You will love it!! The clarity, the tone, and extension of a DHT plus a better bass grip courtesy of the F4. What is not to like?
I am a very happy camper.
What DHT preamp are you building?
Abe
Ugh, I cheated and had Radu Tarta (of simplepleasuretubeamps/shiny eyes) build one for me. It's just a single stage design built around the EML-20A mesh: EML-20A DHT Preamp – Bartola(R) Valves
I was going to build one myself, but read a very excited build thread where two guys agreed to both build a 01a based pre. After 14 pages of them trading building joy, frustrations, and troubleshooting, the entire process ended ended with... "well, there's a lot of hum" for both of them. That likely possibility and the high voltages convinced me to have an experienced builder put it together for me. Seemed like a tough place to jump in for my first tube build.
Anyway, it's a dual chassis design with a tartuga ldr remote volume control on its own power supply. I've read enough about DHT preamps that I'm very hopeful it will out perform my 6sn7.
I was going to build one myself, but read a very excited build thread where two guys agreed to both build a 01a based pre. After 14 pages of them trading building joy, frustrations, and troubleshooting, the entire process ended ended with... "well, there's a lot of hum" for both of them. That likely possibility and the high voltages convinced me to have an experienced builder put it together for me. Seemed like a tough place to jump in for my first tube build.
Anyway, it's a dual chassis design with a tartuga ldr remote volume control on its own power supply. I've read enough about DHT preamps that I'm very hopeful it will out perform my 6sn7.
Very nice! It will sound better than your 6SN7 preamp, guaranteed.! IMO, no amount of coaxing (regulated heater and supply, playing with bias points and topology) will make a 6SN7 tube to sound ahead in sonics to a DHT tube. The main difference to me is the clarity of DHT to IDHT's.
I have a 01A preamp amp base on Ale's circuit. I have no hum so I guess I got lucky. The hardest hurdle to accomplish is to get a quiet pair of 01A's. I only buy new 01A's and never from Ebay.
I do not think you will have a problem with hum using 01A preamp to F4 amps. If there is, that is a scream not a hum! So, if your preamp is quiet with your conventional amps, then it will be quiet as a church using the F4 which, IME, the quietest amp I ever built.
Enjoy!
I have a 01A preamp amp base on Ale's circuit. I have no hum so I guess I got lucky. The hardest hurdle to accomplish is to get a quiet pair of 01A's. I only buy new 01A's and never from Ebay.
I do not think you will have a problem with hum using 01A preamp to F4 amps. If there is, that is a scream
not a hum! So, if your preamp is quiet with your conventional amps, then it will be quiet as a church using the F4 which, IME, the quietest amp I ever built.Enjoy!
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Great, you're making me more excited. The EML20A has more than double the gain of the 01a, which is why I chose it as the F4 driver tube. If you read the comments on the link I put above, Ale recommends it and the 01a/801a as the top DHT performers. Also happy that I can buy new tubes directly from EML. I had their tubes in my 300b monos before I switched over to F4s and they were great. Amazing sound and super reliable. I bought mine used and they still tested good four years of daily use later.
I received the chassis and 35V filter caps to replace the 25s I initially installed. These are 22KuF.
I mounted the mosfets and arranged the PT and PSU. I thought about using 3.5" standoffs and mounting the PSU above the transformer, but I'm concerned about heat. I have a few tube amps with exposed toroids and they get pretty warm.
I mounted the mosfets and arranged the PT and PSU. I thought about using 3.5" standoffs and mounting the PSU above the transformer, but I'm concerned about heat. I have a few tube amps with exposed toroids and they get pretty warm.
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I have a 01A preamp amp base on Ale's circuit. I have no hum so I guess I got lucky. The hardest hurdle to accomplish is to get a quiet pair of 01A's. I only buy new 01A's and never from Ebay.
I do not think you will have a problem with hum using 01A preamp to F4 amps. If there is, that is a scream
Enjoy!
I am currently testing a 01A pre based on Ales circuit to drive my F4. Absolutely in love with it, and will become a fully finished build. I ran a 4P1L pre before that which was great, but the 01A is just magical..
Hi,
What about having the transformer in a vertical position, close to the front plate? I have mine config this way. I built the bracket myself from this specs L-Bracket – Toroid
Works fine for my setup, though the volume control on the preamp input is set fairly high attenuating -14db. My speakers aren't exactly efficient either being late 70's vintage KEFs. I cant see it being a problem for anyone...
Everything is going to get warm anyway, rectifier heat sinks and chassis will all happily sit at 50c when up to temperature, the F4 is really an electric heater that makes music!
I get it. It just makes sense to manage the heat in the best way possible. Since heat rises, it seems bad feng shui to put the power supply right on top of the PT. But I'm used to tube amps that supply 300-500V. How hot would this transformer get?
I like this a lot. Thanks!!
It's funny how, with many days passing, many construction-details seem to trickle in.
For example, the use of a 35A rectifier for a perfect ground...
Is this actually best practice, or is there an even better technique (in terms of quality as well as camouflage )? Is it good for F4 too? (Guess it must since it appears at the BA-3-thread...)
Still have to get this stuff into my head...
For example, the use of a 35A rectifier for a perfect ground...
Is this actually best practice, or is there an even better technique (in terms of quality as well as camouflage
)? Is it good for F4 too? (Guess it must since it appears at the BA-3-thread...)Still have to get this stuff into my head...
Nelson Pass showed a bridge rectifier used that way in the "The Zen Variations - Part 1" article back in 2001. It seems as if you have only 19 years to catch up.
Ok! I‘ll do it in my pace, so that’s about 38yrs to go [emoji1787]
You will love it!! The clarity, the tone, and extension of a DHT plus a better bass grip courtesy of the F4. What is not to like?
I am a very happy camper.
What DHT preamp are you building?
Abe
Just got some pictures of my new DHT pre. All breadboarded, just waiting on the chassis build now. Signal path is input > volume control > resistor > eml-20a (mesh) > monolith amorphous core output transformer.
The 20a is one of the lowest distortion, most linear DHT tubes, with a 21x gain factor. Filament is DC regulated. All AC/DC conversion happens in a separate chassis. Volume (and balance) control is a Tortuga board with both ldr and discreet resistor modules (dealer's choice, .5% VS .1% max thd) and an oled display. The VC has its own independent power supply and the display is off unless getting an update command to limit emi. Power supply has a lundhal mains transformer and choke.
Very excited to hear it. I'm hopeful this will be an ideal way to add voltage gain to the f4 circuit. And it'll be simple to mod and improve if I like it.
Hopefully I'll get it in the system by the new year.