Teflon sockets

I have used Jakeband teflon sockets for over 3 years. They are very well made and of high quality. Luciano from Jakeband can provide you with any custom socket you may need. This time, I requested a set of sockets for my 813 transmitting valves, a pair of UX-4 for the 300B and a pair of octal sockets for the driver stage.

813 socket

Octal

UX-4

UX-4

UX-4

Construction overview

Jakeband uses the following materials for the socket:

Tellurium Copper (CuTe) for pins
Virgin teflon made in Germany

The socket pins are machined with CNC from a solid core copper tellurium CuTe with tolerances within +/- 0.01 mm. The contact surface which is obtained is the highest possible.Thus there is a better grip and and a lower electrical resistance and therefore better heat dissipation (e.g. on the filament pins).

The pins undergo three surface treatments:

1° electrolytic acid copper to remove any impurities
2° electrolytic silver 99.999% thickness 20 microns
3° 24k gold thickness 3 microns to prevent oxidation and give more surface hardness

Why using CuTe pins?

The copper has a conductivity rating of at least 100% IACS (International Annealed Copper Standard). Brass has a conductivity rating of 28% IACS. Tellurium copper(CuTe) contact pin provides up to 320% greater conductivity than a standard brass pin

Pin gold plating

The gold plate is 3 micro-inches thick. It is purely there to prevent oxidation (and increases the surface hardness) however doesn’t contribute to the conductive process. In fact gold is less conductive than tellurium copper. The gold plating is direct, nickel free.

Threaded pins

The new sockets come with threaded pins. This is an interesting concept that Jakeband is introducing and will be keen to test various connectors which will simplify the wiring to the socket.

I hope to test the new sockets shortly.

Contacting Jakeband

If you want to request them, you can reach out directly to Jakeband using the following form:

Rolling valves

I’m not a big fan of rolling valves. Perhaps it’s likely to do with the fact that I don’t have too much free time these days. However, I do look into burning in the valves. A noticeable change found on my 4P1L preamp after 350-400 hours use. The microphonic noise reduced to a minimum whilst the sound became more rounded. I added an electronic clock (LCD module) to the HT supply to monitor the exact number of hours between any changes I made to the system. It’s very handy. I’ve been running now the same pair of 4P1L valves for over 850 hours and they sound better than before. No further mechanical expansion noise is heard during warm up, something which was noticeable at the early days of use.

The second aspect I’m also in constant monitoring is the impact of the filament starvation in the 01a. Running them at 20% less current than expected is not recommended as the filaments will not operate at expected target temperature. However, after some years of joy, I’ve not seen any issues. I may remove and trace the pair of 01a in use currently to check their health.

Have fun!

Russian PSE in Steroids (01a into 4P1L) – Part IV

More power

Our previous west meets east circuit can be improve further. In fact, a compromise made with the filament bias design is that coupling between driver (FET follower) and the output stage wasn’t DC. We want DC coupling to get best performance, to ensure we can drive well the output stage and provide sufficient grid current even when not operating in A2. This can be done with filament bias, however, since we are already introducing a negative supply, I’d prefer removing the filament bias and go for proper grid bias to get best performance of output stage in terms of maximum power and linearity.

The below circuit can be easily implemented with just few modifications from previous version:

What has changed here? Not much, the coupling cap C2 is now between the gyrator and the FET follower. The gate bias resistor R6 provides high impedance to the gyrator load to ensure maximum performance of the 01a driver (minimum distortion given size of load). Not as good as previous version, but good enough. The R6 is connected to a potentiometer which sets the bias voltage. The bias voltage is derived from V2, the -50V negative supply. You can see that this circuit will put more stress into the M1 FET as now there is an additional 25V of drop across it so power burned on this device increases.

The output of the follower is directly coupled (DC) to the output stage. The filament bias resistors are removed and we use the Coleman regulators directly on the filaments of the 4P1L.

This amplifier responds better to the grid current of the output stage once the output power goes over 3.5W. At 4.5W the distortion is just above 3% (3.2%) with a 3Vpp input signal. A tad more and you can get to the 5W and a bit more into A2 operation.

Russian PSE in Steroids (01a into 4P1L) – Part III

From Russia with Love

East-West Divide, Copyright by Justmeans

The interesting combination to explore from our previous designs is to mix some western valves like 01a into the Russian parade.

The result would be quite interesting, as the sound of the 01a has proven to be amazing. Therefore 01a driving 4P1L is possible as the 4P1L doesn’t need a lot of drive. Instead of using 4P1L as a driver, we can opt for the 01a which has a similar gain. What is interesting is that the voltage swing required by 4P1L wouldn’t force the 01a outside the zone in which is highly linear, hence, with some modifications, it can work as a great driver here.

The circuit

Instead of starving the filaments of the 01a, given the voltage swing requirements for a driver, we ought to drive it at full tilt. In the circuit above, the 01a hasn’t got the stones to drive the 4P1L pair, therefore we have added a cathode follower as explained here. The M1 follower will then drive easily the output stage.

Russian PSE in Steroids (6E5P into 4P1L) – Part II

Well, it was obvious I couldn’t leave last post as it was. There is an option to change the driver for a different valve. You can use a C3m (low gain in triode mode which is ideal here), a C3g, E180F/E280F. 6S45P or my loved 6E5P (or 6E6P) as the driver. Not longer a 100% DHT, but a nice option for sure. The 6E5P is extremely linear, good driver, with a nice gain (μ=30) in triode – perhaps more than enough for a 4P1L stage and would help in avoiding additional filament supplies.

The 6E5P has curves not dissimilar to the 4P1L as no further distortion cancelation can be seen. Here is the updated schematic if you’re interested in playing with:

Again, the gyrator PCB can be easily used to simplify the build of this amp. The 6E5P is not driven hard, but at a nice current of 20mA which makes the driver operate in a linear region (and with good sound) with just a pair of red LEDs. The nearly 30dB of gain will make this amp to be very sensitive. The 5W can be easily achieved with 1Vpp, so you will need to have an attenuator, no preamp needed clearly. The 6E5P will drive an 300B nicely here which needs the voltage gain, not like the 4P1L.

As you can see, there are plenty of option to try on this 4P1L PSE amplifier.

Russian PSE in steroids (4P1L into 4P1L)

Introduction: DHT madness

I’m not going to dwell on DHT sound. I’d rather say that if you’re looking for a stellar DHT candidate, the 4P1L beats them all. It’s dirty cheap, reliable and sounds amazing. You can go any route you like, it’s your own decision of course. However if you’re looking for a 100% DHT amp to build, here is an interesting example for your consideration.

I’ve tried 4P1L in many topologies. The advantage of its low filament requirements is that you can implement it in filament bias and simplify the circuit significantly.

The gyrator driver using the PCB I designed recently, can be used to avoid iron and have an excellent first stage and make this Russian Amp in steroids: 4P1L driving 4P1L.

One minor caveat around 4P1L in excess. I have found (as well as many others) that if you use too many 4P1L stages (e.g. 4P1L line stage driving a 4P1L-4P1L amp) then it will sound a bit harsh in the treble. i suspect this may be explained due to the H3 component level when triode-strapped. I’d rather limit the number of 4P1L stages to two. You’ve been warned.

The other great thing about the 4P1L is that is quite consistent between samples and easy to match pairs. Also in PSE mode you can drive it to full tilt with only 20Vrms and achieve up to 5W in class A1 with a pair of valves.

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