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In the Forum: Horn-Loaded Speakers
In the Thread: Deep End DIY - Australian take one Macondo.
Post Subject: Before preamplifier changePosted by anthony on: 10/24/2025
Like the time periods B.C. and A.C., I now think of my installation in terms of Before Preamplifier (B.P.) and After Preamplifier (A.P.).
As discussed on these pages, I built a hybrid 10Y DHT preamplifier that had more more gain than the Placette Linestage and also sounded a bit better than the Placette...and a lot better than just about any other preamplifier I had trialled or built. Good sound came fast with the 10Y preamp and thanks to its mosfet based mu-follower it had heaps of gain for my low output sources into Melquiades/Macondo and a very low output impedance, which is what I thought I needed. Macondo was tuned using the 10Y preamp and I was happy.
Then I went from a dac with 1VRMS output to one with 4VRMS output and then one with 10VRMS output. This forced me to shift the autoformer volume control from the output of the 10Y preamp to the input so that it was not overdriven to distortion...no big problem and as far as I could tell the sound was the same in either position. This forced a re-tune of the Melquiades filters as the preamplifier output impedance lifted a little to 12ohm. All good, easy to do.
Now, my only two sources with low output were the phonostage and the Anthem AV processor, so I still needed the high gain offered by the 10Y preamplifier.
There were some problems though. The upper channels in Melquiades had to be tuned quite low (attenuated) because of the low output from the bass channels, particularly the Bass Cannons, thanks to their second order filters and relative inefficiency. The Upperbass horn in this tuning had a 2k shunt resistor dropping its output by many, many decibel. The RAAL ribbon for the HF channel driven by a single stage SET just was just loud enough to match the Bass Cannons, but I really appreciated its contribution to the overall sound.
Sound was excellent in this configuration. Both the Bass Cannons and the RAAL Lazy Ribbon were running unattenuated with all other channels (apart from infrabass) attenuated to suit. The Fundamentals Channel never really satisfied me and it was usually run attenuated much more that I suspect Romy used it...but that is another issue yet to be resolved.
Then I upgraded my dac again...and trialled a very expensive preamplifier...Rerurn to Romy the Cat's Site