Help a first timer to select...

[CJ900RR]

Hi!

This is my first thread, and my first serious attempt to build my first tube amlifier.

For about 3 years ago I got to listen to a DIY-tube amplifier (btw the only tube amplifier I ever have listen to) and it sounded so good! The show was over in 15 minutes but I was stucked. I need one of those

I listen to music allmost every day, and for me the quality is more important then loudness. But my economy sets some limitations and my sound-system consist of a Harman/Kardon AVR 2550 with a pair of Canton LE109. And compared to the DIY-tube i listned to, it sounds like crap...

So what I ask for is some advice for a DIY Tube amplifier, about witch tubes i should use, and mostly importent, witch construction You think would suit me. I have looked at the Internet for a week now and I cant decide. I would like a all-in-one-solution, with a schematic of input-stage, power, volyme-control etc, if that is possible.

And I must point out, im not new to electronic. I work with it and has done it for 7 years, but its mostly digital circuts and surface monted components, so some guidelines would be nice

Oh and 2 more things, a solution containing some of these tubes would be good, I can get the cheep: http://www.elfa.se/elfa-bin/dyndok.pl?dok=2011517.htm

I also have allmost unlimited acces to Caps like these in different values:



Could I use those?

Thank You for your time and best regards
Carl-Johan

[Eli Duttman]

C-J,

Check out "El Cheapo" here.

Your tube source has 12AT7s. 6V6GTs are perfect instead of 'AQ5s. It makes sense to me to source your "iron" in Europe.

[beamnet]

Don't buy those tubes! It looks like Conrad or something like it. probably very cheap chinese tubes...

I use e-bay a lot. Allso, do you have a local site with smal-ads? that has proven to me to be a very good source!

Bas

[CJ900RR]

Hi and thank You for Your replies.

First of all, Eli i think you missunderstod me (maybe because of my bad explenation skills ) but I was not looking for a "cheap" project. It's ok if it cost's a couple of hundred dollars. Even as far as up to 2000 $.

And Beamnet thank You for the tips. I will search e-bay and I have also found out that we have many good tube-dealers here in Sweden, so I will check with them first.

Well as a addon to my first post;

Im looking for a preamp, and a mono-block that matches that preamp. Just some tips about a design (and maybe schematic's if possible) that someone in here as build that You now is good

Thank You for Your time, Carl-Johan

[beamnet]

Do you know what you heard?


A good amp lets you hear very little of the amp itself. Often the amps are made in a way that they are not perfectly linear, but add a little "sweet vaccum tube distortion"

SE means more "vacuum tube sound"

PP means more output power.

Make a list of requirements:

-User interace (buttons, knobs remote control)

-inputs (phono? how many?)

-output power (are you using high effeciency speakers or not)

-output damping (determined by the speaker and filter design)

-weight/size(wife-acceptance-factor)

-looks (dull boring "mount allstuff on a copper plate" or do it the non-tube way and think how to make it pretty )

[Majestic]

Hmm... Well, as as a starter project, the "Bevois Valley" amplifier as described/designed by Morgan Jones in his book Valve Amplifiers seems to me like a good way to start out on the DIY path. He has a couple of other designs of higher power (and complexity) in there too. They seem like very well-thoughtout designs to me.

The Mullard 5-20 circuit (with a triode-strapped input) is an old but very good design using EL34's. Some might accuse it of "lacking refinement" as a design, however, because of it's age! Still, it's such a well-known circuit with good sonics that almost anyone would be able to help you with any troubleshooting that it might need along the way.

I'm sure some other similar ball-park designs have been canvassed on this very forum in the past, so perhaps one of the more experienced members could post a link or search term for you to seek out, should they think of a design that might fit your needs.


As for preamps, the excellent Aikido circuit by John Broskie is earning a great reputation by fellow DIY's on this forum (do a search for threads on it, on this site too). Given it's good PSRR, it would be easy to build and get right without having to troubleshoot annoying hum problems and the like. The fact that it also apparently sounds superb, well... I'm sure that's of interest to you too

[CJ900RR]

Originally posted by beamnet
Do you know what you heard?

A good amp lets you hear very little of the amp itself. Often the amps are made in a way that they are not perfectly linear, but add a little "sweet vaccum tube distortion"

Sadly i have no idea about what kind of tube or schematic that amplifier where made of. It was 3 years ago...

Originally posted by beamnet
SE means more "vacuum tube sound"

PP means more output power.

Ok. Well tuff call. I want good quality sound. Power is nice but not mostly importent. Noob-question ahead: is Class-A better than Class-AB?

Originally posted by beamnet
Make a list of requirements:

-User interace (buttons, knobs remote control)

-inputs (phono? how many?)

-output power (are you using high effeciency speakers or not)

-output damping (determined by the speaker and filter design)

-weight/size(wife-acceptance-factor)

-looks (dull boring "mount allstuff on a copper plate" or do it the non-tube way and think how to make it pretty )

Interface: No more than volume and input select, phono, 1 or 2. Will primarly be used for music.

Output power and output damping: No idea All i know about my speakers (Canton LE109) is the frequenzy-range, 20 - 26000 Hz and RMS of 150 Watt...

Originally posted by Majestic
Hmm... Well, as as a starter project, the "Bevois Valley" amplifier as described/designed by Morgan Jones in his book Valve Amplifiers seems to me like a good way to start out on the DIY path. He has a couple of other designs of higher power (and complexity) in there too. They seem like very well-thoughtout designs to me.

The Mullard 5-20 circuit (with a triode-strapped input) is an old but very good design using EL34's. Some might accuse it of "lacking refinement" as a design, however, because of it's age! Still, it's such a well-known circuit with good sonics that almost anyone would be able to help you with any troubleshooting that it might need along the way.

I'm sure some other similar ball-park designs have been canvassed on this very forum in the past, so perhaps one of the more experienced members could post a link or search term for you to seek out, should they think of a design that might fit your needs.


As for preamps, the excellent Aikido circuit by John Broskie is earning a great reputation by fellow DIY's on this forum (do a search for threads on it, on this site too). Given it's good PSRR, it would be easy to build and get right without having to troubleshoot annoying hum problems and the like. The fact that it also apparently sounds superb, well... I'm sure that's of interest to you too

Thank's for the links. The Aikido circuit looked intresting and i will have a closer look at it.

To both of you, and everyone else, i found this design that i found werry atempting to build; http://www.wdehaan.demon.nl/tubeamps/6336/index.html

Anyone in here who have made one of those?

Again, thank you for your time.

[beamnet]

I personally REALLY love the look of the tube.

For your speaker, you might not habe enough power, but you can very easily go ppp

the driver stage looks quite complex. maybe you wany something a lottle simpler for a first amp, because it enebles you to experiment more...

For a first stage, use 6sn7 like stage. You can pick the 6sn7, or 6j5 if you like the looks more. i used the very rare e1148/7193/2c22 tubes (have a few to sell) which are sonically superior, but require topcaps.

There are heaps of other possibilities.

Then use a good phase splitter. 6n6p is cheap ecc99 good. these amke very tough drivers. You can easily drive a lot of output tubes.

make a cool fixed bias supply. This enables you to experiment with output tubes.

I started off with a 6sn7 direct coupled to ecc99 and kt88 output and after 2 years of experimentation, i ended up quite differently.

Your speakers might like a pp stage because of the power. If you want to go SE, look at 6c33

Bas

(check the impendance curve of your speaker, it should be an easy load if you want to go tube)

[CJ900RR]

Ok. I will go somewhat with your advice and try less difficult one for a first. I found this schematic that i even seem's to understand the most of.

http://www.bonavolta.ch/hobby/en/audio/el34_9.htm

But i still have some questions (offcorse):

It says "R5 should be set for desired gain" and C3 "Should be set for an optimum square wave (1-3,3nF)"

I can check the square wave at my work but how do i know desired gain? And are these 2 values to be "lab'ed" or can i figure it out by math?

And how do i know what kind of trafos to use? I guess i could figure out the power-trafo (TR1 at power), but how about the speaker-trafo (TR1 at the amplifier)?

And finaly, what is V1, V2, V3, V4, V5, V6 and V7 and the power schematic? I have my clues but i want say because im afraid of sounding stupid

It's really nice of you to answer all my questions

And by the way, i also prefer to see the tubes, the look is hafe the charm of the tube amplifier!

[beamnet]

This design uses feedback. feedback lowers gain. It is used to linearize the amp. People have different opinions on feedback.

The square wave thing: If the output transformer starts to roll off aor has severe phase shifts in the audio spectrum, a square wave will reveal that. With the c you can alter the feedback.

The output transformer should have a primary impendance as stated in the schematic. Look for such a transformer at the suitable wattage.

The v1......v7 are the heaters of the valves. Valves have a fillament to heat their cathodes. It makes them emit electrons.

The _in my opinion- weak spot of the schematic is the phase splitter.

the input penhode might not be neccesairy. If you use a preamp

i added the schematic for my amp

Don't look at the weird tubes. The output tubes can be any good output tube. it was designed for 6550/kt88 tubes

The phase splitter is much more descent. If you make a ccs in the "tail" (replace the 10k resistor with a mosfet ccs) it will be even better!

If you like the el34, there is a big thread on it on the forum


I didn't say you should not mount the tubes on top....

Bas