VT120+ open back modification

[dbvt120]

My search for more control over vt120+ sound on the giging volume is getting closer to an end. Not there yet but there is a hope.

I bought brand new vt120+ around 6 weeks ago. It was supposed to be addition and/or backup to my usual giging rig Laney vc30 212 + Fender Pro 185 212 amps (I switch between two using A/B between songs). However, at the shop I tried it on medium volume level that turned out to be lot lower than my usual volume level required to cut throught the mix.

In fact I was hoping to replace Fender Pro 185 with VT120+ as I felt that I might get bit more versatility but after around 6 rehearsals with VT120 did not feel that I understand relationship between the giging and bedrom practice volume so I did not take it to the gig last week.

My concern was that on a high volume it had this very "nasal" style of sound regardless of the amp type and if EQ was tweaked to reduce that I got this horrible high end shrill followed by enormous amount of touch sensitivity. At first I thought I am imagining but band members noticed the same and they said that it was the harshest sound amp I've ever used on a giging volume level.

It was very noticeable on single coil pickups (tele and strat). Little less on humbuckers but "nasal-ness" was still there. No matter what I did I just couldn't get the sound right in a band situation and it was not cutting through. If I got the patch saved for one song it wasn't cutting through the mix for another. Finally I gave up and decided to leave it for later.

I have to admit that on a medium to low volumes vt120+ sounds great. I only use low gain amp models (left hand side of the dial) and no on board effects. Just a little of reverb.

This all seemed very strange to me as I could pretty much get any amp within 5 mins to be able to play it without any major hassles.

So last week while fiddling with my gear in rehearsing studio I looked at my other amps and it struck me that Laney and Fender are open back while VT120+ is closed back cabinet. Didn't think of that before.

So while there, I picked a screw driver and removed the back panel on vt120+.

This "nasal-ness" was gone, and amp suddenly started to sound normal to me. No high end shrill and amp is lot more responsive to EQ and it seems to be lot easier to control on high volume.

I ran another experiment. I removed the speaker cable from my Laney V30 and connected it to VT120+ speakers.

Now, my Laney is 212 model with HH Invader speakers and they were never regarded as great but playing Laney VC30 through speakers on vt120+ open back cabinet did not sound to much different than Laney VC30 through HH Invaders.

Another test I did was to close the VT120+ back panel again and now play Laney VC30 through VT120+ speakers (I've guided cable through one of the vent openings). Once VT120+ back was closed Laney VC30 started to sound very "nasal" and harsh with lot of high end shrill.

So it must be that design of VT120+ cabinet does not work well for playing on a high volume with closed back and that to me looks very strange as it has quite a lot of power.

Only explanation is that they've tuned the cabinets properly for smaller models (VT80+ and smaller that will have to be mic-ed anyway). Of course there is an option to run VT120+ the same way (mic-ed) but I'd like to avoid it.

Has anyone else tried any other vt+ version with open back? What results did you get?

[cosmicrepairdude]

Forgive me if we have discussed this before in any other threads, but did you try stuffing the cabinet with sound insulation material? The easiest to try is a pillow (or pillows, since it's a large cabinet). Keep the stuffing away from the chassis.

Have you read the threads on cabinet stuffing? I don't think any of these amps above the smallest ones sound right until they are stuffed.
unhappy-with-your-amp-s-sound-read-this-t3774.html
http://www.voxamps.com/forum/topic.php?id=3276

[dbvt120]

Yes I actually stuffed the cabinet with speaker damping material, then tried with carpet then added pillow. All this did not change the sound on higher volume. If anything it muffled it to extent that highs where barelly noticable on gentle strumming and then if you hit the strings little bit stronger highs where the only thing you'd notice.

To me it looks now as the cabinet of vt120+ just does not sound good in this "tuned" closed back version. Even Laney VC30 started to sound bad when it was driving vt120+ cabinet on a higher volume and in fact Laney VC30 sounds better, the louder you drive it. Once panel of the vt120+ was removed it all started to sound and breathe lot better.

Amp still sounds great on a low to medium volume, but just doesn't cut it for me playing clean to crunch on my usual giging volume with ocassional boost for solo.

[cosmicrepairdude]

Too bad. I'm guessing a VT100 might have worked out better. Or maybe not.

[dbvt120]

If VT100 is open back design it must sound lot better on high volumes than vt120+ does.

I still think that vt120+ is great sounding amp with quite a good sound, with lots of features. It just doesn't work well for my giging needs. Well I don't blame them and it is not the end of the world. There are plenty of nice giging ready valve amps manufactured by Vox and other manufacturers but I just wasn't prepared to pay the price so I went with valvetronix and overall I still think that it wasn't bad decision.

I'll buy some 16mm MDF panel, and will cut two smaller panels to support amp chasis on the top and another to stiffen the speaker cabinet at the bottom (same as most other open back combos are) and will try it in this semi open back configuration.

Things that I noticed was that in this configuration amp is more responsive to EQ tweaking on high volumes. However the feel and sound on low volume is still the same (which is also good).

Does anyone else own vt120+?
What are your experiences with it?

I've seen one post where shrillness and high end sensitivity has been noticed but that was about all. It seems to me that most of the people are buying smaller VT+ models.

[dbvt120]

Here it is:

IMAG0956.jpg (976.97 KiB) Viewed 230 times

I've done it by cutting two pieces of MDF and painting them satin black using spray can. This way I still have original back panel in garage. Also note that I haven't made any effort to remove white speaker dampening material or paint interior black (will do one day).

My experience is that VT120+ sounds lot better on a high volume with open as oposed to closed back. It feels like it handles power with easy while before it sounded like the speakers were struggling.

Not much difference in a sound on low to medium volume level.

[killersbytrade]

I have a VT120+ as well and noticed the same thing, particularly when using gain/distortion. It gets this nasal, what I call "electric shaver" sound and when you dampen the highs or increase the low end it just turns to mud. I was considering better speakers and have already bought a better tube to try.

Your MDF solution is a hell of a lot cheaper, though. Next time I got to Home Cheapo, I'm going to buy some MDF and foam. Like you said, If I ever need to sell it, I can always put the old back on again.

EDIT: I just tested it with the back off while I was swapping out my tube. Definitely going to do the conversion!

[killersbytrade]

Almost done, but I ran out of black paint. All the important work is done, though. I did the conversion and put acoustic foam on the inside. Looks and sounds 100x better! Once I drop the Weber Blue Dog/Silver Bell in there, it will be rockin and rollin'!