2004 Ibanez Destroyer (DT-200). Fun weekend project after a grinder of a work week. Completely made over with parts on hand.
I have a thing for “pawn-shop” guitars. I’m not talking about Fender’s inspired-by-Urban-Outfitters line of fake thrift store guitars (Fauxnder?). There’s something very attractive to me about souping up weird, poor-selling budget guitars that nobody wants. Sure, they’re sometimes irredeemably terrible. But sometimes gross overinvestment in an undeserving instrument can get you to really interesting places. The fact that something is not “sought-after” just means that nobody’s gotten famous by abusing it — yet. Look at what Sonic Youth did for Jaguars and Jazzmasters. Or what doom metal did for Sunns and V-4s.
I tend to think of guitars in two-dimensional terms — sound and playability. Both of these axes depend on some elements you can change and some you can’t. You can’t change the wood. You can’t normally change the neck or frets. But you can change the pickups, electronics, nut, tuners, bridge, overall setup. If the stuff you can’t change is decent — like this very nice chunk of mahogany here, with a comfy maple neck and rosewood board — then you can change all the other stuff and come out with a unique and exciting instrument. That’s the essence of a “player’s guitar:” placing no inherent value in tradition or resale price, but appreciating the thing for what it does, to the extent that it is an interactive vessel that smoothly facilitates inspiration and expression. In short, its being and doing are one and the same. Collectors might puke, but wow is that kind of guitar fun to play. It’s worth asking: if a guitar’s value, looks, and perfect sound & adjustment make me LESS likely to pick it up and play it, then what is the point? Is it even still a guitar, or is it a guitar-shaped sculpture?
Lots of fancy words for a budget Ibanez. Whatever, it does what I was hoping — sick 80s thrash and old-school death metal tones, in a lightweight and couch-friendly package. Sounds similar to my Les Paul that has the same pickups (a very good thing), but with more snap from the maple bolt-on neck. Great for meedly-meedly with lots of punch. Nice clean tone too, not sterile at all. Way better than the last Ibanez superstrat thingy I played. The neck feels good and the frets are in good shape, and much better leveled than the MIM Fender I bought new in 2007. Remember that this is a Korean-made guitar!
Dork info: 1980 Gibson Dirty Fingers pickups w/ covers added & mild wax potting, swapped out all hardware, Gotoh TOM bridge & tailpiece, Switchcraft switch & jack, Alessandro 500K vol pots & CTS 1M pull-shaft tone control to coil-split the neck pickup. New handmade unbleached bone nut. Set up to my specs here. Feels GOOD, man.29 notes
Roland JC-120UT. Made in 2000. The UT model, which is the current-production one, has a very different rear panel than previous incarnations of the JC120. No external speaker jacks, and it has a mono-out, stereo-return series/parallel switchable FX loop, which operates only on channel 2. It’s a really good FX loop, actually.
The worst thing you can say about the JC120s is that they have horribly flaky unobtanium nuts on all the jacks. They crack, fall off, etc, and they cost five dollars a piece to replace. This amp was missing all but two nuts, and mainly had crudded up jacks and switches, with a few compromised solder joints. It had already had the supply recapped a couple years ago.3 notes
B&K Model 607 solid state tube tester for sale. Fully rehabbed, calibrated, guaranteed. 1% tolerance, <100ppm components in the load and measurement networks, and grounded power cord for safety. Comes with a nice setup book, laminated reference sheet for all the common types, and a 1973 substitution manual. All solid state reliability, does emission testing and has one of the best grid leakage tests ever — functionally very similar to the Sencore TC162. Lightweight. Some nicks and scratches as expected for an old piece. I have a digital service manual for it too.
Probably of interest only to technicians…
I didn’t notice this until recently, because I never had a problem with the reverb circuit in the TSL. The schematic that’s publicly available on the internet (here) shows Rev4 of the reverb circuit PCB. My own TSL has Rev3. If you have to replace a reverb tank in a JCM2000-series amp, you might want to check your revision.2 notes
bdy asked: Hi there, I read article about that Sunn Beta Bass and that remind me my Sunn Concert Keyboard (yes Keyboard - similar circuit as Bass and Lead) is really noisy. All volume are down, no instrument plugged and a lot hiss. Normally I don't care because most of the time play loud but against my other amplifier where they are tube or solid-state is big difference. Compared to similar aged Acoustic 220 is big difference. Is there anything what should I check? Guts looks untouched and original. Thanks
One thing I’ve noticed about the Concerts (as opposed to the later Betas) is that even though they’re solid state, they use carbon comp resistors throughout. So it’s entirely possible that the hiss you’re hearing is just a byproduct of those carbon comps, most of which are probably drifted with age and compromised by moisture penetration. Even when brand new, carbon comps are enormously hissy — and the more current through them, the more noise they make. The hiss is unlikely to be a supply cap because then you’d be hearing hum/buzz. If all knobs are down, then you know the hiss is coming in after the latest stage where there’s a pot controlling the signal. Look for a load resistor after that with a decent amount of current through it, and consider replacing it with metal film. Check values to see if there are any that are grossly out of spec (>20%).
There is NO sonic benefit to using carbon comps in solid state circuits, since the voltages are so low that you don’t get nearly as much of the sweetening effect as in tube amps. It’s obviously neither cost effective nor necessary to replace every resistor in the amp, but upgrading load resistors in the signal path to metal film makes a lot of sense.2 notes
How not to replace the pots on a vintage amp. This is a Sunn Beta Bass, in otherwise very good condition. Some previous owner decided to replace 8 pots on the front panel, but couldn’t or wouldn’t find the right long-leg PC-pin style to mount directly to the PCB. Instead, 8 of the pots have solder lug terminals connected by a rat’s nest of 18-gauge solid core wire to the preamp PCB. The mess of wires picks up noise from the power supply, causes instability in random control settings, and is just waiting to fatigue and break. Worse, the metal shield that keeps the preamp quiet is missing. Worst — some of the pot lugs were never even soldered to begin with.
It would have taken just the tiniest bit of extra effort to do this right. Instead, this person sold the amp to someone else, misrepresenting it as 100% working. It makes me angry that the buyer brought the amp to me, just trying to be responsible and get some routine servicing done, and then I had to tell him that the amp is in fact unusable and unsellable without a significant amount of remedial work.
At the risk of sounding pedantic and arrogant, this is why the answer to 80% of technical questions is “take it to a tech.” I admit there was a time, years ago, when I might have done something like this to one of my own amps, and been ok with it. But I can’t imagine passing the mess on to someone else. It would certainly have blown up in my face, and then I would have had either to admit defeat or to learn something new. The ‘money saved’ by DIY hack jobs is illusory at best, and often ends up more expensive than a competent tech’s bench rate. Don’t get into it unless you’re looking to commit to a hard learning process.12 notes
Anonymous asked: I found a deal on an Ampeg VT-120 and want to try to convert it into a head for bass guitar. Any suggestions?
My suggestion would be not to do it at all. The VT120 has so many problems as it is, converting it for bass would be a nightmare. It’s only 100W, and the unique features it has are not useful for bass players. Low power, triode mode, damping switch — all would just cause the bass tone to be woofy, muddy, one-note blur. The distortion channels do not like low end; it makes them farty-sounding. The reverb feeds back easily when you feed it low frequencies as well.
Anonymous asked: Any experience with 30" instruments? I'm a guitarist thinking about playing bass for a project, considering either a 30" bass (4 string) or the fender bass vi. To ease the transition. I know the vi uses specific strings could I still tune either to a#fa#d#gc?
I’ve never owned a 30” instrument, so I couldn’t really tell you. People do all sorts of things to the Bass VI, though. It seems plausible that it could be used as a baritone guitar. I would stay away from a 30” 4-string bass. I have a 34” bass tuned standard and haven’t found it difficult to play at all, but have often thought that the action was too high and string tension too low. I can’t imagine trying to make it work on a 30” scale — it might end up being counterproductive and turning you off from bass for good.1 note
Two 12-gauge homemade Speakon adapter cables, one to binding posts for a bridged-mode rack power amp, and one to 1/4” for use with an Ampeg V-4 and bass cabinets.
Speakon is one of the best connector standards ever invented. It has mostly only been used in PA gear until recently, as it’s started showing up on high-powered bass amps. 1/4” speaker connectors have lots of problems:
Speakon has none of these problems. It locks in place, it can handle four separate conductors for biamping or stereo applications, it’s insulated, you can put 10AWG wire in it, it doesn’t require soldering, retains the cable jacket with a ratcheting clamp, and nothing gets loose over time.
I make all my own cables. I don’t do this for sound, except to the extent that I like to use ultra-low capacitance cable with really good shielding for my instrument cables (reduces noise and treble loss). It’s mainly an issue of reliability — particularly regarding speaker cables. With a tube amp, if the speaker cable goes open, you’re looking at a new output transformer in many cases. I repair amps like this all the time — someone stepped on the cable and it pulled out, the solder cracked, the connector bent, it wasn’t making good contact, etc. People end up paying a lot of money to fix something with a simple and preventable cause. Bass amps with bridged-mode options are using Speakon for safety reasons now, but I wish that guitar amps and cabs came equipped with them too. It would save people a lot of grief from the inherent unreliability of the 1/4” connector for speaker applications. I’ve been retrofitting all my cabs with jackplates that have both 1/4” and Speakon connectors.
The cable itself matters too, to the extent that it needs to be flexible, abrasion-resistant, and able to carry the necessary current without resistive losses over the length you need. I go overboard with gauge, typically using 14 or 12AWG. It has no effect on the sound, but does seem to make for a more reliable cable in some cases. There’s no sonic reason to use anything heavier than 16-gauge for guitar, but if you swap cables between guitar and bass setups a lot, you might need something heavier for the bass stuff. Higher power into lower impedance means lots more current. And the longer a cable is, the heavier the gauge it has to be to avoid resistive losses.
Cheap vanilla zip cord is great for most speaker applications, but I’ve taken to using separate conductors in twisted pairs, to keep down the amount of interference coupled into nearby signal cables. I seal the ends with heat-shrink, lock down the Techflex, and then fold it over in a ‘horn’ shape after the connector is on. Built to have cabinets rolled over it on stage.6 notes
Music Man HD-130 head with tube PI.
This was one of the bummer stories. I fixed it and returned it to the client, then a week later it ate a brand new set of tubes. I had seen the bias voltage drop out when I had it before, but thought that I had addressed the problem — the ground connection for the low-voltage supply had been cracked and compromised, and I fixed that. The amp ran for two hours at maximum power on my bench. But I hadn’t cleared the ENTIRE problem.
In the picture you can see two electrolytic caps on a small board to the left. That board is the low-voltage supply, fed by the orange PT secondary wires. It produces dual-rail +/- 43VDC on the output. Those two caps are the filters for each rail, immediately after each half-wave rectifier. The bias supply is tapped off of the negative rail of this supply.
The arrow on the right points to the bias control and a set of zener regulators that knock the +/-43VDC down to +/-16VDC for use in the preamp. They have their own filter caps.
In this case, the two reservoir caps on the left had cracked solder joints. When the amp would heat up, they would lose contact, causing the bias supply to see huge 60Hz half-wave ripple instead of real, flat DC. This meant that the actual grid bias on the power tubes went from -34V of clean DC to an ‘average DC’ of -18V of unfiltered half-wave rectified AC. Instant redplating on all four tubes.
What obscured the issue is that there was still enough DC left in front of the zener regulators that the +/-16V regulated output was completely unaffected. The preamp continued operating normally. This is a case where a seemingly rational assumption — that everything downstream of a faulty supply will be affected by its malfunction — was completely wrong, and cost a lot of unnecessary time and money as a result.9 notes