Bartola® Valves

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 pre-amplifier designs. Now, I used the power of PCBs to build some additional supporting modules to speed up my breadboarding over the IKEA boards. Not the most elegant approach, but building becomes a very fast process this way.

You will see what I’m saying when you see a few of the following additions:

Turret and 2mm female connectors in a strip

Continue reading “Modular approach (Part I)”

6BS7 low noise pentode

Here’s an interest pentode to consider for phono stages. It was used extensively in instrumentation up until 1980s. There are a few examples around and you can check the Brimar data sheet to see what I’m taking about.

Cap Multiplier boards (Rev04)

After few tests and revisions (Rev 04) I updated the capacitor multiplier board I developed time ago

Cap Multiplier Rev-04: 0-450V variable regulation

6AG5 pentode

Here is a nice sharp cut-off RF pentode with low capacitance, high gm and nice curves: 6AG5.

E282F HP Amp

First and foremost, Merry Christmas! I hope you’re having a great time with your loved ones and good music.

Without a mood for public introspection this time, I have to say that I will celebrate this holiday the best I can. I will be hosting today with a lot of meat, wine and single malt. What else can I do? When I escape from the little ones, will get back to spin some records and hopefully work on the projects.

Headphone Amp Quest Continues

Obviously, I needed to pursue this project further. I’ve been lately listening a lot to HPs as simply is the best choice for me when the young family is in bed. In addition to this, I find the HP setup to force me to connect a bit more to what I’m listening to as I don’t get easily distracted.

ETF.19 – continued

Whether it was a good idea or not to bring the eTracer to ETF was yet to be seen. Fortunately enough, I escaped smartly to become a prisoner of my own suggestion.

Did quite a few tests with the tracer and contributed to avoid auctioning a worn out 45. Instead, the auctioned pair became a single 45. It felt like a nice contribution.

On the flip side, tracing Pete’s 50 mesh stash was a joy. Handled with care his pension investment when tracing them. However, we found a gassy and a open filament one. Ouch. At the same time, saved the curves of a 50 measuring 100% which was really nice.

ETF.19 Starts

Mercury love from J. Jackson and D. Slagle’s mono system

The main system is made up of 833a choke loaded and parafeed output. The driver is a mu-follower made up of a 6N6P loaded with a D3a. Second stage is a 300B with an IT (step-down) into the 833a valve.

Shearer horn on main system. DJ Frank on the back

Shearer horn w/ JBL 2220 drivers, mid horn w/ RCA Mi-9486 dual compression drivers and Dittmar’s tweeter horn

6e6p-dr HP amp – part 3: measurements

As I promised, I took the HP amp back to the workshop for a bit of abuse on the bench. Here are some interesting measurements which correlate with some of my listening impressions so far.

I added a set of 300Ω dummy loads at the output to simulate the HPs. Firstly I tested the optimal circuit which has the Sowter 8665 output transformer in Parafeed mode (4:1) to drive the load. You can get a very clean and flat response across the audio band from 3Hz up to +90kHz. There is a minor hump to be tuned due to the RLC circuit formed by the parafeed circuit. I used a 4.7μF Mundorf EVO oil cap. It’s pretty flat to me, so will leave it there.

The performance of the circuit is amazing. Distortion is very low, up to 0.07% at 100mW (which is VL=5.47Vrms):

6e6p-dr Headphone Amp performance @ 100mW output level

DHT LT power supply PCB tests

I’ve been working on a few PCBs lately with great results. I started with an HT power supply PCB which allows the use of full silicon rectifier bridge, hybrid rectifier (e.g. for damper valves) and any combination of either CRCRC or CLCLC stages with external chokes. Last capacitor is bulky WIMA DC-Link film instead of electrolytic. That worked really well and I’m using it now in a +50/-300V supply for the fixed bias and source follower drivers in the amps.

Teflon Sockets

I’ve got a set of teflon sockets from Jakeband. These are fantastically made to order. Luciano from Jakeband sent me in addition some samples which I will use in the eTracer which I will bring along to ETF.19.

Honestly, these are fine pieces of craftwork. For example, you can measure and let Luciano know the diameter of your 845 (or any other transmitting valves) when ordering these valves so they fit perfectly.

I’ve used these sockets on my projects for years and am very pleased have to say. Of course you pay a premium price as these are hand-made with fine materials. In my opinion, these are worth every cent.

Also I had a pair of RCA sockets, look at them:

They are made on a single piece of tellurium copper. First coating in pure silver 99.99% thickness 18 microns and the second coating Gold 24 K 3 micron thick. Sterling job!

You can contact Jakeband directly to order your sockets. Just use the form I posted years ago here.