1. Summary. 29/07/2012 Steane s Sound Systems Ansett Valve Amplifier Page 1 of 10. Valve PA Amplifier. $103 ebay July 2009

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1 9/0/0 Steane s Sound Systems Ansett Valve Amplifier Page of 0. Summary Valve PA Amplifier. $03 ebay July 009 Steane s Sound Systems Pty Ltd. Model M. Microphone and Pickup inputs via -pin octal connectors ( removed). Microphone input direct to C grid in pentode configuration gain stage to microphone volume pot. Pickup input direct to volume pot. MIC and PU signals from pots are summed and taken to input of C triode configuration gain stage with output to MUSIC Tone pot and SN self-balancing paraphase splitter. Push-pull VGT pentode output to K PP to ohm transformer. HT supply from fullwave centre-tapped transformer using VG diode rectifier and series resistor-choke to cap. The OT has been changed, as the chassis shows signs of having had different mounted parts (XM39 used a 9 model OT). Two resistors and PP stage bypass cap are modern. The input C screen bypass 0.uF cap has been moved to the cathode (?). The banana plugs appear to be add-ons. A quality inspection label is mostly gone can see Wired, Inspected, Tested, Passed, with signatures. Tag with ANSETT A.N.A. BHF 3- added. Output Transformer TU0 000 (K PP, Ω output). Power Transformer 9, Dated XX NOV 9. Choke H at ma, ΩDC, Dated 3 Nov 9 Valves VG no other markings loose end VGT Miniwatt J D D VGT Radiotron 9 HF SNGT Radiotron cracked base C Radiotron (loose top) C Philips? POTs x IRC 0.MEG/C, 09/3, 00. x Morganite 00k Log; S.0 BJ Caps Ducon Aerovox EE 0 uf 00V x3; Ducon uf V x: Ducon ET 09 (code SM) Condition: Surface rust on base plate and on mounting hardware and transformer frames. OT has been changed (other fittings drilled) - present OT probably -0W TU0 (it s not Rola). Possibly 00R added to 0R W Merlin. All grommets for wire pass through and preamp valve shock mount are hardened. All electrolytic aesthetically look fine, but are very old. Changed pot. x C and x V faulty.

2 9/0/0 Steane s Sound Systems Ansett Valve Amplifier Page of 0. Modifications Megger tested power transformer and choke. Check heater voltage versus primary taps. Disconnect HT electrolytics, but leave chassis mounts in place. Remove banana sockets. Insert Speakon connector in octal base cutout. Added input socket on front panel. Added 0k grid stopper to V. Lower grid-stopper of V C triode to 00k. Add 00k grid-stopper to PI input. Moved Pickup pot to pre-pi. Moved tone to work with Pickup pot aka Marshal W tone. Replaced the power cable and faulty Tone pot.

3 9/0/0 Steane s Sound Systems Ansett Valve Amplifier Page 3 of 0 Add 0R V cathode current sense resistors, and wired sense leads to rear panel octal. Changed V grid stoppers to 0k. Add mains switch, fuse, VAC MOV to primary. Added 0.A fuse to PT secondary CT. Added k/30vdc MOV-R protection to OT primary. Added heater humdinger pot. Removed resistor in series with choke. Added snubber capacitor before choke. VS should be about 330V use 00V rated caps. Added neoprene washers to either side of valve base to increase compliance. Replaced in-situ OT with A&R OT9-; k UL with Ω output; High fidelity range suited to V. Similar UL designs for V: o Acro TO-30 OT, k PP, 0W hi-fi o Radiotronics June 9 paper on V UL by Langford Smith and Chesterman. Given the more modern Philips style in a 93 advert, and choke date of late 9 this amp is an earlier model circa Steane s Sound Systems The Powerhouse museum has a microphone from them, with a comment about them being in Melbourne, and then Sydney in 90-0's. They are identified in The Argus in October 93, and again in 9 at 90 Exhibition St, Melbourne. There are adverts in the April 99 Canberra times for "Stanes Sound Systems" who do PA's and sound for venues.

4 9/0/0 Steane s Sound Systems Ansett Valve Amplifier Page of 0 Many adverts in Radio & Hobbies from Sept 9 to Dec 9, with addresses for 0-0 Miller St Melb, and 3 Kent St Sydney, and many state and NZ outlets (eg. Lawrence & Hanson, and Homecrafts) focussing on sound reproduction equipment. 93 advert shows similar casing amplifier with ratings available of 3W, 30W and 0W, and four pots a close descendant. They had associated trading names of BRODERS PTY LTD and UNITED ELECTRONIC SERVICING PTY LTD, and became a registered company in 93 and deregistered in 999. They used a distinctive SSS badge on the amp I have. 93 advert in Radio & Hobbies Graham Scott, Russell St Toowoomba, QLD Measurements Voltage rail regulation. Rail Idle (Wurlitzer OT) Idle A&R OT 9 UL Max output VS 30V (peaks to 30V), 0mVrms ripple 300V 9V VS 0V 9V Cathode.V (ma + ma) W 330R.V (3+3mA) 0R Heater.V Heater Sec HT 3+3V VAC 0Hz nominal applied to TU0 output transformer (this was replaced by Wurlitzer and the A&R OT 9-) Winding Voltage rms Turns ratio; Impedance for K pri; Spec level; Notes Pri P-P: BLU to BRN Sec: GRN to GRN. 3.;.9 Ω; Appears reasonable for K PP Output transformer primary DC resistance: 0Ω plate-to-plate. Now Basso Project Management. Miller St is near northern section of Spencer, between Victoria and Abbotsford. Used by Briginshaw Bros in 9. Now Casablanca Media Corp. Located in central section.

5 9/0/0 Steane s Sound Systems Ansett Valve Amplifier Page of 0 Power transformer primary DC resistance: Ω, 0-0V. Power transformer secondary DC resistance: 03+Ω, V. Choke: Ω dc resistance; H at madc; H at 9mADC. 3mVrms output noise in to ohm load with pots at full level and no input (shorted at socket). Vrms output at start of clipping (W) with Wurlitzer OT. Clipping is pretty symmetric, but undriven side of PI then starts to get a scalloped dip at 0W, which is then max output level. Perhaps change PI for long-tail pair config. Tone control interacts with signal level and loading of C is not symmetric so filter response is unbalanced. Coupling caps reduced to allow tone control to roll off bass. Perhaps change to? Large hum pickup from open C, but this is reduced to negligible level with standard shell metal screen fitted. VS idles at 30V, and droops to 300V at full load. Screen voltage sags to 0V (effectively 0V to cathode) at full load tweaked by reducing dropper to k. Check design may need to modify VS,. To do: guitar check; update this doc.

6 9/0/0 Steane s Sound Systems Ansett Valve Amplifier Page of 0. Design Info. Input Gain Stage Pentode connected C gain stage. Effective signal output resistance is 0k // 00k // M ~ 0K. The C characteristic curves are same as for J, and using J datasheet tables for resistance coupled amplifier configuration with: =300V, RL=0k, Rg=00k, Rc=k, Rd=.M, gives a gain of 0. =0V, RL=0k, Rg=0k, Rc=k, Rd=.M, gives a gain of 93. In-circuit measurement is RL=0K, Rd=M, and Rg~330k (00K//M). For lower, the gain will reduce. Rc and Rd screen should be bypassed note - bypass on screen moved???. Modified to triode stage with relatively low stage gain ~, but total amp gain was too low, so reverted to pentode mode with 0R cathode, 00k anode load, and 0k screen.. nd Gain Stage Triode connected C gain stage. Supply voltage about 0V; effective signal load resistance is 00k//0k//pot; and cathode resistor is K. The plate voltage Vp axis intercept is 0V for no plate current, and the plate current Ip axis intercept is 0V / 0KΩ =.ma. The gate-cathode voltage (Ec on the graph) operating point is at Vgc=.Kx.mA = 3.V, and varies with plate current through the kω gate-cathode resistance with the characteristic shown on the graph as a line passing through Ip=3.mA for Vgk=-V, and through Ip=mA for Vgk=-0V. The intersection of the two lines is the nominal biased operating point.

7 9/0/0 Steane s Sound Systems Ansett Valve Amplifier Page of 0 The input voltage swing limit is from the bias point at Vgk=-3.V and so is fairly unsymmetrical. The triode connection tables in RCA manual suggest an Rc~k to k, which should achieve a better symmetry and the gain is about. K.3 Splitter stage A see-saw floating self-balancing paraphase splitter circuit using a SN. Driven by C so drive impedance is different for each SN triode. Gain of SN indicates imbalance may also be substantial. Cathode bias at about V and.ma per SN triode, and anode voltage at 0+=0V with a 00k load and 0V HT. Output impedances of each side are fairly similar as ra of SN is quite low. Paraphase gain is ~ + (++)/ =..

8 9/0/0 Steane s Sound Systems Ansett Valve Amplifier Page of 0 K. Output Stage In this Class AB push-pull UL output stage, one V tube is pushed into conduction and the other tube is pulled into cutoff, and there is a region of overlap where both tubes conduct equivalent levels of current. The cathodes are biased with a common resistor to ground. The A&R OT 9- presents.kω impedance plate-to-plate OPT for ohm speaker, presents each tube with a.kω load impedance for larger signal currents, and.k loading for small signal levels. Determining a suitable bias current level is not an empirical design approach, rather it is based on the following recommendations: Start with the lowest bias current possible (ie. most negative grid bias voltage), and based on listening tests, increase the bias current until the sound character is acceptable, but: use the lowest possible bias current level, as this generally increases the life of the tubes, and decreases the chance of operating at excessive plate dissipation; and keep the bias current level below 0% of the recommended design max plate dissipation (ie. <9W); and assess the dynamic loadline to see if it moves into region of increased plate dissipation. As the output loading increases, the supply voltage VS sags only a few volts from 30V, due to supply regulation. Plate DC voltage will be lower than VS by an amount up to ~0V; ie. OPT half resistance of about 00Ω with a peak current of up to about 0.A, and cathode bias of 0V. The screen voltage will correspondingly sag. Screen current level increases as Vg approaches 0V, possibly to over 0mA, with an additional drop across the screen stopper resistor. Screen voltage needs to sag to about 0+0=0V at start of overdrive to nominally operate in to knee. The maximum output valve bias current allowed is dependant on the maximum recommended plate dissipation of W for the V: Ibias(max) = Pd / Vb = W / 300V = 0mA. Ibias(nom) = 0. x W / 300V = ma. Assessing the V plate curves, which show W constant power contour, indicates how the plate will start at quiescent level of ma (V=300V).

9 9/0/0 Steane s Sound Systems Ansett Valve Amplifier Page 9 of 0 The common cathode resistance is about V / (ma + ma) = 330Ω at W. The nominal output power of the amplifier will then be: (Imax) x Rpp / = 0.09 x 0.09 x.k / =.W W K K

10 9/0/0 Steane s Sound Systems Ansett Valve Amplifier Page 0 of 0 W K K. Power Supplies The power supply is typical full-wave rectified type using double diode V and a VAC centre-tapped secondary. With a choke input LC filter, this gives about 30VDC at low load, reducing by about 0V for the V, and V for the choke DC resistance, and V for series R, at 00mA.

11 3 STEANE'S SOUND SYSTEMS AMPLIFIER S.N. M VS VS VS D C INPUT OCTAL SOCKET M M TC 0K 0.0u 00K C V 3 MICROPHONE VOLUME INPUT OCTAL SOCKET 00K 00K PICK-UP VOLUME 00K VS C V 3 TC 00K LOG 0N N MUSIC TONE SN V3a SN V3b 3 0K** 3K 0K ** N N 30K 30K uf** 0V + 0R** 3 V V VS 3 V V BRN RD BLU TRANS TU0 K P-P, 0R GR R GR OUTPUT CLIPSAL No.30 -pin socket D C 0.u K u 0V K u 0V HEATER- B 0VAC MAINS 3AG A 0 RED 0 BLU BRN 0 BLK TRANS 9 RED BLK 00V R BLK 00V 03R RED V V V R 0mA 9mA + uf 00V VS 0K 0K + uf V VS + uf 00V + uf 00V TRANS HEATER- WH.3V V BLK Replacement Part ** V, V, V3 on shock mount sockets ANSETT A.N.A. BHF 3- TAG V SN C C B A C base SN base V base V base VOLTAGE RAILS RAIL VS VS HEATER- HEATER- NO LOAD V V V V V VALVE C QTY SN V V 3 Title Size B Number Revision Date: -Aug-009 Sheet of File: C:\Program Files\Design Explorer 99 SE\Projects\Tims Drawn By: amps\amplifier Modules.ddb A

12 D STEANE'S SOUND SYSTEMS AMPLIFIER - MODIFIED S.N. M INPUT.mm Jack C V 00N 0K 0K TC N 3 00K MICROPHONE VOLUME C V TC 3 MUSIC TONE LOG N 0N 0K VOLUME PICK-UP VS SN V3a 3 VS SN V3b 0K N 0K 0K 0K uf 3V + 0R 0W SENSE V SENSE V V V 3 0R CATHODE 0R VS K 30VDC TRANS A&R OT 9- K P-P UL, +R R VS + OUTPUT Speakon - D C M 0 0u 3V K 0u 3V 00K 00K 3K N 0K 3 V V 30VDC K VS C HEATER- 0mA B 0VAC MAINS 3AG A SW 0 RED 0 BLU BRN 0 BLK TRANS 9 RED BLK 00V R BLK 00V 03R RED YEL YEL V x0 00mA V V 0NF 9mA 0K VS 0K + 0uF 00V VS 0K + 0uF 00V + 0uF 00V K TRANS HEATER- GRN.3V GRN V V SN C C 0R B V, V, V3 on shock mount sockets ANSETT A.N.A. BHF 3- TAG 3 CATHODE SENSE V SENSE V A C base SN base V base V base VOLTAGE RAILS RAIL VS VS NO LOAD 30V 0V 0V HEATER-.V HEATER- V V bias 3+3mA;.V VALVE C QTY SN V V OCTAL - REAR PANEL Title Size B Number Revision Date: 9-Jul-0 Sheet of File: \\tsclient\c\program Files\Design Explorer 99 Drawn SE\Projects\Amplifier By: Modules.ddb A