View Full Version : Latino ST-120 vs. ARC Classic 60, SF Power 1, C-J MV55, etc.


whoaru99
02-16-2011, 11:38 AM
So I've been looking at medium (some I suppose might call them high power) tube amps and either shipping is a problem or I'm a day late on the deal.

Generally I've been looking at stuff like Conrad Johnson, Audio Research, Sonic Frontiers, Cary, etc. in the $1k-$1.5K range.

My question is, is Dynaco (Dynakit?) ST 120 from someone like Bob Latino comparable to this general cloth of amps in terms of overall sound quality, or are these brands I've mentioned in the proverbial "another league"?

I'd be using speakers of moderate sensitivity but don't plan for this to be the "party" system in terms of crankability. Ultimately, the tube amp may just run the monitor speakers with a HPF of around 60Hz, with a sub or two to handle the bottom.

mhardyman
02-16-2011, 12:45 PM
I built Bob Latino's ST-70 a few months ago and am powering a pair of Hsu HB1-Mk2 with sub in a classic 2.1 setup. I know the ST-120 is even more of an amp but I have to say, in all seriousness, that the "little" ST-70 will make your ears bleed as it is. These speakers come in at around 90-92 Db sensitivity, depending on who's measuring.

As for the comparisons between the other names, it looks like apples and pears. What flavor do you like? I know that the ST-70 and ST-120 share much the same circuitry and parts quality and I have absolutely zero complaints about what is coming out of it. A very musical amplifier.

whoaru99
02-16-2011, 01:36 PM
What flavor do you like?

That's part of the problem, I suppose. My basis of experience is all with SS amps of what I'd consider good or better pedigree (Yamaha, Audio Research, Mark Levinson, et al.).

I'm not really looking for anything to be added to or taken away from the sound, so to speak, but want to try a roughly comparable tube amp. The reason for mentioning the ST-120 is I can pretty much get a new kit of that any time, rather than try to find one of the others that isn't already sold or someone doesn't want to ship, for similar price.

I already have a Transcendant Sound GG preamp...

mhardyman
02-16-2011, 01:54 PM
As you may have noted from my sig, I too have the Transcendent GG pre and hooked up to the ST-70 it really mates well! I used to have the GG hooked up to SS gear and was thoroughly impressed. Finally getting first the Transcendent T16 OTL, which is no mean slouch, was a revelation. Then building the ST-70 which doubled the power was a match made in heaven.

Please remember that tube watts and SS watts don't really compare. I was concerned that more power was going to be a very expensive problem with tubes but even the ST-70 will drive my old DCM Timewindows which are very hungry.

Have fun!

Bob01605
02-16-2011, 06:34 PM
The Dynaco VTA ST-70 and ST-120 share the same circuit but the components on the driver board are slightly different from one amp to the other. The transformer set is also different.

ST-70 > May be used with 6L6, EL34, KT66, KT77, KT88 or 6550 output tubes. Although rated at 35 WPC, the ST-70 will put out 45 WPC over most of the audio band in ultralinear mode. (without clipping). (see test link below). The ST-70 has 504 uF of DC power storage.

Independent test of the Dynaco VTA ST-70 amp kit (http://www.knizefamily.net/russ/electronics/electron-tube-audio/dynakit-st70/performance/)

ST-120 > Is optimized for KT88 or 6550 output tubes and may also be used with the new Tung-Sol KT120 output tube. Although rated at 60 WPC, the ST-120 will put out about 75 WPC over most of the audio band in ultralinear mode. (without clipping). The ST-120 has 670 uF of DC power storage.

Both amps may be used with either a GZ34 tube rectifier or a plug in solid state rectifier. If you use a solid state rectifier in either amp, I recommend the Weber WZ68.

Bob Latino

jwalker
02-16-2011, 06:47 PM
The Dynaco VTA ST-70 and ST-120 share the same circuit but the components on the driver board are slightly different from one amp to the other. The transformer set is also different.

ST-70 > May be used with 6L6, EL34, KT66, KT77, KT88 or 6550 output tubes. Although rated at 35 WPC, the ST-70 will put out 45 WPC over most of the audio band in ultralinear mode. (without clipping). (see test link below). The ST-70 has 504 uF of DC power storage.

Independent test of the Dynaco VTA ST-70 amp kit (http://www.knizefamily.net/russ/electronics/electron-tube-audio/dynakit-st70/performance/)

ST-120 > Is optimized for KT88 or 6550 output tubes and may also be used with the new Tung-Sol KT120 output tube. Although rated at 60 WPC, the ST-120 will put out about 75 WPC over most of the audio band in ultralinear mode. (without clipping). The ST-120 has 670 uF of DC power storage.

Both amps may be used with either a GZ34 tube rectifier or a plug in solid state rectifier. If you use a solid state rectifier in either amp, I recommend the Weber WZ68.

Bob Latino

Is there any hope of cramming a real (or repro) Dynaco A-431 onto the ST-70 chassis for use with the KT-120? Just thinking that would be a killer setup.

Bob01605
02-16-2011, 07:47 PM
The Dynaco A-431 output transformers will not fit the bolt pattern of A-260-120 output transformers that come with the VTA ST-120 amp kit. You might be able to drill holes in the chassis to accommodate and possibly use the A-431's. From the nature of your question I have a feeling that you may feel that the A-431's might be "better" than the stock output transformers on the ST-120 and maybe "improve" the sound in some way. I don't feel that this is true.

The A-260-120 transformers that come with the ST-120 are USA made and have been tested up to 90 watts continuous with no core saturation. They are interleaved/layer wound with M6 grain oriented silicon steel laminations and are (IMHO) high quality output transformers. Over 100 ST-120 amps in kit or wired form have been sold in the past 2 1/2 years. After listening to the finished product, no one (to my knowledge) has ever questioned the quality of sound from these output transformers.

Bob Latino

jwalker
02-16-2011, 11:03 PM
The Dynaco A-431 output transformers will not fit the bolt pattern of A-260-120 output transformers that come with the VTA ST-120 amp kit. You might be able to drill holes in the chassis to accommodate and possibly use the A-431's. From the nature of your question I have a feeling that you may feel that the A-431's might be "better" than the stock output transformers on the ST-120 and maybe "improve" the sound in some way. I don't feel that this is true.

Bob Latino

I don't remember questioning or implying that the ST-120 transformers are substandard or the overall design is compromised. What I did ask is if the A-431 can be shoe-horned into the chassis. It sounds like it can't without some modification. Which might be fine for a lot of people.

Since the ST-120 shares some lineage with the original Dynaco design, I would say that using an A-431 would be a pretty good way of keeping the guts original Dynaco. I'm all for new advances in winding techniques and materials, but at the same time something wouldn't feel right to *me* if I replaced my A-431 transformers in my Mk III's with say Edcor or Hammond opts. Again, that's just my opinion.

Bob01605
02-17-2011, 07:24 AM
Yes - I can understand your concern in replacing an original Dynaco A-431 with one of modern manufacture. If I had a pair of monoblocks I would want to keep the components on each monoblock the same. That said, it really isn't all that hard to "reverse engineer" any transformer. If you know the core size, wire size, number of turns per winding and the overall winding technique you can create an output transformer that looks like and (more importantly) sounds like an original Dynaco transformer.

I fully understand that it is not fair to judge an amplifier designed in the 1950's (Mark III - 1957, ST-70 - 1959) by what is available today. Except for the output transformers (and of course the original Mullard and USA made tubes that came with the amps) almost everything on the original Dynaco amps can be improved upon with what is available today. The design concept behind the Dynaco VTA ST-70 and ST-120 kits was to have the amplifier LOOK like an original Dynaco amp yet SOUND like a modern tube amp with improvements in light of what is available today.

Bob Latino

WntrMute2
02-17-2011, 07:35 AM
Another vote for the Bob Latino ST-120. Great sound, fun to build, fantastic customer support. Everything is included except solder. I can't compare it to the amps you are considering but I'm going back and forth with my Transcendent SC-150s and am very happy! Go for it!

whoaru99
02-17-2011, 06:54 PM
Come on folks, I know we have more opinions out there than these few. :)

jwalker
02-17-2011, 07:22 PM
Come on folks, I know we have more opinions out there than these few. :)

I had an AR D-76 and still own an AR SP-3. I still have the transformers from a CJ MV-75A collecting surface rust on a shelf in my garage. I measured the transformers and the open-loop bandwidth is roughly the same as a Dyna A431 under the same conditions (they have the same turns ratio and are the same physical dimensions. I wouldn't be surprised if its a near copy.) But I've still not built these into an amplifier so I can't tell how it sounds....

I remember that the D-76 was good and it ran pretty hot (lots of tubes). That's about all I remember.

I think you should be able to get a 70's vintage CJ MV-75 or AR for a lot less than the cost of a new ST-120. I've seen CJ MV-75's go for little as $500 in my area, but $750 seems to be a good price for one in good condition nationally. You can probably get a AR D-76 for that price too.

The disadvantage is that these will be used versus a new ST-120, but the price for the used CJ and AR has already taken 1st level depreciation so the resale value will closer to what you buy it for. This is one of the reasons I rarely buy new audio gear.

JHoman
02-17-2011, 10:33 PM
I bought my Latino ST120 from Craig at NOS Valves. Craig had taken it on trade for a pair of his VRD's. Craig went completely through the amp and made a few changes based on my Klipsch Cornwall I's.

I love the ST120 with KT88's and my NOS Amperex Bugle Boy 12AT7's. The amp has plenty of headroom and makes the Cornwalls really sing. Dealing with Bob on a few questions I have had about the amp has been very easy.

To sum it up, I love my ST120!

GordonW
02-19-2011, 08:17 AM
My take, is that the Latino ST120 and the SF Power 1 will be much more reliable, on a daily basis, than the ARC Classic 60 or the C-J MV55.

Audio Research and Conrad-Johnson tended to run tubes very hard- right to the limit, sometimes slightly beyond- which caused some problems with heat soaking (especially since both of these used, IIRC, phenolic circuit boards). They can start to get noisy (especially the ARCs- they can actually carbonize the circuit boards, causing current leakage!) and need to be serviced to repair heat damage, in many cases.

OTOH, the SF Power 1 and the ST120 both run the tubes in very "comfortable" ranges... I know the SF Power 1 virtually NEVER has service issues, and though I haven't personally dealt with the Latino ST120, from everything I've heard, they're brick-reliable too...

They'll all sound good... so, IMHO, pick one that will keep going, and going, and going...

Regards,
Gordon.

WntrMute2
02-19-2011, 08:32 AM
[QUOTE=

I think you should be able to get a 70's vintage CJ MV-75 or AR for a lot less than the cost of a new ST-120. I've seen CJ MV-75's go for little as $500 in my area, but $750 seems to be a good price for one in good condition nationally. You can probably get a AR D-76 for that price too.

The disadvantage is that these will be used versus a new ST-120, but the price for the used CJ and AR has already taken 1st level depreciation so the resale value will closer to what you buy it for. This is one of the reasons I rarely buy new audio gear.[/QUOTE]

Price for the Latino Amp is about $850 plus a roll of solder. Not a big difference from the used prices you state in exchange for the customer support and the satisfaction of building it yourself.

ducati_EL34
02-19-2011, 09:27 AM
My take, is that the Latino ST120 and the SF Power 1 will be much more reliable, on a daily basis, than the ARC Classic 60 or the C-J MV55.

Audio Research and Conrad-Johnson tended to run tubes very hard- right to the limit, sometimes slightly beyond- which caused some problems with heat soaking (especially since both of these used, IIRC, phenolic circuit boards). They can start to get noisy (especially the ARCs- they can actually carbonize the circuit boards, causing current leakage!) and need to be serviced to repair heat damage, in many cases.


Regards,
Gordon.


CJ used fiberglass boards... So they should not be a problem.

jwalker
02-19-2011, 11:14 AM
Price for the Latino Amp is about $850 plus a roll of solder. Not a big difference from the used prices you state in exchange for the customer support and the satisfaction of building it yourself.

I've not sure if you have an old price list, but the price your are quoting ($850) is with NO tubes and unbuilt! An unbuilt kit with tubes is over $1k. And a built unit with tubes is over $1300. And when you try to sell it within a year, it's going to go for a lot less than that.

In other words, it's significantly more.

whoaru99
02-19-2011, 12:39 PM
I've not seen too many specs on tube amp power supplies, but this info seems to be somewhat of a point for ARC. Their amps having what seems like a lot of energy storage for moderately powered amps. The CL60, for example, indicates 280 Joules of energy storage, some of their units even more, think I saw like 350-something Joules for the VT50 amp, having similar rated output.

Is this way more than other tube amps, or about the same?

thevic24
02-20-2011, 01:53 PM
Here is my .02 worth.

My vote it for the Latino ST120 all day, every day. I had/have the chance to side by side compare this amp next to my dad's fully restored MC240.

The ST120 dose everything the MC dose but 10X better. Now I know its unfair to compare power out put in UL but with the ST120 in Triode, it still seemed to have twice the output of the 240.

IMO, the sound stage of the ST120 is never ending and imaging is spot on.

And just an FIY, I am running a set of Infinity Kappa 6.1's on the 120. They are about 88-89DB and and the 120 will absolutely kick their a%$.

-Vic

GordonW
02-21-2011, 08:04 AM
CJ used fiberglass boards... So they should not be a problem.

If they were fiberglass, then whatever fiberglass CJ used, is also a problem. Myself and BrassTeacher have had to carve out carbonized brown areas from several CJ amp boards, to get them to behave themselves (stop crackling, leaking bias current, etc)...

Regards,
Gordon.