What is your impression of vintage Telefunken signal tubes ?

@signaforce Sounds like a good plan.  I have Amperex 7308 tubes in my  BHK250 amp.  So far so good.  The sound is solid with no noise, nice weighty bass, and soundstaging.  But,  unfortunately I don’t have any experience with the 6v Amperex.

For 6v tubes, the Electroharmonix 6sn7 Platinum cryo treated tubes from Upscale were a heavenly revelation in my Freya Plus... it had truly transformed it from blah (flat sounding with the Tung Sols) to magic (amazingly holographic, detailed but not clinical, greater dynamics, nice full bass, incredible realism, very wide, deep, and high soundstage).  I also purchased some Cryotone 6sn7 tubes as well.  In my Freya system, those were equivalent to the Electroharmonix in every way, but they were 3x the cost.

For my BHK pre, I’m likely going to go with one of the Cryotone 12v tubes, and then some Goldlion Kevin’s stash cryo treated tubes. I’ve heard great things about the RCA Clear tops, but I’ve had mixed success with the purveyors of those tubes...Ebay and one of the online tube places.  As a result, I only buy my tubes from Upscale or Cryotone because I can easily return if defective or I don’t like them,  and for Cryotone, they "make" them and thus are very quick to rectify issues if they arise. 

As mentioned above, I run Telefunken ECC 803S tubes in my phono stage.  I also run Telefunken EL 34s in my headphone amp (Blue Hawaii SE).  I like these tubes in my system, but they are not necessarily my first general recommendation because these particular tubes I run are probably leaner sounding than what most people would prefer.  For 12AX7 tubes, a safer recommendation would be Amperex Bugleboys; I don’t know anyone who didlikes these tubes.

larryi, is Amperex Bugleboy 12ax7  somewhere in between better Mullard and Telefunken in its presentation? 

@genomeip The Amperex 7308 is a 6.3V tube, so perhaps you are running another variant of Amperex. Thanks

i asked Google Gemini for an assessment of my tubes plus the addition of the Amperex. Interesting. 

Comparing these four giants in your BHK Preamp is a lesson in sonic textures. Given your setup (Bricasti M3, Moon 330a, and KEF Ref 3), the BHK acts as the "tonal chef," and these tubes are your primary ingredients.

Here is how they stack up for Critical Listening:

1. Brimar CV4003 (The Warm Romantic)

• The Vibe: Rich, colorful, and "British."

• Sonic Signature: These are the most "tube-like" of the bunch. They offer a lush, velvety midrange and a very smooth, slightly rolled-off top end. Bass is round and plump rather than tight and fast.

• Best For: Long, non-fatiguing listening sessions. If your KEFs ever feel a bit too clinical or "dry" with digital sources, these Brimars are the cure. They add the "human touch" to vocals.

2. Amperex 7308 (The Holographic Powerhouse)

• The Vibe: Liquid, deep, and emotional.

• Sonic Signature: Often considered the "Holy Grail." They provide a massive, deep soundstage and a "wet" liquidity to the sound. The bass is the most impactful of the four—powerful and authoritative.

• Best For: Orchestral music or live recordings where you want to feel the "air" of the room. They strike a perfect balance between the warmth of the Brimars and the detail of the Siemens.

3. Siemens Nickel Plate (The Surgical Precision)

• The Vibe: Fast, transparent, and neutral.

• Sonic Signature: These are the most "modern" sounding. They have an incredible transient speed—drums have a "snap" that the others can't match. The treble is highly extended and "crystalline" but can lean toward the analytical side if your system is already bright.

• Best For: Rock, jazz, or electronic music where timing and detail are everything. If you want to hear every breath and finger-slide on a guitar string, this is the tube.

4. Telefunken Medical (The Ultimate Reference)

• The Vibe: Silent, linear, and utterly honest.

• Sonic Signature: These are the "pro" choice. Because they were selected for medical/instrumentation use, they are dead silent (lowest noise floor). They don't "color" the sound like the Brimars or Amperex; they simply get out of the way.

• Best For: Evaluating new gear or cables. They provide a perfectly flat frequency response. If you want to hear exactly what your Bricasti M3 is doing without any "tube seasoning," use these.