Search found 281 matches

by sbench
Thu Oct 04, 2012 10:53 pm
Forum: Sim City
Topic: Drop Down Menus for selecting your tube
Replies: 28
Views: 62190

Hi Paul, The models certainly are a motley mixture from a lot of sources. As people notice limitations, I'll go thru them and update as needed. Let me look through it and see if I can provide a better model for the 'BH7. From your description it seems as though you are looking for A2 operation. As ...
by sbench
Sat Sep 22, 2012 5:37 pm
Forum: Sim City
Topic: 842 Triode Spice
Replies: 7
Views: 8157

I find that when I do some very complex simulations, the matrix math seems to get complex enough internally to cause those kind of problems. It gets particularly frustrating when you're using LT built in op amps and whatnot. Sometimes using GEAR analysis will relieve the problem. Also, try the .noo...
by sbench
Wed Sep 19, 2012 2:05 pm
Forum: Sim City
Topic: Drop Down Menus for selecting your tube
Replies: 28
Views: 62190

Added 842 to the list. In this version of triode_nh.txt the devices modeled are 01A, 01A_old, 205D, 2A3, 2A3_sofia, 2C51, 3A5, 3CX300, 6AM4, 6AN8T, 6AS7_6080, 4x6AS7_6080, 6AQ8_ECC85, 6BL8, 6BM8, 6BQ5_EL84, 6C33C_sofia, 6C4C, 6C45-PE, 6CG7, 6CW4, 6CG7, 6DJ8, 6H30, 6HV5, 6J4, 6J6, 6N1P, 6N6P, 6SL7GT,...
by sbench
Wed Sep 19, 2012 2:00 pm
Forum: Sim City
Topic: 842 Triode Spice
Replies: 7
Views: 8157

Adding 842 to the Triode drop down list. Enjoy,
Stephie <3
by sbench
Mon Sep 17, 2012 7:22 pm
Forum: Sim City
Topic: 842 Triode Spice
Replies: 7
Views: 8157

As I get an opportunity, I'll create a model and update the files... probably a few days. Unless, of course, someone wants to use that build model I posted and submit the resulting parms. :wink:

Stephie <3
by sbench
Wed Jul 25, 2012 11:49 pm
Forum: Circuits
Topic: for the fun of it screen volume control
Replies: 2
Views: 4892

Hi, Actually that's pretty easily. Replace your screen voltage source (V4) with a "Behavioural source" (BV in the component list). The function exponential function is then implemented as an equation of time. (See the "help" box for circuit elements and scroll to BV. The equatio...
by sbench
Fri Jul 20, 2012 10:59 pm
Forum: Lurkers Lounge
Topic: D3A
Replies: 10
Views: 12679


I think they are still available in Europe. The last ones I bought were in stock in Washington state or Oregon. They are still listed at vacuumtubes.net

Remember D3a = 7721.

Good Luck.

D3a is a very nice sounding tube!
by sbench
Fri Jul 20, 2012 3:17 pm
Forum: Phono
Topic: C3G pentode for phono use ?
Replies: 16
Views: 29762

gurevise: The sim I did was pretty much what was posted in the thread... steep rolloff at high frequencies, leading to amplitude and phase funnies. The AC vs DC loads. Since the 5687 was running unbypassed, the output resistance is higher than you might have planned for. The load on that circuit (n...
by sbench
Tue Jul 17, 2012 1:52 pm
Forum: Phono
Topic: C3G pentode for phono use ?
Replies: 16
Views: 29762

I tend to agree. I did a quick Spice of the comp network and got a reasonably "muffled" response. A "quick fix" is to remove C4, but that isn't the best solution either. Dynamically, with varying signals, the relatively high ratio between "AC load" and "DC load&quo...
by sbench
Mon Mar 26, 2012 2:40 pm
Forum: sbench 101
Topic: RAT tube tester updates?
Replies: 7
Views: 9828

Goodness. That tester seems to keep coming around. I have recently answered a few questions on it on my private email channels as well. :shock: Actually, I think someone actually did a PCB for that. Try the geek zone forum at http://geek.scorpiorising.ca/GeeK_ZonE/index.php If I recall correctly the...
by sbench
Tue Feb 28, 2012 2:50 pm
Forum: Circuits
Topic: GM70 into A2
Replies: 26
Views: 28384

Stephie, How low in impedance does the grid drop do you think when in A2? It didn't seem to drop below 10K if I recall correctly when I was putting them on paper, meaning it shouldn't be to hard to drive if you have the voltage swing. There seems to be many tubes that could drive them, but your loo...
by sbench
Fri Feb 24, 2012 9:51 pm
Forum: Circuits
Topic: GM70 into A2
Replies: 26
Views: 28384

A quick model up shows the GM-70 operating PP Class AB1 (not driven into grid current) can provide about 150 watts. 8kCT to 8 ohm output transformer, 1500 volt anode, -170 volts bias for about 48 mA per tube quiescent current. The 170 volt bias suggests 340v p-p drive (120v RMS) are needed on each g...
by sbench
Fri Feb 24, 2012 3:29 pm
Forum: Circuits
Topic: GM70 into A2
Replies: 26
Views: 28384

P-P makes things easier in a number of ways, since even order products cancel. DC balances so the iron doesn't have to be as large for a given power level, and it is WAY more efficient. You get a lot more power, sometimes 3x as much as two paralleled SE tubes. Many people do not consider even the be...
by sbench
Wed Feb 22, 2012 10:44 pm
Forum: Circuits
Topic: GM70 into A2
Replies: 26
Views: 28384

G'day Drew, Some people are not bothered by paralleling tubes, others find the smearing you mention. I personally find that if you match the tubes AT SEVERAL OPERATING POINTS in the range you are expecting to operate, then they behave themselves and you get no smearing. The problem with matching onl...
by sbench
Wed Feb 22, 2012 2:44 pm
Forum: Circuits
Topic: GM70 into A2
Replies: 26
Views: 28384

I have made A2 amps from 841s and 809s. I find them quite good, but not quite as warm as A1. What I find in the 841 amp is a very detailed and accurate sound. Pleasant to listen to, but somehow darker and more sterile sounding than A1 amps. The real key in those amplifiers is to make the transition ...
by sbench
Tue Feb 21, 2012 10:07 pm
Forum: Circuits
Topic: GM70 into A2
Replies: 26
Views: 28384

That's an excellent point. I've never physically met a GM-70, so the sounds are only from second hand info. Also, it is now ALWAYS true that the "hottest" operating point corresponds to the best sounding one. The data above is only from a theory view... I've built 845 amps, but not GM-70 o...
by sbench
Tue Feb 21, 2012 8:56 pm
Forum: Circuits
Topic: GM70 into A2
Replies: 26
Views: 28384

For A1 operation, it looks like 30 to 35 watts into 10k is about the limit. The 50 watts I described above does include transformer losses etc, so from a practical viewpoint you are probably comparing a 30 watt A1 to a 50 watt A2 amplifier. For that added power, you end up with a 3 stage vs 2 stage ...
by sbench
Tue Feb 21, 2012 7:18 pm
Forum: Circuits
Topic: GM70 into A2
Replies: 26
Views: 28384

Awww, over 2kV of output? :wink: What Spice land shows is 6SN7 as a cathode follower: +300 volts on the plate, -127v on the cathode and a 30k resistor to -350 volts. The -127v couples to the GM-70. Adjust the bias by pot on the grid of the 6SN7. The gain stage is a cascode 6N1P/6N1P stage, with a 15...
by sbench
Tue Feb 21, 2012 3:55 pm
Forum: Circuits
Topic: GM70 into A2
Replies: 26
Views: 28384

Hi Drew and all, For the GM70, one operating point appropriate for A2 operation looks like it could be 1250 volts and 100mA, loaded into 12.5k load. This would require about -128 volts on the grid and about 300 volt peak to peak signal (Limits of -278 volts and +22 volts). Into 12500 ohms, that woul...
by sbench
Tue Jan 03, 2012 6:01 pm
Forum: Sim City
Topic: A tale of two simulators
Replies: 3
Views: 6558

Dave is right, and something that trips up some people using LTSpice. The value that you enter in LTSpice for "amplitude" is peak, not peak to peak nor RMS. You can easily verify this by plotting that "250 volts" in LTSpice. As entered, the rectified output should hover near 250 ...
by sbench
Fri Dec 16, 2011 3:12 pm
Forum: Sim City
Topic: InverseRIAA Generators
Replies: 3
Views: 6325

The 0.1 estimator is ever so slightly low, as you pointed out. (by .089 dB). If you want it EXACT, then the normalization should actually be 0.10105. You can set it up in LTSpice easily enough... just do a frequency response (AC) analysis from 999 to 1001 Hz, using 1000 or 10000 steps. The 0.1 facto...
by sbench
Mon Dec 12, 2011 5:38 pm
Forum: Sim City
Topic: InverseRIAA Generators
Replies: 3
Views: 6325

InverseRIAA Generators

I noticed we have several essentially identical Inverse RIAA generators being used, so I thought I'd do a sort of universal one. Place the attached INVRIAA.ASY file in the spice library symbol directory (under "special functions" is a good choice), and the attached INVRIAA.TXT file in the ...
by sbench
Mon Nov 28, 2011 4:32 pm
Forum: Attenuators
Topic: concerning slagle transformer VC
Replies: 2
Views: 3046

Well, now,,, let's not get too hasty. :o IF you're willing to alter things ever so slightly... You *could* :wink: separate the "top"winding (the one going from the top of the autoformer to the first tap point), and call that the input; making it a transformer! Then, assuming you're happy w...
by sbench
Wed Nov 02, 2011 6:40 pm
Forum: Sim City
Topic: Drop down transformer models for LTSpice
Replies: 13
Views: 30630

For the capacitance, a LOT depends on how it's wound. For instance, bi-filar winding increases the coil to coil capacitance, but also provides better coupling than isolating the windings which decrease the capacitance but also the coupling. Ballpark values? Perhaps 100pF pri to pri, 50pF sec to sec,...
by sbench
Wed Nov 02, 2011 2:01 pm
Forum: Sim City
Topic: Drop down transformer models for LTSpice
Replies: 13
Views: 30630

P.S. You can trell you got it right if....

Connect the primary to a voltage source whose internal resistance is what youassume to be your primary impedance level (1.5k) and the secondary to your 8 ohm load. Run an AC simulation. Read the voltage on the PRIMARY. Should be -6dB.

-Stephie
by sbench
Wed Nov 02, 2011 1:56 pm
Forum: Sim City
Topic: Drop down transformer models for LTSpice
Replies: 13
Views: 30630

Hi Again. Essentially correct! Your two primary inductors in series would be 12Hy with 25 ohms each, giving a coupled inductance of 48Hy. The impedance ratio=the inductance ratio, so for a 1.5k impedance primary and an 8 ohm secondary, the total secondary inductance is .256Hy with .26 ohms. Since yo...
by sbench
Tue Nov 01, 2011 9:52 pm
Forum: Sim City
Topic: Drop down transformer models for LTSpice
Replies: 13
Views: 30630

Hi Christian, What's the resistance of the primary? To a very rough approximation the ballpark inductance can be approximated by the formula R/(2*pi*f). You *could* assume 1.5k/25 = 60Hy, but I would bet that it is lower than that. Sometimes the LF response assumes a low source resistance. If the pr...
by sbench
Fri Oct 21, 2011 8:13 pm
Forum: sbench 101
Topic: Subwoofer Single ended tube OTL amp?
Replies: 6
Views: 18858

Lowthers also have reasonably high efficiency, so the power output required isn't too high, making it nice for OTL purposes. One could argue that having an output inductor required disqualifies things from OTL status. The above amp would NOT be good for wideband; you'll hear the "breathing"...
by sbench
Mon Oct 03, 2011 10:03 pm
Forum: sbench 101
Topic: LR frequency anomolies.
Replies: 2
Views: 5748

There were a number of value changes between the Lundahl iron and your nickel. Remember the HF iron from Lundahl was 450mH and yours is 1H. That necessitated R changes. The "stock" values with your iron aree R1/R14=169k. R7/R19=13.3k. R2/R15=5.62k and R8/R20=750 ohms. If he has those value...
by sbench
Mon Oct 03, 2011 2:57 pm
Forum: sbench 101
Topic: LR frequency anomolies.
Replies: 2
Views: 5748

Hi Dave. I'm sure I have the file... I'll have to go searching for it and there's probably only a value or two tweak to fix it.

Sorry for the late response... I was out of country for a couple weeks with my sister.

Stephie <3