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-   -   Pre-Amp For my Tubelab Simple P-P (http://www.diyaudio.com/forums/tubes-valves/217606-pre-amp-my-tubelab-simple-p-p.html)

Einric 9th August 2012 04:02 AM

Pre-Amp For my Tubelab Simple P-P
 
I currently have an Aikido All In One populated with matched 6CG7's, the real ones with the shield.
I have started ordering parts to begin the build of my TL Simple P-P.
Will my 6CG7 Aikido be ok for driving the Simple P-P?
Should I change the drive tubes to something with less gain?
I love how it sounds as is, but I will be integrating the Aikido into the same chassis as the P-P to be a nice big pile of tubes so I want it to be right.

Thanks

DualTriode 9th August 2012 06:16 AM

My thought is that a buffer with a gain of < one is all that you need. Any more gain will be burned off in the volume control and result in a reduced Signal to Noise ratio.
I use an Aikido Cathode Follower following the volume control.
DT

Davec113 9th August 2012 06:26 AM

If the simple PP has the same gain as the SSE you do not need a preamp with gain. I am running a 12BH7 driver in my SSE and it needs about 12 dB more gain and just built an Aikido with 6SN7 tubes, which are the octal equivalent of a 6CG7, so it has 20 dB gain... it is 6-9 dB too much, so not too bad... I plan on changing the driver stage (eliminating the electrolytic cathode bypass and maybe the CCS) which will lower amp gain a bit. So I agree a preamp with a zero gain buffer might be the best bet.

SGregory 9th August 2012 12:45 PM

Bootstrapped 6v6 is a good sounding one two. Zero Gain.

cjkpkg 9th August 2012 12:59 PM

Quote:

Originally Posted by SGregory (Post 3120157)
Bootstrapped 6v6 is a good sounding one two. Zero Gain.

+1 on the 6V6...I had mine running on a breadboard and it sounded terrific with the SSE, although my chassis ended up being about 1/4" too short...ARGH!!!

So now I am back to the aikido 6CG7/5687...

Next project is to get a good regulated PSU for the 6V6 and a proper chassis and get that up and running, it was THAT good.

Einric 9th August 2012 02:15 PM

So the general consensus is that I need to reduce my gain level.
OK.....so what low gain twin triode should I use in the driver stage of my Aikido to drop some gain off.
I will be using the volume control I currently have on my Aikido.

boywonder 10th August 2012 04:35 AM

Quote:

Originally Posted by Einric (Post 3120288)
So the general consensus is that I need to reduce my gain level.
OK.....so what low gain twin triode should I use in the driver stage of my Aikido to drop some gain off.
I will be using the volume control I currently have on my Aikido.

Does the Aikido build manual still have the tube table(s) in it? Peruse the table and pick some low gain combos. They will most likely require a few R changes and possibly tweaking your B+ from where you are now.

Einric 10th August 2012 01:38 PM

It does.....However they all seem to have input gain around 19db.
I am open to looking at 8 & 9 series twin triodes I just don't know whick ones sound nice.
My 6CG7's are really nice.
If I have too much gain would I be better off maybe switching to a 100k Pot from my 50K?
Then I just can't turn the knob up all the way?

boywonder 10th August 2012 03:32 PM

Quote:

Originally Posted by Einric (Post 3121498)
If I have too much gain would I be better off maybe switching to a 100k Pot from my 50K?
Then I just can't turn the knob up all the way?

That doesn't help........the higher load from the larger R pot makes life a little easier for your source, but may increase noise and you are still wasting gain since the pot will be turned way down.

Ideally you want the pot wide open/fully clockwise at your loudest listening session, since technically it doesn't make much sense to amplify the signal all over the place only to crank back the volume knob. If you never turn it up more than 12 o'clock say, you have too much gain (which is very common).

That's why unity gain preamps (buffers) are fairly popular around here. They provide enough current to drive long cables, feed a bi-amp system, etc. but don't provide any gain. You can get no gain with a passive pre (just a vol control and input selector) and sometimes this works fine, but if it cannot provide sufficient current FR can suffer.

Keep in mind that the potentiometers only subtract, both the 50K and 100K are roughly zero ohms when turned fully clockwise.

BillEpstein 12th August 2012 12:26 PM

Quote:

Originally Posted by DualTriode (Post 3119906)
My thought is that a buffer with a gain of < one is all that you need. Any more gain will be burned off in the volume control and result in a reduced Signal to Noise ratio.
I use an Aikido Cathode Follower following the volume control.
DT

Is this the kind of circuit you mention?

ACF-2 Octal Aikido Cathode Follower Kit


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