New Project Amp

[petesz]

So, does anyone here own or know anything much about Elk amps? I just bought this one, as a kind of refurb project and intro to amp diy:

Sound is pretty interesting, there seems to be low, medium, and high gain inputs. Sounds very thin though, even with the bass cranked its very trebly. Theres also a lot of hiss and the occasional pop sound, im assuming that means it needs new tubes..? The reverb is pretty cool, sounds nice except for the popping sounds when you turn it up. Anyone know what that might mean? Vibrato is broken, gonna suss it out and see if its fixable. Also, sounds absolutely terrible with any overdrive pedal, it just seems to kill the bass even more and makes it very buzzy sounding. Sounds cool with my tonebender though, very nasal but totally garage rock.
Anyway im gonna open it up on the weekend and have a geez, see if theres anything instantly noticeable.. Ive read that old amps like this can have fried capacitors, does anything think replacing the caps would be worthwhile?
Any advice/info/opinions on where to start welcome!

- I just recorded a quick clip, demonstrating clean sound and then with some reverb : http://www.users.on.net/~w2620/Elk.mp3

[TRADAmpGuy]

Old amps, especially if they have sat for a few years, generally need a cap job. This entails replacing all of the electrolytic types in the power supply and also the bias supply (if it's fixed bias). Also, if there are any electrolytic caps used to bypass any of the cathode resistors in teh preamp, they should be replaced also. A good shot of cleaner/lube in the pots, cleaner (no lube) for the tube sockets and jacks and a tube socket tensioning are also good practice. The popping and crackling sounds might be bad plate resistors... maybe. If you have any more questions, feel free to ask. Im more at home in amps than pedals... hoping to fix that here

[jkokura]

That's cool Pete! Take some pictures so we can see what's going on in there. You're right that it's very trebly... I wonder if it's supposed to be some kind of Princeton Reverb clone of some sort... Princetons sound fuller than that.

Jacob

[jtn191]

here's some info on the company http://drtube.com/guitamp.htm#Elk

you're right about it being awfully bright   

[petesz]

And that soundclip was with the bass turned all the way up, and treble about halfway.. although i was using a telecaster which is naturally pretty bright. I'm thinking maybe its based on something like an AC-30? It really doesn't sound fender-ish (although it looks it).

Hey Trad, what does a cap replacement mean in terms of sound? And where is a good place to buy amp replacement parts? Also do you have any recommended reading for a noob like myself? I had a browse on the geofx and ax84 sites mainly reading the safety tips haha. I may have a bunch more questions coming over the weekend..

[timbo_93631]

I get most of my amp parts from these places:
http://turretboards.com/
http://www.triodeelectronics.com/
http://www.hoffmanamps.com/MyStore/perlshop.cgi?ACTION=enter&thispage=partsenter.htm&ORDER_ID=!ORDERID!
http://www.mojotone.com/

[TRADAmpGuy]

I like changing out caps on amps that are 10 years old or older. The electrolyte dries up over time and can cause the cap to fail... either by not doing its job and causing all sorts of hum, ghost notes and flub in the bottom end. Or they can short out and take all sorts of expensive parts with them. Its rather cheap insurance against more expensive repairs down the road. As far as cathode bypass caps, it will change the gain character of the preamp tube that is is used on.

Which model it this BTW? I'd like to see the tube chart and maybe a schematic on it and I might be able to tell you if its going to be a bright amp on purpose or if something isnt quite right with it and possibly offer some ideas to tweak it more to your liking.

I use Mojotone and Antique Electronic for parts. Gerald Weber has a few good reads, "Tube Amp Talk for the Guitarist and Tech" and "Tube Guitar Amplifier Essentials" are two that I'd recommend. Another good read of a more general nature is "The Guitar Amp Handbook" by Dave Hunter.


Hope this helps and keep me posted

Brian

[oldhousescott]

This looks like it could be the schematic, or at least close enough.

http://drtube.com/schematics/elk/es-30.gif

I second TRADAmpGuy's suggestion about replacing all the electrolytics, even the cathode bypass caps.

[petesz]

Thanks for the info everyone.
As far as i can tell from old photos, this is an Elk EL-30 head. I cant find a schematic anywhere. The es-30 was a 15w model, not sure if its close... im having trouble understanding it..

So ive opened it up and had a good look.. man its a messy job.. parts going everywhere. Cant see anything instantly noticeable that would indicate why its so bright/why the vibrato is broken. Ended up just cleaning the pots,knobs, faceplate and having a good look around.
Ive taken a bunch of pictures, maybe somebody can help me decipher whats going on in there?

PICS: http://www.users.on.net/~w2620/elkpics/

As far as i can tell, the picture that shows the back of the amp, left to right is:
Two can capacitors, im assuming these would need replacing too. Why are these here?
5AR4 - rectifier tube
2x EL34 - the power tubes
An unbranded USA 7025 tube which is apparently a renamed 12AX7.
6AQ8 - What this for? The reverb?
2x 12AX7 - preamp tubes..?
All the tubes look to be in pretty good nick, but they are labelled Made in Japan so im thinking they are around 40 years old and due for a change..

I also realised it doesnt have a standby switch, would it be easy enough to add one in?

So now im pondering.. if i do replace all the caps and tubes (costing about $200) and maybe tweak a few values here and there, is it going to sound much better? Im worried that the transformers might not be very good either. Or would i just be better off salvaging the chassis/cabinet and building a better circuit/new amp inside it (might cost ~$400) ? Hmmmmmmm

[oldhousescott]

I would bet the EL30 is very similar to the ES30, excepting the output tubes. One thing I'm not seeing in your amp are the cathode bypass caps. I see one at the end of the board. The linked schematic shows four. That could just be a difference in the models, or someone could have clipped them out at some point. The bypass cap that is there looks too new to be original. Oh wait, I see another one on a separate terminal board. That one looks to be the same vintage as the other. I guess they could be original. I would change them anyway.

Those are probably the original tubes, and they look fine visually. No signs of loss of vacuum. The 12AX7 for the trem needs to be a strong tube for the oscillator to work, and the cathode bypass cap needs to be in place and in spec to get the maximum gain from the tube.

The can caps are for the main power supply. I can't tell if they're original or replacements, but you might as well replace them. JJ or F&T make good replacement can caps. I see one other large electrolytic, and that could be the bias cap. It should be replaced as well.

With a 5AR4, you don't need a standby switch as the rectifier will bring the B+ up slowly.

The 6AQ8 is a stout dual triode tube, one half of which is used to drive the reverb, the other half of which is used in the PI. It's interesting that the other half of the PI is just a 12AX7 section. Seems that would cause the PI to be unbalanced, but maybe that was what they were going for.

The rest of components look to be pretty good stuff, paper-in-oil caps, molded paper and mica caps, carbon-film resistors. There are a few carbon-comp resistors in there, and they may have drifted significantly over the years. It would probably be worth checking them and replacing any out-of-spec pieces with carbon-film or metal-film varieties.

The tone stack looks like a modified James/Bax stack, so definitely not Vox or Fender. There is a good bit of treble-peaking sprinkled throughout the circuit, so I can see where it could be a bit bright, but if the bass is basically non-existent, it's time for a cap job. Not knowing the provenance of the amp, it's just a good idea anyway.

[timbo_93631]

...but if the bass is basically non-existent, it's time for a cap job. Not knowing the provenance of the amp, it's just a good idea anyway.

+1

It would be a good idea to get it back in working order and then make decisions about modding it.  Those are actually pretty nice sounding amps and well constructed vs. many Japanese tube amps of the era.  I would expect it to sound much fuller after a cap job.  It is a bit of luck that it has 50uF/50uF cap cans, you can get JJ's from turretboards.com for around $12 IIRC.  Just do the electrolytics and see what you think.  It is actually much more tidy inside than the Valco/Supro amps I love.  If you get it operating properly and it is still too bright for your tastes, it might be perfect for someone that plays a Les Paul or a country player.  It would make a good ebay candidate or I am sure many others here would be interested in it, myself included.

[timbo_93631]

Yunno, after looking around a bit it seems that amp is pretty intreresting.  Most of the one channel Elks with that set of controls have 2 x 6BQ5/EL84 output section, I haven't seen a 2 x EL34 that isn't a two channel amp.  It is like a custom amp 30, but with the custom amp 50 output section.

[petesz]

Awesome, thanks guys SO much for all the info, you rule! Im trying to do lots of reading to understand what all these things mean as well, so I think im slowly starting to get my head around it (at least a little bit)!
Ok so i'll start by replacing the caps, and see how it goes from there. No need to wreck a perfectly good amp
Again thanks heaps for taking the time to school me!

[petesz]

Also! There are 9 or so capacitors hiding underneath the board..

[bigmufffuzzwizz]

I'm sure those crazy 80's/90's japanese pysch bands used amps like this. A lot of those bands sound very tinny and trebly but in a great way!!