[MasterHiFi]

Hello All,

New here to audiocircle and glad to be aboard. Picking up lot's of useful information, especially as I try to (not so) gracefully make the transition from SS to Tubes, and consider options for ever-increasing digital playback, i.e. FLAC, MP3 as well as Streaming (visit RadioParadise.com for some of the BEST online listening you'll ever hear!)

Anyway, hope that I can contribute as much as I am learning from all you experienced members.

Looking forward to meeting so many of you. One tiny bit of advice that I can share right here and now... TURN IT UP!!

Regards to all,
Dan
MasterHiFi

[FullRangeMan]

Welcome aboard Dan
How many tube Watts do you need?

[Wind Chaser]

Welcome, Dan. I recently made the transition from tubes back to SS!

[MasterHiFi]

Welcome aboard Dan
How many tube Watts do you need?

Hi FRM,

It's funny you should zero in on that specific issue - should I be checking my house for listening devices?

Well, it so happens that I have a problem in that regard. My speakers, as measured by John Atkinson, come in at a measly 87 db, they are large and I often like to listen loud. They are the classic Snell CVs, and even though they're spec'd at 91 db, I think Kevin Voecks, the engineer who designed them who now designs for Revel, was just too embarrassed to put down anything under 90 db. That's my working theory at the moment, anyway.

So way back when they were reviewed by Stereophile the actual efficiency was exposed, which seems about right for anyone who has owned them. But as a result, I require LOTS of power. No boutique SET amps need apply.

In fact, I've got a pair of old tube PA amps that I am planning on having turned into hifi amps. Once complete they should produce 90 - 100wpc running 6550s and crush the full audio bandwidth (a bit of acceptable roll-off below 28Hz at full rated output).

Can you recommend any good techs who like to rebuild old tube amps and do it well? I was hoping to have Dave Gillespie do mine, he is meticulous and extraordinarily knowledgeable, a true artisan, but his schedule is really backed up right now... Any good recommendations highly appreciated.

Great to meet you,
Dan

[MasterHiFi]

Welcome, Dan. I recently made the transition from tubes back to SS!

Hi WC,

Great to meet you! I'm reading your post... Hey, NO, we don't need you! 

Sorry, I was just telling some paramedics who showed up on the scene that everything's cool, you're okay. 

Seriously, though, what made you go BACK to SS after tubes? I can honestly say that I have not seen that before, so I'm just curious what were your motivations? Was it more about convenience than sound, or is tube equipment ill-suited to your space / location, or did you change a piece of equipment for which SS worked better?

Would love to hear your thoughts. Just as long as you don't give up music...

A pleasure,
Dan

[JakeJ]

Hello and welcome to AC, Dan.

[JLM]

OSHA warns that extended exposure to greater than 85 dB will result in permanent hearing loss and/or pain.  (I mow with hearing protection.)  In my wanderings the average serious listening is done at 85 dB (average).  Do you own a sound pressure level meter?


Good tube and SS amps should sound very similar.  Big wattage tube amps aren't cheap or small.  They generate lots of heat and tube rolling/keeping the tubes matched can be a headache.  Plus you can't leave it warmed up and ready to go.  And of course tubes blow.  So yes, tubes require more involvement/commitment.  OTOH tubes clip in a friendly manner and typically have big power supplies so the common advice is that you can do with half the wattage of SS.  If you like it loud and have 87 dB/w/m speakers in an average room, you'll probably need at least 100 watts of tube amplification.

As a speaker guy I'm committed to SS.  My experiences with tubes over 40 years:

1.)  I home auditioned a tube/SS preamp that sounded the same to me either way (and an expensive NOS 6SN7 tube blew during the trial). 

2.)  Also owned a DAC that had a tube that could be bypassed and couldn't tell the difference (even though the tube wasn't cheap and was recommended for that particular DAC). 

3.)  I trialed one tube integrated amp at home that had great tube palpability but lots of bass flab (poor damping factor) that I couldn't live with.

4.)  Owned another tube integrated amp (Stereophile Class A rated).  Rolled output tubes, one set was 'warm' (don't want everything colored), and only one other set (6550's) sounded better than my old Class D SS mono-blocks that cost half as much and required zero user involvement.

Don't believe the hype.  Honestly listen for yourself.  Why do you think so many swap so much gear?

[Phil A]

Welcome!

[ArthurDent]

Greetings & Welcome to AC Dan   

[FullRangeMan]

Dan with this low efficiency speaker I suggest you a Class D or SS as Odyssey. I cant recommend any tube technician.

[dB Cooper]

Another option might be one of the Fer-Valve hybrid amps from Audio by Van Alstine. They probably won't sound like an all-tube power amp if that is the signature you're looking for, though.

[MasterHiFi]

OSHA warns that extended exposure to greater than 85 dB will result in permanent hearing loss and/or pain.  (I mow with hearing protection.)  In my wanderings the average serious listening is done at 85 dB (average).  Do you own a sound pressure level meter?


Good tube and SS amps should sound very similar.  Big wattage tube amps aren't cheap or small.  They generate lots of heat and tube rolling/keeping the tubes matched can be a headache.  Plus you can't leave it warmed up and ready to go.  And of course tubes blow.  So yes, tubes require more involvement/commitment.  OTOH tubes clip in a friendly manner and typically have big power supplies so the common advice is that you can do with half the wattage of SS.  If you like it loud and have 87 dB/w/m speakers in an average room, you'll probably need at least 100 watts of tube amplification.

As a speaker guy I'm committed to SS.  My experiences with tubes over 40 years:

1.)  I home auditioned a tube/SS preamp that sounded the same to me either way (and an expensive NOS 6SN7 tube blew during the trial). 

2.)  Also owned a DAC that had a tube that could be bypassed and couldn't tell the difference (even though the tube wasn't cheap and was recommended for that particular DAC). 

3.)  I trialed one tube integrated amp at home that had great tube palpability but lots of bass flab (poor damping factor) that I couldn't live with.

4.)  Owned another tube integrated amp (Stereophile Class A rated).  Rolled output tubes, one set was 'warm' (don't want everything colored), and only one other set (6550's) sounded better than my old Class D SS mono-blocks that cost half as much and required zero user involvement.

Don't believe the hype.  Honestly listen for yourself.  Why do you think so many swap so much gear?

Hi JLM,

A pleasure to be sure. I know I've seen your avatar before, just can't place where ATM. But your points are valid. I've done some thorough reading regarding the differences between even Vs odd harmonic distortion and even more importantly, as you mentioned, I believe that the bigger yield is with a tube Preamp section, with diminishing returns at the amplification level. And yes, getting high power across the entire audio bandwidth using tubes is not only difficult, it tends to be an expensive endeavor.

In the end, what really matters most is what our ears tell us, though many (read: most) will find it difficult to separate their preconceived notions from their listening experience. I honestly enjoy the natural harmonic distortion of tubes, at least at the Preamp level. It's quite likely that I would not be able to discern an audible difference between a tube amp and a high quality SS amp. In my case then, it really just comes down to my perceived "synergy" with both tube power and pre. And there is also a bit of "can I do it?" factor involved.

As you also mentioned, without good damping factor in a tube design, the result is boomy, flabby bass. Being that my speaker. are particularly inefficient, the challenge is substantial. Add to that the fact that, relatively speaking, I am poor as a church mouse. Now what do I do? Funny I should ask myself! (This is tongue-in-cheek, BTW. Please do NOT get the impression that I take myself too seriously.)

So, as I mentioned above, I am looking into converting an old early sixties pair of tube monoblock PA amps into legitimate, hig.     fidelity amps suitable for home stereo critical listening. (<<-- that chopped off word "high" and inappropriate period with weird spacing is some bug in this typing window. Similar situation above and probably more to follow, so I apologize but I'm not drunk - it seems beyond my control.)

So, to make a long story longer, what I bought a number of years ago was a Bogen brand MO-100A monoblock, and then a while later, another one. I was going just based on the size of the Power Transformer and Output Transformer. And I just held onto them and did nothing. I read a thread on AK or Antique Radio Forum about how one guy took an MO-200A, the  200 watt version of the same amp (vs 100 watts per monoblock) and split it into a 100wpc stereo amp, loaded with the original and very expensive 8417 tubes that are no longer in production. There were a few other threads regarding both versions, and some  used  the original tubes while others converted theirs to run on KT88s but otherwise did not do a great deal of mods, though they liked what they heard.

Finally, in 2016, Dave Gillespie on AK did a full testing and rebuild of an MO-200A. What he found by properly testing the transformers, tubes and circuit is that the amps, designed for sound reinforcement and other industrial applications, were built for reliability, longevity and low maintenance - not for musicality, which makes sense. As per those goals, the amps performed remarkably well. They intentionally rolled off the frequency response above 10k, as well as below 200Hz, IIRC. Not good news for home stereo use.

After some serious testing (Dave Gillespie is a tube circuit guru) Dave found that by using the appropriate tap, switching to 6550s and some redesign of the circuit, the amp was capable of reproducing 28 - 20kHz at full power! And using just two of the 6550s per channel (the other two tubes were redundant, but made the amps more reliable for their original purpose), the MO-200A version put out about almost 110wpc. Furthermore, at around 85% of full power, the amp produced the full audio spectrum, right down to 20Hz, without breaking a sweat. The transformers stayed remarkably cool, even through Dave's extended stress tests, and the circuit required relatively minimal negative feedback to keep measurable distortion at a very acceptable minimum. And due to the size/strength of the transformers, the sine wave demonstrated incredible attack and control, even at full rated power, visually illustrating the amps tight control of the most demanding bass signals. When I think about the acclaimed Citation tube amps (I don't claim to know the specs on every model), what I remember was that the transformers get really hot and the circuit required a LOT of negative feedback to control distortion.

So, the challenge is, "can I do it?", especially for my demanding speakers and lack of $$? With an initial investment of less than $150 per amp (sans tubes) and the brilliant, hands-on research and development of Dave Gillespie, plus the added expense of paying someone to do the work (if I possessed the knowledge and skill, I could do it myself - Dave posted the schematic for all), as well as the cost of tubes, it appears that I could have a pair of amps that will perform as well, if not better, possibly, than some of the finest vintage tube amps available, at least among the higher powered push-pull variety.

Could I get as good, if not better sound and performance with a good quality SS amp? Probably, but wouldn't it be cool if I had all that tube power at hand and managed to compete with or even out-perform some of the best vintage tube amps around? I think the amp would sound a little sweeter by that measure alone.

When I get a chance to get to my main PC I will try to post a photo of the MO-200A that Dave rebuilt and the owner refinished, making an unattractive industrial amp into something of a looker.

Here is the link to Dave's development thread on AK:


http://audiokarma.org/forums/index.php?threads/the-mighty-bogen-mo-200a.556575/

On a final note, I do plan to power my dual 12" stereo sub, and possibly the lower end of my speakers via bi-amp, with large SS amplifiers. I'll play around and see what works best, but extra low end muscle will not be overlooked.

I'm still curious, though, (unless he's answered since I last refreshed, how embarrassing that would be) as to why Wind Chaser went from tubes back to SS? It's a valid question, no?

Love the discussion, BTW, thanks!

Dan

[MasterHiFi]

Welcome!

Please allow me to reply with a formal Thank You and pleasure to meet you to Phil, as well as AurthurDent and db Cooper - there you are! I bet you have a nice rig from all that cash we've been speculating about! Seriously, though, I did consider some of the hybrids, even some of the hybrid preamps. I think I have fallen in love, however, with the larger tube 6SN7 design created by Roy Mottram and improved upon by Don Sachs. It's an interesting thing, making purchasing decisions based solely on users' reviews. That never would have happened 30 years ago.

And JLM, speaking of 30 years ago, I used to sell hi-fi back in the day, and you would be surprised how many customers I had to warn against using their new Klipsch Chorus or K-Horns at harmful levels. At which point I was promptly ignored, of course.

Myself, I only occasionally turn it up LOUD. But on those rare occasions I do want my system to perform. Right now I'm using an Adcom amp with the GTP-555II Preamp - Tuner. When I do crank it up, in my opinion it begins to sound strained and the soundstage doesn't hold together, the instruments start to sound mashed together. I know it's not the speakers, they are capable of much more.

My real goal, and the reason I'm particularly interested in a tube Preamp is that I'm kind of an imaging freak. I LOVES me some transparent and holographic imaging. Although I've read a great deal about the AR, Cary, CJ, etc., I am really sold on the idea of the bigger tube in Mottram's circuit. The transparency and focus just seems to be there, and not at BAT prices.

Any thoughts?

Dan

[MasterHiFi]

Hello and welcome to AC, Dan.

JakeJ, hi! Now I KNOW I read some of your posts over in the Don Sachs Preamp thread, no? Do you have a DS-2? Can't recall. FWIW, that thread absolutely has me sold. This is value audio at its best, meticulously crafted by someone who really is in it for the joy of music. I just hope I'm not confused, perhaps it was the Tekton Design Impact thread I'm recalling... I should sell all my gear for a solid state memory chip implant in my brain, that's what I should do.

And for anyone who is interested, this is a pic or two of the Dave Gillespie rebuild of the Bogen MO-200A, and cosmetically re-done by Rampt, the actual owner of said amp:
















Again, this is now a 200w monoblock converted to stereo, pushing well over 100wpc with only a slight roll off below 28Hz at full power, with low distortion, and now only using two 6550s per channel. The big trannies keeps the sine wave tightly controlled at all measured frequencies, even at full output, all while barely getting warm. If you know what these amps typically look like when you find them, Rampt did an amazing job getting her all dressed up for the prom.

Regards to all,
Dan

[Wind Chaser]

Hi WC,

...what made you go BACK to SS after tubes? I can honestly say that I have not seen that before, so I'm just curious what were your motivations? Was it more about convenience than sound, or is tube equipment ill-suited to your space / location, or did you change a piece of equipment for which SS worked better?

Hey Dan,

I've owned a number of tube amps and other pieces of tube gear over the years. For me it is first and foremost about sound quality. Despite my speakers being fairly sensitive @ 94 db, the impedance curve proved to be too much for my 8 watt SET amp. So I tried a modest SS amp and ...

In addition to sound quality, I like the fact that I can leave the amps on 24/7. No warm up time required ever. System is always on, up and running ready for serious or casual listening without wasting tube life. And yes, the sound quality is superior to every SET amp (PP need not apply) I have ever heard or owned.

[MasterHiFi]

Hey Dan,

I've owned a number of tube amps and other pieces of tube gear over the years. For me it is first and foremost about sound quality. Despite my speakers being fairly sensitive @ 94 db, the impedance curve proved to be too much for my 8 watt SET amp. So I tried a modest SS amp and ...

In addition to sound quality, I like the fact that I can leave the amps on 24/7. No warm up time required ever. System is always on, up and running ready for serious or casual listening without wasting tube life. And yes, the sound quality is superior to every SET amp (PP need not apply) I have ever heard or owned.

Hi WC,

I'm glad that you found the right combination for your system. For me also it is about the sound, or even more specifically about the music. When I'm listening, I want to be enjoying the music, not thinking about my equipment (not unlike sex, no? ). For me, I have not been able to entirely get my speakers disappear, and I hold no illusions that a tube amp will solve this issue of, however I do think that a quality tube Preamp will go a long way towards this end. The tube amp option is more for the challenge of seeing if it can be done.

Often it is just the synergy between components that determines what sounds best, as seems to be the case with your system. If you don't mind me asking, what speakers are you using? Also, in my experience a tube Preamp will provide 90 - 95% of the sonic benefits of a tube setup. Have you tried a tube pre & SS amp combo? And what amp did you settle on that worked so well with your speakers?

In the end, I don't think there is any one "right" way to do things. Everyone's experience is different.

Dan