6n6p tube as output tube for small guitar amp

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I am hoping to attract Waveborne's attn with this -- but of course I am open to all input.

I would like to use the 6n6p in a "flea-power" guitar amp like the AX84 firefly. I have asked folks in that forum -- but no one seems to have the experience with the 6n6p. Among my questions are:

1. Best output impedence for the 6n6p in this application. Given that it is a guitar map - some level of mild saturation is desired.
2. Recommendations for preamp tubes to "overdrive" but not necessarily distort the 6n6p.
3. Boosting 2nd harmonic - what would be the best way to boost the 2nd harmonic of this tube when used at the output? I want to tune this amp for use with single coil pickups which benefit IMHO from a "dark" sounding amps.

Thx much.
 
My thought is to parallel the two sections to get a reasonable output impedance. For hi-fi, the triode seems to like a lower voltage, higher current idle condition (maybe 20mA, 110V) which also necessitates a low grid voltage. For your application, a higher voltage lower current idle condition will satisfy your drive/2nd harmonic requirements better. But this makes the output impedance suffer. Hence the suggestion to parallel sections.
 
You will get more 2nd harmonic distortion in SE mode than PP, but you will also get more susceptance to line frequency noise coupled from the PS.

Operating in the non linear portion of the plate curve will give more even harmonic distortion as well, but it limits output current as it pushes you into a lower bias configuration. As zifgzagflux stated, operate with higher voltage and lower current. The tubes are relativly cheap, so you could parallel two tubes (4 triodes).

I don't think the impedance is that crutical since you can choose the OPT to support it, unless you are thinking OTL.

How much power do you want to achieve?
 
Sure, if to go for 2'nd harmonic SE amp is desired; and paralleled triodes will give you more power.

A typical isolation transformer with 120V secondary will give you 170V rectified, it is what you need for 6N6P output.

I would try a typical 4K SE transformer, individual 390 Ohm in each cathode, or 6V 15 mA bulbs instead of them.
 
I just happen to have a firefly sitting on my desk untested. You may need to tweak the bias, and account for the 6.3v heaters and pinout of the 6n6p's but otherwise I think the circuit would work just about as-is.

If you're just trying to save $ you can use 9AU7's for the output. They can be found for $1 but you'll need a separate heater voltage.
 
typical 4K SE transformer, individual 390 Ohm in each cathode, or 6V 15 mA bulbs instead of them.

Thank you much - that will save me many hours - much appreciated. What Russian triode(s) would you recommend trying to *over*drive (and *mildly* distort) the 6n6p?

Gimp -- I would say anything over .75W would be *gravy*. Also -- I AM thinking OTL as well - I guess - but isn't one of the main reasons for OTL more linear response with LESS distortion -- wouldn't it defeat my purpose in the end or is there a way to allow the 2nd harmonic through in OTL? That being said -- I am REMAIN interested in 6n6p OTL -- it is still of interest for a mostly clean sort of amp or preamp. thx.

Thanks much to all -- I successfully snared the two gents I wanted to talk to about this :D.
 
Is the 6n6p really a ECC99?

Seems to me there is much confusion about Russian triodes -- take 5 EBAY vendors and they all claim different "equivalents" for the various tubes ...

For example -- the latest seems to call the 6n6p a ECC99. What is the opinion here? I am not sure I really have a reference point to know *what* a ECC99 is? Some places I read say it is an audiophool's 12AU7 but the specs don't seem to support that.

At least in my mind it is time to look at these tubes as themselves. Waveborn has made the statement in other threads that -- they sound great if you only know how to use them? Guess that is what I am here to find out starting with a simple design like the firefly. Although that is only a starting point -- that design was meant for different tubes.

http://www.ax84.com/index.php/oldprojects.html?project_id=firefly
 
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Jungle -- Sorry for the absence -- life just does not give up easy sometimes :).

Anyway - this schematic is facinating - particularly the limiter circuitry. Please discuss this effect and how you use it?

Also -- I presume the 125V @ 60mA near the PT pertains to the secondary - correct? thx. again.
 
Proper use of Russian tubes - the rest of the story

Back again - sorry for the delay -

When I mentioned the firefly design I was interested in more than just the output tube. I would also be interested in finding out Russian tube replacement suggestions for each of the tube in the design - along with the required component changes. My object here is not to reinvent the firefly -- but rather to *learn* about the proper usage of Russian tubes as themselves rather than as replacements for western tubes. The more hints you can provide the better. Hope you are watching Wavebourn. thx.

firefly.jpg
 
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Think it is right --

Gimp -

No I think 22K5 impedence is correct - I downloaded this from the "old projects" area on AX84.

There is a guy who sells OTs for this project and he lists the impedence as 22K5 as well. See the OT5PP...

P-P OUTPUT XFMRS - A Thermionic Webplace

Let me take the opportunity to highly recommended the offerings from Musical Power Supplies. I have had great luck using both his PTs and OTs. Matt is a great guy to work with as well. :)
 
Moonbird, try here for info on 6N1P and 6N2P.

Ian - this is good info. much appreciated. I too would like to see a PP schematic for the 6N6P from jungle as well as some info about the limiter circuit (interesting thing to put in a hifi amp don't you think? -- at least I *think* it is a hifi).

I am still hoping to hear from Wavebourn -- this thread is trying to get more info about a statement he made in another thread where he claimed that many Russian tubes don't sound good because they are not used correctly. I picked the Firefly as a discussion point because it uses multiple triodes and would be a great (easy) platfrom to start experimenting. I am very interested in which tube would be recommended for the cascoding, for example.

I am hoping Wavebourn will share some of his experience in how to make these tubes sound their best. :D
 
Tubes of any nationality / origin not sound good because not properly used. :)

Speaking of guitar amp, Gregg's amp is very well designed. I recommend you to build it as is. Vary - Mu limiter in his amp is nice for a lead guitar! But even don't think of using it for hi-fi - distortions will sound horrible.

You may modify the amp a little bit, if you prefer a single ended sound for your guitar. Just use a gapped output tranny and parallel triodes as discussed earlier.

Good luck! :eguitar::smash:
 
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