6SL7 instead of 6N1P in this schematic?

[bradberry00]

Cool! This will primarily be a phono amp with a grado ph-1 phono pre in front....and possibly an ipod from time to time (will the internal amp of the ipod be enough?)

one more question, and this may be crazy talk...to double the gain, could i run a 6sn7 for each channel wired in parallel...my brain is just working, might be more work than its work.

I may just build it with the 6n1p first and build a second later.


thanks so much for you help so far!
-david

[Jebem]

Concerning the sound quality... The 6SN7 is one of the most linear tubes ever made.

The sound is very good to my ears, and it can beat the 6N1P when properly implemented.
You may like to try some NOS tubes if you fancy paying for them, instead of the chinese and russian specimens.

That said, the 6N1P is also an excellent tube, more modern, showing very low internal resistance and medium amplifier factor, very good for a driver stage, and usually very well manufactured in the russian motherland..

[bradberry00]

while I am on a question asking roll...I am pricing parts for the build and seeing what I have in my parts pile (from building guitar amps) and I found two extra chokes. Looking at the schematic I posted, it calls for a 10H 200mA choke. I would like to use what I have on hand being a pair of 5H 120mA 115 Ohm chokes. would a pair of these run in series equalling 10H work even though the current rating would be lower than called for, is 120mA enough?

thanks
-david

[Jebem]

Well, looking into your schematic table for the cathode voltage, the worst case scenario using 470 ohm resistor (560 + 3K in parallel) will give about 77mA per output tube, and about 66mA per tube if running the cathodes at 560ohm.
So, the total output tubes current will be a minimum of 132mA or 154mA depending on the bias you set.
The input tubes will consume a minimum of 8.8mA.

So the total current will be about 162mA minimum on the worst case scenario.

I would use a minimum choke of 250mA to have some headroom on the power supply. A stressed power supply will kill the amplifier ability for great sound.

Also make sure the chokes you select are appropriate for CLC filters (Capacitor input, as stated in the schematics), as it are different (at the iron construction and used air gaps) from the ones we use for LC filters (Choke input). This is just a optimization, but it counts for the final sound.

As a temporary fix, You may use your two 5H chokes, one per channel, but then You need two output capacitors (the one referenced as 100uF in the schema).
This will be a better solution, as You will have independent filtering per channel, despite only using 5H / 100uF filters, because the load current per channel will also be half of the calculated value.

One side note, make sure the power supply caps can stand a minimum of 500Volt, because the maximum unloaded voltage can be as high as 490Volt (350VAC times 1.414).

Cheers.

[dickot]

Great thread...8^)

[bradberry00]

Nice...now I just need to finish up a project I am currently working on and try to put together all this information!

[Jebem]

Originally Posted by bradberry00

one more question, and this may be crazy talk...to double the gain, could i run a 6sn7 for each channel wired in parallel...my brain is just working, might be more work than its work.
-david

Unfortunately to have more gain You actually need two stages one after another.

Paralleling the tubes will give You a lower internal resistance and double the anode current of the stage; also theoretically the noise can be lower too.

Cheers,
Jose

[bradberry00]

I am nearly ready to order the parts for this build....what should the voltage rating be on the power supply caps? will 500volt be enough for the 100uf cap? I am planning to run this power transformer http://www.classictone.net/40-18029.pdf

thanks,
-david

[fp2000]

I'd like to know if there has been some progress and if you already have heard how it sounds so you can provide feedback. I am planning on doing something similar.
For the 400V rating cap I think 500v will work just fine, but if you want extra protection you can always run two 200uF in series with a rating of 350v or maybe higher if you have any available. two 350v will take 700v.
let us know on the progress