Pedals for Harp Amp

Your harp rig needs some delay. Some guys prefer reverb, but for me a little greasy slap-back is exactly the right sound. Debates rage about which delay pedal is the "best"... Digital or Analog? Digital offers a greater range of delay times and effects, while analog sounds warmer and has a more natural decay to my ear. I've tried 'em all, and I use the Ibanez AD-9 analog delay pedal.

Some players insist the more expensive sister to the Ibanez pedal -- the Maxxon -- is superior, but I honestly can't hear the difference, and it costs more than twice as much. I don't demand much from a delay; in fact I usually set it and forget it. I just need a little thickener and I'm a happy harpoon man.

You may not know it, but you also need this Boss GE-7 EQ pedal. This thing is the harp player's best friend. Vintage tube amps have little or no tone control, so if you need to tailor the frequency curve of your mic you need an external tool to do it. This is just the ticket

This pedal has 7 useful bands. I use it pretty much as shown: I roll off the highs and also cut the lowest band. The slider to the right of the 7 EQ bands is a gain control that allows you to make your mic as "hot" as you like, to drive your input tubes crazy. This pedal is a must-have.

I admire the harp players who use the digital processors and modelers; their sounds are very cool. But for me the best processor is a smelly old tube amp all heated up and smokin'. These two pedals enhance the great tone without introducing any digital harshness.

The pedals are pictured next to my EV M43U mic which I sent to Greg Heumann at BlowsMeAway Productions for a little retrofitting. He shoe-horned a Shure CM element into that little mic body and it is now my best-sounding mic. Excellent workmanship. Greg's stuff is highly recommended.

My Current Favorites

-1970 Fender Champ, hot-rodded for harp, 6 watts
-1950s Masco ME-18 (2x6L6) w/Avatar 2x10 cab, 25 watts
-1947 Gibson BR-6 (2x6V6, 10-inch field coil speaker, one knob, killer tone), 12 watts

This is a list of the stuff I take when I play out:
(One or two of the amps, and...)

Boss BCB-30 Pedal board
-Boss GE-7 equalizer
-Ibanez AD-9 delay
-Sabine FBX SL-620 feedback exterminator
-Visual Sound 1Spot power supply

Fender Tweed Harp Case
-20 Hohner diatonic harmonicas
-1946 Astatic JT-30 mic w/crystal element
-Custom JT-30 mic w/Shure CM element
-EV M-43U mic w/Shure CM element
-Small flashlight

Musicians Friend large tweed gear bag
-Rhythm Tech Mountable Gig Tray
-Harmonica Honker mic
-Bottle o’ Blues mic
-Hughes & Kettner Red Box Pro
-Two 3-foot Planet Waves speaker cables
-Two 20-foot XLR cables
-Four instrument cables
-Two extension power cords
-Morley ABY pedal
-Monster power conditioner/ground tester
-Spare tubes
-Spare fuses
-Business cards
-Pen
-Leatherman tool
-Phillips screwdriver
-Zoom H4 digital recorder (optional)

Harp Amp Project - Fender Silver Face Champ

Last year I bought a very nice 1970 Fender Champ guitar amplifier to use as a small blues harp amp. I made a couple of modifications to it right away to make it more suitable for harp (lower gain preamp tube and bigger speaker) and to make it safe to use (three-prong grounded power cord). The tone was a little ratty and boxy when I first got the amp, but those early modifications made it better without sacrificing its vintage collector value. Now I’ve decided to forget about keeping the amp original. Instead, I will make a series of careful modifications to make it the ultimate SF Champ for harp.

First a little background on the Fender Champ amps. The Champ is the smallest line of Fender tube amps, generating about 6 watts of power. The Champion amp first appeared in the late forties, and in the fifties the Champs – and other Fender amps – were covered with Tweed. In the early sixties the design of Fender tube amps was known as Black Face, for the black panel around the volume and tone controls. In 1968 this changed to the Silver Face design, which was produced until 1982. Fender Champ amps after that are not really desirable as harp amps for a variety of reasons. So the good Fender Champs are known as Tweed, Black Face, and Silver Face. The Silver Face is the most recent and thereby least valuable. You can buy good examples all day on eBay for $200 - $300.

The Champ amps have a very simple circuit called Single-Ended Class A. In general that means the amp has a single power tube that drives the speaker. The standard tube compliment in all Champ amps is: 12AX7 preamp tube, 6V6 power tube, and 5Y3 rectifier tube. It is the simple circuit that makes these amps sound cool with blues harp. When you turn up the volume knob on a Champ, the sound does not get any louder after you pass 5 (out of 10) on the knob. After 5 the tone just gets more distorted and compressed… more colorful. A well-sorted Champ near full crank is a wonderful thing to hear. Eric Clapton recorded the song “Layla” this way.

So then… the first modification I made last year was to swap out the 12AX7 preamp tube with a lower gain 5751. The biggest challenge in playing amped blues harp is audio feedback though the speakers, and the lower gain preamp tube will allow you to get to the sweet spot in the power tubes before you get to the squealing feedback level. It is a very careful and tricky balancing act that changes in every venue you play. A lower gain preamp tube is the required first step. I prefer the 5751; other harp players like the AY7 or the AU7. Each has a different level of gain reduction. It is a matter of taste, playing style, and your harp microphone.

The next step was to install a larger speaker. I chose the Jensen vintage re-issue P10R, a 10-inch 4-ohm 25-watt guitar speaker with a ribbed, seamed cone and alnico magnet on a 1-inch voice coil. I picked this speaker because the original Jensen P10R was legendary as original equipment on some fantastic vintage Fender amps used for harp, like the tweed Bassman or black face Super Reverb (Paul Butterfield in particular). The reissue P10R speaker, however, lacks much of the warmth of the original.

At that time, I decided to preserve the originality of my Champ by mounting the 10-inch speaker over the 8-inch opening in the baffle board for the original speaker. That way the mods were reversible and I could restore the Champ to vintage condition if I wanted. But the small opening in front of the bigger speaker made the tone a little boxy and nasal, and after more than a year of playing through this amp and tweaking it around its vintage margins, I have decided to sacrifice any collector value it may have for the sake of getting the ultimate SF Champ tone for harp.

Here are the steps I have chosen in my quest for tone:

-Cut the baffle board to properly mount a 10-inch speaker. The opening needs to be offset slightly so the speaker will clear a can capacitor that sticks down from the chassis.

-Swap out the 5Y3 rectifier tube for a 5V4. The rectifier tube converts AC power to DC, which is what the other components need to see. For a variety of technical reasons, the 5V4 rectifier tube will make the Champ sound louder and punchier with more note definition and better bottom end. The trade-off is it gives less sag. Sag is a cool sound a harp amp makes when its power tubes momentarily run short of DC power when a loud note is played. This may seem like a bad thing, but it sounds cooler than shit on big harp amps like the Fender Bassman. With small amps like the Champ, sag almost never occurs because the little Class A amps are almost always cookin' at full heat anyway, and the sound is so compressed you cannot hear the sag. I have ordered a NOS (new old stock) 5V4 tube from Tube Depot in Memphis. [Update: Got it! NOS Sylvania JAN 5V4G]

-Alter or disconnect the negative feedback circuit in the Champ. Fender’s goal for its guitar amps was a sparkly clean tone, and one way to do this was with a negative feedback circuit. It was thought that power tubes introduced distortion, so Fender engineers looped an out-of-phase portion of the output signal back to the preamp section. That way the distortion cancelled itself (sort of), but it meant they were siphoning off some of the Champ’s power for the sake of clean tone. Amped harp does not need sparkly clean tone, and distortion is our friend. Many pro players swear by this modification, saying it makes the Champ louder and warmer, while a few others say it can make the tone gritty and harsh. (Heck, I live for gritty and harsh tone!) So I have decided to install a potentiometer in the NFB circuit so that I can dial down the negative feedback from the factory setting to nothing – or anything in between. Old vintage amps actually have wires and resistors and things; not just chips and printed circuit boards. This is a pretty simple mod that requires drilling a hole in the chassis and mounting the pot, and connecting two wires.

-Install a 10A125-O Weber speaker. This is Weber’s best vintage-style speaker for harp. It is 20 watts, 3.2 ohms, alnico magnet with 1.25 inch voice coil. The cone is not ribbed. This is a punchy speaker known for warm tone, early breakup, loud, compressed at high volumes. Since it is 3.2 ohms (which is what the Champ expects to see) it may be marginally louder than the 4-ohm Jensen I have in the amp now. The Weber speaker is $95 (!)

Those are the four steps I plan to make on my quest for tone. As you read though the list you may notice that all the steps promise to make the amp louder, but that is really not the goal. This amp is mic’ed through the PA in almost all gigs anyway, so volume is not an issue . The point of being slightly louder is to give me a broader range of tonal textures before the Champ’s output tube just compresses it all down to that lovely honk. As it is now, my Champ is kind of a one-trick pony, but it is a beautiful pony that can do one helluva fine trick.

* * *

Above is the original Champ the day I bought it. Pretty, eh?



Above is the Champ cab cut for the 10-inch speaker opening. That is the Jensen P10R speaker, soon to be replaced by the Weber 10A125-O.

This is a photo of the Champ's guts. The negative feedback loop is the yellow wire that goes from the speaker tap (top, second from right), around the tube socket, and then connects to the resistor on the circuit board.

Updates: More project photos. The amp is finished and sounds sensational.

I replaced the old RCA speaker tap with a 1/4 inch Switchcraft phone jack. This is a very simple mod. The phone jack fits perfectly in the hole in the chassis for the RCA jack.


This the the 10-inch Weber 10A125-0 speaker mounted in the Champ cab. The Weber speaker is the most important step in the project, having the biggest impact on the tone.

The Presence control on the back of the Champ is the potentiometer installed in the negative feedback circuit, another simple mod. 10 = factory setting of negative feedback; 1 = zero negative feedback. For blues harp, 1 sounds best, so the thing to do on your Champ is to just disconnect the NFB loop. This involves unsoldering one wire. You can see the 5V4 recto tube on the left. The power tube has since been swapped for a NOS Blackplate GE 6V6.

Update: Here is a link to a short sound clip of this Champ amp in it's final form... My ultimate SF Champ for harp. In this recording my friend Miles Nichols is playing a Fender Tele through a 1964 Magnatone amp; the Champ is mic'ed with a Shure SM58: Magnatone Blues

Review: Masco ME-18 Amp built by Harp-L member Jim Rossen

I'd like to report on the Masco ME-18 amp I bought from Harp-L member Jim Rossen. These old 1950s-era Masco PA heads are legendary harp amps, and Jim's work on it is first class. He completely serviced the amp, including replacing all the capacitors and b+ dropping resistors. He redressed the wiring and used shielded cables to minimize noise and maximize tone. It came with a quarter-inch input for a harp mic, two quarter-inch speaker outputs (4 and 8 ohms), and two big 6L6 Coke bottle power tubes. The amp is in overall beautiful condition. When Jim shipped the amp to me it was packed better than any piece of gear I have ever bought, new or used.

I consider myself very fortunate to have this amp. Jim does not crank them out… As I understand it this is more of a hobby.

How does it sound? It sounds exactly as Jim said it would: Huge bottom end and fat, textured tone. I would stack this amp up againstany other, bar none.

For several years I lived within two miles of Skip Simmons. I've been to his farm a few times. I've even met with Skip at his bridge. Skip did some work on my vintage tube amps, and he loaned me a Newcomb E-10B tube amp he had built for harp. I've played his Masco amps, and they sound fantastic. The Masco amp I bought from Jim Rossen is at least equal to Skip Simmons's amps in sound and performance. It is one of the best-sounding harp amps I have ever heard.

I bought the Masco from Jim for a fraction of what you would normally pay for such a fine amp. I added an Avatar 2x10 closed-back cab, Weber and Jensen speakers, and Weber Beam Blocker diffusers. This harp rig blows away most boutique combo amps costing 2 to 3 times as much.

Of course, I have no connection to Jim Rossen's amps except I am a very enthusiastically satisfied buyer. Jim is not aware I am writing this. I hope he does not mind.

Thank you, Jim. I strongly recommend Jim's Masco amps to anyone thinking about moving up to an elite harp amp, for a lot less money.

Review: Weber Beam Blockers

I tried the Weber Beam Blocker diffusers in the 2x10 cab I use for larger club dates. The Beam Blocker is a simple device that mounts in front of your speaker, behind the baffle, with a small dome in the center. The curved part of the dome faces the speaker and diffuses the "beaminess" that emanates from the center of your driver.

It works. The speaker is a lot less directional and sounds warmer, fuller, and more balanced in the room. As a side benefit, it cuts down on feedback problems through the harp mic. Any small help with feedback is a miracle for harp players.

In my configuration, I have the Beam Blockers in a 2x10 closed back cab from Avatar (quite large for a 2x10). The speakers are a Jensen Mod 10-35 and a Weber Signature 10-25, both with ceramic magnets. Mounting the Beam Blockers involves removing and replacing your speakers; that's all. I've heard complaints from guitar players about a rattle in their cabs, but I've never had that problem. I can't see how that would happen if everything was properly mounted and tightened.

This seems like a good device for harp players, but I don't know of any other harp players who use them. Have any of you tried these? I give the Weber Beam Blockers a big thumbs up.

Review: Hughes & Kettner Red Box Pro

The H&K Red Box is a small DI box that takes your amp's speaker signal as its input, and converts it to a balanced line-level signal to send to your PA or recording mixer. Since the signal is post-power tubes, you get all the tubey goodness in the sound, unlike many Line Out signals. All I own are vintage tube amps with no Line Out at all, so I was very interested in trying the Red Box.

Harp amps often need to be mic'ed, and the Red Box is a good alternative. With the Red Box you never get room effects or bleed-over, and you don't have to futz with the mic placement and angle to get good tone. With the Red Box your "mic'ed" tone is totally repeatable no matter where you play or how little time you have to set up. The Red Box needs no batteries or power adapters; it runs on the phantom power that comes back along the XLR cable from the mixer.

How does it sound? I think it sounds great. It is possible to get a better sound with the right mic and the perfect mic placement, but not often and not easily. The Red Box has a speaker cabinet simulation that gives you a good-to-great sound every time.

First I tried it with a hot-rodded 1970 Fender Champ. Several months ago I replaced the Champ's RCA speaker tap with a Switchcraft 1/4 inch phone plug, so hook-up was easy: The Champ speaker out goes to "Input" on theRed Box. The Red Box has true bypass to send the signal back to the speaker. An XLR cable connects the Red Box to your mixer. I had the cab sim switched on for this recording. The Red Box also has a ground lift switch in case you get some hum. I warmed up the tubes on the Champ so it would get a little hair on the notes, and turned the volume to 6. I hit "record" on the computer and played for a while.

The sound on the recording was impressive. The room I practice/record in is kind of live and boxy, but the recording had none of that (of course). It sounded like a perfectly mic'ed amp, with all the lovely power tube distortion. It did not sound exactly like the Champ, which is a great-sounding 6-watt harp amp, but it sounded very good.

Next I tried it with the Masco ME-18 amp and 2x10 Avatar cab. I wanted to see if the Red Box made it sound the same as the Champ. No way. It reflected all the things I love about the Masco: Huge bottom end, less compression, thumping power. Once again, the Red Box didn't sound EXACTLY like the Masco and Avatar, but it sounded really, really good.

I think the H&K Red Box could be a great tool for harp players. On stage it makes it a breeze to send a good signal to the PA to augment your tube amp. In studios that prefer to use a DI, it sends a better signal that includes your power tubes as an integral piece of your tone package. A pro guitar buddy swears by the Red Box, and he persuaded me to try it.

The street price for the current H&K Red Box is about $120. I found mine on eBay for $55.