Using a bigger Output tranny?

[Bluefinger]

Not really, everyone who builds harp amps tends to use adequate transformers, Harp Gear amps used Mercury Magnetics who claim a 20% increase in current handling.

Hmmm ... I might get the Mojo Bandmaster tranny or maybe the Super Reverb unit ... but I will probably start with the regular Bandmaster tranny (MOJO769).

This won't be very practical, should you find yourself needing to cut better on stage, you can't pull the amp's back panel off during a number. Nobody builds an amp with a fixed, unbalanced PI, they can all be set to stock at the turn of a knob.

Probably ... I still don't know what to expect from this control so I'll decide as soon as I have done some testing. At this time I am just leaving room for some options in my battle plan. In the end I will probably either put it in place of the presence control or dump it completely ... I really can't tell yet before I even heard it's effect.

5881WXT, they are a bit on the stiff side for guitar, but will give best projection & detail of the 6L6/5881 variants in a 3x10"/4x10".

ok, I might give them a try. They are pretty cheap compared to others so what the heck ... they are 30 watters, right?

"I think in an amp that size I don't need extra headroom anyway." Well by virtue of being 3x10", it will give away a little volume to a 4x10", so unless you are running at very high plate voltages the amp will stil be in the mid-size category...but I love the way 3x10" sound.

And that might be just the size I need. We do retro stuff with a moderate drummer and upright bass. I used to play with a harp player who was great but the Bassman he used was too loud (I know they have volume controls but nobody wants to use them). That's overkill for what we do. I have a feeling that the Bandmaster is just right.

"The first step will be to build something that suits my own playing." How would you characterise/describe that?

Hard to say ... I have not found my perfect amp yet. I do not like RI Bassmans because they are too aggressive sounding. My more or less stock Tweed Super sounds good but is a bit too spongy for a live situation (although it's useable). My Tweed Pro with a vintage Jensen C15N is by far the best. It's got the right size, has good definition and still sounds dirty. I might as well build me another Pro but I would like to try a different speaker configutration as well. I do play chromatic as well and like good cut and definition without being obnoxious but I love that Masco type sound of the Meteors as well and I'm a die hard Little Walter fan. I really need to try different options to know what I really want ...

[MWJB]

Well there's no one amp that covers the Little Walter sound, but there are a few things that are pretty common to many amps of the period. I'd go with a larger cathode resistor at V1, say a shared 1K or 2.2K per triode. Cathode bias...will be handle by your switch, also try cathode bias without the power tube bypass cap. Most of the amps from LWs golden period would not have had NFB, perhaps your variable NFB will do the job, or a NFB defeat switch? Removing the global NFB will cut available volume before feedback a little, but the brassier tone might make up for it enough to be livable with. You probably won't like the cold bias idea, but I'd still build in the possibility as your cathode bias switch will have the hi current side of things handled.

[Bluefinger]

Well there's no one amp that covers the Little Walter sound, but there are a few things that are pretty common to many amps of the period. I'd go with a larger cathode resistor at V1, say a shared 1K or 2.2K per triode. Cathode bias...will be handle by your switch, also try cathode bias without the power tube bypass cap. Most of the amps from LWs golden period would not have had NFB, perhaps your variable NFB will do the job, or a NFB defeat switch? Removing the global NFB will cut available volume before feedback a little, but the brassier tone might make up for it enough to be livable with. You probably won't like the cold bias idea, but I'd still build in the possibility as your cathode bias switch will have the hi current side of things handled.

Thanks!!!! Just because it worked for LW does not mean that it's gonna work for me and I'm not that much of a copy cat so I'll give all options a fair chance ...

[JoeM]

...
1) start with a 5E7 Bandmaster
2) use Weber 10A125 speakers with H-dustcap
...

Bluefinger,

Just to comment on this. I built a 5F6A clone, but I used a Weber 5E7M chassis and the 5E7 cab with the sig10s speakers. (Used the stock iron too). Make sure the top speaker will clear the OT. The particular way Weber had the holes for the OT, I had to remove the bellcover to clear, but I've seen other 5E7s with the OT in a slightly different mounted position that may have allowed for better clearance. You'd hate to have the chassis all completed and then find out it wont clear the speaker.

[Bluefinger]

Thanks for the hint ... usually I check this but it would definitely be annoying if I forget to do so ...
Funny you mention this. I already had similar thoughts, just the other way around. I thought about using a 5F6 chassis forthe 5E7 so I can have a full BMT tone stack plus an additional control for variable -FB, power tube unbalancing or whatever I decide to use it for. Mojo can do custom cutouts but I might have a custom cab built by a friend anyway ...

[angerboy]

A friend of mine near Boulder, Dan Treanor, has a Weber 5E7M amp that is stock except for speakers. He used a mix of Vintage Series Webers. That amp sounds great. I've played it a few times and liked it as much or more than some of the boutique amps. So my only suggestion would be to build it and play it for a while before modifying it. You may like the sound.

[Bluefinger]

I have already built a couple of those amps for myself and other players (actually 5F4s and 5E5As) and just because I like this circuit so much is why I choose to go that direction. Still I think that it's usability for harp can be improved with a view tweaks. Trying a couple of mods is more a passion than necessety for me so there's no way around it

[Bruce / Mission Amps]

I have already built a couple of those amps for myself and other players (actually 5F4s and 5E5As) and just because I like this circuit so much is why I choose to go that direction. Still I think that it's usability for harp can be improved with a view tweaks. Trying a couple of mods is more a passion than necessety for me so there's no way around it

I've built a fair number too.
I built one special 25-30 watt 5F4 harp amp for some pro players I know and sent it down to be used in the back line for the live shows at the Blues Music Awards, now always called the Handy Awards.
With respect to harp playing, I had a hard time getting the E series tone stack to really sound good. It has a lot of midrange.

And speaking of Dan Treanor, I played with Dan a couple weeks ago here in Denver... he used a friends Masco 18 that was rebuilt by Jim Rossen (found on WeberVST BBS) and then I modded a bit more.
Very nice tone and Dan is pretty darn good to.

http://bluesharpamps.blogspot.com/20...pped-into.html

[Bluefinger]

Ok, I have finally decided to try all those harp mods on my beloved 5F4 without messing up it's usability as a guitar amp. After spending the whole day in the workshop, trying all kinds of things of things, here's my conclusion:

o) I increased the filtering to 100µF, 47µF, 22F and 33µF. This tightened things up considerably but voltages stayed pretty much the same. It is definitely an improvement for the harp. For guitar it's different but not necessarely better or worse. I have to get used to it but I assume I can live with it.

o) There was already a switch in the amp, than disconnects the preamp -fb loop. It's great for guitar but not so for harp because headroom is reduced by a fair amount. I only engage it when use with guitar.

o) I tried the suggested cap and pot at the global -fb loop to get more bottom end but it didn't give me very audible results, although I tried all kinds of values. I removed it again.

o) I used the ground switch to disconnect the global -fb loop. This one works great with harp and guitar. I like it! On and off is all I need, no need for a pot.

o) I dumped the presence control and removed the corresponding .1 cap completely. The 2x10" speakers are bright enough for all applications. I won't miss it a second.

o) That hole was used for an unbalance pot for the PI. While that sure is not a MUST HAVE in a harp amp, it gives the breakup quite a different character. I find this very useful to go from sweet to gritty.

o) replaced the Tung Sol 5881 RI tubes with TAD 6L6. Now it doesn't work so hard and starts to feed back later.

Things left to do:

cathode bias (where the heck can I put that witch?)
lower preamp voltages

since I really like that amp as it is right now I might leave those for a future amp.

Thanks to all your tips this is finally a great harp amp. Next friday it will be put through it's paces ... we'll be playing with Steve Guyger and he will have the questionable honor of playing it live for the first time with it's current setup.

all the best

Herbert

[MWJB]

Cool, I look forward to an update.

[Bluefinger]

The more I play around with this amp, the more I like it. At least I have debunked the myth that a good harp amp is a bad guitar amp. It kills for both applications. I get to like the tighter filtering for guitar as well. Now I am really curious what Steve thinks about it.

[MWJB]

Before the 1990's there was no such thing as a "harp" amp, amplified harp was just recorded on amps, principally designed for guitar but manufacturers also expected mics to be plugged into them, PA's in the modern sense didn't arrive until the late 60's. Ergo, any amplified harp recorded prior to the 90's (everything by Jacobs, Horton, Butterfield) was recorded on 'non-harp specific' amps.

Of course, some amps just turned out to more suitable for harp than others, but even dedicated harp amps still share a round 95% (some have more than this) of their components with amps used for guitar. Some completely stock amps make awesome harp amps. It's analageous to mugs...a tea mug is only a tea mug when it has tea in it, fill it with coffee & it's a coffee mug :-)

A 2x10" amp tends to have more common factors that suit getting the best out of both harp & guitar than many other amp configurations.