input tube for this purpose

[pjd3]

Hey there, just a "pick your brain" question for the conception of a future project.

I put together a guitar that I use for only one purpose. For the use of an Ebow. It will never be strummed and never be picked. Only one note at a time, lyrical melodies. I have my other guitars for strumming and picking.

It has one pickup, a Dimebucker in the neck position. With Ebow, the Dimebucker yields an extremely extended high frequency, to the point where the area of 7-9KHz is very pronounced and I normally EQ a mid size notch around 8.5Khz to tame the "angry beehive" that exists there. The other important consideration is that with the Ebow, the Dimebucker has a "huge" amount of gain with the guitar volume pot all the way up. For example, it seems like I have the volume knob at 5 or below to equal an output under normal playing conditions.

I envision one day building up a stereo tube amp as to use a nice reverb/ambience processor and would consider tube send/returns for each amp and its speaker. So for this, I'd be looking for a very clean, sweet n rich stereo tube system, perhaps 20 watts per amp or so. I actually wondered if something based on a Princeton amp would do the trick. Sure don't see whynot.

So off the top of your head, based on your experimenting with the various 12xx7 tubes, what would you see in say, a Princeton type amp that would fulfill this application? Where would you start with tube types? I've only ever played with 12ax7's and 5751's.

Of course, I would venture into experimenting with the various tubes, and that's how I'll truly know for sure but, just curious to hear what your suspects may be based on the application I've described (rich, sweet clear and clean single note singing melody with stereo reverb)

Thanks!
Phil D

[xtian]

Tubes are linear devices, you know. They have no inherent frequency response, unlike speakers. Sorry I can't help with your tube question.

BUT! Lower your pickup!

[pompeiisneaks]

Yeah the tubes don't change the treble/bass response, that's in your tone shaping networks like treble/mid/bass or coupling caps etc.
~Phil

[MakerDP]

A Princeton-type amp would work great.

I would just build a simple Fender-type one-tube gain stage designed around a 12AU7 for lower gain. You are going to have a hard time getting 20W out of that so it may need to be 6L6-based. That should handle your gain issues. For your bee-hive issue, there is no shame in using a notch filter like an EQ pedal in front of the amp.

[pdf64]

I know its an anathema to most guitarists, but, err, try plugging in to the 'low' input

[pjd3]

Thanks everyone,

I think my comment on the 8.5k beehive may have got misconstrued as me expecting frequency tailoring from a tube. Naw, I wouldn't have expected that. But, I may find value in folks that have experimented with the 12xx7 variants and noticed certain things about their texture in some ways, maybe the highs seem different from one to another given a similar gain structure. Its probably just gain that alludes to perceived differences but, having not been there yet, I'll be needing to start somewhere so, others opinions and findings are fine to me.

It is reasonable to think that keeping it down to one or two gain stages is a factor to a more clear, hi-fi or less distorted sound. And thats what I'm getting at I guess, looking for those things that wont exacerbate all those naturally occuring searing highs. For instance, I don't think too many stages of 12ax7's plus a 12ax7 in a LTP phase inverter would help that. I might expect a cathodye PI to be more compatible for the application. Maybe some retuning of the EQ might help. This amp won't be for Jimi Hendrix. But, Sluckeys plexi I'm building now, Jimi might like it.

I kinda like the idea of bumping up the output section to 6L6's and a low gain pretube. Sounds like the right direction.

Also, can someone comment on what you can expect from a cathode biased amp tone/response-wise as compared to grid bias?

Thanks guys,

Phil D

[MakerDP]

Also, can someone comment on what you can expect from a cathode biased amp tone/response-wise as compared to grid bias?

Here is a great read. The direct answer to your question is about 2/3 of the way down.

http://valvewizard.co.uk/pp.html

If you are after a clean "hi-fi" sound you will probably want to go with fixed bias.