Please recommend me an amplifier design.

[Eli Duttman]

Originally posted by JayH3
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.

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?

[JayH3]

Originally posted by Eli Duttman



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?

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.

[Eli Duttman]

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.

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.

[JayH3]

Originally posted by Eli Duttman


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.

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

[Eli Duttman]

Originally posted by JayH3



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

Look here. The volume control circuitry at the I/P of "El Cheapo" is exactly this type.

[JayH3]

Originally posted by Eli Duttman



Look here. The volume control circuitry at the I/P of "El Cheapo" is exactly this type.

Thanks Eli. That was helpful.

[John L]

Originally posted by Eli Duttman



Look here. The volume control circuitry at the I/P of "El Cheapo" is exactly this type.

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.

[Ty_Bower]

Originally posted by John L
so how much does this "El Cheapo" put out?

Data sheets say the 6AQ5 (and 12AQ5) can be used for about 10 watts in push/pull configuration.

http://www.nj7p.org/Tube4.php?tube=6AQ5

[Eli Duttman]

Originally posted by John L


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.

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]

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.