“tube pulling over current”? What means this?
And young Master Scott is sending me a couple also. These guys can’t be beat.
This will clear it all up. I say this with a healthy dose of sarcasm. I understand some of this but certainly not to much of a depth.
“The 6DJ8’s transconductance parameter is highly prized, but also disputed. To give me an intuitive handle on transconductance (gm), Bev (Harold Beveridge) said, “We, and many Europeans, do not generally use µmphos (micro-mhos) as most American engineers do. We say, ‘one milliamp per volt for transconductance of one millimho’ (which is 1,000 µmphos).”
Thanks for that. I clicked the link and read until I could no longer keep both eyes going in the same direction…
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in the bhk pre, are the tubes in the headphone loop?
PS Audio equipment chain all powered by P-10 regenerator.
DMP à DS Sr. à BHK Preamp à BHK 250 power amp à Polk Audio SDA SRS-2 speakers
PS Audio I2S, Grover Huffman XLR ICs, Grover Huffman speaker cables.
SR Blue fuses installed in DMP and BHK Preamp.
I initially upgraded from stock tubes to the BHK-recommended Tungsram 7DJ8 tubes (“platinum grade” and “cryoed” from Kevin Deal at Upscale Audio) in both BHK 250 and BHK preamp. Those have stayed in place for a year or more — so they are my “baseline.”
I have now auditioned Amperex 7308, Telefunken PC88 / 7DJ8, and lastly Telefunken E88CC / 6922 tubes (all “platinum grade” and “cryoed” from Kevin Deal at Upscale Audio) in the BHK preamp ( with the Tungsram 7DJ8 remaining in the BHK 250 amp for all these auditions ). Each set of new to me NOS preamp tubes was given ~ 80-100 hours prior to critical listening sessions, which included PS Audio “One” SACD, “The Quality of Silence” SACD by Steve Davis Project, Roxy Music “Avalon” SACD, Jimi Hendrix “Blues” CD, “Gob Iron” CD, Joni Mitchell “Hits” CD, etc.
All statements are “to my ears with my system.”
Amperex 7308 creates a very noticeable shift in energy balance – less energy in higher frequencies, but added some detail and “texture” to mids and bass compared to the Tungsram 7DJ8. Interesting sonics some may hear as an improvement. Probably blacker background/less noise than the Tungsram. Is this the source of the extra “texture” or is it more energy in the lower frequencies? Or both?
Telefunken PC88 / 7DJ8 (Upscale indicated these tubes as actually manufactured by Siemens) - gave a definitely more “vivid” presentation than the Amperex 7308, but with energy distribution perhaps more similar to Tungsram 7DJ8 than to the Amperex 7308.
Telefunken E88CC / 6922 — “Transformational.” “Another level.” I would even tell BHK himself I suspect he hasn’t heard his own creation to its full potential if he hasn’t heard the BHK Preamp with these tubes or similar installed. Dead quiet background – to my ears a “neutral” presentation , with greater detail at all frequencies but still very musical presentation like the Tungsrams. Increased soundstage in all dimensions (height, width, depth).
The Telefunken E88CC / 6922 are staying in the BHK preamp.
I am wondering what these tubes (Telefunken E88CC / 6922 ) will bring to the BHK 250 amp next down the chain. Is it possible that would create too much detail and thereby seem less “musical?” That remains to be heard.
I have ordered another set of Telefunken E88CC / 6922 to try in the BHK 250, or for backup.
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I would think so as they are on the input side but I don’t know for sure. How about if you pull a tube and listen?
Still enjoying the Amperex 7308 with ~200 hours. They were just what my system ‘needed’ vs. the Tungsram, which I find in retrospect, meh plus and the stockers just meh.
Yes, the BHK preamp is a vacuum tube preamplifier and its stage drives the internal zero feedback headphone amplifier so you’re listening through a tube at its input.
Thanks Paul
thank you for sharing your process, findings, and detailed notes. Very much looking forward to seeing if these tubes do the same for the BHK250 too!
FYI,
DMP is running 3.07 code – some fraction of sonic improvement may be attributable to that update…
DS Sr. DAC is running “Redcloud”
Further listening results with Telefunken E88CC / 6922 in BHK Preamp:
The most stringent test yet – “Beethoven Symphonies Nos. 5 and 7” SACD, Vienna Philharmonic, conducted by Carlos Kleiber. Telefunken E88CC / 6922 handled the vast range of dynamics on massed and solo instruments beautifully and conveyed the emotions in the music to where I was waving my hands as the virtual conductor (playing “air” conductor wand if that captures it better…). To my ears, extended frequency range , superior tone and timbre ,and greater clarity than either Amperex 7308 or Telefunken 7DJ8.
Michael Hedges “Aerial Boundaries” SACD – faster “attack”/leading edges, superior sustain and decay on guitar.
Henryk Szeryng – JS Bach Sonatas and Partitas for Solo Violin, CD1 – again faster “attack”/leading edges, superior sustain and decay on violin.
Pandit Hariprasad Chaurasia, “In a Mellow Mood” CD - again faster “attack”/leading edges, superior sustain and decay on flute.
“The Allman Brothers Band at Fillmore East” SACD, Disc 1 – the superior clarity and faster attack was evident in the percussion, mouth organ/harmonica, keyboards/organ, and vocals in “Statesboro Blues,” ”Done Somebody Wrong,” “Stormy Monday,” etc.
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yes indeed
That was a nudge to Ron…he loves new tubes. It appears Kevin has a bunch of these TF E88CC, I’ll probably wait and save up some lunch money, mean while I’m loving the Amperex 7308 and my new found love for HQP new ext2 filter.
Negatory. I’m loving the Amp 7308’s. And sometimes Uncle Kevaroonie can be confusing. He said the TF 6 volt sound exactly like the 7 volt. But perhaps I’ll try them when it starts snowing anyway.
The Telefunken E88CC are expensive, but “amortized” over hopeful life of tube, are worth it to my ears.
I tell myself that about all the tubes I buy
muh bruthuh
Here’s yet another weird thing: A couple weeks ago, at least one of my Telefunken 7DJ8’s failed. Uncle K replaced them under warranty and I just got the replacements and they are truly sublime. Very detailed and crisp but with zero grain up top. But most noticeable is that the bass seems deeper and has a newly defined leading edge. Nice.
But that’s not the weird thing. This is it: One of my audiophile buddies came to dinner with his wife and she handed me a box of tubes that he no longer needs, having switched to all ss (Pass). I tried his TF 7DJ8’s and they sounded completely different; dull and lifeless. Huh!?
And Brett66–I know you’re going to ask, so yes, clearer, cleaner top end and that wonderful bass definition but they don’t have that fabulous honey-delicious mid range of the Amperex 7308 which makes the A7308 still my favorite so far.
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The sound quality discrepancies with the tubes in question sound like the difference between used and unused tubes. And yes,Amperex is a killer tube. I use the 12au7 7316 in my pre and none better have I heard…
Last evening while listening, my right channel went out. I have yet to have a chance to swap two tubes to see if it failed or if the driver circuit or other in the BHK failed. The right channel became somewhat noisier about a month ago so it may have failed.
Guess the DS will be driving the M700 directly while it travels to Boulder and back…