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Dirty-South Blues Harp forum: wail on! >
Isaac's Valve Jr. Mods -- a short story.
Isaac's Valve Jr. Mods -- a short story.
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isaacullah
814 posts
Mar 10, 2010
5:09 PM
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NOTE: I've just edited this slightly for clarity and readability, and have corrected some component values.
So I've had my Valve Jr all of 3 days now, and I knew something had been done to it that made it not as harp friendly as the one I tried in the store. When I bought it (from a guitarist), he said that the previous owner had done "a gain and tone mod" to it. He clearly had no idea what had really been done to it, and only knew that there had been a "gain" and a "tone" knob added to the faceplate. What kind of a tone control? How does the gain control work? He did not know.
So, while the amp sounded good, it did not have that deep rich crunch that one in the store had. It was always a bit bright and too punchy, and I couldn't get the volume up enough to hit the sweet spot before feed back. Also, the tone control seemed to be sucking A LOT of volume.
So this afternoon, after a frustrating morning of PhD dissertation work that I couldn't really get my head into, I decided to procrastinate a little bit by cracking the amp open and see what had REALLY been done to it. Since I was going to be under the hood anyway, I had a look over at the instructions for the Lone Wolf mods, which re-voice the amp for specifically harp. Armed with that knowledge, and my "advanced dabbler's" understanding of amp topology and electronics, I dove in.
First off, it was clear that who ever had done the mods was NOT a pro. Obviously it was someone who, armed with a soldering iron and a nincompoop's unknowing bravery, had purchased a "mod and upgrade" kit from one of the numerous internet business pedaling such wares. How do I know they really didn't know what they were doing? Well, for one, they had replaced some perfectly good components with "better" ones (ie. someone had sold them stuff they didn't really need), and all the wiring was done really really poorly. There were leads left uncovered all over the place, cold solder joints left and right, the hole underside of the board was covered in burned flux, and the holes in the chassis were drilled with what looked like the dullest, rustiest old twist-drill bit you've ever seen (ie. they didn't use a nice, metal friendly, step-bit).
The "gain" mod was a silly one. It added a second pot to the regular pot, with a few caps to ground here and there. Really, all it was was a second volume control in parallel with the first. each controlling slightly different frequencies. It was coming out, no doubt about it.
Then there was the tone control. It was a highpass filter put in AFTER the volume/gain pot. A nice volume sucking one too! All three controls taken together, that's a signal loss after a signal loss after a signal loss! It was coming out.
There was one good mod done, which was to put a larger cap on the output tube's grid. The stock is 22uf, and the mod is 1000uf. This is better for the bass response, and I have seen it mentioned in multiple places as being a good mod to do. Good. Leave it in.
So, since I was yanking this stuff out anyway, I decided to just go ahead and do all the Lone Wolf mods. I had all the components in my parts bin anyways, so what the heck. But what to do about the extra pot I had left over? I had the hole in my chassis, so I needed to put something there. Aha! I had it... A master volume control! This works well since the stock "volume" is actually in between the two preamp stages, and so really it is a "drive" control anyway. Putting a pot between the preamp and the power amp stage will be a true volume control, and will let me keep a nice dirty tone (from overdriving the preamp) at lower volumes (by dialing down the master volume).
It's simple to add this in. You use a potentiometer as the leg of the resistive divider network between the preamp and poweramp. You'd be fooling with this network anyway if you were doing the Lone Wolf mods. You just make sure that the series resistor and the pot to ground have the same ohmic value (i used 500k each), so that when the volume is all the way 'up" (max resistance) the power tube sees the right voltage (around 30), but when it's down (0 resistance), the signal will go all to ground.
So, I did all the rest of the mods except that I didn't yet add the second input (I didn't feel like drilling), and I used 0.15uf coupling caps (it's what I had, and it doesn't really make any difference 0.1uf to 0.15uf.). I had to fix a lot of faulty solder joints and A LOT of bad wiring (damn that unskilled hack solderer/guitarist!), but in the end I fixed it all up very nicely.
So how does it sound? It sounds AWESOME! I can get full volume without feed back using my "DIY bullet mic" that has a Mid-Z Audio-Technica dynamic element (similar to an SM57). When I use my Turner +1 mic with it's hot High-Z crystal element I definitely get feedback a 3/4 up, but the volume at 3/4 with that hot element is just as loud when I have it dimed using the dynamic Mid-z element. And the tone is the same, but a little punchier becasue the crystal carries more highs. I can't get nearly full volume or a very good tone with my low-Z mics (sure PE57, other dynamics), but that's becasue the input is loaded to see a hot signal. Adding the second input will take care of this.
The "drive maxed out" tone is very nice. Warm, tubey, with some hair on it. Not overly crunchy, but definitely dirty. Very nice. I can keep this tone at any volume by maxing the "drive" and adjusting the level with the master volume control. I can get a nice warm clean sound with plenty of volume by putting the drive at 3/4. I like the tone best at about halfway round. It cut's the highs just a tad, but keeps it all very focused. This all through my DIY 2x8" cab with vintage ceramic speakers that came from an old electric organ (which are a fantastic and very cheap source of very good, harp-friendly speakers).
I WILL do the high/low input mod. I want to be able to use this with my PE57, which I can't right now.
The moral of the story is: if you don't know how to mod it right, don't mod it! Get someone who knows how to help you, or let them do it for you. Also: Never trust a guitarist! ;)
After the Lone Wolf mods, this amp is a BITCHIN harp amp. WAY better sounding than the stock amp I tried in the store, and way way better how it sounded when it was "modded for guitar". This is the best sounding amp I've ever owned, and the one of the best I've ever played through.
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The magnificent YouTube channel of the internet user known as "isaacullah"
Last Edited by on Mar 10, 2010 6:58 PM
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Cisco
90 posts
Mar 10, 2010
5:29 PM
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Isaac,
Tube amps RULE!!!!!! Now you know why. If you're ever down in Tucson look me up and we can play around with a couple boutique harp amps and some great tweed guitar amps for harp and a bunch of vintage mics - also you can drink some of my home brewed Belgian beer on tap and properly corked Belgian beer bottles (30 years experience brewing!!).
Last Edited by on Mar 10, 2010 5:38 PM
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isaacullah
815 posts
Mar 10, 2010
6:42 PM
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Cisco, next time I'm down there, you are ON!
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The magnificent YouTube channel of the internet user known as "isaacullah"
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wheezer
152 posts
Mar 10, 2010
6:46 PM
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Hi Issacullah,
This are the components of the tone mod I did to my HB GA5 (same as an Epi. VJ but comes with a tone control and the amp is 40% cheaper to buy).
Kit: 2 Alpha 24mm 1M log pots
1 500pF/500V silver mica capacitor
1 10nF/600V Sprague Orange Drop 715P capacitor
1 10K 0.6w metal film resistor
I don't pretend to know what all these different bits and pieces do but when you follow the instructions and fit the kit (you have to do away with the origional tone and volume pots and their associated small PCB's)
it trans forms the amp.
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isaacullah
816 posts
Mar 10, 2010
7:10 PM
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Hi Wheezer, Thanks for the info! I've certainly heard that the GA5 is a good little amp for harp. Concerning the mods, where did you find the instructions? I'd like to read them to see what exactly is changed in the circuit.
The silver mica and orange drops are certainly better quality caps than equivalent film caps, and certainly better than ceramic ones. The only thing is that I'm not so sure that you can actually hear the difference in the quality of sound between the same value film cap and the same value silver mic or orange drop in an amp that is supposed to sound dirty. In a super clean amp or a hifi amp, yeah, you might notice it, but in a harp amp or a guitar amp, I'm not sure. Certainly it's worth buying caps with tighter tolerances (ie. an "G" cap with 2% deviation tolerance from the nominal value will probably sound better than an "m" cap with 20% deviation tolerance), but I'm not sure it's worth spending a bunch of dough on fancy material caps. For all I know, using rough-sounding caps may actually be helping the tone of a dirty amp! But this is all my personal opinion, and I know lot's of other folks who disagree with me, which is totally cool! ;)
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The magnificent YouTube channel of the internet user known as "isaacullah"
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wheezer
154 posts
Mar 11, 2010
4:13 AM
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@ Issacullah,
Instructions came with the kit. The kit is the Alnicomagnet Brownface Tone Control and it's good to know that the components are of good quality. The kit cost £9.99 (about $15) and came with full instructions
including a "free" how to modify effects pedals.
Nigel, of Alnicomagnet, is a really helpful guy and I did ask him about a conversion kit specifically for making these amps even more harp friendly but he said that as he did not play harp he did not know exactly what would be required.
Nigel can be contacted via his Youtube channel.
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isaacullah
817 posts
Mar 11, 2010
9:58 AM
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Thanks for the info Wheezer. If it's a brown-face tone control, I certainly can figure out what the circuit is by googling the nets. I'm fairly pleased with the treble-cut tone control that the Lone Wolf mods incorporate. A treble cut is a good control because it absolutely does not affect the volume of any of the signal below the high-cut frequency notch (as set by the value of cap you use). Adjusting the pot in such a treble-cut tone control only sends more or less of the higher frequencies (above the notch you set) to ground, while letting all the lower freqs pass by. It gives you really good control over feedback since usually it's the high frequencies that are the culprit. You can dial it in to have enough brightness to make your sound punchy, or you can pull it down to make your sound darker.
All in all, I'm VERY pleased with the Lone Wolf mods, and I think the addition of the master volume control really makes this amp versatile.
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The magnificent YouTube channel of the internet user known as "isaacullah"
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toddlgreene
1010 posts
Mar 11, 2010
10:09 AM
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Isaac, you're so happy, you're glowing thru the forum! Randy Landry came to our meeting last night and brought my Epi combo home with him to mod-I can't wait! Yeah, that treble cut seems like a must-have in my book. Wish I was as handy as you and not an electrophobe, so I could do it myself.
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Todd L Greene. V.P.
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Bluzdude46
528 posts
Mar 11, 2010
2:31 PM
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I like the treble cut and use it pretty drastically. A coupla guys in the Frederick Harp club preffered a little more treble. Great tube amp wish it was 15w
I put a 10 band graphic equalizer in front of the Bogens for a little bit better grip on feedback I still think I'm buying a Kinder AfB when I have the funds. Easier to dial in
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The Original Downtown Philadelphia Fatman... Accept No substitutes!
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Ryan
208 posts
Mar 11, 2010
2:44 PM
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Are you going to post a video so we can hear how it sounds?
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isaacullah
820 posts
Mar 11, 2010
5:58 PM
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Ryan, the video is being uploaded as we speak (er, uh, type)! I will post it as soon as it clears YouTube.
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The magnificent YouTube channel of the internet user known as "isaacullah"
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djm3801
319 posts
Mar 12, 2010
2:33 PM
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Hey, Isaac,
You know, with the knowledge you have, and knowing how cheap parts are, and being able to document what you have done, you can make a buck selling this stuff in kits. Some of the prices I see on the kits in the net are absurd. A well documented travel you had here on the Junior!
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isaacullah
832 posts
Mar 12, 2010
5:41 PM
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thanks djm. I know I *could* put together some project kits, but that's not really my thing, you know? I'm all about just sharing my experiences and any little knowledge I have with others. I'm a full time PhD student, and that takes priority over a lot of other things for me right now. This is the stuff I do to stay sane while doing grad school! If I were to try and make it a business venture, no matter how small of one, it would take some of the joy out of it for me!
Now that's not to say I wouldn't put together a bunch of components and some instructions/supervision for someone in some kind of trade/barter situation. Yeah, I'd totally do that.
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The magnificent YouTube channel of the internet user known as "isaacullah"
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jawbone
267 posts
Mar 14, 2010
8:00 AM
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It bugs the heck outta me when someone so young is such a smarty pants!!!!! (I need emoticons here ;-) ;-)
Hey Isaac, I finally got a Harp Break pedal, having a lot of fun with it!! Have you seen those projects using all the parts from burnt out flourescent bulbs?
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If it ain't got harp - it ain't really blues!!!!
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isaacullah
834 posts
Mar 14, 2010
4:10 PM
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Jawbone, yeah I've seen them! They are guaranteed to give you one *bright* sound! (har, har, har!). Actually, I think they will sound very harsh for harp since the transistors and diodes and caps and stuff in those CFL's weren't picked for their audio qualities. Probably the metal/thrash guitarists will like the flavor they produce. It's a pretty cool recycling/reusing idea though
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The magnificent YouTube channel of the internet user known as "isaacullah"
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blueswannabe
38 posts
Mar 15, 2010
4:04 AM
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Isaa,Saw the youtube video. The amp sounds fantastic.The master volume control sounds like a great idea too. The amp sounded like a Kalamazoo Model 2 to my ears.
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Bluzdude46
536 posts
Mar 15, 2010
6:29 AM
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I was considering doing mods on the Epi for People, but experimenting on electronics takes up enough time I should be using for practicing or playing that I decided not too. Isaac, welcome to the Jr modders of Harpdom. I may not be a REAL electrical wiz, lets face it there are some ugly solder joints inside my boxes. But I noticed when you're on stage and Blowin' harp, the people that come up and tell me they like the sound never ask to look inside the box!
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The Original Downtown Philadelphia Fatman... Accept No substitutes!
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isaacullah
836 posts
Mar 15, 2010
10:19 AM
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@Bluzdude: That is true! The "prettiness" of the joint's don't matter too much for the sound, but, you CAN hear the effects of certain types of really bad solder joints. They can induce a kind of static, or if the joint is loose, the sound can go in and out as the joint flexes. This was case for the amp I bought, and is probably the reason I got it for such a good price. It takes a while to learn to solder nicely, and it also takes a little investment in equipment and supplies (like a good quality low-wattage soldering iron, copper de-soldering braid, shrink tube, and a collection of various gauge solid and stranded core wire), but I think it's pretty important. Probably half of all "oh crap, i did something and now my amp/effect doesn't work any more!" type questions on the various music electronics boards I frequent come down to problems with soldering. Cold solder joints, broken solder joints, solder bridges, flux bridges, broken leads, heat-burned components, exposed leads making a short, etc. So, while does not need to look "pretty", it's pretty important to do it properly!
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The magnificent YouTube channel of the internet user known as "isaacullah"
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