Speaker crunch and VVR

[TomOlsen1]

Hi guys

Among my recent shows, we had a 5 day run at the Johannesburg civic theatre. I usually don't get the luxury of being able to refine my set up in one venue night after night, in fact due to the large number in festival shows in the past few months I've gotten very used to line check only.

So, having the chance to really play around with mic placements etc was a rare treat for me outside of studio. And together our sound engineer and I came to a rather interesting discovery:

I play a Lite IIb with VVR (Valvepower trad head) with a 2x12 cab loaded with G12H30's. As this was a theatre venue, I have my cab turned facing the back to keep the sound man happy. VVR is at 60%.

After the first show was done, I showed the engineer the difference in sound with VVR at 100%. He loved it, loved the extra body and girth it gave the tone and the rounder sound as the speakers rolled off a bit of the "fizz". I was pleased!

However, listening back to the 2 track recording straight off the desk, the guitar was less present in the mix with the speakers pushing more air! This sound would then requre re-eq-ing.

Basically, I'm grateful that we have the luxury of VVR, allowing us to choose our amount of speaker distortion in addition to our preamp and power amp clipping. And some of the "fizz" produced by EL84's is downright essential to cutting through!

Any opinions/experiences?

[colossal]

Tom,

Very interesting observations. Are all of the voltages VVR'd throughout (meaning preamp, phase inverter, and power amp) or just the phase inverter and power amp? Also, are your G12H30s Anniversary or Heritage?

Thanks.

[TomOlsen1]

Hi Colossal

The whole amp is scaled, and the G12H's are the anniverary model. Just interesting to hear the effect speaker crunch has on the sound, and I dig that you can dial in just the right amount with the VVR.

[colossal]

Tom replied: The whole amp is scaled

It seems that from reading past threads, most of guys here scale just the PI and PA only so as to retain the distortion characteristic at lower volumes. It is interesting that you are getting a drop in the crunch, likely due to reduction of signal going to the PI when the preamp is operating at lower plate voltage. That's great it gives you that specific level of control you need with the addition of scaling the preamp as well. There's no right or wrong of course, only what sounds good.

Do you find that the 18W Lite is really LOUD with a 2x12 to the point where in a small space at cranked volume (7-10 on the Volume) with efficient speakers (like the G12H30s), it can be just too much? I'm trying determine just how loud they are relatively to say a 6V6 Plexi which, when operating at 440V on the plates is cranking out somewhere in the neighborhood of 22-25W.

I am building a pair of 18W Lites (with some tweaks for flexibility) to run in stereo and will be running them with a 1x12 with a Heritage 30 each. I was planning to include a VVR as it's really not much extra work to do so but just trying to get a feel for how much volume to really expect from a cranked 18. I have heard they are only marginally less loud than a 22W 6V6 Plexi type amp (freakishly loud amp!) played through a 2x12.

[guitarmike2107]

mmm could be that with the change in voltage of each stage and the resulting change in operating conditions you are likely affecting the harmonic content at output??

also room dynamics change at different volume levels as well as the ear response.

but the point is that an amp that sounds great by itself does not always sound great in the mix..

[TomOlsen1]

@Colossal
First off, I'm not getting a drop in amount of gain, but rather noticing the colouration that speakers driven hard can bring to your tone. And Fletcher-Munsun (not sure of spelling) curves would generally indicate an increase in percieved bass and treble at higher volumes, although the G12H's pushed seemed to roll a little of the tops off in a way both myself and the engineer liked. It just required the guitar sound to be re-shaped at the desk side after the change, even adding a bump to 1k.

An 18 watter paired with a 2x12" with effecient speakers like G12H's is damn loud! I have no problem keeping up with a drummer, and often in rehearsal conditions I have to put the VVR to 40%, which starts to starve the tubes a little. Even on open air stages at 7000 pax venues I often can only open it up to about 70%. Of course, this will depend on your soundman's needs/demands/facist tendencies.

VVR is downright essential! Whilst I do think that amps sound best with preamp, PI, power amp and speakers all crunching nicely, 18 watts is still very loud and sometimes requires reigning in. The lack of NFB also helps produce a very loud, rich 18 watts.

Two lites in stereo sounds sexy! My next project is going to be an 18 watt plexi with 6v6's, I like your style. Also, from what I understand, some guys in the Lite camp like to scale the whole amp. This was my first build, so it was a kit. Sounds great though.

@Mike - Man, you're telling me! I'd installed a switchable zobel filter on my amp to compensate for when I have to use less than ideal speakers. Whenever I switch it in, I switch it out again five minutes later. But, as toppy as the amp seems when I play on my own, it needs the sizzle and sparkle to cut through. At the end of the day, Volume at 3 o clock, tone at 3 o clock and the 18 sits in the mix perfectly. Gotta love these amps!

[colossal]

Tom replied: @Colossal
First off, I'm not getting a drop in amount of gain, but rather noticing the colouration that speakers driven hard can bring to your tone. And Fletcher-Munsun (not sure of spelling) curves would generally indicate an increase in percieved bass and treble at higher volumes, although the G12H's pushed seemed to roll a little of the tops off in a way both myself and the engineer liked. It just required the guitar sound to be re-shaped at the desk side after the change, even adding a bump to 1k.

Tom, thanks a lot for the detailed update. I have read similar accounts about the G12H rolling off highs (for the better) and especially the Heritage. I have a pair of Heritage 30s here and will put them in service when some 1x12 cabs I have coming arrive.

Tom also said: An 18 watter paired with a 2x12" with effecient speakers like G12H's is damn loud! I have no problem keeping up with a drummer, and often in rehearsal conditions I have to put the VVR to 40%, which starts to starve the tubes a little. Even on open air stages at 7000 pax venues I often can only open it up to about 70%. Of course, this will depend on your soundman's needs/demands/facist tendencies.

Wow! That is really good to know. Ok, I will definitely add a VVR I had been told on good authority that a cranked 18W will be perceived pretty much as loud as a 22W 2x6V6 Plexi (which is freakishly loud with a pair of Greenbacks in a closed back cab)) so with efficient speaker(s) I'm sure an 18W will be very much on par.

Two lites in stereo sounds sexy! My next project is going to be an 18 watt plexi with 6v6's, I like your style. Also, from what I understand, some guys in the Lite camp like to scale the whole amp. This was my first build, so it was a kit. Sounds great though.

Yes, I have read as much as I could here on accounts of guys using a VVR for 18W preamp/PI/PA scaling as well as just PI/PA. You will quite happy with a 6V6 Plexi. Are you going to use the 18W power amp values or Mark Huss' design? Mark's design is awesome and very Marshally sounding. I am using a PT with 345-0-345 and that gives about 440V on the plates. I did use both a 1k 5W sag resistor and 10H choke in series between the first two 47uF caps. I prefer it with the 1k added. I have also tried the amp with the preamp cascaded and more JCM800 values and that is a *fantastic* sounding amp as well. You won't be disappointed. Very loud too so a VVR is a good option!

As for the stereo Lites, I want to build them to stock Lite IIb specifications but add a couple of mods which will allow some tonal variety. So when played together they are not just two of the same thing, but can have some difference to add a little more tonal complexity to the overall sound. I am thinking of having V1a/b switchable between the stock 820R/47uF (combined cathodes) and 2k7/0.68uF and 680R/3uF (separate cathodes but common anode) to generate some nice harmonics. I have a few other ideas in mind but don't want to stray too much from the classic design initially. Both amps will be run with 1x12 with a 16R Heritage 30. If that just doesn't do it for me, I will add an additional 1x12 with a Blue. Tonally, this is very close to my goal for the sound: http://www.retrokingamps.com/bytes/ceda ... rack02.mp3 I love the tight, low end and the harmonic richness and clarity.