Blues Master Amp, Again

[ayan]

In December 2007, I posted about my latest build:

http://ampgarage.com/forum/viewtopic.php?t=4028&start=0

If you followed that thread, you know I eventually gave up on the amp, and turned it into a Skyliner HRM. I struggled with that for a while and got rid of the HRM. I then went back and put the HRM board in the amp and tweked for weeks, taking the amp to gigs, only to turn it off and using a non HRM amps instead. Now the Skyliner HRM amp didn't sound bad. If you haven't seen these before, it is our own Geek MacDaddy playing the amp at my house:

http://youtube.com/watch?v=TMx_IdSRcHs
http://youtube.com/watch?v=bKzPtBTassc

The amp did that higher gain stuff pretty well, but the lower gain stuff was no good. Also, the transition from PAB off to PAB on in OD mode was not smooth due to the HRM (works well for me in non HRM amps).

A week ago, I decided to go back to the Blues Master and play with that circuit again. The amp is mostly like S/N 199, has 220K/150K, 180K/120K plate load resistors, correct cathode bias resistors with 5uF bypass caps across the board. Pre OD network is 470K//47pF + 120K + 100K trimmer + 4.7K tail. OD grid stoppers are 68K and 180K. V2a coupling cap is .001uF (715P orange drop), and the rest of the non electrolytic caps are PS series. V1b's coupling cap is .02uF, as are the PI output caps.

Tone stack is Blues Master with 47K slope, boost is the mega boost and I did keep the higher PI plate load resistors, 110K and 100K, while making the rest of the PI Blues Master. Clean Master has a 47pF brightness cap, I use none on the OD Master. HRM settings are: Mid at 11.5K to ground, Bass at 70K to ground, Treble 50K between wiper and bass pot. I do have 330pF from plate to cathode on V2a and V2b.

The clean sound of this amp is trued and tried, and it's very nice. The overdrive is pretty cool as well, and I didn't have a problem with it before. It sounds a bit like a Marshall, maybe the JTM 45 variety. The problem for me, before, was the megaboost. This time around I spent a lot of time dialing the amp, the HRM controls, and think I got to a good place with it. I experimented a lot with "tails" for the Middle pot, and tried a number of different types of netoworks there. For now, I have no tail.

The key to dialing the amp, IMHO, is to turn the presence control up and tweak the HRM after doing so. The presence works very well and adds a nice flavor to the tone, it makes the sound very "elastic," very unlike the conventional Dumble presence control which sounds very stiff. As Chris and I discussed the other day, the presence can be turned to about 9 and the amp will still sound sweet. At 10, it gets harsh.

So that's pretty much that for now. I will take this guy to a gig and see how it does, but I am very optimistic going it. The sound is very soft, and not unlike a non HRM in may ways, but thicker sounding.

Gil

[UltraHookedOnPhonix]

Thanks for the info Gil. What iron and power tubes are you running with that combo?

[ayan]

Thanks for the info Gil. What iron and power tubes are you running with that combo?

PT = Magic Parts Twin Reverb style
OT = Heyboer multi-tap Twin style
V4-V7 = JJ 6L6s

There probably is some additional information on the original thread about this, which I referenced at the top.

Cheers,

Gil

[UltraHookedOnPhonix]

Ooops! that's right, I remember that thread.

It's going to be interesting to hear what you have to say about the amp from a gigging standpoint. I find myself crankin the presence and dimming the bass (non-HRM) in loud situations or else it dissapears in a pool of mud. I've come to realize the Dumblelator chops off a lot of the higher frequencies so to compensate I turn on one of it's bright switches or crank the presence. You are running yours with a loop right?

[UltraHookedOnPhonix]

Double

[ayan]

Ooops! that's right, I remember that thread.

It's going to be interesting to hear what you have to say about the amp from a gigging standpoint. I find myself crankin the presence and dimming the bass (non-HRM) in loud situations or else it dissapears in a pool of mud. I've come to realize the Dumblelator chops off a lot of the higher frequencies so to compensate I turn on one of it's bright switches or crank the presence. You are running yours with a loop right?

I run my amps with a loop, yes, and I never use either the amp's or the Dumbleator's bright switches. On the non HRMs, I don't turn the presence past 2 o'clock, in other words, it's off. My amps are definietly not muddy sounding, I have been tweaking and re-tweaking to get them to the right place since I use them live and with a full band which includes three horns. Deviations from the standard implementations which I have included are one or more, or none, of the following: lower V1b cathode byapss cap, such as 1uF (I currently do not do this); adding a frequency selective pre OD network in some amps (only have it in one of three amps, at the moment, .0047uF//4.7Meg before the 220K resistor in non HRM high plate amp); always using the right master volume brightness cap.

I can't emphasize enough how much better the 100K amp is at cutting through than the higher plate resistor variety. Now, the Blues Master persence control is another matter all together. I like the "feel" of the amp when it is turned up, whereas I don't like the feel of the traditional Dumble presence control. So rather than tweaking the amp with the presence off, as I do in the non HRMs, I tweaked the BM with the presence at about 3-4 o'clock.

Gil

[tubedogsmith]

Is there a schem of the "mega boost" here anywhere?

[ayan]

Is there a schem of the "mega boost" here anywhere?

I am sure there are a few schematics floating around here. However, it's very easy: lift up the ground from the middle pot on a Fender tone stack. That is the megaboost.

Gil

[jaysg]

Is there a schem of the "mega boost" here anywhere?

[ayan]

Is there a schem of the "mega boost" here anywhere?

Right, except that boost wastes half of a relay. Once you lift the tail of the Middle pot, there is no point in breaking the connection from input to wiper.

What I do with the other half of the relay is what Dumble did in Carlton's amp and in S/N 243: connect the .005uF from the J/R switch to the PAB relay and the other connection on that relay pole goes to ground. Thus, when in Jazz mode, when the PAB kicks in you lift the .005uF cap from ground.

Gil

[jaysg]

Closer?

[edit] Updated

[ayan]

Closer?

Almost spot on! The .005uF cap goes to ground via a 22Meg resistor when PAB is ON, just like the tail of the Middle control pot does.

Gil

[Normster]

Welcome back to the dark side, Gil.

I find that I like having the bright switch on for both clean and OD, but it gets harsh in PAB. The solution for me was to use two terminals of the PAB relay to switch out the bright switch in PAB mode. I also find it very useful to put the mid shift on a relay so it can be switched from the floor using a 3-button switch. The mid shift is a nice "in between" boost when in OD. Fattens up the OD but isn't quite as agressive as the mega boost.

[ayan]

Welcome back to the dark side, Gil.

I find that I like having the bright switch on for both clean and OD, but it gets harsh in PAB. The solution for me was to use two terminals of the PAB relay to switch out the bright switch in PAB mode. I also find it very useful to put the mid shift on a relay so it can be switched from the floor using a 3-button switch. The mid shift is a nice "in between" boost when in OD. Fattens up the OD but isn't quite as agressive as the mega boost.

Hi Norm,

I do remember your 3-button footswitch at NAMM. Possibilities are endless, aren't they?!

Cheers,

Gil

[Tonegeek]

Welcome back to the dark side, Gil.

I find that I like having the bright switch on for both clean and OD, but it gets harsh in PAB. The solution for me was to use two terminals of the PAB relay to switch out the bright switch in PAB mode. I also find it very useful to put the mid shift on a relay so it can be switched from the floor using a 3-button switch. The mid shift is a nice "in between" boost when in OD. Fattens up the OD but isn't quite as agressive as the mega boost.

+1 on the footswitched mid boost. If I had to choose 1, I would take the mid boost over the PAB. My mid boost is a little tamer than the real deal though (1.82n vs 2n). In combination with PAB it has the effect of providing degrees of boost more so than changing the EQ. I find the mid boost is a little smoother sounding than the PAB, except that when both are on it is rock city!

I imagine you are sacrificing the switched bass wiper to do the bright switching. I tried a PAB/mid boost thing (labelled it PAMB) using one switch and it worked very well. I did not miss the slight drop in bass with this setup. It depends on how your bass is adjusted as to how much it will affect the tone when you don't switch the wiper. If it is up half way or so, you really don't notice that much. Its just when it is below half way that you start noticing a drop in bass response when switching only the bass to treble legs while still leaving the bass wiper connected. Still, doing the wiper too is the best way if you got the relays for it...