Getting into Tube Equipment

Ralph,
I've been reading your posts for a while, very insightful and much appreciated.

About 4 ohms vs 8, couple questions...

- Isn't the lower impedance floor also a key consideration in amp matching? I'm using EL4s (4 ohm port) to drive 4 ohm speakers, that according to JA at Stereophile are" 5 ohms for the entire audioband other than the region between 100 and 300Hz, where it reaches a minimum value of 3.5 ohms at 165Hz". There are some 8 ohm speakers with minimums well below 3, isn't this a significant consideration?

- My volume levels are fairly low, wouldn't material distortion only begin when you push the amp nearer to its limits.

Thanks, looking forward to your comments on this.

Hi, there are a number of kit tube phono pre's that work very well and are fun to build.  It gives a person great satisfaction to tell others "they built it themselves".  Bottlehead  offer two alternatives at reasonable prices.  Add a passive volume control, the Dyna ST-70 amplifier you've dreamed of, and speakers you like, and together with your turntable setup you will have the system you've always wanted.  Trust your ears to help you choose the items, and you won't go wrong.  Have fun and welcome to the world of a wonderful sounding stereo.  I had a Dyna Pas3 for a few years, and although I enjoyed it, I found the Bottlehead phono pre-amps much better, and I own both models they offer.

Great discussion, especially the Dynaco stuff . In my youth I had a pair of Dynaco MK III’s powering my JBL Century 100’s . Home built SS pre amp with tone controls . Garrard 40B with Audio Technica cartridge followed by a Pioneer PL -117 . It was fun . Home built cables and stock power cords . My how things have changed . Currently running a Dennis Had Inspire . I have a huge stash of tubes. SED EL 34’s and KT 6550’s, NOS GEC KT66’s and KT88’s . NOS Tungsol 6550’s too . New Gold Lion , Psvane Ti and Tungsol Kt120’s . I also have a big selection of 6922 drivers and rectifier tubes . I run NOS Telefunkens and Seimens in my preamp. Currently powering Zu Omens . Have Heresy II’s And JBL 4312’s and bookshelf’s in the closet . I’m one of those weird people that prefers KT’s over EL34’s. And I definitely prefer Telefunken over Mullard driver tubes . However the FX1 and rectifier Mullard’s are the Bomb ! Saving up for a NOS WE 422a. Everybody’s taste varies . If you have the right speakers you’ll enjoy low power , if not go 60-100 wpc . My Dynaco SCA-35 and FM3 were sweet as a kid , but no match for today’s stuff. I’m considering Mr Latinos 120’s , or a Rogue Stereo 100 in order to use my JBL’s again . Good luck to you . Everybody here has enjoyed a “ Good Experience “ albeit slightly different . YMMV but your satisfaction will be great ! Best wishes and happy hunting, Mike B.

@buellrider97 "I definitely prefer Telefunken over Mullard driver tubes . However the FX1 and rectifier Mullard’s are the Bomb !"
You have an excellent ear and excellent taste, Mike.  Another pair of MKIIIs, or MKIIs or MKIVs would make some great music, and bring you a lot of happiness

@trelja , thanks for the compliment. I’ve tried NOS Mullard drivers , but they are like pushing the Dolby noise button on an old cassette player . In keeping on track with an excellent discussion . Would you or anyone please share on the new Dynaco MK III kits . 60 Watts is the minimum for a new amp . Being frugal I’ve looked the Latino 120 amp . But I don’t like the non detached power cord and the inputs on the front . I like his mono blocks a lot . But the MK III kits from the competition look very interesting . I’m capable of building all of the kits and have enough tubes to run them . Another member shared some great info on the driver circuits . But my question is sound quality of Bob Latinos two amps and the MK III copy’s . I’ve been avoiding buying the originals even though it was a great experience. I’m very familiar with Dynaco and Rogue “ House Sound “ . So knowing my taste please chime in . Also I hope this honors the original question and adds to the thread, especially since the authors speakers need wattage in the 50 plus arena . Respectfully, Mike B. 

- Isn't the lower impedance floor also a key consideration in amp matching? I'm using EL4s (4 ohm port) to drive 4 ohm speakers, that according to JA at Stereophile are" 5 ohms for the entire audioband other than the region between 100 and 300Hz, where it reaches a minimum value of 3.5 ohms at 165Hz". There are some 8 ohm speakers with minimums well below 3, isn't this a significant consideration?

Yes, and Yes.

If playing tube amps, I think I mentioned earlier that one has to beware of speakers with dual woofers- when you see that, make sure that the woofer array is not wired to be 4 ohms, or you simply won't get everything out of the amp that you intend.

In the old days, when tubes were the only game in town, speakers were more efficient and 16 ohms was a lot more common. This is for the simple reason that there is no sense in making the tube amp (or any amplifier for that matter) work hard for its keep. You want the amp to be effortless. It makes a difference!

Count me in as a guy who prefers the KT-88. 

Just sayin. 

@buellrider97 thank you for your kind words, as well.

You would do extremely well with the MKIII. They will put out the horsepower you want. You also do a little better with them on the 6AN8 pricing and availability instead of the ST70’s 7199. As I stated previously, you need to consider the coupling caps in regard to low-end performance. As the MKIII caps are already larger than the ST70, you get more bass out of the box, but may want to take one more step there. If you decide to go with the Latino 120s, you’ll still do very, very well.


I mentioned mostly taking the new kit route with the ST70 for cosmetic reasons, unless you find an affordable unit to salvage its transformers. As you well know, the original MKIII transformers are true beasts, and beyond most of what we see in current tube amplifiers up to $10K. With that, I suggest a different tack, get a pair of original MKIIs or MKIIIs as I don’t think we can beat those trannies.

Unless you find them with pristine (not likely at a reasonable sum) chrome or the very cool restomods folks like Will Vincent produce, I’d then order the gleaming, mirror finished stainless steel chassis and parts kits from Kevin at DynaKit Parts in NJ. Again, I think your taste will align with mine in thinking the original, more simple, and more immediate, insightful sound of the original Dynaco circuit bests the succeeding efforts to improve upon it with the Mullard’s higher gain, and increased circuitry / parts count. As many replacement boards have come down the pike in the past, I would love for someone to produce one of the original Dynaco circuit implementing a double triode phase splitter / driver (I won’t mention also removing the negative feedback loop, and making the appropriate compensation in gain), but with such low volumes these days, how could it be profitable enough for them to happen? I’ve hardwired a couple on my own with 8 pin and 9 pin tube sockets pre-mounted on terminal boards you can source from a place like Antique Electronic Supply. This sort of thing is stepping out there a bit - you might consider it a tangent or something to consider one day, but for now, just prefer to get a straight version of something working. But I’d also still look up Bob Latino for a modern set of RCA jacks and loudspeaker binding posts. You raise an excellent point on the power cable, and that’s a must have.

Since you already have a nice stash for rectifiers and output tubes and are ready to go, there’s not a lot else to consider. They’re wonderfully simple amplifiers that sound a lot better than today’s audiophiles expect, and prove more than reliable.

Hope you enjoy the ride!

Bob Latino's kits are definitely a good way to go.

+1 Sound is excellent. Preferred over PrimaLuna PL5 and NuForce ST-10 which I also own.

As built by VTA, the M-125's were very noisy, but can be quietened quite a bit. In my case, almost 40db.

Complete instructions:
http://ielogical.com/Audio/VTA_M-125.php