guitar amp DIY ?

[soundguy]

well, Id like to have an amp that could accomodate both a KT66 and a 6v6 in a single ended output. Id also like to use a 6sn7 in the preamp and definitely a 5y3 rectifier. Obviously Im into hacking together something new, but so long as I used a big enough power transformer, could I roughly base it around a champ? Figure something like that thrown together with mercury magnetics iron could make for something hopefully, pretty awesome.

This of course is geared for studio work, power output is of no concern what so ever.

dave

 

[T-Beam]

Just wondering....where do you buy the turretboard stuff? I mean the "soldering-pins" and the boards without holes and copper.

 

[vibrolax]

[quote author="T-Beam"]Just wondering....where do you buy the turretboard stuff? I mean the "soldering-pins" and the boards without holes and copper.[/quote]

Sorry I forget the European name of the turretboard material. In the USA, it's called G10-FR4, tradename Garolite. I get it from McMaster-Carr www.mcmaster.com. I get it in 300 mm x 2400 mm sheets, 1/8" thick. I like the colored stuff - blue is part # 85345K422.

I get turrets from Mouser Electronics, www.mouser.com. There are many styles of turret lug. My favorite is 534-1509-4, which is a two-level lug with a slightly larger through hole in the center.

-Jon

 

[vibrolax]

[quote author="soundguy"]well, Id like to have an amp that could accomodate both a KT66 and a 6v6 in a single ended output. Id also like to use a 6sn7 in the preamp and definitely a 5y3 rectifier. Obviously Im into hacking together something new, but so long as I used a big enough power transformer, could I roughly base it around a champ? Figure something like that thrown together with mercury magnetics iron could make for something hopefully, pretty awesome.

This of course is geared for studio work, power output is of no concern what so ever.

dave[/quote]

Accomodating a KT66 and 6V6 shouldn't be a problem. A few comments about your other wishes...

Why do you want a tube rectifier? The current draw from a single ended amp is constant, so there is no sag effect. The 5Y3 has just enough current capability for a KT66.

Why a 6SN7 for the preamp? It's a bit low mu (20) for a guitar preamp, especially if you include any tone control at all. Do you want only clean? Maybe you meant a 6SL7, which has a mu of 70.

Mercury Magnetics iron is good, but spendy for quantity 1. The discount for quantity 5 is pretty good.

Some alternatives you may want to check out: http://www.allenamps.com/parts.html#transformers
and
http://www.heyboertransformers.com/tubeamps.shtml

Heyboer reportedly does custom/semi-custom work at reasonable prices.

-Jon

 

[vibrolax]

[quote author="WJS"]If you're looking for something low power and kinda crunchy, try a 12ax7 pre into a 6sn7 driving a 300b. It wont do more than 15-20 watts but will definitly give some power amp crunch. I build this as a project a few years ago, it definatly has a unique sound as a guitar amp. esp. into a mashal stack
the 300b is a very linear tube but when pushed it gets a little upset, just enough to sound awsome.
[/quote]

A 300B guitar amp is definitely far from the beaten path. A SE 300B is good for 8 clean watts output. An expensive tube (even the Chinese ones) to be abused in an overdriven guitar amp. Single ended triodes can "work" in guitar amps, but in my experience they sound much darker than any semi-conventional guitar amp design. Then there's the 300B's odd filament voltage and OT impedance needs.

Another way to scratch the SET itch is to include a switchable triode mode for pentode/beam tetrode tubes such as EL34/KT66/KT88/6550, etc. Most of the opinion I have seen is the switch gets left in pentode mode after a few minutes of playing with triode.

-Jon

 

[AnalogPackrat]

Jon,
Ooh, that simplified AC-30 looks fun. I've always wanted a Vox, but I sure as hell don't need anything that loud. Looks like it would be easy to knock it down to just a pair of 6BQ5s to make an AC-15TB. Even that's pretty loud for me--I hardly ever play my SF Deluxe Reverb because of that.

Soundguy--what kind of tones are you looking to get from your tube swappable amp? A little bit of everything? Seems like you could go a long way with creative preamp stuff, variable feedback ("presence" control), and a choice of 6V6, 6L6/KT66, or EL34 for power tubes.

I've got a SF Vibro Champ that I really like (with an upgraded Jensen 8" AlNiCo speaker) and a modded Champ12 (SE 6L6) that is fun, but needs more surgery and maybe a better speaker. I often run both of these little guys at the same time (sometimes in asymmetrical "stereo") and they really complement each other. The Vibro is more clean/spanky/sparkly while the Champ12 has a nice grinding midrange that I like.

Analog Packrat

 

[WJS]

just a little note on the 6sn7, they do use a lot of juice and dont give much gain, (hence the 12ax7) but if you like the sound. and there are benifits to having a tube recifier besides sag. the warm up is easier on the other tubes and the psu caps. it kinda eliminates that big knocking of all of the iron trying to fill all of the empty caps instintaniously.
you might want something rated for a little more current than a 5y3 though, depending obviously on your needs


my 300b cost about 60 us. it sounds sick with the preamp clean, or just bypassing the preamp. If you overdrive it like i'm doing sometimes, it isn't too dark, but seems to give anywhere from that kinda bluesy sound to a well rounded grunge.

also it is a 5 volt heater... its not too odd.


doing a SE amp is deffinatly not what most guitar amps, because of the lack of output power, but sence this isn't an issue, best of luck!

 

[vibrolax]

[quote author="WJS"]... and there are benifits to having a tube recifier besides sag. the warm up is easier on the other tubes and the psu caps. it kinda eliminates that big knocking of all of the iron trying to fill all of the empty caps instintaniously.
you might want something rated for a little more current than a 5y3 though, depending obviously on your needs

doing a SE amp is deffinatly not what most guitar amps, because of the lack of output power, but sence this isn't an issue, best of luck![/quote]

There isn't much of a warm-up benefit with directly heated rectifiers like the 5Y3. You also need to limit the first filter stage capacitance (or add series resistance) with any tube rectifier, as the iron will be happy to exceed the rectifier's surge current rating filling it up.

Single ended guitar amps are not unusual. Single ended directly heated triode guitar amps are unusual. But that's the beauty of DIY: you can make what you want, no matter how unusual it is.

-Jon

 

[vibrolax]

[quote author="AnalogPackrat"]Jon,
Ooh, that simplified AC-30 looks fun. I've always wanted a Vox, but I sure as hell don't need anything that loud. Looks like it would be easy to knock it down to just a pair of 6BQ5s to make an AC-15TB. Even that's pretty loud for me--I hardly ever play my SF Deluxe Reverb because of that.

Analog Packrat[/quote]

Yep, even 2 EL84/6BQ5's are way loud for many situations. One set of experiments I'll pursue at some point is with lower-powered pairs of true pentodes that can cop some of the cranked push-pull EL34 vibe. Candidates include 6CL6/6197, EL95. I've already had some success with 6K6's.

I be thinking this thread belongs in the drawing board area...

-Jon

 

[Nat M.]

well, Id like to have an amp that could accomodate both a KT66 and a 6v6 in a single ended output.

This might be helpful to you, Soundguy. It's an amplifier plan on AX84.com that can use lots of different octal tubes (KT66, EL34, 6V6, 6L6, etc.) with some specified cathode resistor and output impedance changes.

http://www.ax84.com/dynpage.php?pg=projects&project=p1-extreme

I've been working on it just this morning. Here's the schematic:

http://195.178.239.50/ax84/media/ax84_m261.pdf

I'm a hack, and I messed up something in my switches, so I can't tell you how I like it. I am using a 6X4 rectifier and a standby switch with a separate jewel light, none of which is really necessary, but I just wanted to learn by trying.

In the message boards on the site (link is on the P1-extreme page) people discuss implementing a switched cathode resistor and the problems with it.

 

[vibrolax]

[quote author="Nat M."]
...I am using a 6X4 rectifier and a standby switch with a separate jewel light, none of which is really necessary, but I just wanted to learn by trying. ...[/quote]

The 6X4 recto is rated for 70 mA DC current. It may not last long with an EL34/6L6/KT88 etc.

-Jon

 

[T-Beam]

[quote author="vibrolax"][quote author="T-Beam"]Just wondering....where do you buy the turretboard stuff? I mean the "soldering-pins" and the boards without holes and copper.[/quote]

Sorry I forget the European name of the turretboard material. In the USA, it's called G10-FR4, tradename Garolite. I get it from McMaster-Carr www.mcmaster.com. I get it in 300 mm x 2400 mm sheets, 1/8" thick. I like the colored stuff - blue is part # 85345K422.

I get turrets from Mouser Electronics, www.mouser.com. There are many styles of turret lug. My favorite is 534-1509-4, which is a two-level lug with a slightly larger through hole in the center.

-Jon[/quote]
Thanks Jon...now I have some clues to look further in Europe for it, it may be a little bit too expensive to ship from US.

 

[PRR]

> I be thinking this thread belongs in the drawing board area...

Maybe. OTOH, you sorta don't "draw" a guitar amp. You can't design them, you have to experiment. You have a few stock circuits, you solder them up, play, and change things to taste. Lab-work, not drawing board work.

 

[vibrolax]

[quote author="PRR"]> I be thinking this thread belongs in the drawing board area...

Maybe. OTOH, you sorta don't "draw" a guitar amp. You can't design them, you have to experiment. You have a few stock circuits, you solder them up, play, and change things to taste. Lab-work, not drawing board work.[/quote]

I agree that the design work ends on the bench as you change things to taste, but I think it takes boatloads of experience before one can be a successful guitar amp hacker cutting and pasting on the bench from the get-go. I'd estimate a beginner's probability of success following this method to be very low.

It's difficult to make 50-100 connections without making a mistake, lacking a good drawing to check your work against. Until you get to the point where you can recall big chunks of the circuit from memory, it's foolish to begin without a drawing. It sucks to fry a PT or OT because you didn't check the wiring against your drawing. Even cutting and pasting is design, properly done on the drawing board.

Rant off. If you're happy to have this stuff in the lab, I'm happy.

-Jon

 

[CJ]

I posted this KT66/6SJ7 grid leaker a while back.
Sounds ok. Having as many amps as you can store is the way to go.

Open back cabinets shape the sound a lot. No matter how much you tweak a circuit, that speaker cabinet is going to keep you in a certain envelope.

 

[NewYorkDave]

Here's the basis for my 2-watt amp:

I laid out and punched/drilled the chassis in one burst of activity, and haven't had time to do any more work on it since! I hope to finish it sometime this year :wink:

The holes on the front panel are slated for (left to right): input jack, volume, bass, middle, treble, presence, pilot light.

 

[Sammas]

I've been thinking about ordering a Matchless clone kit from this group. I know a few people who have build them and say they are great!

http://www.ceriatone.com/index.htm

 

[mhelin]

[quote author="T-Beam"]Just wondering....where do you buy the turretboard stuff? I mean the "soldering-pins" and the boards without holes and copper.[/quote]

You can find it from the country east from and next to Sweden,
see http://www.uraltone.com webshop.

The item to buy there is "Kudosbakelliittilevy 3*60*275mm", that size is enough for one amp. Remember to order also the turrent tags.

-Mikko

 

[soundguy]

hi guys-

Im thinking about changing the 12ax7 preamp to a 6Sl7 in a champ/princeton type circuit. Has anyone ever done this? What is the output difference between a 6sL7 and a 12ax7? Whats the small tube gain equivalent for the 6SL7?

Is there a site that has spec sheets for tubes commonly associated with audio? All the sites I go to have a million tubes and I can never find "usable" voltages, just maximums and stuff. That would make for a good meta.

dave

 

[NewYorkDave]

Frank's is the mothership for tube datasheets on the internet:
http://www.tubedata.info/

Tube datasheets will tell you most of what you want to know, but you may need to put a little work in (e.g., drawing load lines on the plate curves). But for a quick reference for typical voltage amplifier setups, consult the "Resistance-coupled amplifier data" found in most tube manuals. This 6SL7 datasheet includes such a chart:
http://www.mif.pg.gda.pl/homepages/frank/sheets/093/6/6SL7GT.pdf
In many tube manuals, these charts reside in a separate appendix at the back of the book.

The 6SL7 is a high-mu dual triode not very unlike the 12AX7, but with a somewhat lower amplification factor.