Category: 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

CCS in power supplies

The use of CCS in HT power supplies is well known, however generally misunderstood why it can be a good addition to some circuits. There is an excellent article from Gary Pimm which has been lost and luckily I found it on my archive. Here it is in case you haven’t read it. Worth it as a refresher or for anyone who is new to the subject:

Continue reading “CCS in power supplies”

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 

300B SE Amp – here we go

A Brave New World

Surely you’re as tired as I’m with COVID-19. One of the best things I can do to distract my mind is to keep myself away from social media. Every stone you turn, there is COVID or a statement about it. I won’t moan as I have a job for now and a healthy family. Some members of my family were infected but nothing major. I can only say is that the world has change. And so my day to day life looking after the young family whilst working is a real challenge. Starting my fifth week of lockdown, I have to distract somehow my mind at times, otherwise will go mad.

A New Concept

Continue reading “300B SE Amp – here we go”

Mini Hybrid Mu-follower board test

 I had a  go first at a mini-gyrator board using SMD. Blimey, it’s hard work to get all these crammed into such a small footprint.
I did a quick test with a D3a and worked fine at 100V/10mA (low voltage of course). It was +35dB flat up until a couple of Mhz. Even the over-current LED works!
Footprint is as small as you can get: 45mm x 25mm 🙂
More to report later!

VT-25/801a/10Y DHT Preamp with SiC filament bias

For quite some time now I wanted to share one of the variations of the famous VT-25/10Y pre-amplifier. As usual due to work, business travel and family duties, I’ve struggled to find the time to update the blog.

Continue reading “VT-25/801a/10Y DHT Preamp with SiC filament bias”

D3a driver w/ Rev08 board

A friend from Canada ordered a pair of boards and I used the opportunity to test the newly arrived hybrid mu-follower (aka as gyrator) Rev08 PCBs.  He will be using these boards in the 300B design posted here.

Continue reading “D3a driver w/ Rev08 board”