janalon

Which amp was this? I do not recall and if I mentioned a bias rating it was probably not a cathode biased amp. On the tube covers... push slightly down and rotate about 1/8 turn CCW. On tube vendors .... I have a few I really like on my GAB website in their own area. Hughes & Kettner Puretone, which is a 25w Class A amp. Thanks for the info!

As far as I can tell, these are the power tubes are the real Svet's. I'm not certain about the pre's- I can't seem to figure out how to get them out of that metal casing. Rest assured, there are proper pre's in the preamp section. As a matter of preference, I really loved the Rubies; they made my semi-hollow humbucker guitar sound shimmering and glassy. Whereas the Svets sound much more midrance, and with my guitar combo sounds too bluesy. I am not certain about the current bias of the amp. My tech explained that this amp is auto-bias. As far as the pre-rating, I'd like something that had a clean tone, but would give some slight overdrive / warmth / grit when pushed with my Dos Mos booster pedal. BTW does anyone have a link to a recomended business where I can make this tube purchase online?

Hey Myles, I own a Hughes & Kettner Puretone amp. I immediatly fell in love with its tone- clean, glassy, swirly tone that could be pushed into a soft overdrive. The amp came stock with Ruby EL34BSTR power and 7025/E83CC High Grade pre tubes. Sometime last year the amp was service by a trusted amp tech, and he replaced all my tubes with Svetlanas. First thing I noticed was that my amp's volume significantly increase in output volume. Secondly, I lost that slight overdrive- when pushed, the amp had more of a crunch. I was wondering two things. First, would you agree in my assessment in the difference between these two tubes? Secondly, I prefer the Ruby's tone and response. Should I go back to using the EL34Bstr, or would you recomend another make of tubes?

Hey, Any noticible differences in characteristics between the Ruby EL34B-STR and the "real" Svetlana: tone, breakup, volume dynamics, etc.? Or is it mainly choosing a brand at that point?

Hey, I have owned my Hughes & Kettner Puretone 25w for several weeks now. Considering I purcahsed the amp used, I don't the life of the tubes. I'm getting them replaced, as I can hear the symptoms of worn tubes. Here is my dilema- the certified H&K amp technician is a 2 1/2 hour drive. Their expected turnaround is three weeks. They recommend Tube Amp Doctor / EL34B - STR and 12AX7A preamps. Considering the wait time, I am considering looking elsewhere. Bob at Eurotubes recomended a matched pair of JJ EL84's and two ECC83S's (one balanced for the Phase splitter). I don't feel comfortable making the change myself, and don't have a local amp tech that I trust. I opened the phone book and made a ton of calls. Through my research, I came back to a tech within a hour drive. He came with several referrals. I spoke with the guy, and he seemed fairly knowledgeable. He was surprised that the amp was only 25w, and didn't take EL84's. After some conversation, he recomended Svetlana EL34's. His wait time is 1 week (or 10 days with the holiday). I love the stock H&K Puretone sound, and want to maintain or improve upon it. Most of all, I love the clearness, bottom end, and "swirl". Maybe that is a Vox "shimmery" sound with more thickness / bass. What is your recomended course of action? Myles, I've read through your guide and the JJ's seem OK, and Svetlana seem to fair well. I haven't read a review on the EL34B - STR, but would be more than happy to keep the stock sound.

Hey Caevan, Turns out the solution to my problems was much simpler than I expected. As of last nite, I became so frustrated with the tone / sound quality that I went out to Home Depot to purchase an alan key to open the 3/4 back and take a look at the tubes. Turns out that the alan screws doesn't open the back, but holds the tubes / inards of the amp in place. I screwed everything back in, and pushed up on the power tubes to make sure they weren't jostled loose. Whoala, all of my problems fixxed- the hiss went away and full bite / bass was restored. The amp shipped with tubes attached. I am theorizing that one of the power tubes slipped down, causing a hiss and loss of tone. I guess I pushed the tube back into place during this incident. I will still take it to a certified service technician to have it retubed and looked at thoroughly. Better safe than sorry, eh? BTW thanks for the tube guide Myles. Quite a thick read that should enrich my overall knowledge on the topic. Joe

Joe, You need to see that you have the same output tubes for a start, and then set the bias the same. Then the hard part starts .... preamp tubes. They are a total crapshoot unless you can replicate one amp to the other in the preamp tubes, especially V1 and the phase inverter. Just because you use the same make or type of tube nothing is assured as they can be 50% or more off from each other which is very common. Have something down 25% in V1 and right there you are very different. You have to duplicate current output and transconductance as well as the rise time of the tube. That is what "blueprinting" is all about ... knowing what is in the amp, being able to replicate it, and go up, down, or sideways from there in a known environment. OK, let me ask two simpler questions then: 1) If I brought the amp to a certified / preferred / authorized H&K service technicial, would they be able to get the right setting for tubes given this description? 2) Outside of Amp A sounding like Amp B, are there tubes you would recommend for this amp in particular, or to achieve that sound I described? Thanks again, Joe

Hey Miles, I did a general search for Hughes & Kettner / Puretone and Class A amps and didn't find my answer to the topic, so I thought I'd write. I bumped into the amp tone of my dreams at a local Guitar Center- the Hughes & Kettner Puretone. Cost was $1300. I managed another Puretone through Instrument exchange for $300 less. Knowing the quality control, I made the bid with confidence. When the amp arrived it didn't have the same tone and bite as the one I played. The guys at my local GC were kind enough to let me bring in my amp and compare the two point to point. Beyond cosmetic differences, they appeared exactly the same in all regards. Because of the back protection, I couldn't compare the exact make of tubes, but they both appeared to be stock as far as I could tell. I'm guessing that tonal differences may be due to the tubes (or bias, whatever that is) My preference was for the other amp, that had a tight bass, clear highs, was warm and glassy at the same time. Everything sounded well pronounced. The Class A growl could be heard at lower volumes. My amp had flattened highs and less bass range. Tone knobs did less to shape the sound. There wasn't as much growl. I want to have this amp, my amp, to have the same tones as the other one. Hopefully this will be an issue of new tubes. My question is this: what tubes do you reccomend, how can I get breakup at lower levels, and does the bias need to be adjusted? Sorry if this was wordy, But thanks for your help, Joe