By Enzo Grazioso
Grundig Box 850a…..revised The Grundig Box 850a speakers probably represent one of the best value-for-money hi-fi components of the 70-80s era. I didn’t want to upset this product too much but…a minimally invasive job. Apart from the color of the box in a nice brick red Audio-Tekne style I replaced the electrolytic capacitor in the midrange cell ( poor and cheap ) with a MIT Multicap 15uF MKP… and finally I changed the connectors…
Let’s get one thing out of the way: I love the 2A3 power tube. With appropriately sensitive speakers, I’ve long found that this tube just gets me a bit closer to the music than anything else. I’ve felt this way about every 2A3 amp that ever crossed my path – and fortunately, I’m not alone in this regard. Ask a group of tube amp lovers which is their favourite of all the directly heated triodes,…
Ampex 960 ( valve ) reel to reel machine play 1957 tape Edmundo Ros & Orchestra Rhythms of the South with 2010 active Ampex Speakers ( 10 Watt build in 6V6 push-pull amplifier )….lovely sound…. …I forgot, I too was born in 1957.
Over the past 10 years I have focused on Russian tubes from the era 1960-1980 and have discovered numerous types with very interesting characteristics. Signal tube like 6n6p, 6j51p, 6j9p, the high gain planar triode 6s17k, the strong, linear driver as 6e5p, power tubes like 6c4c, 6c33c, 6s18s and 4p1l. This last DH ( direct heated ) pentode has the reputation of amazing performance and low distortion in triode mode. After many days of breadboarding,…
I thought to write these notes on a topic that is mostly neglected or not always well highlighted: ground connection. Please look at the follow schema about an easy SE tube amplifier: We see a long ground wire and and a connection to metal chassis. But the question is: how is this connection made in practice? after many years of tests in audio devices I can assure you that this topic is very, very important…
A LCR phono stage is probably one of the most challenging circuits to build in audio.There are several approaches to low noise tube RIAA stages. 1. Negative feedback RIAA. I think 90% of the phono preamps in the hi-fi market are configured this way: an RC network in the feedback loop implement the active RIAA filter. Low cost solution = poor performance. 2. RC type: a RC network between two gain stage achieve the RIAA…
Falstaff Hybrid Circlotron Power Amplifier is an excellent design but in truth too heavy and also very expensive so I thought of a lighter version …a kind of small Falstaff…………. R O B I N !!!! I tried to simplify the schema and reduce the number of components but without penalizing the audio quality too much. I found a little magician: the E180F tube ( or russian equivalent 6j9p ). This gold pin, long…
Mimì, my stand-mounted, two-way, reflex-loaded loudspeaker equipped with a ¾” soft-dome tweeter and a 6.5″ bass/midrange unit is a very well sounding speaker but after 5 years I’m thinking an upgrade…mybe an AMT tweeters !!! The AMT Air Motion Transformer is a truly exceptional transducer invented by Dr. Oskar Heil. The diaphragm, housed in a very strong magnetic field, pushes back and forward from itself in a physical motion similar to that observed in…
There has been considerable debate over the characteristics of tubes versus transistors….. The goal of this hybrid power amplifier is to take advantage of best performance of both technologies tubes and solid state device. Tube is highly linear without negative feedback, smooth clipping, wider dynamic range, characteristics highly independent of temperature, and so on…but its disadvantages such high-impedance devices that usually need a matching transformer for low impedance speakers. I prefer to…
The beating heart of this project is the 12B4-A. This 5.5 W single indirectly heated triode an amplification factor μ of only 6.5, coupled with a plate resistance of a only 1kΩ , is the ideal candidate for a great linestage. Due to low μ I opted for a plate CCS ( Constant Current Source ) A CCS presents an ‘infinte’ AC load to the tube, maximizing gain. This high resistance load to the plate,…
