If you find out the specs on that PT you will know fo sho on the heater current thang.   EL34's draw around 1.4 amps apiece for their heaters.  Impedance on the primary side of the OT will be slightly off running el34's, but that probably won't be a serious problem. 

In my correspondence with Nik during the ordering of my amp I asked about using el34's, and he replied that the amp was wired in the output tube sockets to take them, it's part of the regular design on the 50w HRM I own.  There is more than enough capacity in the PT to handle the increased heater current from a pair of el34's.  One guy on our forum is running a pair of 6550's in his 50 watter biased at 50mv, running at very loud volumes for long periods and he reports that the PT  still runs cool and has been reliable for several months.  The PT in mine runs cooler than nearly all the other guitar amps in my stable.  I am running vintage el34 RFT's at 39 and 42mv.  They are slightly mismatched, and the tones/sustain are wonderful with them at that setting.  Dropping the bias down 3-4mv yields a slightly brighter tone, and a bit less bloom on the long sustained notes.  I have also run a pair of very tightly matched vintage Sylvania 6l6gc's at around 35mv, fat, warm and huge tones gush out of that amp with those.

I'm curious about that...I'm going to try mine with a Bedrock 651 1/12, a Mesa 2/12 Maverick, and a Siegmund Midnight Blues Breaker head.  Can't do clips, but will post my impressions.  Your words, please from your experiences?      

Just sayin... if you were to compare Nik's prices compared to other D-style amp builders for something similar you would be more than a little pleased at what you got for what you paid.  I'm VERY thankful for the opportunity to own mine.  Glad things worked out for you!

I use an active volume pedal by Hilton electronics, it works very well with the amp by itself or when using the c-lator...

Yep, as far as efficiency the JBL G125 I previously suggested is rated at 102db 1 watt 1 meter...the 15" version is the G135 and it is rated 104db.  Either speaker is pretty phenomenal.  Just hard to find...

What a cool idea...a bass amp that sings with overdrive harmonic goodness! 

 

JK! 

It's hard to find one, but a JBL G125 would pair very well with an EVM 12l.  The JBL has more mids and a smoother top end distorted, it has a 12 1/2 lb. magnet structure, 3" aluminum flattened ribbon wire VC, and is similar in efficiency and wattage rating.

For the lower wattage amp thang, I took a lowly silverface Champ and ripped the guts out, built my own turret board for it with top end parts, replaced both trannys, stuck in a vintage CTS squaremag 8 incher,  then lifted the ground from the bass pot as a happy accident, left it that way for some serious ballsy tones like you are talking about. 

+ 1 on the speaker thang.   

Also have a 50 watt HRM, and that thing through either my 2/12 filled with JBL g125's (102db 1 meter 1 watt) gets quite loud with plenty of chean headroom, or for overkill/volume war/outdoor stuff I have a 2/15 filled with JBL g135 (104db 1 watt 1 meter.)  Efficient speakers like that with my little Frank-en-Champ?  I have to turn it down or stage volume is too loud, even with a single 6v6 for 6-7 watts using that particular little monster.  It has a bad case of short man's disease and wants to be a Marshall stack.

@boldaslove6789

Your comment about the Telefunken 12ax7's got me thinking about the D-style tones i'm hearing on many youtube clips, particularly the smooth compression and harmonic bloom.  Usually they are NOT my fave guitar amp tube, but when I thought a bit about their sonic characteristics I realized that they might work well in my new HRM. 


So I found a NOS testing balanced within 10% 12ax7 smooth plate and stuck it in v1, found a strong Philips labeled Mullard Blackburn factory 12ax7a/7025a for v2, and another strong and very tightly balanced 12ax7 Telefunken smooth plate 12ax7 for the PI.  Then for the same kind of compression characteristics and brighter top end that the ribbed plate delivers compared to the smooth, I stuck a strong, balanced within 10% Telefunken ribbed plate in my C-lator.  I originally started out with a pair of GE VOS 6l6gc's, but later found a pair of VOS Sylvania 6l6gc's on fleabay with Conn organ labels on them, they run balanced within less than a half mv of each other at 38mv.  I have read that HAD used the Syl 6l6gc's in many of his builds.  To help hasten burn in, I left the amp and c-lator hooked up with all boost switches on and OD engaged all night two nights in a row without an instrument cable plugged in,  the trannies were only warm, not hot in the morning.   That made a welcome difference in the amp's tones.  Lacking a better description, the amp opened up more at given gain settings than before as far as harmonic content.

I got exactly the kind of results I was hoping for.  Without the c-lator hooked up I got everything from BF cleans to some nice Marshall-y crunch. (the first Marshall jtm45's used 5881's !!)  I love what the tone, boost, and OD trim knobs do for versatility!  Adding the c-lator without effects to the fx loop gave up the magic sustain goods I had heard, and with some very sweet harmonic bloom.  I ordered my amp with only one mod, a lift negative feedback switch. Using that flipped toward the front of the chassis smoothed out the overall tones as well, more in line with the kind of tones found in the original OTS.  Haven't touched any internal trimmers right now and don't feel like I need to.

SAWEEEEEEEEEET! 

Excellent!  I like hearing from one who doesn't follow the herd, does his own science experiments, and gets good results.  I am still breaking in my 50w HRM and even after running it all night the trannies were surprisingly cool.  If they are like that running kt88's that is a huge bonus, 6550's are pretty huge sounding as you have indicated earlier.  Saweeet!

+1  The amp was not designed for that tube, there is some over capacity built into the power supply and OT, but likely 6550/kt88 is capable of pushing things a bit too far as far as plate current draw, especially at high volume settings.

Cool!  Sounds by the choices of speakers that you own that you don't exactly follow the herd as much as you use your ears...   I'm curious about the Altec 417's, I have a 16 ohm 418b, basically a 15" with similar motor as 417.  Love that speaker clean, big, round, fullrange, and dirty it has a lot of bite to it, more snarl for a given amount of gain than my JBL's do, they are designed to be more smooth while playing in the dirt than their aluminum domed forbears. 

I'm guessing that you have experience with at least 40-50 watt amps based on your already owning 6l6 amps.   Personally, 50 watts is still pretty loud and proud, with sufficient headroom for my needs, but I also don't mind a bit of hair in my loud cleans according to my pick attack.  I'm glad for separate master volumes for clean and OD channels in my HRM!  It does the classic clean fender tones very well thanks to the bright, mid, and deep switches.  And you will be able to do the bias tweaking yourself after reading the amp manual, with the help of those trained ears of yours too!  I have heard that the 100 watters don't have to be very loud to sound good, my 50 watter sounds great even at small room volumes through my cabs.  i'm sure I'll love it when I decide to stick in a pair of those el34's.

to the OP question...

Why not get both tube types?  I'm pretty happy with vintage Sylvania 6l6gc's in mine and I have a couple sweet sounding vintage pairs of el34's waiting in the wings, one Tesla, one Siemens.  The 50 watt HRM I have has plenty of both volume and girth in the tones it provides, especially through the JBL filled 2/12 and 2/15 cabs I use with it.   Cheaper and easier to obtain and tightly match pairs of tubes than quads if you want to do that.

Peace.

@fatfretter

FWIW, I chose the 50 watt HRM because...

I liked the idea of a hi and low input, I don't have a need for the FET input,

I liked the idea of separate master volumes for each channel,

I liked the OD trim on the back of the chassis, and

I liked the idea of the TMB tone stack trimmers for the OD channel,

I liked that the amp is designed to run either 6l6's or el34's,  

I like the potential for the huge amount of tones readily available in that design, but all the options available also meant that I had much more to learn to get things sounding the way I like.   I am VERY pleased with my amp.