Lower watt output TWs?

[RJ Guitars]

All the Trainwreck builds are 30 or 35 watts, which is going to work well in a studio environment and have the killer reputation for delivering the goods in a large venue gig situation (not stadiums or concert halls). I think the 30 watt versions sound better than the 15 watt versions of the Liverpool and Rocket builds. Power scaling or choosing a different set of output tubes is the only way to get an Express with reduced wattage.

My Rocket amp got fizzy sounding at low volume levels (bedroom x 3 and less) when I power scaled the whole circuit. It kinda makes sense because you have very little voltage on the preamp tubes when you get the voltage way down where you want it on the power tubes. Most vacuum tubes still work but not that well when you operate them at voltages less than 100v. I think just scaling the power tubes would be preferable but that can also change the dynamics of how an amp responds to your playing. Maybe Dana (UR12) might give us some of the benefit of his experience in how best to implement the power scaling options for a given set of circumstances.

If you are going to do real studio work I'd say go with the best sounding amp you've got and play it at the volume it sounds best. Balancing your volume in a gig situation and maintaining your tone can be a bit more challenging. If you figure out something that works it would be cool if you'd share it with us here.

rj

[UR12]

There is no perfect scenerio for adding a VVR or any other power scaling method to a tube amp. It depends a lot on the amp circuitry and what you want from the end result. Having said that, when it comes to an Express or Liverpool, IMHO, I think the best way to go is to regulate the entire amp. Thats just because of the gain structure of the amp. When you look at something like a Marshall or even a Rocket, it may better suited to go with just the power section and leave the preamp alone. Thats because it develops preamp distortion long before the power section does any clipping, especially in a MV amp. Some amps like the 18 watt marshall and even the vox amps sound good with the power and PI regulated. You have also got tremolo and reverb to think about in some amps. Reducing the voltage on a LFO may make it speed up. So each amp can be a challenge on what the best method to use may be for the best result. The other thing that I might add is that you can always change the value of the resistors that set lowest voltage limit on the VVR (and even the highest voltage limit on the fixed bias model). Find out how low you really want the amp to go and set the range so it doesn't get so low that it sounds fizzy or has scratchy vol pots. There is a range on the VVR where you should be able to turn down the voltage without a huge noticable difference in tone. At lower volumes there are a lot of things that come into play that are more about how hard you are driving the speaker than other things. If you're into speaker breakup then you won't get that at low volumes. You may need to experiment with the installation of the VVR to get it to do what you want it to. People need to put some thought or experimentation into getting the VVR setup sounding best in a particular amp. It is a lot easier to design an amp around the VVR than to retrofit one into an existing amp for these reasons. There are a lot of Boutique amp companies that have gotten excellent reviews on their amps using the VVR under various names, because they have taken the time to get it right. It's funny. I hear every now and then where someone has tried to install the VVR in an amp and gave numerous reasons why they thought it sucked. Then that same person will go out and buy an amp built by acme amp co or somone that has power scaling and give it rave reviews not knowing it has the same exact VVR board installed in it that they said sucked.

I also find it interesting, your comment on a 15 watt Liverpool not sounding as good as a 30 watt liverpool. I haven't found that to be the case at all and I have customers that like the 15 watt version a lot better than the 30 watt version. A 30 watt amp with two tubes removed or switched out isn't the same as designing a 15 watt version from the ground up. The OT, the NFB resistor value may need to be changed or component values in the PI, pulling or switching out two output tubes may make you voltages go up across the board making the amp sound and react different. By far, the biggest comment I get regarding the Express is that it is just too loud for most club type venues. I think the VVR does an excellent job making this amp more versatile for playing any venue out there.

Merry Christmas everyone and hope you all got some cool stuff from Santa

[MCK]

Dana, a theoretical question based on your comment on how you feel it is better to regulate the whole amp as opposed to the power section only. Does this then equal more or less to running the whole thing on a Variac? How would you compare the VVR setup to a Variac situation? Just trying to educate myself. Not a loaded question per se. Thanks much!

[UR12]

Dana, a theoretical question based on your comment on how you feel it is better to regulate the whole amp as opposed to the power section only. Does this then equal more or less to running the whole thing on a Variac? How would you compare the VVR setup to a Variac situation? Just trying to educate myself. Not a loaded question per se. Thanks much!

If you regulate the whole amp it would be like running it on a variac. Unfortunatly the variac would also lower the heater voltage which is not a good thing. The VVR leaves the heater voltage normal and just regulates the B+ or B+ and bias

[MCK]

Got it. I understand the concept now. Thanks.

[zambo]

I want to hear a 6k6gt version of a express. should be less than 10 watts and still a pp amp. Anyone tried this? I saw a 6k6 mini tweed deluxe on youtube that really sounded sweet. an express would be even sweeter! I built a se el84 at 5 watts and a se el34 at 10 watts with express preamps that sound pretty good but I think pp is kind of required to sound really good. anyone tried this?

[harryk]

I just made a Bassman 5F6-A Jr. with 2xEL90/6AQ5 tubes. With them you get some 10 W output power. I also made one mini Express with a 2xECL86 power amp giving some 10-12 W. If power amp is very small, you cannot get much useable clean headroom out of it. I made also one amp with 2x6AK6 tubes which give some 2-3 W but it was not Express preamp.

[RJ Guitars]

...I also find it interesting, your comment on a 15 watt Liverpool not sounding as good as a 30 watt liverpool. I haven't found that to be the case at all and I have customers that like the 15 watt version a lot better than the 30 watt version. A 30 watt amp with two tubes removed or switched out isn't the same as designing a 15 watt version from the ground up. The OT, the NFB resistor value may need to be changed or component values in the PI, pulling or switching out two output tubes may make you voltages go up across the board making the amp sound and react different. By far, the biggest comment I get regarding the Express is that it is just too loud for most club type venues. I think the VVR does an excellent job making this amp more versatile for playing any venue out there.

Merry Christmas everyone and hope you all got some cool stuff from Santa

Thanks Dana,

Merry Christmas to you and the whole TAG crowd.

My ears generally like the sound of a quad of output tubes over a pair, but that observation is limited to what I've heard which certainly leaves the possibility that some great "single pair" amps are out there for me yet to discover. In this case my statements are loosely directed at the iterations of the Trainwreck circuits I've seen and heard... but only a limited observation.

You make an excellent point that optimizing a circuit for a certain set of output tubes involves consideration of many factors. That is a great list you've offered that will help several of us when start down that path.

When I first started working with the Rocket circuit I found that my 15 watt version (dropping out two output tubes) produced almost the same volume level but lacked the fullness. Admittedly I found it hard to work on optimizing a 15 watt version of that circuit once I recognized that the best I could hope for would be to duplicate the 30W tone at essentially the same volume level.

I do think the Power scaling option greatly expands the usefulness of a 30 watt amp and in my case took the good part of that tone down to a volume level something like 5 to 10 watts.

While I recognize that complexity usually brings trouble I am curious if individual VVR's on the preamp and output sections might allow me to go down even further in volume? Dunno if anyone ever tried this or not?

rj

[harryk]

I use VVR in one of my amps to scale preamp first stage plate voltages from 170 V to 270 V to achieve Deluxe, Pro, Super and Twin Reverb voltages when needed. Higher voltages mean more headroom and dynamics. In this case I call my application "Dynamics". I have also successfully used VVR to limit 2x6AK6 power tubes plate and screen voltages under 300 V, still maintaining higher voltages in preamp section. I think that it is only a matter of imagination how you can benefit of VVR technology. Harry

[RJ Guitars]

I want to hear a 6k6gt version of a express. should be less than 10 watts and still a pp amp. Anyone tried this? I saw a 6k6 mini tweed deluxe on youtube that really sounded sweet. an express would be even sweeter! I built a se el84 at 5 watts and a se el34 at 10 watts with express preamps that sound pretty good but I think pp is kind of required to sound really good. anyone tried this?

There is a local government salvage place close to my home and I bought a ton of odd tubes over the past few years. I do have a few 6K6gt tubes and lots of other choices as well. I've slipped the 6K6gt tubes into circuits but have not made any attempt to build an amp around them though. If you don't mind posting the link it would be interesting to see the youtube video you mentioned.

I just made a Bassman 5F6-A Jr. with 2xEL90/6AQ5 tubes. With them you get some 10 W output power. I also made one mini Express with a 2xECL86 power amp giving some 10-12 W. If power amp is very small, you cannot get much useable clean headroom out of it. I made also one amp with 2x6AK6 tubes which give some 2-3 W but it was not Express preamp.

I've made several amps with 6AK6 tubes and I have a ton of 7 pin tubes that I am working up in a Liverpool circuit. I was able to get decent headroom and great clean tones with both 6AK6's and 6AQ5's. Did you make any adjustments like the ones Dana mentioned above when you put the 6AQ5's into your Bassman circuit? I am working through that exercise right now on my 7 pin Liverpool build, using the previous builds and Merlin Blencowes book as a guide.

rj

[harryk]

I have a fixed bias version where bias is adjusted to appr. 70 % of 6AQ5 max 12W dissipation. My PT is a Hammond with 2x250 V, which produces some 325 V to power tube plates, despite 250 V is an official maximum plate voltage. I have now played some hours with that amp without any problems. 6AQ5 tubes are pretty cheap to experiment with. By now I have built almost 100 different Bluetone tube amps for guitar and bass players and it is always a joy to experiment with new tubes and configurations. Harry

[UR12]

.

While I recognize that complexity usually brings trouble I am curious if individual VVR's on the preamp and output sections might allow me to go down even further in volume? Dunno if anyone ever tried this or not?

rj

I use VVR in one of my amps to scale preamp first stage plate voltages from 170 V to 270 V to achieve Deluxe, Pro, Super and Twin Reverb voltages when needed. Higher voltages mean more headroom and dynamics. In this case I call my application "Dynamics". I have also successfully used VVR to limit 2x6AK6 power tubes plate and screen voltages under 300 V, still maintaining higher voltages in preamp section. I think that it is only a matter of imagination how you can benefit of VVR technology. Harry

I have experimented with individual regulators for each stage in an amp and made them adjustable using trimmer pots. This allowed me to dial in any voltage I liked on any stage. It makes for a good test bed to test different preamp stages under different voltages. The B+ sets the headroom for the stage but it also controls the gain of the stage. Here is a pic of a amp I built in early 2008 incorporating regulaters for each stage in the amp. I am in the process of trying to take this to the next level in a 100 watt amp I have designed. I have been working on it for over a year now and without letting too much out of the bag, I hope to use a single or dual control voltage(s) to do some very cool things with the gain sturcture of the amp on the fly.

[leodiditright]

UR2, Dana Hall, makes a dynamite sounding "2 Hole" Liverpool I think they power out at 15 to 18 watts, still way loud but the tone is still there.

Mine runs 15 watts and has a 10.5k OT. It also has a built in
VVR that will let you go down go bedroom levels. The two holers
are great sounding amps if you do your homework
and do it right.

Are you selling this amp? I can't find it on your website.

[UR12]

UR2, Dana Hall, makes a dynamite sounding "2 Hole" Liverpool I think they power out at 15 to 18 watts, still way loud but the tone is still there.

Mine runs 15 watts and has a 10.5k OT. It also has a built in
VVR that will let you go down go bedroom levels. The two holers
are great sounding amps if you do your homework
and do it right.

Are you selling this amp? I can't find it on your website.

Yes we sell 15 watt 2 x 12 combo. If you go to the webpage and check out the Gallery you will see some of the amps we build. Shoot me a PM or email for more info.

[leodiditright]

Mine runs 15 watts and has a 10.5k OT. It also has a built in
VVR that will let you go down go bedroom levels. The two holers
are great sounding amps if you do your homework
and do it right.

Are you selling this amp? I can't find it on your website.

Yes we sell 15 watt 2 x 12 combo. If you go to the webpage and check out the Gallery you will see some of the amps we build. Shoot me a PM or email for more info.

Thanks. head too? I'm not playing combos.