Dear Swampwalker : In absolute terms I agree with you: " every design involves trade-offs ", like anything in the life: there is nothing perfect.
Your post give me the opportunity to do a " stop on the road " ( thx for that ) and " see " which are our Phonolinepreamp trade-offs :
first, the whole concept design: it is a true balanced input to output, non feedback, direct coupled, dual mono, pure class A, fully regulated input to output with a dual mono external power supply and current drive whole design with a " ground plane " approach.
This topology is for the three separately stages that composed the Phonolinepreamp in an integral unit: MC stage, MM stage and line stage: as a fact this Phonolinepreamp has three independent preamps.
In my opinion we don't have any trade-offs here.
second, circuit diagram ( layout ): this is something that after 12 years of work José perfectioned. The latest modifications we did it in this year. We research everything about the RIAA eq., MC/MM and line stages and today we can say are almost perfect.
Here to our knowledge there is almost no trade-offs, but who knows: ?
third, parts we use it: in those 12 years we almost tested ( matched ) the whole critical and non so critical parts like: transistors, Fets, teflon capacitors, resistors, solder, buffers, connectors, switchs, attenuators,
power transformers, etc, etc. Btw, our design don't use any signal cable internally, everything is soldered to our 4 layers boards. Where were necessary we use military specs parts and 0.01% limit on the value parts.
Here I think that we can have some trade-offs: these trade-offs could be the whole limits and quality of those parts. THis not depends of us, we use it only the best.
fourth, circuit boards: we use one of the best/quality boards supplier that we can find and it is in Silicon Valley.
can we have a trade-off here?. I think not but it could be.
fifth, power supply, this is it:
To complement our balanced design's inherent power supply rejection capability, we have designed an audio grade power supply that takes power quality to a new degree. The power supply is located in its own separate chassis in order to minimize any possibility of interference in the analog signal stages of the preamplifier. The power supply has been specifically designed to be an improvement over battery supplies having very low noise and low impedance . Some of the characteristics of the power supply are: Discrete dual mono design with 4 ultralow noise supplies for the left channel and 4 ultralow noise supplies for the right channel, dual high-quality toroidal transformers, AC power RFI/EMI filtering, extended power range of +/- 20 % of the nominal input, and high quality military-grade power connectors.
Is there " land " to improvement?, maybe, but for today we are satisfied.
sixth, the interface with the outside world: Ultrawide bandwidth output buffers.
There are 4 ultrawide bandwidth class A balanced output buffers responsible of interfacing the preamplifier to the outside world with transparency and current capability to drive even the most difficult loads and cabling. Every channel has 4 independent power supplies, two of them
dedicated to the balanced signal stages, and the other two dedicated exclusively to the output buffers. The adoption of this strategy is simple to explain: No matter how difficult the output load is, the preamplifier will always deliver the optimal signal quality at its outputs.
I think no trade-offs here.
I know that our Phonolinepreamp is not perfect but we are still trying to achieve that target.
The result of our work is a preamplifier combining
the purity and transparency of a passive preamplifier with the speed, dynamics and drive of an active preamplifier.
Well, what can I say?. I don't want that you think that I'm conceited, no: the fact is that we are proud of what we have and we want to share with you and every one our achievements about.
Regards and enjoy the music.
Raul.
