#1
I'm building an amp. Looking for schematics.

I want it to be single ended and low watts. I want a glassy scooped sort of Fender sound that stays mostly clean. Blackface/Silverface era sounds. I want a full TMB tone stack.
I'm trying to keep transformer sizes down, so going up in power is not bueno.

Champ is definitely too dirty and mid-focused. Princeton is better, but the tweed Princeton is the only single-ended version.

Has anyone tried "blackfacing" a 5f1, or 5f2a design, or know of any other designs that might work.

Of course I know enough to swap in lower gain preamp valves, or increase negative feedback, but it would be nice to hear about others experience with this if there's anyone who has given it a try.
#2
I thought all Blackface amps were A/B and not single ended. That push/pull design defined the BF sound. Princeton probably has the best BF signature tone at 12w but I believe it is A/B. Pick your poison.
Last edited by Cajundaddy at Jan 26, 2016,
#3
black faced amps are all push pull.
Jumping on dat gear sig train.
PRS Hollowbody II / BKP Warpigs
Strandberg OS6T / BKP Aftermath
Strandberg OS7 / Lace Poopsticks
Skervesen Raptor 7FF / BKP Warpigs
Skervesen Raptor 6 NTB / BKP Juggernauts
Hapas Sludge 7 FF / Hapas Leviathan
Anderson Baritom / Motorcity Nuke BKP Sinner Anderson H2+
Warmoth Baritone / BKP Piledriver
Ibanez Rg2120x / BKP Nailbomb

Blackstar ID:Core Beam
#4
So I either give up on single-ended or I give up on the Blackface sound?
I give up on Blackface then.

Know any toneful, 5 to 10 watt single ended amp that stays mostly clean?

Not hi-fi clean. Definitely want it cleaner than a Champ though.
#5
you can build a blackface circuit with 2 6aq5s for 10 watts.

if you just want a bigger single ended amp you can build the champ circuit with a 6l6 or a kt88. same circuit but bigger transformers.
Jumping on dat gear sig train.
PRS Hollowbody II / BKP Warpigs
Strandberg OS6T / BKP Aftermath
Strandberg OS7 / Lace Poopsticks
Skervesen Raptor 7FF / BKP Warpigs
Skervesen Raptor 6 NTB / BKP Juggernauts
Hapas Sludge 7 FF / Hapas Leviathan
Anderson Baritom / Motorcity Nuke BKP Sinner Anderson H2+
Warmoth Baritone / BKP Piledriver
Ibanez Rg2120x / BKP Nailbomb

Blackstar ID:Core Beam
Last edited by AcousticMirror at Jan 26, 2016,
#6
Even the Tweed Champ opens up a lot if you run it through a high efficiency 12" Emi speaker. The stock 6" was about 94db spl and a big piece of that tweed midrangy tone with early breakup.
Last edited by Cajundaddy at Jan 26, 2016,
#7
What about:
Start with 5f1 schematic
Replace the single volume control with a full tone stack.
Would that be too lossy to drive the second half of the triode?

Edit:
Probably not. Blackface champ has bass and treble controls.
Maybe get rid of the cathode cap on the preamp and get an oversized transformer?
Last edited by paul.housley.7 at Jan 26, 2016,
#8
i don't know what you are trying to do.
5 watts clean is 5 watts clean. a bigger transformer isn't going to fix that.
Jumping on dat gear sig train.
PRS Hollowbody II / BKP Warpigs
Strandberg OS6T / BKP Aftermath
Strandberg OS7 / Lace Poopsticks
Skervesen Raptor 7FF / BKP Warpigs
Skervesen Raptor 6 NTB / BKP Juggernauts
Hapas Sludge 7 FF / Hapas Leviathan
Anderson Baritom / Motorcity Nuke BKP Sinner Anderson H2+
Warmoth Baritone / BKP Piledriver
Ibanez Rg2120x / BKP Nailbomb

Blackstar ID:Core Beam
#9
From your sonic description I am thinking a BF Champ circuit, cool bias, lower gain preamp tube, and a quality speaker is likely exactly what you are looking for. Lots of pristine clean with a little bite at full tilt. If I were going to build one, that would be it.
#10
Yeah yeah.

And I've been doing my googling too. I've found a few accounts from people who tuned their champ to be cleaner and they didn't seem to like it, but they all like the tweed champ vibe so of course they wouldn't want to lose that. For me on the other hand, I'm not so interested in the tweed champ sound.

So is the de-tuned champ sound "bad", or is it just too different from the tweed sound?
Or in other words, should I still be open to going more to a blackface Princeton topology?

Hard to tell from watching vids.
#11
I am treating this as a design exercise and an experiment.

The idea is that I'm going to start with a very low wattage rock or metal amp - think Snott Watt, Firefly, etc... - and add a clean amp to it in the same chassis.
It's not exactly bi-amping, but that's the closest I can think to paint the picture.

As the rock amp will be in the 1 to 4 watt range and will be more mid-focused, I figured I could match to that a slightly higher watt clean amp that has scooped mids.
I want to see what's possible with this. Maybe it'll sound like ass when I play then together, but at least I'll have two more amps to play with.

That's also why I'm trying to avoid having the push-pull power amp on the clean side - because I'm worried about the size of the PT. Too many tubes (I'm already up to 5) and this could get way too heavy. I'm already going to have to have two separate OTs, so I have to budget my power carefully.
#12
Sounds like a grand science experiment into the unknown frontier. Why re-invent the wheel when you could build a 2 channel amp with switchable preamp circuits for clean/dirty that share the same power amp section?

One of the defining characteristics of a BF Champ is more clean headroom, later breakup. One of the defining characteristics of a Tweed Champ is early breakup and rich creamy harmonics at full song. Trying to make one circuit design emulate the other may end in tears.

I have spent most of my bench time repairing and tuning amps, not creating an all new hybrid dual power amp circuit from scratch. This project is above my pay grade. Good luck!
Last edited by Cajundaddy at Jan 27, 2016,
#13
Sounds like a grand science experiment into the unknown frontier. Why re-invent the wheel when you could build a 2 channel amp with switchable preamp circuits for clean/dirty that share the same power amp section?


I have to agree with that. It's already possible to build a 2 channel amp, DIY sites all over the place should have all the schematics and layouts you could hope for, and the Champ preamp circuit is hard to beat for a clean low wattage amp. I have a 74 Champ, same as blackface since CBS made no changes to it or the Princeton until much later on. Before I rebuilt it and modded it to handle a 6L6 tube, it was pretty much a standard Champ, started breaking up around half volume, and at band practice once I got in with bass and drums it was hard to tell it was breaking up even cranked to 10.

Since doing some work on the amp it seems to growl a little more, but is still mostly clean until about half volume. And half volume is plenty for practice at home. Onstage it won't work, because it still sounds like a cheesy 8 inch speaker. But for practice at home, it can't be beat.

The only way to get cleaner with a tube amp is to use a lower gain preamp section and a lower gain preamp tube, like a 12AU7. You can fine tune the preamp circuit to give you more clean headroom, but after a certain point it's going to start sounding wimpy.

Look around and see if you can find something on the preamp sections of Gibson and Hiwatt amps, both had a reputation for nice cleans, that's why David Gilmour has played Hiwatts for 40 years. I played a 60's Gibson 2x12 combo at about 50 watts in a music store, it was hard to get the thing to pull off a dirty sound. Combination of clean preamp and good speakers...

For speakers, EV has a reputation for speakers that don't break up as fast as Celestions, for example. I haven't checked in a while, but other companies may be making good speakers for cleans too. Check around and try them.

I would agree with Cajun, start looking at a 2 channel option. One transformer each, input and output, different gain levels in the preamp sections. And you can do it with either the single ended Champ version or the push pull Princeton.

I had a friend in Louisiana who built several Princeton clones, everything from straight Princeton to one with a foot switchable Marshall preamp section. The cleans were great, the Marshall side screamed, and with the wattage still down around 15 or less, plenty loud even for onstage use. And if you mic it, then pump a little back into the monitors, volume can be as low as you want it.

Oh almost forgot...I found out a while back the Champ has a resistor tied to the tone pot and ground. If you disconnect that resistor, it sounds like the thing is running through a distortion pedal. I thought about modding mine so I could do it with a footswitch, but don't want to drill any holes in a vintage Fender Champ...

You can find a schematic and board layout at the Fender Amp Field guide, look at the Blackface Champ link.

http://www.thevintagesound.com/ffg/

That resistor tied to the bass pot makes a huge difference. I don't know how it works electronically, but disconnect one end and the amp screams like a gorilla with his balls in a vice. Reconnect it and you have a standard Champ...pretty simple mod, tie it to a footswitch jack and it should be usable any time. I just don't want any new holes in my amp...
Hmmm...I wonder what this button does...
Last edited by Paleo Pete at Jan 27, 2016,
#14
I believe I could build a two channel clone amp that would satisfy anyone, but attempting to reinvent the wheel seems so much more interesting to me.

You guys are giving me so many ideas right now though. More than you know.

Here's an idea of why this is important to me.

Let's say you wanted to have a Champ, but louder. Being single-ended, the OT gets huge very quickly as the wattage increases. Doubling the wattage from 6 to 12, and then again from 12 to 24 means using a huge OT. For your troubles you get about 6 decibels.

But if you simply use a second (identical) champ you can get nearly the same 6 db. There's a lot of reasons for that and the most obvious one is the fact that you're using two speakers instead of one, but it adds up and you can (maybe) circumvent the OT problem in this way.
For a historical example, I'd like to suggest that the Grateful Dead's wall of sound and also car audio enthusiasts have demonstrated some of the benefits of adding drivers. It's a complicated subject but I'm trying to learn it.

So yeah I'm building a champ, but more importantly I'm trying to build more than one, and I also want to cross the idea with other amps as well.
#15
One reason you have more pristine cleans with the black face amps is that the anode voltages are run MUCH higher than the tweed era. You can get cleans without this, but higher anode voltages give you a lot more "room" before you start to break up.

One option is to look at the blackface champ and then increase the negative feedback resistor to change when breakup occurs and to use a fairly clean and high efficiency speaker.