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Modular approach (Part I)
As time is very limited these days, I’m focused in continuing my modular building approach in LEGO style. I have developed several PCB modules which are flexible to be used in multiple amplifier and...
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UX-120 DHT
I’ve got hold of a NOS quartet of UX-120 Radiotron valves made in 1925. These are 95 year old beauties. Unbelievable how well conserved they are and operate. This valve developed by RCA was the first...
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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...
View ArticleLundahl Transformer PCBs (LL1943 and LL7903)
I made a few additions to the PCBs available. Check these out: Moving Coil Transformer (1:16 or 1:32) – (LL1943) High Level Mic Transformer PCB (1:2 to 1:8 configurable) – (LL7903) Available until...
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300B filament supply
In the process of rebuilding my old 300B amplifier, I decided to make a new filament power supply. It all came up around the components I had at hand, so it could’ve been improved but that meant extra...
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Goodbye McCoy
I hate saying goodbye. However, that’s life and it’s sad to see the great people jump on the next bus. I was very young when I first heard McCoy Tyner. I was learning saxophone when obviously Coltrane...
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The return of the Mule (RE084)
It’s been a while since I experimented with preamps again. I settled as a permanent setup with my 01a/ER801a which I love. However, I wanted to continue with my experiments so I built a new Mule, let’s...
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46 driver
I love the 46 DHT. To the extent that I went on the crazy idea to implement it in filament bias. It was my winter heating indeed. Stupid idea, but sounded brilliant. I had several questions about the...
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01a Preamp from South Korea
Time ago I made a set of gyrator boards for Chul in South Korea. His build skills are amazing and look at his work below. I love the structure and design, it’s simply beautiful. Chul asked me also to...
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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...
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Mini CCS
Mini-CCS 3 x 4cm footprint PCB Long time ago I developed a CCS board which provides full flexibility in terms of FETs/MOSFETs used. It was a 2-terminal CCS, a very well known circuit. Recently, I...
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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...
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VT-25 Preamps in Lockdown
One positive thing I can get out of this COVID-19 lockdown is that people are building more audio equipment. Here is a great story from Sridhar Ganti who has built a few DHT preamps over the years....
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300B SE Amp: build part II
Slowly making progress during the lockdown period. Over the past few weeks I managed to achieve quite more than I was expecting. The fixed bias and 300B filament supply board (board 1) needs to be...
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300B SE Amp: build part III (Layout)
Playing with the layout a bit, here is a view of potential layout of the amplifier board. The PCBs for mounting sockets, turrets and switches are very handy. It accelerates the build process and...
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300B SE Amp: build part IV (Board 1 finished)
Board 1 completed Wiring job is done. The fixed bias supply delivers from +50V to -300V. It has more voltage capability as am planning to use this same supply for future builds (e.g. 845 SE). The...
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300B SE Amp: build part V (Fixed Bias)
Last year I developed a voltage reference using an HV LED. Unfortunately these devices from OSRAM seem to be discontinued. I managed to buy enough parts for my own use though. What is interesting from...
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300B SE Amp: build part VI (Fixed Bias Board)
And the fixed bias PCB is completed. All individual PCBs mounted over a ground plane PCB. It will be a stacked build. On top of this PCB, another one will hold the driver. Firstly the D3a in a hybrid...
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300B SE Amp: build part VII (D3a driver)
It didn’t take long (or at least as long as I thought it would) to finish the driver board. It has a D3a hybrid mu-follower with SiC cathode bias arrangement: D3a Driver Board Finished The board is...
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300B SE Amp: build part VIII (Cap Boards)
I made a set of useful PCBs. They are intended to mount large (big really big) film capacitors: WIMA DC Link ones! WIMA DC Link mounting boards + PIO cap board I use the cost-effective 45μF/600V (MF...
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