The Allegro UA2.5 Price $999.00. Three watt all vacuum tube amplifier.
Buy link at the end of the description of this product.
This is the latest in La Dolce Audio's tube amplifier designs. This is an all vacuum tube amplifier design. This is an integrated amplifier and we prefer you use it without a preamplifier. This way the sonic signature of it will be preserved as the designer intended but will work with any preamplifier that we know of, including those putting out higher voltages above 4 volts AC. We may release a mono-block version later of this design.
Specifications:
3w to 5w power output depending on the tubes, normally around 4 watts is realistic. We have gotten anywhere between 3.5w to 5w with this design depending on the vacuum tubes used.
4Ω or 8Ω impedance outputs either can be used because no harm will come to the amplifier by using either with speakers rated between 4 Ω or 8Ω.
Distortion varies depending on the wattage level output and the positions of the feedback/bias switches on the front of the amplifier as well as the specific tube type used. The front panel switches tailor the sonic signature of the amplifier to better mate to speakers, enhance recordings and meet the preferences of the listener. They also affect the damping factor of the amplifier to work with a wider range of speakers. With these switches, this amplifier can sound anywhere between a single-ended triode like a 2A3 to a full-throttle pentode amplifier. Pentodes have a sound unique to them.
To be honest, distortion is what single ended vacuum tube amplifiers are all about. Single-ended amplifiers have more distortion than most other types of audio amplifiers. We tailor the distortion to give a sonic signature that we found is desirable, giving a transparent but lively sound to the music. We can no longer say a single-ended amplifier of this type can not do some types of music well but other types not as well, it can do all types of music well. As to if one is better sounding on this amp compared to another will vary depending on several factors, the type of source used, the speakers used, the positions of the sonic enhancement switches on the front panel, and the preferences of the user.
Features:
Vacuum tube amplifier design.
Linear power supply.
Integrated amplifier design.
Amplifiers come with a matched pair of 6Y6GT tubes.|
Additional matched pairs can be purchased upon request.
New old stock vacuum tubes. The 6Y6 beam power pentode, and Russian 6N6P.
Single-ended pentode topology.
Japanese Z11 iron core output transformers with 4Ω and 8Ω speaker taps.
Two inputs with rotary selector switch.
Output transformers are resin-filled aluminum cans to reduce vibration and emf induction.
Sandblasted anodized all-aluminum chassis, with copious ventilation for cooling. We use a dual chassis, a chassis plate within the chassis to allow for more cooling and isolation of tube heat from other parts of the amplifier.
Rubber bottomed feet to prevent the amplifier from scratching your furniture. These rubber feet can be replaced should they ever wear out by the user, as they are simple "O" rings.
Sound enhancement switches, the amplifier with these switches can have as many as 24 different sonic signatures, per set of tubes.
Designed so that three different NOS vacuum power tubes can be used. The 6Y6G, 6Y6GT, or the 6Y6GA. Of these three types, they all sound slightly different as each matched pair of those three types.
Therefore with 24 sonic signatures per tube pair type, and three types of 6Y6 tubes available, this amp can have 72 different sonic signatures. In addition to this the amplifier can use a few different types of vacuum tubes for its driver tube used to drive the 6Y6 tubes. It comes with the 6N6P, but there are variants of this tube as well. Since this tube is the little sister to the 6H30P, and of those variants can work in this amplifier as well. If you can afford a 6H30P-DR tube, we recommend you try it in this amplifier, as it adds a new level of sonic bliss to this amplifier's experience.
Aproximate measurements 12" x 10.57" x 6" with the 6Y6GT as shown.
The following photos are meant to give the potential buyer an idea of the layout of the entire amplifier.
Common Questions
So why a 3 to 4 watt vacuum tube amplifier?
Well for two very simple reasons, one it is easier to create a high quality tube amplifier if its wattage is lower, and two it is less expensive because tube amplifiers require transformers to operate and transformers are a major cost in their design.
With the Allegro line of amplifiers the focus is kept on affordability where it doesn't sacrifice sound quality, this may at times mean these amplifiers will have a somewhat limited life span of about ten to twenty years before needing some maintenance to operate optimally.
Why an integrated amplifier?
Because this way you won't need a preamplifier, I have had customers not get the most out of an amplifier design because they didn't have a quality preamplifier up to the task. This way also we can keep the signal path as short and as simple as possible. The more that is in the signal path the more that can take away from the fidelity of the amplifier.
What speakers should I use?
Preferably speakers over 95dbs w/m sensitivity, because this allows the amplifier to not have to work so hard so as to produce dynamics. This can become a problem with speakers that are very low in sensitivity. Although some speakers below 95dbs w/m sensitive with very easy impedance plots such as single driver speakers with no crossovers can work very well. On the links page are some speakers we know will work with these amplifiers.
Will these amplifiers work well with digital and analog sources?
Yes, in fact, you may find you get more from your sources because tube amplifiers have higher imput impedance inputs making them easier to drive than some solid-state amplifiers. Where a solid-state amplifier has an input impedance between 10k to 50k generally, a tube amp has generally 100k to 250k ohm input impedance. This makes it easier for the source to feed a fully dynamic signal to the amplifier, this helps sources do what they do and sound their best. Some DACs with R2R ladders with no buffer stages really benefit from an amplifier with a high input impedance, sounding very dynamic and having better quality bass.
How long will the tubes last?
The power tubes should last for a few years, there is no need to replace the tubes unless you notice they are NOT sounding good. Some tubes when they get old you will notice you gradually have to turn the amplifier up louder and louder to get the same power from the amp. Or the plate on one or both of the power tubes will start faintly glowing red, and eventually get brighter and brighter red. At this piont the amplifier should no longer be used with those tubes. Played occasionally the power tubes can last a decade or longer, played every day perhaps a few years. We do NOT recommend replacing the tubes just because you have used them for a while.
The input 6N6P tube will take many years to wear out, perhaps more than a decade, but usually one triode inside starts to wear out first and you will notice that the balance between left and right channels is off. If you decide to upgrade to the 6H30P tube, that tube may last the lifetime of the amplifier, as it takes the average person many many years to listen to 10,000 hours of music which is its rating. But that rating is when it is operated at full power, less than full power any tube will last longer, those numbers are minimum lifetime estimates by the manufactures. Since these tubes run at less than one half their full power ratings it is possible they could last many times their rated lifetime in hours.
What are, and how do I use the switches on the front panel?
These are sonic enhancement switches, they change the sonic signature of the amplifier. Some of these switches change the bias of the class A operation of the tubes, some change a local feedback loop to full feedback, one-half the amount of feedback, or remove the feedback loop entirely.
Pentodes are field-effect devices, as such, they adhere to a rule that in effect says that you can get a disproportionate output compared to the input. Basically, this means they can enhance dynamics both small dynamics called micro-dynamics or what we perceive as details, or macro-dynamics or what we perceive as a punchy lively presentation. The local feedback loops that are switched with this amplifier help you decide if and how much the amplifier will "enhance" the music changing its sonic signature as you do this. This dynamic alteration of the music of course measures as distortion, so removing imposed local feedback loops increases this effect on the music.
So you will need to get use to each switch and what is does sonically to the music, usually no matter the type of music each switch will do the same thing when switched up. All the switches in the down position the amplifier should operate in its lowest distortion levels. We are continuously experimenting with circuits for pentodes, and how circuits affects their perceived performance, we have used these switches in developing circuits and values. We liked the ability to change the circuit and the sound so much we found we couldn't live without them, so we decided to put some of these in this amplifier for you to enjoy as much as we have. These switches we found can bring new life to some recordings, and in different positions tame a recording of lesser quality. Likewise, some switches although not directly changing the frequency balance of the amplifier seem to enhance bass response, some bring out midrange vocals and instruments. Also the way the amplifier clips changes with how these switches are set. it is like having many different amplifiers in one, before you even consider rolling tubes.
You can read about Pentodes more in our "Why Pentodes?" paper that explains them more.