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DISCLAIMER: Vacuum tube circuits work with dangerously high voltages. Do not attempt to build circuits presented on this site if you do not have the required experience and skills to work with such voltages. I assume no responsibility whatsoever for any damage caused by the usage of my circuits.

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Showing posts with label 10Y. Show all posts
Showing posts with label 10Y. Show all posts

Saturday, July 19, 2014

10Y Preamplifier 'Landscape Style'

Hi!

The portrait style chassis with the controls at the front and the connectors at the back receive a lot of positive feedback. Yet there are many who prefer the classic landscape chassis style. Here are some photos of a new preamp built in this format.




It shares the same basic circuit design as the recently built portrait 10Y line stages, like this one. The difference is the chassis only. This particular preamp will be used with the no compromise 6CB5A amp which was built last year.




Therefore the same wood and color scheme is applied. The PSU also got some vintage panel meters for voltage and current.




This chassis style is more cost effective than the portrait style and assembly is much easier since the entire circuit is mounted on the top plates.




Best regards

Thomas

Thursday, June 26, 2014

Differential 10Y Line Preamp, Part 1

Hi!

I am often asked when I will finally present a push pull amplifier. In fact I am often perceived as being prejudiced pro Single Ended. While I do like the sound of my single ended designs, I am by no means religiously bound to this concept. In fact I did build push pull amplifiers in the past and probably will do so in the future. At the latest when somebody orders a push pull amplifier from me.

Such has happened for a preamplifier. A user of my 10Y line stage asked me for possibilities to upgrade it. So I proposed a differential version of it.




Differential in this case means that it will be a self balancing circuit. The beauty of such a concept is the possibility to build it without any capacitor in the signal path. And that's how this line stage will be done. Lot's of iron, no capacitors in the signal section. Everything decoupled from the power supply. Of course that means that 2 10Y tubes will be needed per channel. 4 of them in total. This is the top metal plate of the signal section:




The left half will be occupied by filament chokes. For the 4 sockets to fit, I had to use some different ones as usual, which have a smaller footprint. These allow the vibration damped sub assemblies to be narrower.

I often get emails about my technique of vibration damped sub assemblies for the tube sockets. So I will show this a bit more in detail in this first part. These are the basic elements used for that:




A rubber cylinder with metal threads at both ends. Threaded metal blocks get attached at either end.

The small metal plates which carry the tube sockets have threaded holes on the bottom:




Tube socket mounted:




Then the metal blocks get attached to the plate with screws:




The rubber elements screw into the sides of these metal blocks:




The small wire is there to make an electrical connection from the sub plate to the main plate. Another set of the metal blocks goes onto the other side of the rubber pieces:




The outer metal blocks get attached to the main metal plate:




View from the other side:




Stay tuned for updates on the construction of this preamp.

Best regards

Thomas

Wednesday, March 5, 2014

The 10Y / 45 drives 45 / 2A3 amplifier

Hi!

After the posts about the rather high power 211 amplifiers, here some pictures of a recently finished pair of flea power mono amps.




These mono amplifiers are similar in construction, chassis layout and parts choice  as the 10Y/45 drives 45 amps shown last year. Except that this time also the output tube can be selected between two types: 45 or 2A3.

The amplifier set consists of 4 chassis. Two amps with separate power supply for each.




Same chassis design as the remote controlled 10Y line stage in the previous post with which these amps will be used. Both the driver tubes and output tubes have DC supplied filaments for zero hum operation. Elaborate filament supplies with separate filament transformer and LCL filter chain for each tube ensure best sound quality without impact through the filament supply. In my opinion a properly DC heated 45 even sounds better than an AC heated one.

With both driver and output tube selectable, these are actually 4 different amplifiers in one. Some might find the configuration 10Y drives 45 a bit ridiculous since the driver tube is physically larger than the output tube:




But anybody who heard this configuration with it's very detailed and beautiful sound accepted it as a viable combination.

The 2A3 driven by 10Y looks a bit less strange:




The 10Y is a good candidate to drive the 2A3 with a 1:4 input transformer this gives reasonable input sensitivity. Sensitivity is the lowest with the combination 45 drives 2A3. Similarly low for the 45 drives 45 set up. This configuration needs about 2.8V RMS to reach full output power of 2W. While low this is still reasonable in most systems.




The sound of this combination is well worth it. A 45 lovers dream! Pure 45 bliss, especially with the globe UX245:






This is not just double the 45 fun, it is 45 squared!

Some more views of the amp:






The amp section from the top:





The entire set of 4 chassis:




I am enjoying these amps during their one week test run, before they are picked up by their new owner.




So is this as far as you can get in terms of 45 amplification? Stay tuned for more 45 bliss in upcoming posts.


Best regards

Thomas



Friday, February 28, 2014

The Remote Controlled 10Y Preamplifier

Hi!

I am not really a big fan of remote controls. I prefer to physically interact with the audio gear in the same way as I prefer the interaction with vinyl as a medium over digital formats. Whenever someone asked for a remote controlled preamplifier I refused to do it usually with a little joke that the exercise of getting out of the chair to change volume is rather healthy. But then came this nice chap who already has a 10Y/45 power amplifier and convinced me that remote control for the volume is essential for him. It would have been a shame if that 10Y/45 amp would continue to be driven from a different preamp. So here it is, my first remote controllable line preamplifier.






The circuit, parts and design are the same as those of earlier implementation of the 10Y preamp. The line stage can be equipped either with a 10Y (10, UX210, VT25, VT25A) or the slightly uprated transmitting tube 801A (801, VT62) which will be covered in a future Tube of the Month article. Volume control is done with a Tribute line output transformer which has a tapped secondary.

So how to implement the remote control? A solution would have been a PCB with a bunch of relays which are then controlled by the remote. But the preamp should still have that classic old school look and feel. Which means a solid volume control switch which always indicates the volume setting rather than a digital LCD display. Although my professional background is in digital microelectronics I chose rather not to reinvent the wheel but use an existing solution. Bent Audio offers a remote controlled stepper motor along with the IR receiver and a nicely made metal handset. So I emailed John Chapman of Bent Audio and ordered a set. John is a very nice guy who was very helpful to sort out some minor mechanical issues to combine the remote control system with an appropriate switch.

The motor is mounted on the back of the switch and turns it up or down as the remote control is used. The switch can also be turned manually. So the marker on the volume knob always indicates the volume setting. When the preamp is turned off and back on the volume is at the same setting as before without the need of any memory storing the value or special relays which hold their setting.

This is the motor mounted to the switch which has already the teflon insulated silver wires attached which will get soldered to the transformer volume control:




The preamp has two single ended inputs and two balanced inputs with separate input transformers. The input transformers are mounted right behind the input selector switch:




The stepper motor and it's control electronics only need a single supply between 9 and 12V. Quite convenient, but the motor needs to have considerable torque to rotate the switch. When in operation it consumes current peaks up to 1A. Although the digital control circuit goes to sleep mode and turns it's clocks off when not used, I didn't want to supply it from one of the filament supplies. So it got it's own independent supply with a separate power transformer. This power supply is placed in the external PSU chassis along with filament and high voltage supplies:




The remote control system PSU even got it's own smoothing choke.

The top plate of the signal section with all the signal wiring in place:




The inside of the completed signal unit:




The completed preamp with power supply:




The front:




The two balanced inputs have separate sets of input transformers. One wired for 1:4 step up (+12dB) and one wired 1:1. In addition there are two regular single ended inputs.

The back sides:




The umbilical between PSU and preamp needs 9 separate wires for all the different supply voltage and safety earth. A 10 pin umbilical is used.


The preamp section from the top, with the remote control:




Preamp equipped with globe tubes:





View from the side:




The globe in these photos are the magnificent 1602 triodes. A special low microphonics version of the 10Y.




Best regards

Thomas


Saturday, February 1, 2014

Making of a 300B Amplifier, Part 2 : Amp Assembly

Hi!

In part 1 about the single ended 300B mono blocks, I showed the assembly of the power supply. This post shows the assembly of the amp chassis itself.




The amp chassis are constructed in a similar style as the PSUs. Output transformer, interstage transformer, capacitors and tubes are visibly mounted on the top plate. The rest is going inside the wooden enclosure, mounted on a sub assembly:




That's the two filament chokes, one for the 300B and the other for the driver tube which can either be a 10Y or a 801A. And a B+ smoothing choke for each stage. close to the front plate an input transformer is mounted to give enough gain with the low mu driver tube.

The top plate carries the transformers, caps, tube sockets and bias resistors:




The photo shows it with all the signal wiring completed. I chose some transformers form my stock of original Hirata Tango. The output transformer is a very rare permalloy core NY-15-3.5S:





The NC20 serves as interstage transformer.




The sub assembly inserted into the frame and pre wired:




The top plate added and wired up:




The finished mono block:





The right side with the driver tube and capacitors, varnished in a beautiful metallic bordeaux red:




The left side showing the transformers and Western Electric 300B output tube:




Some views from different angles.





The top side:




The driver tube, here a RCA 801A:




The amp equipped with a globe UX210 as driver:




The output tube :







Stay tuned for part 3 with photos of the entire set of 4 chassis and a first listening test.

Best regards

Thomas