Beautiful build! Excellent quality, all the way around. Certainly commercial quality; no doubt these are for sale.-?
Beautiful circuit boards and chassis wiring. Congratulations on a fine build; I'm sure it sounds as good as it looks!
I'm surprised at the regulated screen voltage supply- tell us more about that!
Love the Tesla tubes... and the toroid!
Beautiful circuit boards and chassis wiring. Congratulations on a fine build; I'm sure it sounds as good as it looks!
I'm surprised at the regulated screen voltage supply- tell us more about that!
Love the Tesla tubes... and the toroid!
Here is my 80 watt valve amplifier.
Sounds fantastic, very detailed sound.
Sounds fantastic, very detailed sound.
An externally hosted image should be here but it was not working when we last tested it.
artosalo,
Should the 6F12 pentode screen be bypassed to the cathode rather than to 0V?
Generally want to keep screen to cathode voltage (Vg2-k) constant, as drawn the global feedback is also being applied to the Vg2-k but if I worked out phase correctly then it is being applied as negative feedback as a small "ultralinear" style feedback. Is this what you intended?
Cheers,
Ian
Should the 6F12 pentode screen be bypassed to the cathode rather than to 0V?
Generally want to keep screen to cathode voltage (Vg2-k) constant, as drawn the global feedback is also being applied to the Vg2-k but if I worked out phase correctly then it is being applied as negative feedback as a small "ultralinear" style feedback. Is this what you intended?
Cheers,
Ian
The chassis is obviously factory made. Front and rear panels are anodized and other parts matt painted.
All texts were made with laser and will not wear ever like printed texts do.
I have sold some of these amplifiers, but it surely is no business.
During prototyping stage I noticed that the linearity of the QQE03/12 depends of the g2-voltage and therefore I made it easily adjustable.
The optimum THD can be found at a bit highe (220V) voltage than the manufacturer recommended.
Similarly, the THD of 6f12p is slightly smaller when screen grid is bypassed to ground and not to cathode.
All texts were made with laser and will not wear ever like printed texts do.
I have sold some of these amplifiers, but it surely is no business.
During prototyping stage I noticed that the linearity of the QQE03/12 depends of the g2-voltage and therefore I made it easily adjustable.
The optimum THD can be found at a bit highe (220V) voltage than the manufacturer recommended.
Similarly, the THD of 6f12p is slightly smaller when screen grid is bypassed to ground and not to cathode.
So far, I have two main hollow state amps I've been listening to ever since I designed and built them
The Vixen: This one was the first hollow state design I did in 2005. Glowey bottle coolness: orange glow from the voltage reference. 6CB6 error amp and pseudotriode 6AQ5 as series pass device.
6J5 -> 6SL7 LTP -> 6SN7 Cathode follower grid drivers -> PP 807 finals (Class AB1: Po= 30W) Fixed bias with active screen regulation, lNFB + gNFB. Solid state PS with CLC filtering.
Le Renard 40W Monoblock from 2007.
6BQ7A Cascode LTP -> 6FQ7 Cathode follower grid driver -> PP 6BQ6GA finals (Class AB1: Po= 40W) Fixed bias with active screen regulation and user variable gNFB (0 -- 13dbv). Hybrid hollow state PS (5U4GB for positive rail, CLC filtering. SS diodes for the negative rail, CRC filtering.
Some more glowey bottle coolness: the big cathodes of those 6BQ7s really show up.
The Vixen: This one was the first hollow state design I did in 2005. Glowey bottle coolness: orange glow from the voltage reference. 6CB6 error amp and pseudotriode 6AQ5 as series pass device.
6J5 -> 6SL7 LTP -> 6SN7 Cathode follower grid drivers -> PP 807 finals (Class AB1: Po= 30W) Fixed bias with active screen regulation, lNFB + gNFB. Solid state PS with CLC filtering.
Le Renard 40W Monoblock from 2007.
6BQ7A Cascode LTP -> 6FQ7 Cathode follower grid driver -> PP 6BQ6GA finals (Class AB1: Po= 40W) Fixed bias with active screen regulation and user variable gNFB (0 -- 13dbv). Hybrid hollow state PS (5U4GB for positive rail, CLC filtering. SS diodes for the negative rail, CRC filtering.
Some more glowey bottle coolness: the big cathodes of those 6BQ7s really show up.
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It is based on other guitar amplifiers.
Volume control into gain stage.
Another gain stage into tome control.
Another gain stage into a phase splitter into 4 el34's.
It doesn't really have enough distortion for rock guitar but it sounds nice when used for other types of guitar sound.
It is incredibely detailed after using SS class d and class AB amps.
My Citation II died recently, and I have borrowed my Bro's hand built "Mercenary Field Amplifier"
which is an OTL integrated dual mono amp that uses (4) 6SN7's driving (8) 6AS7G's
with (2) 6CG7's driving the (2) 12AU7's in the preamp.
Its a Great amp. Too bad I've got to swap it back after he repairs my Citation II.
which is an OTL integrated dual mono amp that uses (4) 6SN7's driving (8) 6AS7G's
with (2) 6CG7's driving the (2) 12AU7's in the preamp.
Its a Great amp. Too bad I've got to swap it back after he repairs my Citation II.
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Is that a MOTOR? GENERATOR? -Nice Chassis! "Mercenary Field Amplifier" sure fits! What's under the brass security caps - bias and balance adjustments?
A Zero-center meter - for Bias, or ??? -I like the look of the meter, it really fits the whole look.
Just LOVE the overall appearance! A great look! Great alternative to Steampunk! -Looks like something out of a bunker, somewhere in the desert...!
Well... you know the Citation II is a great amp too! A true classic, up there in the top tier. It'll be good to have that back too, I'm sure.
A Zero-center meter - for Bias, or ??? -I like the look of the meter, it really fits the whole look.
Just LOVE the overall appearance! A great look! Great alternative to Steampunk! -Looks like something out of a bunker, somewhere in the desert...!
Well... you know the Citation II is a great amp too! A true classic, up there in the top tier. It'll be good to have that back too, I'm sure.
Awesome but gentle reserve grunt is my listening HiFi amp. Class A 2x20W; AAB 2x50W;AB 2x250W; choose ones B+ settings and bias on this leviathan. This amp encompasses switchmode power and requires considerable understanding of engineering specifications and magnetics. Audio b/w each channel 250W, 15Hz-55Khz and a distortion ~0.2%. Balanced Line inputs. Hum and Noise -85dB both channels.
MI mode easily accomplished with deliberate distortion in the o/p stage.
With a little skill, most constructors can deal with the metal work to cope with a finished chassis of nearly 50kg total weight with bracing and stenciling.
richy
MI mode easily accomplished with deliberate distortion in the o/p stage.
With a little skill, most constructors can deal with the metal work to cope with a finished chassis of nearly 50kg total weight with bracing and stenciling.
richy
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Richy-
I believe you showed us a corner of this beast earlier in this thread- The chassis machining really caught my eye- the hole pattern around each tube, the nameplate (or ??) with its beveled edges, countersunk flathead Phillips machine screws throughout- really great craftsmanship!
The specs are just as impressive- 0.2% THD at 250W is just amazing, and -85dBV 20kHz noise is hard to beat! -or did you mean that the noise is -85 dB Re: clipping? I can't imagine building a QUIET switchmode supply for this beastie- must have been fun!
I'm an SPS neophyte. I've co-designed just one, approx 300W off-line converter. Kinda scary to turn it on, there's no such thing as "soft start", e.g. variac- it either works very well, or it blows up in your face. And there's no such thing as an off-the-shelf design here, you really have to know magnetics. REAL engineering!
I like your small-signal tube retainers! -How did you do the lettering?
You've done a beautiful job in so many areas: circuit design, SPS design, mechanical design and in craftsmanship. Nice amp!
I believe you showed us a corner of this beast earlier in this thread- The chassis machining really caught my eye- the hole pattern around each tube, the nameplate (or ??) with its beveled edges, countersunk flathead Phillips machine screws throughout- really great craftsmanship!
The specs are just as impressive- 0.2% THD at 250W is just amazing, and -85dBV 20kHz noise is hard to beat! -or did you mean that the noise is -85 dB Re: clipping? I can't imagine building a QUIET switchmode supply for this beastie- must have been fun!
I'm an SPS neophyte. I've co-designed just one, approx 300W off-line converter. Kinda scary to turn it on, there's no such thing as "soft start", e.g. variac- it either works very well, or it blows up in your face. And there's no such thing as an off-the-shelf design here, you really have to know magnetics. REAL engineering!
I like your small-signal tube retainers! -How did you do the lettering?
You've done a beautiful job in so many areas: circuit design, SPS design, mechanical design and in craftsmanship. Nice amp!
Kruesi,
"As my Bro wrote" About the OTL integrated dual mono "Mercenary field Amplifier".
The Amp cabinet was constructed from recycled knotty pine tongue & groove paneling, aged copper; fashioned into edge trim. Rusty screws & some old
luggage hardware.
There's an Ei-core transformer concealed inside of an old gutted-out Emerson electric motor casing; mounted on top of the amp cabinet that supplies the
Hi current Mu follower preamp (6CG7's driving 12AU7 output tubes). Each Mono amp has (2) vigorous toroidals supplying the filament & B+ demands,
in total; Juicing (4) 6SN7's and the (8) 6AS7G's etc!.
The Preamp features a Master Volume Knob, L-R Trim knobs, input select knob, Headphone output. An upward movement of a hand lever on the left
side of the Mercenary Field Amplifier activates an industrial on / off button switch lighting up a jeweled lamp indicator for the Preamp. The Amplifier also
has on / off - standby switches with jeweled lamp indicators and A quick check and adjustment via a built-in switchable (L-B-R) null meter with precision
trim Pots helps to keep the unit within the Zero Zone. 8 ohm speakers work and sound great with this unit.
Incorporated into the amp are (8) dedicated Brass cap & chain covered fuses to guard the 6AS7G output tubes, limiting current and to protect against tube
failure and possible speaker blow-out. Speaker demise can happen from an intense sustained motor force of the voice coil hammering away on the speaker
cone that will cause a mechanical blowout and lets not forget that a thermal short will most certainly leave you mono-fied; Your speaker mortified (Dead);
Thus terminating one or both of Your Beloved twins.
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Kreusi, that monster 250+250W amp:-
The cue behind the consistent holes in the 4mm top plate is to make a dummy piece up drill/ get the locum exact and use it as a template. Nothing is difficult one you know how! It was based on KT88's with 4" centres, so I applied it for the KT90's.
The FFT plot of the spectrum.. despite using hard switching in the power supply, the level of noise is very low. Much reliance placed on the correct ferrites amorphous toroids and careful screening..
I too have studied many other contributions on these threads, and the level of engineering is quite remarkable. The proof of the pudding and knowledge of the enterprising discipline lies underneath the crust.
Keep up the good work.
richy
The cue behind the consistent holes in the 4mm top plate is to make a dummy piece up drill/ get the locum exact and use it as a template. Nothing is difficult one you know how! It was based on KT88's with 4" centres, so I applied it for the KT90's.
The FFT plot of the spectrum.. despite using hard switching in the power supply, the level of noise is very low. Much reliance placed on the correct ferrites amorphous toroids and careful screening..
I too have studied many other contributions on these threads, and the level of engineering is quite remarkable. The proof of the pudding and knowledge of the enterprising discipline lies underneath the crust.
Keep up the good work.
richy
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Richy-
It is such a breath of fresh air to see a project that has been engineered, not cobbled together. Nice Job! I'm impressed with the harmonic content: Just noise, it looks like; minimal 3rd, 5th and 7th-order - and beyond that, nothing that I can see except noise! The truly remarkable thing is how QUIET the switcher is! I can't see ANY signal over the noise at the switching frequency.
Yes- the knowledge lies beneath the surface; audio (and especially tube design) is an area that for some reason points strongly to the glitz and glamour whilst leaving the fundamentals often enough lost in the dust. It is indeed a pleasure to see a design that is both original and based on good engineering practices.
No reason not to marry solid-state and tube-type design; sometimes a triode is Just The Thing to use; other times the best device for the job is a MOSFET. Nice job on the switcher -AND on the amp!
It is such a breath of fresh air to see a project that has been engineered, not cobbled together. Nice Job! I'm impressed with the harmonic content: Just noise, it looks like; minimal 3rd, 5th and 7th-order - and beyond that, nothing that I can see except noise! The truly remarkable thing is how QUIET the switcher is! I can't see ANY signal over the noise at the switching frequency.
Yes- the knowledge lies beneath the surface; audio (and especially tube design) is an area that for some reason points strongly to the glitz and glamour whilst leaving the fundamentals often enough lost in the dust. It is indeed a pleasure to see a design that is both original and based on good engineering practices.
No reason not to marry solid-state and tube-type design; sometimes a triode is Just The Thing to use; other times the best device for the job is a MOSFET. Nice job on the switcher -AND on the amp!
Zandru is your brother? Cool! A hobby to share,He makes the most interesting things.
A link to his site:
Flickr: zandru's Photostream
