Zhin
86 posts
Dec 17, 2008
8:24 PM
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Hey guys about a month ago I bought myself an Epiphone Valve Special 2nd hand. It's a 5 watt Class A tube amp. Uses 2x 12AX7 tubes in the preamp and one EL84 at the output. Has a bass/mid/treb tone control and gain/master volume control.
Some favorable mods have been done to it too by the previous owner! For example it's noisy tone sucking DSP had been removed. And a hardwire bypass added from the preamp to the output section of the amp circuit.
I'm looking into ways to improve the tone of the amp. I feel that the amp has a lot of potential for putting out a great tone that has clarity, detail, and depth. I'm looking for suggestions and advice on what can be done.
The 10" stock speaker has been changed to a Celestion Tube 10" (ceramic, 30 watts) (rest of specs here: http://professional.celestion.com/guitar/products/originals/spec.asp?ID=12)
I am using a "sound-king" (600ohm-50Kohm) inline impedance adaptor and a Shure Beta 57a microphone.
I would like to know if this setup from a technical standpoint is a "good" amplified harp setup... There are certain aspects about it that I'm not too sure about and I can only trust my inexperienced ears (only started playing harp around the mid of 2007). I basically like having a distortion and break up like that Chicago tone but more detail and depth to keep up with times. Is this what you call a "rock" harp tone? :)
My question is am I using the "right" kind of speaker? I know that ceramic doesn't break-up as early as alnico. And ceramic has a warmer tone than alnico. I personally do like having a warmer tone but I like my break-up too! Is 30 watts too much? I was told that the less wattage on the speaker the easier it is to saturate it..
My ears tell me that the speaker has a limited range of tone and they sound a little bit on the brittle side... sibiliant at times. They can punch through a loud band mix really well though! Certainly sounds better than the stock Epiphone amp speaker for sure (the guy put it in a cab and gave it to me as part of the package). I'm considering changing the Celestion speaker if there's a better replacement. I don't think I can afford Jensen blue backs though... :p So some budget conscious suggestions would be much appreciated.
As for the tube configuration I seem to prefer the stock 12AX7 (JJ's) configuration in the preamp because they seem to be giving a better low end for the tone (and more dynamics). There's more "depth" in the sound I suppose. I tried putting a 5751 in the first slot (input stage) and keeping a 12AX7 in the second but found that tone to be very harsh and flat sounding regardless of what kind of gain/tone setting I'm using. Are there any other better combinations? I'm a little afraid of using 12AU7's because they might damage this PCB circuit board amp and I can't find 12AY7's here in Malaysia. I can only use 5751 and 12AT7 as an alternative. Any ideas?
When I play through this amp I notice the tone seems to be at it's best when I set all tone knobs to 12 O' Clock. Any suggestions for something better? As for the gain, I like the sound I'm getting around 2 O' Clock. I push the volume up as loud as I can depending on the venue.
Hope I can get some suggestions. I use this Epi amp for gigs and recording so it's really important to me.
For jams I just use the champ model in my Digitech RP150 amp modeling unit. :p
Last Edited by on Dec 17, 2008 8:51 PM
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x55jgp
Guest
Dec 18, 2008
1:39 AM
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Google epiphone amps and accessories forum and sewatt.com. Both these sites have a wealth of info on epiphone amps
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MrVerylongusername
61 posts
Dec 18, 2008
1:42 AM
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Unless you have an issue with feedback (which you haven't mentioned, so I'm guessing not) then I'd leave the preamp tubes as they are. That's really the only reason to do it. I think with a small amp you are very wise to be cautious, as not all circuit designs can cope with the voltage changes.
If you are cutting through the mix with a 5W amp then you have a very disciplined band - lucky guy! Swapping the preamp tubes will lower your potential overall volume too.
Sorry - I don't know much about speakers so I can't advise you on that one.
With a small amp, I'd always have the master volume on max and then push the gain to the point of feedback, then back it off so there's no ringing. I'd be pushing the bass a bit harder too to compensate for the small speaker and cutting the mids to control feedback. Every rig is different though and everyone's tastes in tone differ.
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Zhin
87 posts
Dec 18, 2008
6:38 AM
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I know how to deal with feedback and usually don't have a problem with it.
As for being cautious, it's only because I read that a lot of modern tube circuit components may not be able to handle the extra voltage that lower gain tubes like the 12AU7 add.
The 5751 is only slightly different and has the same amount of gain as a 12AT7 which is why I tried that instead (but didn't like it).
As for my band, we are very careful not to step on each others toes. We respect each other... well.. it's also because I put them together so they definately make sure I'm heard. :p My guitar man actually asked to study my amplified harp frequencies so that he could design a tone for himself that didn't get in the way of mine. Sweet huh?
Hmm... I'll still need answers for the speaker thing though. I'm fearing that I may not be overdriving the 30 watt speaker with my 5 watt amp... I read somewhere that having less wattage (and smaller magnet size) is what you need for speakers to break up/saturate early (nice for harp).
Last Edited by on Dec 18, 2008 6:42 AM
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MrVerylongusername
65 posts
Dec 18, 2008
7:43 AM
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Did you see Adam's vid on amps? - not the Youtube, but the pay for Quicktime one. He talks about speakers a lot - particularly what makes a good one for harp. If you haven't downloaded it - It's well worth it.
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Luke Juke
Guest
Dec 18, 2008
8:19 AM
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E-mail weber speakers and ask them what you need. They usually reply within 24hrs and will give their exac recommendation, telling you what model you need, what wattage, whether it needs to be doped and whether you need a smooth cone or ribbed cone. Weber speakers are reasonably priced and of excellent quality. You cant go wrong
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Luke Juke
Guest
Dec 18, 2008
8:22 AM
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There is also someone on ebay under the name of alnicomagnet who sells a mod kit for the valve junior which might fit the valve special. You could email him and ask
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Zhin
88 posts
Dec 19, 2008
5:45 PM
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MVLUN, I've already watched Adam's video quite some time ago.
I don't think he talked about speaker wattage in relation to overdriving them though.
Luke Juke, I guess I could e-mail weber speakers if I don't get sufficient answers here. Was hoping for answers from other harp players who are not selling anything.
The other thing is also then someone else can benefit from these posts in the future. I know I'm not the only one who'd like to know more about speaker saturation/overdrive...
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Luke juke
Guest
Dec 20, 2008
3:24 AM
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The lower the watt saving of the speaker then the quicker it breaks up. Ie. If you put a 50 watt speaker in a 5watt amp then it would be very clean sounding with only distortion coming from the amp and no speaker break up. Whilst a 10watt speaker in the same amp would give lots of break up
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