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Author Topic: New Horn friendly amplifier worth checking out - part 2  (Read 18345 times)
Randy in Caintuck
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« on: August 26, 2012, 05:58:50 PM »

After living with the La Dolce Audio Virtuoso (6CA7) amplifier for a few days, I feel that I now know it well enough to offer a few thoughts on it.

When Terry first brought the UA1 amp to my attention, he stated that he wanted to provide a "taste" of the beauty of pentode amps to music lovers for a modest and affordable price.  After hearing it in my system (and especially with "firebottle's" vinyl front end), I figured that Terry was pulling my leg and was having a good laugh at my expense ..... the UA1 was a lot more than a "taste" ..... more like a four course sonic meal.

Well ..... Terry wasn't woofin' ..... if the UA1 is a four course meal, the Virtuoso is a full blown banquet.

Before anyone thinks that the UA1 is now to be thrown out with the bath water, I hold to my original thought that this modest little amplifier is one killer piece of music making magic with a top notch digital or a vinyl front end.  The down side is that it is not very forgiving.  If you have a hot or thin sounding CD, the UA1 will make you head for the hills ..... but, with a well recorded CD or piece of wax the amplifier will put a king sized smile on your face ..... and with 6 mighty pentode watts it will light up a wide variety of speakers, including The Horns.

The 6CA7 amplifier will do everything the UA1 will do ..... and then some.  The way the prototype that I am listening to is set up includes two toggle switches on the top ..... one a three way, the other a two way.  I am not smart enough to know exactly what they do and will leave the technical end of things to Terry to comment on if he so chooses, but I will say that the two switches offer an amazing variety of sonic options ..... from "laid back" to very dynamic, from "honest" to rich.

I have played a ton of different types of music and CDs with a wide range of "recording quality" and the amplifier makes all but the most atrocious sounding disks very listenable.  The good ones made my jaw drop .....  Shocked

It seems that a well-designed pentode amplifier is very dynamic by nature ..... and the UA1 and 6CA7 amps have this trait in spades.  But, there is a lot more than just dynamics at play here.  The clarity and focus are something special on both amplifiers ..... but the 6CA7 amp has a richness and fullness beyond that of the UA1.  If a person enjoys the effect of having the lead vocalist standing in front of them and giving a "private concert", they will not be disappointed with the Virtuoso.

OK, Ed, I will throw you a bone .....   Wink   the Virtuoso combines the best traits of the beauty, warmth and musicality of my Decware amp and 300B with the spank and death grip on the speakers of the UA1 ..... it would be hard to ask for more.
Terry rates the amp at 8 watts per side ..... but it sure sounds like a lot more.  With any of my current speakers it puts a life sized group of instruments and vocals in the room.

I'm not sure exactly what Terry will be asking for this amplifier, but if musicality and realism are the ultimate goal, it absolutely flogs amplifiers I have heard and owned that cost a lot of money.  The two amplifiers that I have personally heard that can "run" with this amplifier are WAY out of my price range.  

I have no financial interest in La Dolce Audio and (to the best of my knowledge) Terry has no photos of me in embarrassing situations ..... so my comments are straight up and sincere .....  Roll Eyes
Firebottle (Rob) will be hearing this amplifier in the next week or two and it will be interesting to hear his comments.

I know that most of those who will be reading this have probably read hundreds or thousands of "reviews" on audio gear and there are only so many "superlatives" that can be attributed to a piece of audio gear ..... but I would be greatly amazed if anyone that hears this amplifier with a decent front end and speakers is not bowled over.  

Will I be buying one of these amplifiers when they are in production ?  Absolutely ..... highly recommended   Grin

Randy
« Last Edit: August 26, 2012, 06:02:21 PM by Randy in Caintuck » Logged

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Randy in Caintuck
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« Reply #1 on: August 26, 2012, 06:17:39 PM »

I knew I forgot something .....  Embarrassed

There will probably be some changes in the production amplifier (maybe not), but here is the amplifier I am listening to without the toggle switches added on the top .....






Larger photos here and here.

Randy
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Capt. Z
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« Reply #2 on: August 27, 2012, 01:39:21 AM »

I envy you guys who live over in the US and are able to catch one of Terry's amps on the 'road trip".

Having a toggle switch to change the sound and mood according to your mood can be a lot of fun.

Wondering how Terry's amp compares to Bruce's OTL amps.
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2wo
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« Reply #3 on: August 27, 2012, 08:26:13 PM »

Terry, If you need any photos of Randy in embarrassing situations, feel free to contact me Grin...John 
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TerryG
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« Reply #4 on: August 27, 2012, 08:42:52 PM »


Well that was a very nice review, I am so happy Randy liked this amp.   Thanks for take the time to right what you liked about the amp.  So far it doesn't seem like I will need any embarrassing photos of Randy, but it is good to know who has some just in case.

I was telling him I thought this amp was better, then I started to get nervous that perhaps I might be giving him an expectation that this won't be able to deliver.  Or perhaps I like a sound that Randy does not, or that I am so filled with being a proud creator of an amp that even it was bad it would sound good to me.    

The really odd thing is, that I feel this urge to say to Randy,  "You haven't heard anything yet".  Because this amp I don't feel is the very best amp I can make, I have some things that I feel would make a better amp, but I have been saving those secret weapons for the KT120 tube, because it can deliver 20 watts in SEP mode perhaps more.  I did get this wild hair, because they have the same pinout as the 6CA7 tube, to put a pair of KT120's in the 6CA7 amp, and instead of the 8 watts I was getting with the 6CA7 it put out 11 watts and sounded better to me.  So I thought it totally feasible that I could make an even better sounding amp with the KT120 vacuum tube.  

To me the only better thing than a really nice sounding amplifier, is a nicer sounding amplifier with much more wattage, because I like to jam out once in a while.


Terry
« Last Edit: August 28, 2012, 05:53:33 PM by TerryG » Logged

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Randy in Caintuck
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« Reply #5 on: August 28, 2012, 01:12:03 PM »

Terry, If you need any photos of Randy in embarrassing situations, feel free to contact me Grin...John 

John,

I thought the rule was "what happens at the Horn Fest, stays at the Horn Fest" .....  Grin

See you at Horn Fest 2013,

Randy
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steve f
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« Reply #6 on: August 28, 2012, 02:52:24 PM »

Randy,

The Horn Fest statute of limitations.. There is one Huh

Steve
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steve f
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« Reply #7 on: August 28, 2012, 05:11:04 PM »

Terry,

It's not nice teasing us like that. Every next step appears to be a big one. Might as well say "You ain't seen nothin' yet."

Steve
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TerryG
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« Reply #8 on: August 28, 2012, 06:20:11 PM »

Terry,

It's not nice teasing us like that. Every next step appears to be a big one. Might as well say "You ain't seen nothin' yet."

Steve


Steve,

Well I guess that is what I am saying.  This entire journey has been about, how to get this really good sound I get with Pentodes with more wattage.  And I am getting closer to whever ever that limit all the time.   I didn't expect to get better sonics with more wattage, that was a real bonus!

I am always so interested how every decision I make leads me on a journey, I enjoy the journey almost as much as the result, a I always so curious what will be the end result though.  I always do a worse case and a best case scenario, and it always usually ends somewhere between.  With these pentodes I guess I keep underestimating the best case.  Because I keep thinking best case they sound a LITTLE better with more power output, but what ends up happening is more power and much better.   

Well I didn't get as much of a power increase from the 6CA7 that I thought I would, an EL84 has a plate wattage of 12watts and I can get 6watts at the speakers.  A 6CA7 has 22 watts at the plate, and I get only 8 at the speakers.  The math says I will get, with the KT120, 60 watts at the plate and 20 watts at the speakers. Can anyone explain why these ratios don't stay the same? 

Although I must say I am pushing the SV83 a little hard, the tubes are so cheap I don't think anyone would mind retubing once every couple of years.  The 6CA7 should last that long or longer, I don't know about the KT120 yet, it will all depend on how it works out once I get it working in an amp. It may be that I get 24 watts and can back off to 20 watts to help the tube last longer, they are about $100.00 for a pair you know.   

I am not above abusing a tube with more plate wattage dissipation that it is suppose to have if it isn't starting to glow red hot yet.  The 6CL6 (not 6CA7, this is not a typo) is a good example, I can exceed its max by 10ma and the tube doesn't seem to mind at all, same with the 12HG7A.  I did cause a pair of SV83's to die once by running them up 125v past their max and twice their current max, this was over four times their maximum plate dissipation.  I just wanted to see how they would sound and where they would fail.  I got nervous at that point (after stair stepping up to that point), and turn them back down, but two days later they threw in the towel after that experience, they were old tubes already.

I do love running a hot rod amp though, nothing like hearing anything running full throttle, although the SV83's really didn't sound much better about the same, but the power output at the speakers was amazing.  I figured I was getting 20 watts from a pair of SV83's at least.  I ran them for about an hour at this level, it was really cool but I was expecting fire works the entire time (talk about nervous listening and cringing at music peaks) , but since I didn't want to buy a new pair of output transformers I chickened out and turn it off and reset the bias to normal levels.

Say anyone want for me to make them a hot rod SV83 amp at 20 watts power output that you have to change the output tubes every couple of hours?  Would sound really cool!!!  You might get three hours out of them with a good cooling fan.

Terry
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« Reply #9 on: September 01, 2012, 09:52:14 PM »

Randy,

Any more comments on the 6CA7 amp? Or is it on its way to the next audition?

Steve
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TerryG
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« Reply #10 on: September 02, 2012, 12:54:06 AM »

The 6CA7 amplifier will do everything the UA1 will do ..... and then some.  The way the prototype that I am listening to is set up includes two toggle switches on the top ..... one a three way, the other a two way.  I am not smart enough to know exactly what they do and will leave the technical end of things to Terry to comment on if he so chooses, but I will say that the two switches offer an amazing variety of sonic options ..... from "laid back" to very dynamic, from "honest" to rich.

Randy

Since Randy and the other person that had this amp in his home for a while (George) very much liked the switches on top of the amp I think I will keep them in the final production amplifier.  I was expecting everyone to find a switch setting that they liked and then design the amp to have that sort of feedback combination.  So I will explain what the two switches are doing, you have your choices between the both of them of six different sonic signatures. 

The three way switch in the forward position flips in a global negative feedback loop(NFB), it is not super aggressive, but enough to cut the amps gain by about 6dbs.  In the middle position with this three way switch there is no global NFB, but local feedback on all tubes via the cathode resistors.  The back position on the three position switch, switches in a couple of Cerafine bypass caps on the cathode resistors of the driver tube taking away the cathode feedback.  The driver tube is a 6N6P tube, which is the little brother to the 6H30P-DR tube, it has a little higher plate impedance but the same medium gain, with very high Gm.  This tube is the best sonics for the price in audio today, bar none.

The two way behind the 6CA7 tubes merely switches in an out a pair of Cerafine caps on the 6CA7 tubes to bypass local feedback on those tubes, this gives the amp a little more gain yet, and a little more dynamics as well.  So you have the three positions of the front switch with the two positions of the back switch.  With the front switch flipped fully forward and the back switch forward you get a very easy effortless sound, with maximum sweetness.  With the front switch flipped fully back and the rear switch flipped back as well you get a very lively super dynamic sound. All the other settings lands you somewhere between those two types of sonics.  But not any setting made any recordings I have sound harsh or tough to listen to like the UA1.  This amp also has a bit more content below 300hz, making it sound very full bodied and with a lot more authority than the UA1.  It has a lot more weight than it should at 8 watts because of this, and thus sounds like a really good 15 watt solid state amplifier.   I have my opinions on which switch settings the amps bass output sound more full and solid, but some have disagreed with me so I don't know now.  After all who am I to argue with an Audiophile and his perceptions?  Right!!   

I also tried this amp with several speakers between 4 ohms and 16 ohms and it sounded very nice with them all, so I must have struck the sweet spot with regard to impedance right.  It has in it right now the JJ 6CA7 tubes, but some say that there are a lot better EL34 tubes out there, more detailed EL34 tubes that cost much more.  I can not imagine the amp being more detailed than it is right now, both it and the UA1 are equal in that regard, they just have different tonal balances, and the 6CA7 Virtuoso makes all recordings sound very nice, where the UA1 can sound harsh with poor quality recordings.  So far only tubes have this ability to make a poor recordings sound better, I have not heard solid state amps do this.  I designed a buffer circuit about 8 years ago that did this very nicely while adding in a more dynamic sound, and excentuated detail.  Tubes are some nice things to work with when it comes to audio.  But when it comes to design solid state is much more predictable, solid state components do not vary as much per piece like tubes, and they do not seem to wear out to where you have to change out transistors.  You just can not get sonics like you can with tubes from solid state very easy.  There only a hand full of solid state amps that I feel compete with tubes.

Terry

 
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Randy in Caintuck
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« Reply #11 on: September 04, 2012, 06:57:03 AM »

Randy,

Any more comments on the 6CA7 amp? Or is it on its way to the next audition?

Steve

Hi Steve,

The plan was to have Rob (firebottle) visit me for a listening session and then take the amp to his crib for a listen with his vinyl rig.
The way things worked out, Rob will be on vacation for a couple of weeks and our plans have been postponed until he gets back ...  Cry

I do have some additional thoughts on the 6CA7 amp and will post them later tonight when I get home from work.

One thing I really want to do is a side-by-side comparison of the 6CA7 amp with the UA1 amp.  That might be postponed for a short time as well ..... as I just sent the UA1 back to Terry to have it put in a nice looking chassis and have a second set of inputs installed.

The listening session at Rob's house with his analog front end made me want the second set of inputs for a possible future turntable purchase ..... I really never thought I would go there again, but I heard some things from the UA1 when spinning wax that made me shake my head .....  Shocked

No matter how good a digital rig is (and i have heard and owned some of the very best) it just never gets the sound of a cymbal right ..... or a violin / fiddle.  I have no idea why, but it's true.  My digital front end sounds superb with vocals and 98% of the instruments I listen to ..... but those two instruments elude its grasp.  With Rob's vinyl front end, I heard violins and cymbals hanging in the air like they were living things, with the tonality absolutely perfect ..... amazing !!!

There are several stores in my local that sell used vinyl in good condition for very attractive prices ..... so it seems like a no brainer.

If you hadn't noticed, I really like that "ugly little amp" ..... which won't be ugly for much longer .....  Grin


Best wishes,

Randy
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steve f
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« Reply #12 on: September 04, 2012, 04:07:28 PM »

Randy,

I have a really strong vinyl setup. Four turntables, different arms, and cartridges.  I also am a fan of cheap digital. Just two different DVD Blu Ray players.  I have tried some big money digital rigs, but quite honestly, my cheapies are as good. I've played a record on my system, and the matching CD at the same time switching between the two. On really good recordings, they sound a lot alike. (At their worst, CD's can be horrible. Remember that Big Brother & Holding Company CD at the last Zenfest? I have a good original pressing that sounds great.) I agree that records do have more air and high frequency tone, but quite often digital has better low end. I'm tempted to try some specialty CD's which pay extra attention to microphone placement. I do love playing records though.

Steve
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TerryG
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« Reply #13 on: September 04, 2012, 04:40:49 PM »


Well now that Steve opened this can of worms I don't mind letting a little more slope out making this thread a little icky.

I have done extensive experiments with vinyl and digital, and found that the main difference is in the recording/manufacturing of the CD's.   First and this is proven fact at this point, that modern sound engineers are compressing the sound to make things more listenable with mp3 players.  Second I can take any manufactured CDs and just by making a burned copy of them they sound much better, so the original however they manufacture them is not as good as a burned CD.    I have my favorite black Memorex  CDRs that I use, but almost any will do, and I burn no higher than 16x, that seems to make a difference as well, usually tough below 8x. 

Next I can make a CD copy of a LP that sounds within a hair breadth of the LP, but since I have over 1000 LP's at this point I am not about to make copies of my LPs when some I play once every few years.   Another thing is that the program I use to make a CD from an LP is Audio Cleaning Lab 12, it has the very best digital processing, to take out noise and to enhance the signal.  But you can not do much in the way or digital processing because you will get digital noise in the recording, you do so in very measured doses.  But I suppress pops and clicks, to about 50% of what they were, and I also use a dynamic expander very mildly, along with some added bass boost.  This creates a CD that sounds often times even better than the vinyl recording, and the small amount of noise between songs is more nostalgic than a niusanse. 

Long story short CD's can be as good as LP's but for some reason the industry is missing he boat.  The only better CDP that I have heard that I thought sounded better than mind was a +$5K Wadia rig, other than that I haven't heard any.  Likewise I have not heard any high dollar vinyl rigs that I felt were worth the money.  They were better but by a small margin.  To me the phono preamp is more important than the TT, and the cartridge is more important than the TT.  If you have basic stuff down with the TT then it will sound pretty good.

CD's are better with bass contend, and they are also better at reproducing piano without wow.  But vinyl has the edge because of the older recordings were just plainly better, even not so great music was great on vinyl, and some of these muscians were actually very very good.  Prince's Purple Rain LP was much better than I remember, and the music is much better than I remember as well.  Kenny Rodgers must have had an awesome sound engineer as his LP's are fantastic recordings that you can not get the same quality in CD with.   I could go on and on, so I am not giving up my vinyl rig, but it isn't Red Book fault CD's don't sound good, and it isn't the CDP manufactures always.  Although of the five CDP's I own some do not sound as good as others, and I am all in for a modified player, I think this is the way to go if you want good digital.

Next I am going to be getting a computer server, I can not think of anything more user friendly.  Other than streaming internet of an unlimited library of music, but I want that as well.

Ok enough of my tagent material on this thread, Randy said he was going to update us on his 6CA7 experiences.

Terry

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Pit Hinder
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« Reply #14 on: September 04, 2012, 04:46:27 PM »

Affordable CDplayers beat lousy "vinyl-to-mp3" vinylscratchers.
But a decent turntable, and Julie Driscoll singing "Wheels on Fire"...you gotta be deaf to not get goosebumps.

   Pit
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