JoaMat

Pick a lead. Ordered transformers for DHT filament. Not sure the brain was involved.

This is what it looked like with adapter boards replacing the small tubes - ECC88/6922/6DJ8.

Only change to PSU was reducing +250V to +150V. For amplifier I changed batteries from 740V to 640V. Also the 68V grid voltage was reduced to 33V, but that is taken care by the resistor on the small board with two 2sc3840. Maybe one should build a modified T2 with lsk389 for input and EML 20B-V4 for output....

Made those a couple of years ago. All information you need can be found here.

Have listen to the DHT carbon style for three weeks now. It’s bloody good – think I like it more than the T2. Below is a draft of how a smd version of DHT might look.

Thanks! Great have you guys around.

Regarding transformers and humming. Is it the transformer itself that hums? Or is it something else that hums due to the magnetics caused by the transformer?

Will the opto servo be able to control offset without the trimmer/tail resistor?

Sold rk50. Got money enough for tubes, bottle of single malt and flower to wife.

EL60 is said to have the same characteristics as EL34 but it has 9 pin socket. The adapters are bought via eBay and quality seems OK. IMO EL60s are very good sounding tubes.

Nice connectors. I really like the color of the male. Help appreciated. PM sent.

Neutrik male pins, right? Can they be bought somewhere? Don't like to slaughter good XLR connectors to get them.

Life is short. Would T2 accept EML 20B-V4 tall base? Yes, she does! For how long?

Here is a Blue Hawaii I built a couple of years ago. Just removed the EL34 (left channel) and put the EML 20B-V4 tall base in place. Held my breath, closed my eyes, pulled the trigger and…. it works

EML 20B-V4, tall base

I’m actually reading the information Emission Labs sent me with the tubes. Regarding filament they say: “The filament voltage must be exactly as specified, under all circumstances. Slow-start filament electronics taking longer than 10 seconds, are not allowed, otherwise this may damage the tubes” “Stand-by mode should not be used with directly heated tubes.

I can’t hear any AC hum – doesn’t mean that there isn’t any though. The filament transformer gives [email protected] out. In order to reduce voltage for tube heating (5.0V +/-5%) I’ve put wire wound resistors in series with heater. Below shows the small board with terminals and resistors mounted to Kevin’s main board on two stand offs. For info I followed this link and bought some SiTubes filament supplies. They work OK for a quarter of an hour or so than the voltage drops to a few tenths of a volt. After some cooling down they are fit for fight again. I should have red data sheet. Maybe this would do if you really want DC heating. Probably overkill??

You are right. Even when completely dark the tubes can be barely seen. Very disappointing, but the sound is OOOK!!! Maybe I should turn up the variac, it’s only at 67% percent...

Continued the rebuilt. Emission Labs DHT Tubes, EML 20B-V4. To the left is variac. Its purpose is to set the two small transformers to appropriate voltage for the filament.

625 mW is more than enough. Max power dissipation of mpsa/w06 is less than 60 mW.

What is printed on the PCB - MPSW06 or 2SC2240?

Thanks, so the servo keep the offset to zero from the start (except from the first seconds when power on) and further on without any fluctuations?

Thanks. Does it mean that you have zero volt offset even from the start?

Anyone that have tested the opto servo. How does it work?

You can’t just replace the mpsw with the 2sa/2sc components that way, can you? I think their pin layout is different.