power scaling vs smaller amp

[TimS]

Working with someone on an amp build and was hoping to get some opinions on this topic.

The amp in question is going to be a modified Blonde Bassman. It will be played primarily through 1X12 cabinets with Celestion-style speakers. Unlike many people who use Bassman amps for their clean headroom, I will mainly be playing it cranked or close to it, both straight in and with an assortment of boosts and fuzzes. My goal is to maintain the characteristic sound of the amp as much as possible, but at a lower volume. The way I see it, I have three options:

1) Build the amp with the stock power section and use power scaling to bring it down to a reasonable level. This has two huge advantages: the amp will definitely sound like a Blonde Bassman, and there will be plenty of headroom/volume on tap should I ever need it. However, I wonder if, since I will rarely get to play the amp anywhere close to full out, this might be a suboptimal solution. I know big amps can sound great at low volumes when they're used for clean headroom, but is it really the best way to go to build a large amp for cranked sounds when I know it will almost always be heavily power scaled?

2) Build the amp with a smaller power section. Perhaps something with two 6v6s for instance. The advantage is that it will allow for cranked sounds at normal playing volumes without the need for power scaling/attenuation. The disadvantages are that it will probably lose some of the characteristic Bassman flavor and that, depending on the gig, I may find myself short on headroom/volume.

3) Split the difference and build the amp with a smaller but still fairly large power section (perhaps something along the lines of a Super) and use power scaling to bring it down further. This could either be the best or the worst of both worlds. On the one hand, it wouldn't require as much power scaling to bring the amp down to normal playing volumes and there would still be plenty of headroom/volume available should I need it. On the other hand, it would probably still lose some of the characteristic Bassman sound without getting quiet enough to crank at gig volumes without attenuation.

So what do you guys think? What is the best way to reproduce the sound of a larger amp at lower volumes? And are there any other options I'm overlooking?

Thanks. =)

[selloutrr]

Personally I would add a PPIMV and replace the 25mfd @25v cap coming off of pin3 of V1 and/or V2 with a 250MFD 12V cap (better bass response) and run the ch. volume at 9 for overdirve and the master at 3~4 for volume. then if you want the Bassman stock sound turn the preamp down and the master full up. it's a great mod!

[FYL]

There's only a 3 dB diff between an amp using 6V6s and 6L6s, you need at least 10 dB to perceive a significant loudness difference. Go Power Scaling with 6L6s - scale from the PI up and add a good master volume, either a bootstrapped PIMV or a PPIMV -if you want to keep nice power disto at decent levels.

[Structo]

Yeah, I would go with 6L6 as well unless you really like the tone of the 6V6's.

I just think the 6L6's have more balls, more throaty low end.

If you are set on getting power tube distortion type tone, then I'm not sure any scaling or MV will get you there short of running an attenuator.

My experience is with the Dumble type amp and I really like how that Master Volume works.
Sure you sacrifice a little bit at lower levels but it still sounds pretty good.

So I would either use that pre PI master or use a PPIMV like the Lar/Mar MV.

The boot strap MV does work pretty good in some amps.

So I would try several things before committing to drilling holes.

BTW, the VVR is really only good up to around 50 watts and you will easily exceed that if you push the amp.

[FYL]

BTW, the VVR is really only good up to around 50 watts and you will easily exceed that if you push the amp.

VVR isn't Power Scaling, even if derived from earlier London Power approaches.

[mcrracer]

BTW, the VVR is really only good up to around 50 watts and you will easily exceed that if you push the amp.

VVR isn't Power Scaling, even if derived from earlier London Power approaches.

What is it then?

[FYL]

What is it then?

VVR is VVR, a variable voltage regulator based on KOC's very early Power Scaling topologies.

Power Scaling is a trademark designating a set of technologies developped by KOC and licensed by London Power.

Real Power Scaling allows for the instantaneous control of all voltages, node by node if needed, in nearly any amp - up to 800V B+ is supported using standard components. Two or three generations ahead of VVR and similar approaches...

[Richie]

VVR is VVR, a variable voltage regulator based on KOC's very early Power Scaling topologies.

This statement is incorrect. Just one of those things that does something similar,but is not based on anything from KOC. The orignator of the VVR had never read KOCs books or knew who KOCwas.
My brother Dana has been around electronics since we were very young.
He was the one who got me hooked on working on my own amps from the start. He used to repair electronic equipment,and old tubes amps.
Even gave some classes on tube amps may years ago. It got to the point he was doing so much,he kind of got burned out on amp stuff. And got away from it for a short while.

I got him interested or back in to building and desiging amps. He was building an amp,and had ordered a PT for it,and they sent a PT that supplied too much voltage.
He brought the amp over for me to check out,since i play guitar,and he is a drummer. The amp had a knob on it,and i asked what that did. He said it lowers the voltage on the B+,so he wouldn't cook the tubes..
Explained he had to put this circuit in th amp,because the PT supplied the incorrect voltages. And was waiting on the correct one to come in.
Once i played the amp,my mouth dropped open after he showed me what it did, i stopped playing and said.. You know how many people would want one of those.
So he made up some boards and made a couple kits. I've used the VVR in bassmans and super amps, 50 watt marshalls,deluxes and many others with no problems. May have to do a couple things, but they do work in those amps. Just wanted to explain,that nothing at all came from KOC about the VVR. Except KOC badmouthing on his site.

[Structo]

And I believe that VVR is public domain, correct?

I kind of have a problem with Mr. O'conner.
At his forum every time he answers a question he refers to his expensive books.
I guess that is marketing at it's best.
Then all the module type gizmo's he sells, add up quickly.

[FYL]

This statement is incorrect. Just one of those things that does something similar,but is not based on anything from KOC. The orignator of the VVR had never read KOCs books or knew who KOCwas.

Power Scaling has been used by KOC since 1990 or so. The basics, as used by the VVR and similar devices, are described in the Power Scaling section of TUT 4. The original VVR came to the market a few months after KOC had published it. It's very close to the original London Power PSK released in 1995. But this could be a mere set of coincidences.

OTOH, the VVR2 and VVR3 use a Mosfet-based proportional regulator (a small VVR controlled by a dual-ganged pot) in their bias sections, while KOC uses a more complex BJT-based tracking regulator. Very different designs, even if the dual-ganged pot approach is fully described in TUT4.

[FYL]

And I believe that VVR is public domain, correct?

Dana's design has been published but not explicitly put in the public domain.

I kind of have a problem with Mr. O'conner.
At his forum every time he answers a question he refers to his expensive books.
I guess that is marketing at it's best.

KOC makes a living building and selling kits and amps as well as writing and publishing reference-grade technical books. He doesn't like people looking for free advice but offers excellent support to his customers.

Then all the module type gizmo's he sells, add up quickly.

Flexibility is the key. A nice DC Power Scaling solution for cathode-biased amps, including two voltage regulation modules (yes, two, as KOC prefers to scale each stage or tube independently) a top-notch PEC Mil-spec pot as well as full "drive compensation", KOC's parlance for master volume, retails for $50. The fixed bias version includes all of the above with an added bias tracking module for $78. Nothing else is needed.

[TimS]

I greatly appreciate the responses. I would also greatly appreciate it if you guys wouldn't mind taking your discussion of the merits of KOC's business practices elsewhere as I'd like to keep the thread on topic and avoid animosity. Thanks!

[TimS]

Also, does anybody know where the Blonde Bassman gets most of its overdrive from when cranked? I know the Tweed Bassman and most Marshalls get the bulk of it from the PI distorting, but is that still the case with the Blonde or is there more actual power tube distortion happening here?