PVB has it right. 

NO mods to the amp at all.  I start with clean gain at 6 on the dial, get a bit of fur/harmonic feedback on the edges with pedal full down, clean at minimum.  Then I go to OD no boost, match OD channel master volume same or slightly louder than clean + PAB with what OD trim , OD gain I like (trim 10:00-ish or slightly less, goose the OD gain knob on front to noon-ish.) 

Clean, louder with PAB, then OD no PAB as dirtier alternative to clean+PAB same ballpark-ish overall volume, finally OD+ PAB for max volume and gain. 

Can't emphasize the importance enough of using a very high quality volume pedal, not some cheapie with a pot in it.  That user-preference range of adjustment thang is critical, as is no treble rolloff coming from the volume pedal at lower volumes, you'd lose harmonics otherwise.

Higher OD trim settings yield more compression, I try to avoid lots of compression, but if you wanted to do that, by goosing up the OD trim you get enough compression for that volume pedal to act like a gain control with not very much increase in volume in OD modes.   It's possible to set the pedal range up to go from clean to scream with a single channel amp, or however you want the 4 modes in an OTS type amp to behave.  All four modes sound good, so I use 'em.  Hope this helps.  It sure helps me when playing out!

Hi, and yes, I'm ready to be ducking rocks thrown at my head, but here it goes...

No amp mod is absolutely necessary if you get the right volume pedal!

Am not a big fan of any volume pedal that has a pot in it, I hear too much roll off of treble and harmonic content at lower volumes.  So I have an active pedal steel volume pedal that works very well and provides a bit of clean boost.  Has range control for minimum volume setting, and it exhibits tonal consistency between minimum and maximum settings, no treble rolloff, it uses optical components rather than a pot.  Here's what I have: 

http://www.hiltonelectronics.com/lowprofilepedal.html

It is wonderful to use with my el34 loaded 50w HRM with the LNFB switch.  Has one mono input, two mono outputs.  Also has a trimmer to adjust treble, full up it actually brightens the guitar tone somewhat, so I set mine for a slight amount of roll off until the guitar sounds the same treble-wise running through the pedal as straight into the amp. 

I enjoy using all four modes from the footswitch.  I set the OD trim and gain in OD mode for that prototypic smooth Carlton-ish gain/tone at my pedal's personally set minimum, and it can go right on up to an awesome sounding Marshall-y roar when the pedal is depressed, continuously variable between the two extremes.  I get a huge variety of volume as well as gain/tones that way, and nice to have the ability to easily control dynamics, swells, etc.  I can have great control over harmonic feedback and sustain too.  May not be for  everyone, but I'm VERY happy with this setup when playing out.   

Glad they worked out well for you.  Mine are staying in for the time being as well. 

...Cheaper than Amplitrex price fo sho, especially in the land of ebay for trannies.  But even so, for da money I can always visit my tube dealer buddy an hour away in Salt Lake City. 

Silkytubes on eBay is his handle, he mainly serves the cork sniffin' HIFI weenies, but rest assured, if it's got tubes , he's got 'em in spades.  Don't waste his time tho.

Here's the stupidest reply yet... 

Why not build up a single ended amp power section with some sort of rheostat/pot  or other device(s) to vary screen and b+ voltage and use it to measure plate curent draw from batches of a given power tube tube type?  Sounds like a possible ampgarage project...and would not cost over 2 grand.  My tube dealer friend in SLC has a rather impressive tester that can vary the plate and screen voltage all over the place.  But it's big and bulky, however, it can process quite a few tubes at the same time.

Keep your eyes open for a vintage Hickok tube tester.  Pretty decent, the later ones with solid state guts are more affordable, think that the model 6000 is that model, but not absolutely positive.  I use it mainly to test preamp tubes. 

When it comes to power tubes, tube testers are pretty much useless.  The voltage used in tube testers is not the same as in an amp, usually less.  Even Maxi-matchers aren't all that wonderfully accurate, because most amps don't run their b+ at exactly 400v, it's usually above or below that figure.  With that said, if someone gave me a Maxi-matcher I'd be happy to give it a home right next to my Hickok...

If I can, I like to get amps with a bias adjustment and bias balance adjustment, most of my push pull amps use two, not 4 power tubes.  I have three boutique amps with that feature, and I like that very much.

Hi Sean,

Yes, no prob.  I'm currently running vintage Siemens el34's in mine.  During a long thread of notes between Nik and I during the order process I learned that the standard HRM circuit power section is el34 friendly.   

Me likey.

Hello from another newbie.  I agree that part of due diligence for a new forum member here and elsewhere is to research posting histories.  It has saved me some questions, and it also pointed me in the direction of Merlin's book, which I purchased and am bit by bit learning from it.  My tube amp knowledge is very imbalanced...I know vintage tubes like few do but my knowledge of circuits and corresponding math equations has been much less.  Am learning bits and pieces from here and the ampgarage.  Fun!  A while back I did up a turret board for a BF Champ with some parts of my own choosing.  Now after I have spent some time here It'll be a blast to get back into it and apply what I've learned here and elsewhere. 

Somewhere in my basement lies a long-unused and nonworking condition Magnatone PA head with a pair of 6v6's, tube rec, and really big, rusty looking iron for a 6v6 amp.  So my dream project is to yank the trannies and do up a Martin/Dearmond type circuit for a pair of gorgeous sounding 40's vintage RT 6f6g's, but stick in an f/x loop, one of the most gorgeous sounding pentodes I've had the chance to listen to.  Have a lot of homework to do at the amp garage and personal reading...thanks to all who post helpful info here, it's nice.

Peace.

@soundperf

No changes to the amp are needed to run el34's, it comes ready to go either el34 or 6l6.  How could a Hot Rodded Marshall NOT be able to run el34's??   Well, Hot Rubber Monkey, anyway...

I think I can get it to sound like traditional OTS pretty easily.  When negative feedback is employed, it sounds very OTS-like.  With it lifted, add more gain to OD trim and OD gain and you get to Marshall territory pretty quick, and it's pretty fantastic either Dumble-y or Marshall-y.  It does this running el34's or 6l6's.  YAY!

I think that I'm going to leave it with el34's for a while, but if I get to play some outdoor gigs I will stick the 6l6 Sylvanias back in for the added girth they provide, perfect for an outdoor stage.  Then there's the pairs of 6bg6ga's and adapters I had done up for it...  6l6gc Sylvania tones in the Sylvania 6bg6ga for a fraction of the price.  Similar guts, different pinout. 

 

FWIW it's easy to get the kind of tones the OP was looking for out of my regular 50w HRM with the lift neg feedback mod.  It actually was a bit too bassy with Sylvania 6l6's through my 2/12/s, 1/15, and 2/15 cabs so I stuck some Siemens el34's.  Get the gooey stuff everyone loves on the OD, then kick the OD trim to !!:00-noon, OD gain to 4 or more, and hold on to yer butt!  Very Marshall-y sounding, especially with the neg fb lifted.   A tube cocktail in the preamp of fave NOS tubes will make a monster.  Hard to beat an HRM for versatility.

@dt125...

About five months of burning in have happened, the amp has opened up during that time!  I swapped a couple tubes around in the preamp from what I started with.  V1 was a telefunken smooth plate, but the amp got a bit darker after burn in so the 'funken was yanked and I stuck in a 1961 or 1962 Raytheon long plack plate 7025, in V2 I had a Mullard blackburn 12ax7 shortplate with Philips labeling.  I now have a Blackburn Microtech e813cc, made only a few months before the revived old Mullard plant finally went under and in PI the telefunken smooth plate still sits there.  I tried a bunch of different PI tubes, but the 'funken did up the best harmonic bloom at the lower gain settings on the OD channel.  Stuck some vintage Siemens el34's sitting at 39 and 42ma.   The amp has more detail overall and more harmonic richness. 

Great thread... 

Here's 2 more:  JBL g125 and g135.  Not made anymore and hard to find.  Both have the same motors, 3 inch flat ribbon wire voice coil, 12 1/2 pound magnet.  They came from some of the same engineers that did up the Altec 417/418 and EVM 12l/12s/15l speakers.  g125 is rated at
102db 1 watt 1 meter, the 135 at 104.  Frequency response from both speakers is perfect for D-style tones. 

JBL took in most of the guitar speakers in the market over a 3 year period into their lab to do the research to come up with these, and they only sold them for a year or two.   

I have an ev 12s style speaker made by Altec before EV came into existence.  It is very similar to the 12l except for a slightly shallower cone.  Between the JBL and the EV type the JBL is darker and a bit smoother.  Both have big bottom, full mids, and top end capable of reproducing excellent harmonic detail.

Niiiiiiiice!

I have not played through a BM, but do have a 50w HRM with the lift negative feedback switch mod.    Flip it one way, you get the signature smooth Dumble-y tone, flip it the other way, you get a bit more top end sparkle/crunch to your clean and overdriven tones.  I can get Fendery or Marshally tones out of it, and it sounds great with el34's or 6l6's.  I run vintage old stock tubes in it as well as the c-lator.  I absolutely love it.  I enjoy playing the one hollow body guitar I own through it, especially on the jazz side of the rock/jazz switch.  When I first got it, I was absolutely floored by the variety of tones that could be coaxed out of it.  Recently it made it's playing out debut amp only, without the c-lator, into a 1/15 Jensen Vibranto filled vintage Gibson cab at a local open mic/jam thang, and at the end of the night the drummer came up to me and with a very direct and sincere look said "you have really great tone." 

A couple of the most well respected forum members here recently responded to your post, and they are right in that you would enjoy either amp.  Main point of mine is that the one I have covers a huge amount of tonal ground very, very well, and I think that it would cover all of your tonal desires as well as any amp out there possibly could.  The c-lator is not necessary, but at the same time it is a wonderful addition, get them both.

Did you say "Hiwatt?"  Hey What?



Peace.