[Frihed89]

Quote:

Originally Posted by Skylab /img/forum/go_quote.gif Erikzen - the amp was very well packaged when you sent it to me. I don't think this was your fault in any way. In fact, it's nobody's "fault" - it's just the issue of a prototype which got a healthy workout and got tired So no worries!

Yes...worry a lot about shipping, unless you get it right and are willing to pay for it.

I import a lot of gear from North America, and I have seen it all, believe me.

Correct, secure packaging is, to my mind, NOT an extra, even if it costs $200, or more.

The best shippers I have come across use custom make high quality foam, form fitting "jigs" for their products. The jigs are made of this textured "crunchable" cell-like medium hard foam. The jig is then surrounded, on all six sides, by somewhat softer - it gives a little - foam, about 2.5" thick. This is put in a box. I then ask the mfr to do the following (or if I am in the US I ship it to myself, repack it and send it on to Denmark via USPS): add more foam (or Styrofoam corner pieces) and double boxed. The result: nothing shipped in this manner has been damaged: 2 preamps (one of them in 2 pieces), a 2-piece headphone amp, 2 more headphone amps, and 2 pairs of mono-blocks. The mfrs who do this start out with a custom foam design from a local vendor and then learn how to duplicate it on their own.

If you think this is over-kill, it's not. Of the 2 unprofessionally "home-packed" items i received, both were damaged on their way to Denmark. One was a write-off. The other cost almost as much for me to repair as to buy it!

 

[fkclo]

Quote:

Originally Posted by Frihed89 /img/forum/go_quote.gif My question is for the designer. If any one knows him, and you think it relevant, can you pass my question at the bottom along? I read all the URLs and this amp sounds very promising to me. The 6SN7GT was designed to run at 300 VDC plate. The 6BX7GT and 6BL7GT were designed for 500 VDC. I can run them at either voltage in my MPX3 SE Slam as output tubes (and have a Supra power supply to deal with this) and let me tell you they both sound a lot better at 500VDC than 300VDC. Now, I see they are slated for all of the slots in the cascade circuitry, as are the 6SN7GTs, so I concluded the plate voltage must be around 300VDC on all these tubes? Mikhail is using a cathode follower as I recall and this is a cascade, which I know little about, so my "untuttored" comment is: Is my comment about the different voltages a potential issue?

To my knowledge the latest round of design fine tuning has Phil moved towards an all 6SN7 configuration. Phil seems to be extremely impressed with the last iternation - so much so that I think he is close to finalising and freeze his design. I have no idea about the plate voltage though.

Kind regards,
F. Lo

 

[Frihed89]

OK, I was just reading the information in the URLs, and I saw pictures posted on a picture site of the circuit board and the top that indicated all 3 tubes could be used in every position (except the rectifier, of course).

 

[Skylab]

Yeah I believe that the current planned config is 6SN7 drivers and 6BL7 output tubes.

 

[Frihed89]

Quote:

Originally Posted by Skylab /img/forum/go_quote.gif Yeah I believe that the current planned config is 6SN7 drivers and 6BL7 output tubes.

Then he is running the 6BL7s at the higher plate voltages? That's a question. Also, if he can run the 6BL7 models, he can also run the 6BX7 models. The 6BX7GT can really sound good if it is driven by a slightly warm 6SN7GT (like the Raytheon) in my MPX3 Slam SE. But some like its dryness, as is.

 

[fkclo]

Hi all,

Further to the tour of the prototype to a few reputed head-fiers, Phil has done a lot of tweaking and tuning to his baby project. With his permission, I am posting some updates as extracted from our email exchange.

I hope this will keep everyone informed of the development of this much anticipated amp.

Please do note that as I am not an expert in amp design so for questions about this amp please post them here and hopefully Phil may read and respond.

Quoted (mid-Feb 2009) (by Phil) :-

[size=small]I received the Valvecode back from the machine shop with all the mechanical damage fixed. ......

After setting up both the input and output stages to Textbook 6SN7 ideal. I listened to both the Russian and Chinese 6SN7’s and found the china tubes a lot better so I used these for further evaluation. Since changing to 6SN7 values, only the 6SN7 works properly in the input position. The 6BL7 you give up a lot gain however still plenty for HD650’s also the bass gets way too lose and uncontrolled for my liking. One 6BL7 had a slight hum; however, it was a previously abused tube. The hum issue seems to be outdated in fact, it is about 70 dB down from 1 volt now...

The all 6SN7 gives a presentation that is slightly better than the previously all 6BL7 voicing. The all 6SN7 are smooth as silk and extended on the top end approaching solid-state extension and on at least one SACD selection may have exceeded anything my ears have ever experienced in top octave extension I was very pleased.

The 6SN7 dose however have limitations and being a low current tube even transformer coupled the overall presentation is polite as opposed to dynamic in fact its identical to vintage LUXMAN equipment polite extended at both ends and ultra clean. But still gutless. I soon forget about rock and pop music and look for something more minimalist to see where this Configuration fits musically. Coral music such as Arvo Part is stunning a complete rendering of all details layering and micro dynamics. Flute and strings re also extremely well served, as is voice.

Installing the 6BL7 in the output position leaving the 6SN7 in the Input added dynamics yet still maintained the tonality of the 6SN7. The 6SN7/6BL7 Combo in the 6SN7 optimized Amp works for a wider verity of music for me. With the greater punch and dynamics from the 6BL7 Micro dynamics are incredible and second only to the headcode that I have heard.

In conclusion, the 6SN7 configuration is for mega inner detail supper low noise blacker than black backgrounds and a somewhat polite refined and dignified sound, however for my wide musical styles this would require another Amplifier to use for music not suitable for this Amp such as Rock and pop. This is the best Amp for chamber music woodwinds and flute. (Superb flute in fact).

I am now listening to the 6SN7 driving a 6AS7GA. This has potential after reconfiguring the output stage for the 6AS7 leaving the optimized 6SN7 input stage intact I have a sound classic Mesa Boogie style lots of Bass more bass than LISA at full bass boost however frequency response shows this as flat so we have to re-voice the output stage for more refinement. This has potential, as one will not ever think this configuration is thin sounding. In addition to bass heavy, the sound is not thick and slow it as if threes a nimble sprinter waiting to shred off excess clothing to gain Agility. Tonal and timberial accuracy is maintained. So I believe this holds promise I am going to fine tune the voicing with this tube set to my liking and see what happens sonically.

Technically the cascode topology is perfect to compensate for the Limitations of the 6AS7 sutch as low gain and poor low-level linearity. In addition, the series connection allows operation on power supply voltages twice of what a simple common cathode configuration allows. Unfortunately the Amp must be built to ether the 6SN7/6AS7 or the 6SN7/6SN7 platform so it is not something you can just swap tubes out with. The 6SN7/6SN7 platform will accommodate the 6SN7,6BL7,6BX7 family of tubes used as output in the Valvecode or the 6AS7,6080 series of tubes as output valves. ....

..... as I would surly love the mega detail intimate experience of the 6SN7 Platform for my meditative choral and ambient music plus Acoustic guitar and Latin jazz on the Side. However , for rock and roll Blues and Country the 6AS7 platform is for me.[/size]

UnQuote.

More to follow.

F. Lo

 

[fkclo]

Here is further work by Phil as I was informed in late February 2009

Again, this is an extract from my email exchange with him. I am sharing this with Phil's prior permission. It is worth noting that Phil will be implementing his famed Bass Boost in the Valvecode.

Quote :

[size=small]I have been tweaking the VALVECODE a lot lately. I was impressed with the 6SN7 enough to use them as the tube to optimize the Valvecode Around. I tend to agree with you that I should not allow others to influence my voicings, because I do this as a labor of love for music and thus the music must be served over Personal biases. ........ I thus will continue to make my equipment natural detailed and ultra clean sounding to be a very transparent vessel for the music.

The improvements in the Valvecode have eliminated the Hum issue. The cascode circuit while offering stellar Audio performance light speed bandwidth and 1/10 the distortions of a conventional gain stage.

The down side of the cascode is its poor power supply rejection ratio and so the cascode circuit is more susceptible to hum pick up. The power supply is all ready massive with a power transformer that has extremely conservatively rated. Massive rail capacitance installed in the VALVECODE exceeding the installed capacity of a typical High End 50 watt Loudspeaker amplifier. An alternative to this chock filtering used on the Valvecode; chock has are not required or desired as chock’s can actually degrade the sound quality.

I use resistive capacitive filtering big rectifier tube and massive power and output transformers. ........ I also don’t like DC powered filaments because of the switching spikes, these spikes cause listener fatigue and can be responsible for hardness in the high frequency range. However now that I have a very silent background the true capabilities of the Valvecode become more apparent. Micro dynamics is stellar as is rendition of inner detail. Separation of closely related voices and interments are fully flushed out now. Imaging has always been a hallmark of my Amp designs and the Valvecode dose this the best out of all my Amps even the 3 channel designs.

After I was satisfied with the sound from my computers sound card, I moved the Valvecode to my primary system. This is where its TURE capabilities are showmen. I listened to three of the Cd’s ....and noted no flaw on any of them except some digital clipping on one song. Amazing how resolving an amp must be to pick up that. .... you will truly love the VALVECODE. It sounds nether solid state nor tube now, however most casual listeners sight unseen think it’s solid state. Flutes are a hard to get right and most all solid state gear make flutes sound hard and or metallic and this is what initially got me started looking into tubes.

The Valvecode as it now sounds with the 6SN7’s as both output’s and input tubes sound as sublime right up there with the HEADCODE however offering slightly different flavors. Both are dynamic POWERFULL. Oh and to finaly crown the amp an official Philip LaRocco design, I have added bass boost.[/size]

Hope you folks enjoy this.

Best,
F. Lo

 

[fkclo]

This is the last update I can offer as of now.

A while back I discussed with Phil about the potential of small, 9 pin tubes (12A?7, 6DJ8...) on his ValveCode and this update, which I got quite recently, focused in this area. However, given what have been achieved with a all 6SN7 platform with bass boost I personally do not think we are going to see 6922 tubes fitted on the ValveCode as standard.

Quote :

[size=small]... one valvecode almost ready for ..... rewiew and the 2nd valvecode soon to follow. The 1st unit should be finished by the end of this month.

I have been evaluating the 9 pin miniature tubes on the input. The 12ax7 and 12at7 family of (NOS) tubes were worse sounding that the China and Russian 6SN7's, so i abandoned there platform and moved to the 6FQ7 platform because these sounded alot better.

I also have lots of (NOS) RCA,GE and imported 6FQ7, 6GU7, 6DJ8, 6922, 6BZ7, ECC85, these all fit into a 6FQ7 socket and work great in the Valvecode although the circuit values could be adjusted to take full advantage of the 6DJ8/6922 tubes, however they perform at least as well as the others....... so in the interest of future compatibility i will leave the 6SN7 component values unless someone spicificaly requests the 6DJ8/6922 only and lose the ability to roll 6sn7/6FQ7 types. I must say the (NOS) sound alot better than new. you also can use the sophia 5U4 equlivelent rectifier tube.

..... wanted you to know i did test the small tubes and the valvecode is on track.[/size]

Unquote.

Regards,
F. Lo

 

[Skylab]

I am really looking forward to getting to audition the final production version of this amp! Phil told me it shouldn't be too much longer...

 

[ppl]

THE INPUT TUBES of the VALVECODE are Dual TRIODE type 6SN7, 6SN7GT, 6SN7GTA. Any 6SN7 compatible tube will work in the VALVECODE Input position. The below operating points are based upon a unregulated B+ Voltage of 391 volts at the Plate load resistor of the input tube. The Bottom section of the 6SN7 has a plate to cathode voltage of about 97 volts and a quiescent Class A Current of about 2.6 mA resulting in a power dissipation of about 300 mW in the Bottom section. The Top section being in series with the bottom section has the same standing quiescent current of 2.6 mA of the bottom section. With about 94 volts plate to cathode voltage, thus resulting in similar dissipation of the bottom section for a total power dissipation of both sections of the input tube of about 600 milliwatts. These operating conditions are comfortably within the operating guidelines of the 6SN7, ECC23,CV-181 type of tubes and thus should give extremely long service life in the input position.

THE OUTPUT TUBES of this Amplifier can be ether the 6SN7GT, 6SN7GTA.6BL7GTA, 6BX7GTA. Only Late model 6SN7GT or 6SN7GTA versions of the 6SN7 types are to be used in the output locations. Preferred Tubes are the 6BL7GTA or the 6BX7GTA. The VALVECODE’s. The output stage is actually driving the Load, this load in the VALVECODE’s case is its highly reactive Output Transformer, and the headphones connected it. The output stage operated heavily into Class A1 comfortably drive these coils with low distortion and stunning linearity taking full advantage of the extended bandwidth linear cascode output stage. The operating parameters of the tubes used in the output stage are close to their maximum power dissipation. Therefore, tube life of the tubes used in the output stage will require more frequent replacement than the input tubes. Do not use the 6SN7, ECC32 or the CV-181 in the OUTPUT POSITION. The 6SN7GTA is Biased at 20mA is dissipating 3.6 watts Quiescent per section (7.2 Watts total) the 6BL7GTA is biased at 40 mA and thus has twice the quiescent power dissipation(14.4 Watts total) of the 6SN7.
OUTPUT TUBES
6NS7GT,
6SN7GTA
6BL7GTA
6BX7GTA
INPUT TUBES WITHOUT AN ADAPTER
6SN7
6SN7GT
6SN7GTA
6BL7GTA and the 6BX7GTA
ECC32/CV181

The cascode arrangement places each section of the dual triode in series so matching of sections is not required however matching of Tube pairs between channels will maintain perfect channel gain balance between channels. One of the clearest explanations of the advantages of the cascode circuit I have found on the web is a slide show lecture from MIT ONLINE.

 

[Skylab]

Thanks Phil!