A belated test of this simple, yet effective PCB. I made it as small as possible, however in order to provide flexible connections, it’s actually double the size. Still at 4 x 4 cm is small enough.
Author: Ale Moglia
"A mistake is always forgivable, rarely excusable and always unacceptable. " (Robert Fripp)
300B Emission Labs
Back at the beginning of the year I purchased a pair of Emission Labs 300B for my new amplifier version (still working on it). I own several 300Bs but was keen to try these out given their reputation.
Jac from JacMusic sent me a matched pair which I traced them with the eTracer:
Pentode Differential Pair (Hybrid Mu-follower)
Pentode drivers are very interesting. You can get excellent results out of them. Here is my version of a differential pair using pentodes. I want to try them out in the 45 PP design I wrote previously Continue reading “Pentode Differential Pair (Hybrid Mu-follower)”
45 Push-Pull Amplifier
Chasing that sound
The 45 DHT is probably one of the best sounding valves out there. In fact, I have struggled to get a similar level of detail and timbre in a 300B or 4P1L output stage. Even my 814 SE Amplifier (which was class A2 and had thoriated-tungsten filaments) couldn’t replicate that sound. I posted time ago my incarnation of the 45 single-ended amplifier here. The main challenge with this valve is that it can only put out there nearly 2W, not more. With its 10W anode dissipation, you will struggle to get more juice from it in class A at a low distortion level.
However, if we look at a push-pull amplifier with the 45, we can hopefully retain the timbre characteristic of the valve, despite it won’t be a single-ended one. Well, I love good PP amps, so why not?
Bootstrapped CF (SLCF) PCB tests
Long time ago I used this SLCF circuit as an output buffer with excellent results. It sounds as clean as it can get in my opinion. Recently, I made up a PCB to hold this circuit with a varied of options:
New listening room
The new listening room (at least for some time) is now ready. One of the loft rooms is now purposed for guests and for music. Everything is set up. The 4P1L PSE with Monolith Magnetics S9 OPTs, the ER801a driver plus the 01a preamp are in place. Have the DAC and the Lenco turntable as sources. A Kozmo stepped attenuator and input selector. Subwoofer, record cleaning machine and the Alpair 10 in the reflex boxes. I removed the dome tweeters to experiment for a while.
My Starlight transport and discrete DAC are on the box still. I need to fit the CD towers on the wall first. Tons of CDs to rack again. Yet, TIDAL is a good alternative. Love exploring other records I don’t own.
At the moment playing the Howling Wolf record we enjoyed late at night with Jeffrey Jackson and Dave Slagle at ETF.18.
Life is good….
Hybrid Mu-follower (aka Gyrator) Rev08 PCB Update
It’s been far too long since I last posted on this blog. With the limited spare time I’ve got these days, I concentrated in setting up the new workshop and system since we moved back to our place. I’m nearly there, so now it’s time to get back to work
I made some updates to the “gyrator” PCB. I’ll stop referencing it gyrator from now on, since the name is misleading. However, it got popular that way. Nevertheless, it’s a hybrid mu-follower circuit but if only if you take the output from the anode, it behaves like a “gyrator” from a frequency response perspective. If you’re interested in this circuit in more detail, please read the lecture I gave last year at ETF.18. You can download it from here.
Back to the board, here are the few changes made:
- Moved the trimpot P1 for easier fixing of the board with the M3 standoffs.
- Added a gate stopper resistor (R9) to avoid oscillation at low anode current (<10mA) when using high-gm MOSFETs in the lower position J4. This was evident with devices like BSH111BNK
- Added an LED (D4) indicator and a series resistor (R8) at the drain of M3. This enables indication of:
- Normal operation subject to value of R8
- Source current into load (e.g. like in A2 operation) subject to value of R8.
- Short output to ground. Depending on duration and current limitation of power supply, this may prevent damaging M3 MOSFET. Not guaranteed, but in some scenarios will work.
Continue reading “Hybrid Mu-follower (aka Gyrator) Rev08 PCB Update”
ETF.18 DHT Preamps Lecture
ETF.18 has been an emotional journey. I moved house literarily when I got back from ETF so my life has been more than hectic over the past few weeks.
I promise I will do a write-up of this amazing experience. There’s a lot of people out there who would love to attend so is my duty to reflect and share as much as I can.
In the meantime, I wanted to share the lecture I gave at ETF on DHT preamps. It was a challenge on its own but went really well. This was my first ETF and without knowing the audience I had to guess the level of detail, entertainment and expectations of an unknown audience. I knew a fair bit of the ETF folks, but audience was big and wide.
I struggled to find the time to prepare this lecture I have to confess. Between moving house, house building works, my second daughter’s arrival , weekly work travel and everything else, I seemed not to find the time to get this done. Thank you Morgan Jones and Rod Coleman for proof-reading and making this an easier task.
I hope you enjoy it. There are some notes on the slides I put together for the people who didn’t attend ETF. Otherwise the slides aren’t of much use on their own.
I’m writing this blog entry whilst enjoying the lovely Bourbon that Pete Millett gave me on the way back. Thanks Pete!
ETF Lecture on DHT Preamps (with notes):
DHT-Preamps-ETF2018-final-notes
ETF Lecture on DHT Preamps (slides):
ETF.18 getting ready
ETF here we go!
Packing up the system for the shootout 🙂
