Tag: gyrator PCB

DHT LCR RIAA preamp by Salvatore Aragona

Here’s a very interesting project worth sharing to all, hopefully will inspire some of you on the same journey. Achieving a quiet and good sounding LCR phono stage is not a simple project:

Hi,

I wanted to share with you the satisfaction of completing the most challenging project I’ve tackled so far, and I wanted to thank you and Rod Coleman for the fantastic PCBs you provided. It is a phono stage built entirely around DHT triodes and SITs, featuring LCR RIAA equalization. Here are the key details: 1) First stage: two 3A5 sections in parallel with a UTC A-30 anode choke and 0.15µF Miflex KPCU capacitor; filament bias using a Pathaudio resistor; 45V anode, 2.2mA. 2) Second stage: 2SK79 SIT with a Tamura A8713 interstage transformer and SiC diode + resistor bias; 58V, 5.8mA. 3) LCR RIAA network with Noguchi Finemet-core inductors, Teflon capacitors, and Charcroft Z-Foil resistors. 4) Noguchi 600:50k Finemet-core transformer. 5) 01A tube with mu-output gyrator, direct-coupled (capacitor-less) to a MOSFET source follower PCB regulated at 15mA; 0.33µF Miflex KPCU output capacitor. 6) Four power supplies, each with an independent transformer, diodes, and CRC filter. 7) Anode power supply with a Telefunken mesh-plate vacuum rectifier and cLCLC filter; the first capacitor is 2.39µF, composed of a 2µF military-grade 800V polystyrene unit (actually two 4µF/400V units in series) plus a 0.39µF Audio Note copper-foil PIO capacitor; Tango TC160-35 choke; other capacitors include polypropylene types and Tentlabs MEC50s. 8) The anodes of the 3A5 and 2SK79 are fed by Linear Audio T-Reg V5 series regulators. I’m posting a few photos here; I’d be happy if you published them on your site (feel free to decide whether or not to do so).

The system is extremely quiet and, in terms of sound quality, far superior across all parameters to the Audio Note M5 Signature I previously owned.
Best regards
Salvatore Aragona

LCR by Salvatore Aragona

Credits

Salvatore wished to mention the following people who inspired him and helped to realise this project: Rod Coleman, Antonio Maggio, and Giovanni Giorgianni and myself 🙂

Excellent job Salvatore.

Hybrid mu-follower PCB (Ver 0.8) video

Over the past 5-years I have received several queries about the current limiter resistor and LED additions to the hybrid mu-follower PCB. Although these are explained, clearly not well enough from my side. So I decided to document this a bit more to help out everyone working with this board:

Watch the video here.

This is my first ever recorded video and hopefully there is interest in this format to share some content.

Hybrid mu-follower boards in SMD

I’ve been using these boards for many years now. Haven’t offered them as is required for anyone to be experienced well enough in SMD soldering to get these done effectively. I have a reflow oven so work at scale is easier this way. I’ve been doing a lot of SMD board design and building over the past few years though.

On a busy time regardless, I found the space to build these four commissioned boards for D3a drivers like the ones I used on my 300B amplifier. There seems to be a lot of interest and build work done around this design, so happy to see this happening.

Hybrid mu-follower SMD boards
Hybrid-mu follower board

EF86 – 300B XLS SE Amplifier build

Here is a very nice build from Dan Kercher on his contraption of the 300B amplifier with auto bias. The driver is an EF86 with SiC diode biasing, the topology is a hybrid mu-follower and a source follower drives the output stage. Filaments are DC with Rod Coleman’s board:

Dan Kercher’s EF86 – 300B XLS SE Amplifier build

More details can be found below:

Hi Ale, 

I wanted to thank you for all of your PCBs.  I just finished a project that uses your Gyrators, SiC bias boards, and SiC Source Followers.  I'm so happy with the results.  Details posted on Audio Asylum.  

https://www.audioasylum.com/forums/tubediy/messages/27/276814.html


Cheers, 

Dan 

The low gain DHT pre-amp library

For more than 10 years I’ve been experimenting, designing and enjoying DHT pre-amps. Without over-dwelling on this subject, to me DHT preamps bring the unique sound transparency and detail we all seek for. They can make night or day difference in any system. And is not about gain, hence I’m focusing on sharing this blog entry.

Continue reading “The low gain DHT pre-amp library”

300B/845 Amp: Driver Options

For more than 6 months I’ve been playing with a lot of satisfaction my 300B amplifier with the 47 driver. Since then, I’ve made 2 modifications:

  1. Major one was the introduction of my Open-Baffle (OB) speakers. These are the “Liionidas” based on the LiiAudio C-15 and W-15 drivers. I need to do a proper write-up of these, but have to admit their sound has taken my system to another level. They are simply superb. Detail and dynamics are beyond expectations. Nothing less to be expected from the designer (Leon Huijgen) :

Initial test of the Liionidas OB speakers

  1. Second modification was minor, I removed the Zobel network from the input LL7903 to minimise loading to the source. Also, after several tests I found that the impact in the HF resonant peak is minor as the source has some resistance (below 100Ω) which is beneficial. So the 300B amplifier looks like this now:

Continue reading “300B/845 Amp: Driver Options”

300B SE Amp: 47 Driver

Going DHT end to end

As previously mentioned, I played around with the 46 driver.  I love it sound and is a great valve. However, there were 2 reasons that pushed me to switch to the 47. Firstly, I wanted an extra tad of gain. Secondly, I have a nice stash of RCA 247 globe which measure extremely well. I’ve been reserving it for a 47 PP amp with local feedback (a la Pimm) and hopefully will get to in the future. Anyhow, the 47 in triode mode has a mu of about 8 which in combination with the SUT, gives me good gain to drive my 300B. After tweaking on the bench the stage for optimal swing and distortion performance, I ended up with the following circuit:

Continue reading “300B SE Amp: 47 Driver”

300B SE Amp: 46 Driver (Part II)

The 300B amplifier journey continues as planned. A bit lower than expected, however small steps being made. Recently I mentioned about the 46 driver.

I made some progress on the LL7903 step-up transformer which is wired on 1:8.

Continue reading “300B SE Amp: 46 Driver (Part II)”

3 versions of the gyrator board

Three hybrid mu-follower (aka gyrator) board generations

From left to right: 1) Standard Rev08 PCB with full flexibility of FET and TH components. 2) Rev 1.0s board with SMD except Rmu, protection drain resistor and LED as well as space for any nice big PIO capacitor. 3) the smallest version of all, all SMD except Rmu, film cap and standard TO-220 top FET and multiturn trimmer.

Very happy with the results in the board development. It does take more time and precision (you will need a microscope) to work with the MELF resistors and the SMD components in general. However, it’s worth the trouble if you’re looking to reduce the footprint.