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Here is the circuit I am following (credit to Glassware Audio Design): Some notes: Supply voltage is 250V 20k value I get by parallel 22k and 220k I am using two 6J5 in stead of a single 6SN7GT tube. For the moment I am running the circuit without the cathode bypass capacitor on first...

Let us have a look what is going on: The 6J5 offers the opportunity to do potentially all connections on the tube base itself, without needing a tag strip. Look at the pinout diagram: pin 1 is screen - let us make this the earth point on the socket. pin 2 and 7 is heater - AC 6.3V from...

Hi Jazzy I still am undecided which 6J5 sounds best. This is what the build looks like at the moment. no tagstrips needed when wiring up a 6J5! I have the preamp between my sound card and a JVC A-K20 amplifier. The sound is deep and expansive. There is no comparison to the sound...

Hi All Just in case you missed this event posted here on the forum at DIY for Audio https://www.avforums.co.za/index.php/topic,96577.0.html

Hi all DIY'ers Mars Tube Audio will host another DIY workshop at the end of October in Paarl. Here are the details: Date:    30 October & 6 November Venue:  MTA workshop in Paarl Cost:    R2000 per person for the two day build Kit cost: R9 900 to R19900 So far we have a booking for a...

I would look at the mains (LIVE and NEUTRAL) path for any "death caps" or dodgy wiring/fuse holder/switch. I would guess if you were to earth the chassis to house ground, your earth leakage switch on the mians board might trip.

Hi Ari Thanks for the comment. I am only using one half of the 6N1P. I still need a bit of gain to lower the output impedance with global negative feedback, therefor the high gain of EF86 pentode works fine. Great discussion here: https://www.tube-town.net/cms/?Info/How_To_Use_a_EF86 I am...

Update on circuit: R11 kept at 4K7 ohm C3 enlarged to 270uF 400V (220uF should be good too) R6 changed back to 68K (improves split load inverter load match) C12 47pF I took some voltages: B+ 310V +/- 12V across 390 ohm cathode resistors 6.3V filament voltage with 230V AC mains 282V on...

Here is progress on the rebuild I am currently busy with: PI filter in place. Earth bar across the power amp section in place.

Here is the schematic as it was built over the weekend. Some values were left out: R27 and R28 should be 47 ohm 5 watt R7 and C7 left out for the moment till square wave tests R6 was chosen at 33k. (39k or 47k might be better) R11 was chosen as 4K7. (2K2 might be better) [/list]

This is how the kit wiring looks: I decided to do a complete rebuild and stripped the amp:

Hi Everyone I am rebuilding a Mars 5-10 for a client that wants the gain to tamed. I'll be posting some photos below. But first some technical details. I had some good results using a split load inverter to bring down the gain to a more use-able level. Initially I used the ECC82 with good...

For those interested: Here is a discussion of the 6J5 tube. http://vinylsavor.blogspot.com/2013/03/tube-of-month-6j5.html

Looks like about 24 watts Single Ended at Anode 400V and G2 at 225. Now to design an OPT that can give 24 watts with DC current of 200mA! Time to look at load lines?

I have also wondered about this aspect and decided to leave pin 1 open on projects, and only use pin 2.

Great drivers. Your back loaded horn is probably going to be quite sizeable! You should consider a single ended amplifier with 16 ohm capability (as opposed to a push-pull amplifier) That way you won't exceed your drivers capability. Otherwise an EL84 push-pull should also sound great. Maybe...

47 pages later and I only now see this thread! What a picture on p1! Following with interest.

I have always wanted to hear a frugal horn. Thanks seanjammy, I'll check the sales thread.

Hi cremanic You are doing a great job on the Steinhart, especially the tube sockets! The Steinhart's are a bit tricky, since the protection only switches power on at full voltage. At that point you better hope that the tube is biased safely, otherwise the cathode and/or screen grid resistor...

FM discriminator cap - it had to be 4uF - funny value, but 10uF and 6.7uF in series = 4.01uF... You probably mean parallel BTW that black electrolytic, in the photo you discuss underneath the 4uF cap, looks lightly bulged. It looks like it has had too high a voltage somewhere in it's life.