[Hobbsmeerkat]

Hi all!

I have a Tsakiridis Alexander tube preamp. 6x 12AT7 and 2x 12AX7 I really enjoy it so far, but I want to see how far I can take it.



I want to upgrade the small 450V Mundord Evo caps to Miflex Copper caps. The 15uF caps will be replaced with Sonicaps.
Can I get away with using the smaller 250V KPCU03 caps or should I stick to the larger 600V?

I'd rather make sure I have the correct caps before I jump into taking it apart, modding it, and putting it back together, only have the whole thing blow up/fail cuz the values were out of spec.

Is there a good/safe way to check the actual voltage being run though these Mundorf caps?

I also plan to swap out the two small sand-caste resistors with 5W 2.7 Ohm Mills.

Thanks in advance!

[FullRangeMan]

What are wrong with the original caps and resistors?
Why would you drestroy your new factory condition PCB with a different solder hand made? ?

[Tyson]

Be careful with the Miflex (and Jupiter) wax/paper/foil caps in tube gear.  I've pretty much stopped using them there because almost inevitably they leak due to the heat.  Duelunds, too.

[Hobbsmeerkat]

Be careful with the Miflex (and Jupiter) wax/paper/foil caps in tube gear.  I've pretty much stopped using them there because almost inevitably they leak due to the heat.  Duelunds, too.

Good point.
I think I could fashion a simple heat shields with some strips of cardboard and aluminum tape to isolate the airspace from the tubes without harming airflow, as the tubes sit right below the vent holes in the top panel.

[JakeJ]

Do you not like the sound of the Mundorfs? I for one would like to see a schematic and try to figure out just what the signal path looks like.  I like the overall board layout as it's small and compact which belies short signal paths.

Agree with Tyson concerning the use of wax capacitor components.  I have an MHDT Havana that has been "grannyring'd" and has a pair of Jupiter caps in the output coupling position but as I'm using a tube adapter which raises the tube up out of the components board level and I run it without the top on and they don't get hot so I'm not concerned.

Hobbes, Have you contemplated using component sockets?  Then you could just plug in different brands and technologies of capacitors.
  Examples of discrete component sockets:
https://ie.rs-online.com/web/p/discrete-sockets/1613514
https://ie.rs-online.com/web/p/discrete-sockets/9094354
https://www.digikey.com/en/products/detail/harwin-inc/H3194-46/9827185

Look at the picture in the DigiKey link.  The pin on the bottom gets soldered into the existing hole on the PCB.  Then you can plug in the leads for said test component into the hole in the socket.  Downside is unless the caps are already broken in then it's a long time between comparisons and aural memory comes into play.  There's millions of 'em so you need to do your due diligence to make sure you get the right ones.

Another thought, how long have you had this preamp?  If it's new maybe you should let the Mundorfs fully break-in.  I am going through this with a Sonic Frontiers preamp I had fully refurbished by Parts Connection.  I installed it the main system on 12/23/21, first day of my Xmas vaca and let it run until 12/27/21 and it was screechy nightmare for the first 36 or so hours but it is better now that I have about 100 hours on it.  Still changing though but I knew that going in, these Mundorfs typically take 250 hours or more to settle.  I think the bigger ones take longer due the increased size and area of dielectric.

Just some thoughts.

[borism]

Be careful with the Miflex (and Jupiter) wax/paper/foil caps in tube gear.  I've pretty much stopped using them there because almost inevitably they leak due to the heat.  Duelunds, too.

I also had some Jupiter copper foil/ wax paper capacitors melt in my Almarro a318b. The replacement Russian FT-3 aluminum foil/ teflon capacitors have performed flawlessly and I love the sound. In my Bottlehead Stereomour 2A3 amplifier I preferred the FT-3 teflon coupling capacitors to Mundorf Silver in oil capacitors.

[JakeJ]

That's good info, thanks.

How long did it take to break in the teflons?

[Hobbsmeerkat]

Do you not like the sound of the Mundorfs? I for one would like to see a schematic and try to figure out just what the signal path looks like.  I like the overall board layout as it's small and compact which belies short signal paths.

Agree with Tyson concerning the use of wax capacitor components.  I have an MHDT Havana that has been "grannyring'd" and has a pair of Jupiter caps in the output coupling position but as I'm using a tube adapter which raises the tube up out of the components board level and I run it without the top on and they don't get hot so I'm not concerned.

Hobbes, Have you contemplated using component sockets?  Then you could just plug in different brands and technologies of capacitors.
  Examples of discrete component sockets:
https://ie.rs-online.com/web/p/discrete-sockets/1613514
https://ie.rs-online.com/web/p/discrete-sockets/9094354
https://www.digikey.com/en/products/detail/harwin-inc/H3194-46/9827185

Look at the picture in the DigiKey link.  The pin on the bottom gets soldered into the existing hole on the PCB.  Then you can plug in the leads for said test component into the hole in the socket.  Downside is unless the caps are already broken in then it's a long time between comparisons and aural memory comes into play.  There's millions of 'em so you need to do your due diligence to make sure you get the right ones.

Another thought, how long have you had this preamp?  If it's new maybe you should let the Mundorfs fully break-in.  I am going through this with a Sonic Frontiers preamp I had fully refurbished by Parts Connection.  I installed it the main system on 12/23/21, first day of my Xmas vaca and let it run until 12/27/21 and it was screechy nightmare for the first 36 or so hours but it is better now that I have about 100 hours on it.  Still changing though but I knew that going in, these Mundorfs typically take 250 hours or more to settle.  I think the bigger ones take longer due the increased size and area of dielectric.

Just some thoughts.

I dont dislike the sound at all, but I just wanted to take them beyond their current state with the use of better quality caps than the one currently in them.

I've had the preamp since September, I was borrowing it from a buddy and he let me purchase it from him earlier this month.
It currently has about 600+ hours on it as it was burning in along with my NX-Studios which needed about 500 hours to burn in the Miflex caps in the crossover.

Thank for the tip on the tube adapters/socket savers to raise them up, as well as the socket pins. Trick will be to see how much room they have above them.

I would also like to see a schematic of the component layout, but I dont have the owners manual on hand yet and I haven't seen one online, so I'm not sure if that information exists or is easily accessible. But if I find a schematic ill be sure to share it here.

[JakeJ]

You got my curiosity amped up now.

I took a look at the Tsakiridis Devices website and liked what I saw and read.  Nice gear but there is no US distributor/source, however, may be available to us Yanks via the Canadian distributor.  Very intrigued by the computerized tube tester.

I notice the Alexander has a built in phono stage, nice!  Also it lools like there are two spots for step-up trannies right on the motherboard?

Nice piece, maybe you could write a review on it for us.

[Hobbsmeerkat]

The one distributor my buddy got them from is no longer offering them, so they were available for a short period, but Canadan options will likely be the closest distributor. I also got to borrow a pair of 300B Achilles and the KT120 Apollon monoblocks.

The monoblocks where fantastic, especially with my X-Statiks.
They didn't play as nicely with my NX-Studio, where the tube preamp with solid state power amp was a better combo.

But I don't have enough points of reference for separate preamps to give a proper review, but they do a great job of giving that tube sound without any loss of quality or clarity.

I may ask my buddy if he has some other preamps I can play around with to A/B for more points of reference, where it holds up or falls short by comparison.

But so far I'm really impressed with the sound and quality of this preamp.

[borism]

That's good info, thanks.

How long did it take to break in the teflons?

I don't recall exactly. Everybody states it takes a while with FT-3 teflons. However, in the Stereomour I heard the improvement over the Mundorf  SIO-s immediately. In the Almarro nothing seemed to prevent me from enjoying the sound from the get go.