Hi folks. Happy Thanksgiving! (if that's something you celebrate). It has been many years since I posted here (I had to create a new account). It's good to be back and I look forward to seeing what people are creating these days.
In my holiday downtime I'm pondering a grand winter project/experiment. I have a pair of Klipsch Forte III, which I love. I currently drive them with a solid-state McIntosh MC2205 for both speaker inputs (not bi-amped). In the past I built a pair of 300B single-ended mono blocks and bi-amped with the 300B amps on the mid and high horns, and the solid-state McIntosh on the woofer/passive radiator. I miss the tube/horn combo. The Klipsch really love tubes. Thus, I'm interested in a new bi-amp setup perhaps without the McIntosh. I also want to compare single-ended and push-pull designs (I'm sure that will ruffle some feathers hehe).
At this point I am thinking about two differnt pairs of mono-blocks. One pair parallel single-ended and one pair push-pull. I want to use the same tube type for both amplifiers and I am thinking about basing them around KT88s or 6AS7s. I then want to try different bi-amp combinations of the two types of mono-blocks and the McIntosh and I really want to make as fair of a comparison as possible between the sound of the two very different designs (SE and PP) with the Klipsch. The Klipsch are super sensitive so making a ton of power isn't necessary. I imagine a 30-ish W push-pull design and well under 10W for the parallel SE.
Once designed I'll build the amps on MDF boards initially to conduct the experiment and then after finding what I like, will create final versions with nice chassis etc. And just for kicks, I acquired a full set of driver and output transistors and caps to rebuild the McIntosh. It's possible I'll keep both designs as they may shine for different types of content.
So to recap, I plan to design/build:
(2) parallel single-ended KT88 or 6AS7 based monobkocks
(2) push-pull KT88 or 6AS7 based monoblocks
I am open to suggestion regarding output tubes but want to stick with the same tube for both designs. The 6AS7 is attractive because of price, since I will need a bunch of output tubes (depending on how many end up in the parallel SE design). I think at a minimum 8 6AS7s (4 for each design). Also open to suggestion to existing designs, input stage tube types (I like 6SN7s and have used them in a few builds).
Thoughts?
Thanks for reading!
In my holiday downtime I'm pondering a grand winter project/experiment. I have a pair of Klipsch Forte III, which I love. I currently drive them with a solid-state McIntosh MC2205 for both speaker inputs (not bi-amped). In the past I built a pair of 300B single-ended mono blocks and bi-amped with the 300B amps on the mid and high horns, and the solid-state McIntosh on the woofer/passive radiator. I miss the tube/horn combo. The Klipsch really love tubes. Thus, I'm interested in a new bi-amp setup perhaps without the McIntosh. I also want to compare single-ended and push-pull designs (I'm sure that will ruffle some feathers hehe).
At this point I am thinking about two differnt pairs of mono-blocks. One pair parallel single-ended and one pair push-pull. I want to use the same tube type for both amplifiers and I am thinking about basing them around KT88s or 6AS7s. I then want to try different bi-amp combinations of the two types of mono-blocks and the McIntosh and I really want to make as fair of a comparison as possible between the sound of the two very different designs (SE and PP) with the Klipsch. The Klipsch are super sensitive so making a ton of power isn't necessary. I imagine a 30-ish W push-pull design and well under 10W for the parallel SE.
Once designed I'll build the amps on MDF boards initially to conduct the experiment and then after finding what I like, will create final versions with nice chassis etc. And just for kicks, I acquired a full set of driver and output transistors and caps to rebuild the McIntosh. It's possible I'll keep both designs as they may shine for different types of content.
So to recap, I plan to design/build:
(2) parallel single-ended KT88 or 6AS7 based monobkocks
(2) push-pull KT88 or 6AS7 based monoblocks
I am open to suggestion regarding output tubes but want to stick with the same tube for both designs. The 6AS7 is attractive because of price, since I will need a bunch of output tubes (depending on how many end up in the parallel SE design). I think at a minimum 8 6AS7s (4 for each design). Also open to suggestion to existing designs, input stage tube types (I like 6SN7s and have used them in a few builds).
Thoughts?
Thanks for reading!
Member
Joined 2009
Paid Member
Interesting project.
My 2c, I’m for SE amp on the mid-high with PP amp on the woof. Yes, different amps on the same speaker.
I’ve not enough experience to suggest which of those tubes but I have built a SE with the 6AS7 and it sounds mighty nice although in my case it’s limited by the output transformer. The 6AS7 needs a low primary impedance which is inconvenient and it‘s not a first pick for fixed bias, but with cathode bias it burns lots of heat in the cathode resistor. I’d lean towards the KT88, probably more flexible, run it triode-wired for the SE (and single tube not paralleled), with PP you may like it triode wired but worth also listening to it in UL.
My 2c, I’m for SE amp on the mid-high with PP amp on the woof. Yes, different amps on the same speaker.
I’ve not enough experience to suggest which of those tubes but I have built a SE with the 6AS7 and it sounds mighty nice although in my case it’s limited by the output transformer. The 6AS7 needs a low primary impedance which is inconvenient and it‘s not a first pick for fixed bias, but with cathode bias it burns lots of heat in the cathode resistor. I’d lean towards the KT88, probably more flexible, run it triode-wired for the SE (and single tube not paralleled), with PP you may like it triode wired but worth also listening to it in UL.
Thanks, seems fun to me.
I built one of the OTL 6AS7 headphone amps some years ago and it sounded lovely. I like that tube, but I take your points in leaning towards the KT88. You're probably right as well about running a single KT88 in the SE design. Rough estimate puts that at making about 6W which I think is plenty for the Klipsch horns. And I agree the PP on the woofer and SE on the horns seems the most interesting. The question will really be, how does the PP compare to the McIntosh for the woofers? The McIntosh sounds pretty great.
I built one of the OTL 6AS7 headphone amps some years ago and it sounded lovely. I like that tube, but I take your points in leaning towards the KT88. You're probably right as well about running a single KT88 in the SE design. Rough estimate puts that at making about 6W which I think is plenty for the Klipsch horns. And I agree the PP on the woofer and SE on the horns seems the most interesting. The question will really be, how does the PP compare to the McIntosh for the woofers? The McIntosh sounds pretty great.