammond OPT costs 55 $ per channel, and a power transformer about the same.
an EL34 costs about 10 USD and each small signal double triode (6SN7 etc) about the same.

does this help?
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Old 2nd July 2004, 01:07 AM   #6
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Default A little bit..

yes this does help a little bit. But I was hoping to get more detailed resources. I'm hoping to get a good foundation before I actually start the hands on work.

If it sounds good, I'm willing to put out approx. $250USD for a stereo tube amp.
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Old 2nd July 2004, 04:06 PM   #7
benny is offline benny  Australia
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what i have learnt from the web has been from such a wide number of places that i never took note of, i can't really offer any links.

what i do recomend is buying a good book, something like 'valve amplifiers', by morgan jones. just like the internet, no single book is going to be the definitive source of information, and you are still going to have to fill in gaps with other sources, but a book like this covers a very wide range of topics, and should have you well on the way.

hope this helps a little, sorry if it's not what you want.
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Old 3rd July 2004, 05:02 AM   #8
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I was hoping to stay away from buying books becaues that would just take money away from my speakers and amp. =(

Anyways, I do appreciate your help, thanks.
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Old 4th July 2004, 12:52 PM   #9
MIKET is offline MIKET  United States
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Default A nice tube amp for $250

I'm up to the challenge
Schematic
http://gabevee.tripod.com/2a3diy.html
Output transfomers Hammond 125ESE $32 each
Power Supply Transformer Hammond 370FX 142VA, 275-0-275 @ DC ma 150, 5VCT @ 3A, 6.3VCT @ 5A. $65 each
Choke Hammond 156R 1.5H, 200ma, 56 ohms, 400VDC. $9 each
Chassis Hammond 1444-16, 10"X6"X2" $12 each
from Angela Insrtuments http://www.angela.com/
A pair of 12AX7's $13
A pair of 2A3's $65 from BOI Audio works http://www.boiaudioworks.com/index.p...AdWords&Ad=2A3

This leaves $22 for resistors and caps etc.
Actual final cost might be a little more than $250.
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Old 4th July 2004, 12:56 PM   #10
SY is offline SY  United States
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Default Books

Quote:
Originally posted by turbo_h4
I was hoping to stay away from buying books becaues that would just take money away from my speakers and amp. =(
They're the most important tool you can own.

Besides the book benny recommended, Mr. Jones has a new one out, "Building Valve Amplifiers", focused more on construction techniques, layout, and other practicalities.
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