5F10 Schematic question

[Danelectron]

I recently completed my first successful amp build (5f2) and am using this to compare different components. Sounds really good, I might add.
I am looking for another schematic that is a little higher output. Maybe 10 to 15 watts. I saw that the 5F10 has two 6v6s for the output, so assume it has more of what I am looking for. My question is...on the 5F10 schematic,

(http://www.schematicheaven.com/fende...5f10_schem.pdf) ,

there is what appears to be a diode on what appears to be the power transformers bias tap. What value would I use here? what is its purpose?

Is there another schematic that would be better suited for a newbie who wants a little more output power?

I'm not totally naive, but can say I am learning tons about tube amp design by miss and hit. I previousy reverse engineered a gibson GA-8, which has the same tube compliment as the 5F10 and it sounds O.K. until the volume control gets up around 8 then I get slight oscillation and what sounds like extreme sag. I'm in the process of troubleshooting this build, but am thinking the 5F10 may have better tone in the long run. I was also looking at a fender twin or something with a couple of KT66s or 6L6s.

Thanks for any input or suggestions.

[Tom Phillips]

...there is what appears to be a diode on what appears to be the power transformers bias tap. What value would I use here? what is its purpose?

Is there another schematic that would be better suited for a newbie who wants a little more output power?

Yes that's diode. It is the rectifier for the bias supply. You can use just about any common rectifier diode because both the current and the voltage requirements are low for that spot in the circuit. Many builders use the 1N400X series. I use 1N4007 which has a much higher rating than needed but is inexpensive and already in the shop stock.

I suggest you consider building a 5E3 Deluxe amp. It's a classic, sounds good and there is lots of information and support available.

Regards,
Tom

[Danelectron]

Tom, Thanks for your response. I have several 1n4007s on hand so that's no problem.

I looked at the 5E3 schematic and it looks interesting. Is there any tone or output level difference between the pairs of inputs? I don't really need all these inputs. The signal paths appear identical, but I can't quite see what is happening at the tone pot. I had considered the 5F10 because I could just use one input jack and eliminate the other two without complicating the design. I have no experience with the 6AT6 tube and haven't checked availability of these so I may just build the 5E3 and go from there.

Sorry, I'm starting to think out loud. I have been surfing the faqs and threads on this forum and there is some good stuff here, though some redundancy. Is there a better place to ask simple questions without cluttering up the place with repetition?

Thanks, Dan

[JoeM]

A friend of mine just built a 5F10 clone. He used the 7 pin (6AV6?) as the first stage. According to him, it's cleaner than a stock 5E3, (the 5F10 with fixed bias and NFB), but that's just what he wanted. 6AT6 (or 6AV6) tube(s) dont seem to be too rare.

[Danelectron]

Joe,
Interesting. What is your friend using for pickups? I find my Les Paul breaks up waaay earlier than my strat ( actually at about 3 with the 5F2). Does he get much breakup at all? I wouldn't mind more clean headroom, but some decent distortion at the top.

Thanks for your response. Dan

[JoeM]

Joe,
Interesting. What is your friend using for pickups? I find my Les Paul breaks up waaay earlier than my strat ( actually at about 3 with the 5F2). Does he get much breakup at all? I wouldn't mind more clean headroom, but some decent distortion at the top.

Thanks for your response. Dan

I'm not sure what pickups, but I believe his main ax is a Tele, I know he doesn't own a Les Paul. He's got a web page describing the build:

Green Eagle Amps - 1959 Tweed Harvard 5F10

I'd like to have one these too.

[Tom Phillips]

Nice web site he has there.
I like to build amps that have only one (sometimes two) input jacks.
Unless you are an instructor using the amp with a student I don't see the need for the extra inputs of the old designs.

[JoeM]

Nice web site he has there.
I like to build amps that have only one (sometimes two) input jacks.
Unless you are an instructor using the amp with a student I don't see the need for the extra inputs of the old designs.

I had some discussion with him on the input jacks. I suggested using a 'standard' Fender 2 input arrangement, but I guess he wanted it to be more of an exact clone. If I build one, I'd prefer to use a 12A?7 type for the first stage too, but he found a bunch of the 6AV6 tubes real cheap.

[Danelectron]

If I build one, I'd prefer to use a 12A?7 type for the first stage too, but he found a bunch of the 6AV6 tubes real cheap.

Joe, I imagine the 6av6 may be responsible for the cleaner tone. I think I'll build a 5E3 first, but I may end up building the 5F10. I found a bad connection in the GA-8 I built and got it up and running. It doesn't have much range with the tone control and is quite a bit brighter than the 5F2 I built. I found that I can control the tone with the guitar in a very wide range so it is actually very convenient. I set the volumn and walk away.

Tom and Joe, Thanks for your input. Dan

[NTBluesGuitar]

Hello, all! JoeM has been recommending I come here for a long time. I'm the guy who built the Harvard he linked to here.

It's a really fun amp.

I chose to go with all three inputs to keep it as close to stock as possible, plus looking at it from the top, seeing the three inputs would indicate it's not a 5F2A Princeton. What wasn't affected is that the middle input is, indeed, a middle input. That is, the two on the ends are the typical High-Low Fender style inputs with the appropriate attenuation, but the middle one actually is a median point between the two.

Great little amp. Very clean for a little tweed, but it gives up the dirt like a tweed should once you get higher on the dial.

[Danelectron]

NTBluesGuitar,
Thanks for responding! That is a really nice looking amp!

A couple of questions: What did you choose for a speaker for this amp? I see it's a Weber. Alnico?

Your circuit board looks very nice. Do you make your own? If so, where do you get your material?

What is the purpose of the pot on the left of the power supply filtercaps? Adjustable bias for the power tubes?

What did you use for the power transformer (brand / specs.)?

What style of music do you play through this? What guitar/pickups?

I'm still considering the Harvard 5F10. I'm curious about the 6AT6 preamp. Very interesting looking tube design. Slightly lower gain than a 12ax7 and single triode. Seems like this would allow more clean headroom. I built a 5E3 and really do like it. Much warmer than the GA-8. Not neccesarily better, but different. Good output volumn.

Thanks for responding. Not alot of feedback on this amp design, but it caught my eye a while back so it's good to hear from some experience.

[NTBluesGuitar]

Thanks, Danelectron!

To answer your questions:

-Weber Signature 10S Alnico. GREAT speaker ($45 new!)
-I do make my own. I use 1/16" G10/FR4 Epoxy Fiberglass and I get it from McMaster-Carr
-The pot on the left is, indeed, for the adjustment of the bias
-I used Allen/Heyboer iron (Allen Amplification - Quality Tube Guitar Amps, Kit, Parts, and Repairs). Specifically the TP25 power and TO22 output.
-I'm not a very experienced player, but I'm into blues and jazz oriented stuff mainly. This amp likes Teles and Strats.

Specifically, I made it adjustable fixed bias to make sure I could tweak it for modern tubes. The power transformer from Allen was a perfect fit on the Weber 5F2A chassis, but only has 1/4" clearance inside the cab from the baffle. Not a problem, but the 5F2A cab is kind of thin to begin with, but the power transformer is probably the most important part in this amp. Needed one for the low-watt application with rectifier heater and bias taps.

This amp is best described as a single-channel Deluxe (5E3), that's a hair tighter and a hair brighter. I did run a 5E3 chassis through this cab/speaker and it sounded almost identical and barely louder, so a lot has to do with the speaker, I think.

This is the perfect in-between amp for those who want a little more power than a Princeton, but still want the compact size of one where the Deluxe might be a little too large.

I've read how underrated this amp is, and now that I have it, I can see why. It's got all the feel and response that the low-watt Tweeds have, and is a lot louder than you'd expect, but is not quite as compressed or dirty as the Deluxe. I really like this amp...I'd re-build it again if I sell it.

I actually recently had someone ask me to build one for them, too.

If you're not familiar with Stever Cropper, he is known for recording a lot of his famous work on the Harvard.

From and interview with him:
"Every now and then I’ll pull out my old Fender Harvard that I used on 'Green Onions,' 'Loving You Too Long,' and '(Sitting On) The Dock of the Bay.'"

[Danelectron]

NTBluesGuitar,
Thanks for the info. I just sourced a NOS RCA 6AT6 and tube socket. I have the others. I have a fender 1x10 little combo cabinet that needs a chassis. It's on.

I have an eminence alnico speaker that I'll probably try at first since I already have it, but I do like the weber alnicos also. I have one in a gibsonette that I recapped a while back. It had a shot Jensen in it and when I was looking for a replacement, a friend suggested I try a weber. I don't recall if it is a signature series though.
The transformer was my biggest concern since fender doesn't spec what they use on this schematic and I'm still in the reseach and developement(of my brain)stage on power sections and voltage dividers. Is it O.K. if I pick your brain along the way?

Thanks for rekindling my interest in this amp. Dan

[NTBluesGuitar]

Dan, feel free to e-mail me anytime! My address should be in my profile.

[Danelectron]

NTBluesGuitar,
Hey, I was surfin' for something and came across a site where you profiled the construction of this amp in a forum similar to this. I was rushed for time so didn't get to read it all, but what caught my eye was a response you gave to someone about the preamp tube. You stated that you used a 6AV6 instead of the 6AT6 because of the higher gain. Did you ever try a 6AT6?
Thanks, Dan