• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Please recommend me an amplifier design.

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E

Eli Duttman

Member
Joined 2004
JayH3 said:
I think I have made a decision.

I will use this circuit:
http://www.diytube.com/st70/diytube_st70_B.pdf

With these transformers:
http://store.triodestore.com/sttrbu.html

And this power supply board:
http://store.triodestore.com/st70capupgrade.html

Does anybody have any final suggestions before I start ordering parts? Thanks to everyone for the help.
Click to expand...


Dude,

When you started this thread, you indicated that an "integrated" amp is what you wanted. A Dyna ST-70 or "clone" is a stereoblock power amp. What are you going to do for source selection and listening level control?
 
J

JayH3

Member
Joined 2008
Eli Duttman said:



Dude,

When you started this thread, you indicated that an "integrated" amp is what you wanted. A Dyna ST-70 or "clone" is a stereoblock power amp. What are you going to do for source selection and listening level control?
Click to expand...


I realize this is just a power amp, but I also realized it was getting to be not worth it and maybe unlikely to find exactly what I want and not having the knowledge yet to design from scratch.

I will only have one input so I will need no source selection. That will also be one less thing the signal has to go through.

I will first try running direct and using a stepped attenuator for volume control. If that doesnt work out too well a preamp would be my next project.
 
E

Eli Duttman

Member
Joined 2004
I will first try running direct and using a stepped attenuator for volume control. If that doesnt work out too well a preamp would be my next project.
Click to expand...

If your only source is a CDP, a stepped attenuator mounted in the power amp's chassis may well be sufficient. ;)

Commercial CDPs can drive the IHF "standard" 10 KOhm load. Therefore, that's the attenuator value I recommend. Cap. couple the attenuator wipers to the I/P grid leak resistors. Size those coupling cap. so the high pass poles formed by the caps. and the grid leak resistors "corner" just below 20 Hz. The filters protect your O/P trafos against core saturation. Good channel to channel balance requires the high pass caps. be reasonably well matched. The use of 1% tolerance metal film parts in the grid leak positions is necessary, for both low noise and good channel to channel balance.

BTW, paper in oil (PIO) dielectric parts are a reasonable choice in the high pass filters to smooth out digital harshness.
 
J

JayH3

Member
Joined 2008
Eli Duttman said:


If your only source is a CDP, a stepped attenuator mounted in the power amp's chassis may well be sufficient. ;)

Commercial CDPs can drive the IHF "standard" 10 KOhm load. Therefore, that's the attenuator value I recommend. Cap. couple the attenuator wipers to the I/P grid leak resistors. Size those coupling cap. so the high pass poles formed by the caps. and the grid leak resistors "corner" just below 20 Hz. The filters protect your O/P trafos against core saturation. Good channel to channel balance requires the high pass caps. be reasonably well matched. The use of 1% tolerance metal film parts in the grid leak positions is necessary, for both low noise and good channel to channel balance.

BTW, paper in oil (PIO) dielectric parts are a reasonable choice in the high pass filters to smooth out digital harshness.
Click to expand...


Do you know of any schematics online depicting what you just explained?
 
E

Eli Duttman

Member
Joined 2004
John L said:


so how much does this "El Cheapo" put out? And just how difficult to construct? Since I am a first timer, you will have to speak slowly and use only single syllables.
;) :xeye:
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The 'AQ5 is essentially a 6V6 in a 7 pin mini package. A triode wired "El Cheapo" is good for an honest 6 WPC. Use the DynaClone O/P trafos and ultralinear wired "finals" and 12 WPC are about what you get.

EC's O/P tubes are set up in what I refer to as Class "Ab" (AKA "shallow" Class "A"). Except when peak power O/P is called for, both O/P tubes conduct. At peak power O/P, the "finals" do alternately cut off.

Building an "El Cheapo" is definitely going to test a 1st time builder, but the challenge is definitely managable. Also, help is available, on the linked site.
 
John L

John L

Member
Joined 2001
ai-jane.org/forums/index.php
I will keep all this in mind guys. But first I am going to build George's SimpleSE amp. His directions are so complete that it would be hard to screw up.

Have you seen his instructions located here? They are the most explanatory of any I have seen anywhere. He will have more of his DIY amps made than just about anyone else, because of his documentation, and meticulous care. If everyone did what he did, there would be far more DIY tube projects out there completed.
 
C

Carlp

Member
Joined 2006
FWIW, I'm fairly new to diy audio but I built an El Cheapo and can vouch for it's buildability (???) and value. I built one (triode wired) with partially scavenged parts for under $200 and with my 8 ohm 89-90 dB speakers it's plenty loud for me. You don't say much about what you listen to and how loud, so it's hard to say if it would suit your needs. VERY quiet background, very "black" and quite nice sounding. I haven't tried any of George's designs but he seems well respected and I'd bet they are good. Note there is a TON of good background info and discussion on the El Cheapo thread Eli gave you.

Carl
 
John L

John L

Member
Joined 2001
ai-jane.org/forums/index.php
Carlp said:
FWIW, I'm fairly new to diy audio but I built an El Cheapo and can vouch for it's buildability (???) and value. I built one (triode wired) with partially scavenged parts for under $200 and with my 8 ohm 89-90 dB speakers it's plenty loud for me. You don't say much about what you listen to and how loud, so it's hard to say if it would suit your needs. VERY quiet background, very "black" and quite nice sounding. I haven't tried any of George's designs but he seems well respected and I'd bet they are good. Note there is a TON of good background info and discussion on the El Cheapo thread Eli gave you.

Carl
Click to expand...

I know. It's almost too overwhelming at first glance. Someone perhaps should do like George did, and build one, along with enough pictures to make it easier to follow.

Having read George, and being an amateur photographer, I can appreciate what he is doing. He uses a tripod, takes pics at highest resolution, under a combination of existing light and some artificial light, usually at long exposures. And he takes lots of them, so he can pick and choose.

Most people don't think about the teaching aspect of the pictures, which are worth more than a thousand words each. People really appreciate this.

I'll take the time and go to the El Cheapo thread and try to wade through it. I have it bookmarked.

thanks for the help.
 
J

JayH3

Member
Joined 2008
Ty_Bower said:


Do a little research and consider whether you might want to experiment with a 5751 in place of the 12AX7, and a 12BH7 in place of the 12AU7. You might also be able to use an ECC99 in place of the 12AU7.
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I was thinking of experimenting with different tube types but I think I want to follow the design closely first and make sure everything is working as it should, then experiment.

What I am more concerned with is I think (but not sure) that the 12ax7 in this circuit is used as a phase inverter and eurotubes says to use a balanced tube for the phase inverter. Just want to make sure I am getting the correct part before I order.
 
C

Carlp

Member
Joined 2006
Someone perhaps should do like George did, and build one, along with enough pictures to make it easier to follow.
Click to expand...

John,

I have parts for an "as designed" build (with the Jim McShane parts and the z565 trafos) and could do that when I get around to building it (small kids, you know...). I also wrote a summary of some of the key design consideration posts for the El Cheapo thread that I intended to post to a web site, but then they switched hosting systems not once but twice and I now need to re-check page references and just haven't had the heart to do that. Maybe you've inspired me to find some time to get back to that.

Carl

PS - if you or anyone else wants it, I'd be happy to send a PDF of my un-revised summary and also build notes for El Cheapo.
 
G

G

Member
Joined 2002
JayH3 said:
Just ordered all of the parts I need for the build...close to 700$. Hopefully this will reinstill my love of listening to music that solid state has killed.

Any idea how this will compare to commercially available amplifiers?
Click to expand...

It will blow the doors off anything you can buy at best buy or any of those other sand electronic emporiums. That is as built. Once you get into triode strapping and tube rolling you might just pass out from the ecstasy.
 
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