Home » Audio » Group Build » Here's Guinevere
notes, and a correction. [message #30069 is a reply to message #30064] Wed, 29 December 2004 15:17 Go to previous messageGo to next message
PakProtector is currently offline  PakProtector
Messages: 935
Registered: May 2009
Illuminati (2nd Degree)
Here are some answers:
R3 is a 500k. it serves very little purpose, but is good to put in to take care of smallDC when in operation

R1 is a carbon comp, quarter of a watt. Mouser has them cheap from XIcon. value is between 510R and 1k. I have used 510 with no troubles, but if you find 1k to be a useful thing, bet them in qty...

S2 is the Mute, short it out and you won't have to worry about a 'thump' on start up.

There is a mistake!!!!

P1 in the source-gate circuit should be configurd as a variable resistance, tie the end at the plate to the wiper and we'll be fine.
regards,
Douglas



Re: Here's Guinevere [message #30070 is a reply to message #30068] Wed, 29 December 2004 15:30 Go to previous messageGo to next message
Damir is currently offline  Damir
Messages: 1005
Registered: May 2009
Illuminati (2nd Degree)
Then, IMO it is best to substitute pot with discrete resistor(s). Add a grid stopper resistor, and maybe an additional gread leak. B+ will be about 200V, and Uak~100V-110V. Two cheap red LED in series, and bias voltage Ugk will be about 3,4 - 4V. Ia=15mA seems fine. But, anode of the LED (longer lead) must go to the tube cathode, and cathode of the LED(shorter lead) to the ground. When we reach the final design, I can PC-draw it and send.

Grid stopers [message #30071 is a reply to message #30070] Wed, 29 December 2004 16:13 Go to previous messageGo to next message
PakProtector is currently offline  PakProtector
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The grid stopper is a good idea. I have made the suggestion to buy the 1/4 watt 500-1k grid/gate stoppers in bulk, they're quite cheap in 100 count from Mouser...one size will be close enought to fitting all.
regards,
Douglas


Here's Guinevere/BOM [message #30085 is a reply to message #30067] Tue, 04 January 2005 10:03 Go to previous messageGo to next message
PakProtector is currently offline  PakProtector
Messages: 935
Registered: May 2009
Illuminati (2nd Degree)
Here is the parts list and some options:

Power TX, Hammond 261G6
Power choke, Hammond 157G, 30 Hy/40 mA
Filter Cap, 100 uF/370vac ASC motor Run from 'Midorimeadows' on ebay. Might want to buy two more for the amps-to-come
2x 9-pin sockets
5687 amplifier valve
6CA4 full-wave rectifier
DN2540N5 mosfet's from Mouser 2 minimum, but recommend 6 for later upgrade and spares

510R 1/4 watt carbon comp gate-stoppers Xicon from Mouser
1k/10 or 15 turn trim pots for setting curent 2 req'd
20 mA cheap red LED's
100k audio taper stereo volume pot( the RadioShack Alps is a good one)
4 RCA jacks
5-7.5 uF output coupling caps. ASC from Allied in 330 vac is ~$6 ea.

Filament TX, 12.6-0-12.6 @2A ( 25.2vac CT )from RadioShack
2x 4700 uF, 25V filter caps
~10 1.5R 2W resistors to adjust voltage( C-R-C filter ), Mouser has 'em.
Two diodes, 5A min, 50V min PIV for full wave rectifier( CT is ground )

Mute switch, DPST, on-off of almost any AC rating will do, RS has 'em as well as Mouser.
Main off-on switch--same sources
Fuse and holder, fuse at ~1A, maybe less. Or start at a .25 slo-blo and work your way up.

If I forgot anything, ask 'em if you got 'em.
regards,
Douglas

Re: Here's Guinevere/BOM [message #30086 is a reply to message #30085] Tue, 04 January 2005 16:17 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
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Registered: January 2001
Illuminati (33rd Degree)
Great job! Thanks for the list, that helps a bunch.

Options... [message #30087 is a reply to message #30085] Tue, 04 January 2005 19:38 Go to previous messageGo to next message
PakProtector is currently offline  PakProtector
Messages: 935
Registered: May 2009
Illuminati (2nd Degree)
Hey-Hey!!!,
there are of course a few things which can be changed...

First is the plate loads. Leave some room to convert to cascode circuit. You'll need one more gate-stopper and MOSFET. The heat-sink will get put on the new one, so a bit of flexibility in the layout will probably be useful. One sounds good. Cascode is bloody fantastic. Build with one first, and keep in mind there is some pedal left when you feel the need.

Any rectifier with less than 2A of heater current can be used. 6AX5 and 6BY5, and smaller the 6X5 are octal options. I just got my new PS choke in the mail from Heyboer, a 30Hy monster, at about 3x the current capacity of the small hammond and a quarter of the DCR for the new linestage design... At ~$80 it is a fair fraction of the entire cost of this project, so perhaps later. HTS 8039 if you feel the need.

If the 5687 has too much gain, 12B4 is a good sub. Two of them are required, and heater load is comparable to a 5687. You'll need a third 9-pin socket...or keep the 5687 and get an output TX. So many cool options...
regards,
Douglas

Re: Options... [message #30088 is a reply to message #30087] Tue, 04 January 2005 23:57 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18792
Registered: January 2001
Illuminati (33rd Degree)
Hi Douglas,

That's cool. I'll probably do a version with power supply sans silicon and increase the cap size 2X. I'll also use a fixed resistor instead of the MOSFET. I'm thinking about doing a building block approach where I can jumper in a CCS in place of the fixed resistor. That way I can hear the differences in different configurations, resistor, choke and various forms of active constant current sources. 'Spose the power supply could be modular too, just put a decoupling cap directly across the B+ side of the tube's plate load and ground.

Wayne

Re: Options... [message #30089 is a reply to message #30088] Wed, 05 January 2005 06:53 Go to previous messageGo to next message
PakProtector is currently offline  PakProtector
Messages: 935
Registered: May 2009
Illuminati (2nd Degree)
For that approach, you'll need a higher voltage TX. The higher voltage will also raise the minimum current requirement( so-called 'critical current' ) to achieve choke-input regulation. You might also want to add another stage of filtering to get rid of the last volt or two of ripple.

That's a nice little side-efect of the active load: high PS isolation and high zero-signal current w/o resorting to low value plate loads and high B+.

Applying Ohm's law, getting a 100V drop at 10 mA is only going to allow a 10k plate load. This will create some audible, but perhaps not detrimental effects.
regards.
Douglas

...to the soldering bench Batman!

Re: Options... [message #30090 is a reply to message #30089] Wed, 05 January 2005 07:10 Go to previous messageGo to next message
Damir is currently offline  Damir
Messages: 1005
Registered: May 2009
Illuminati (2nd Degree)
For "passive" experiments, adding C in front of the L (CLC supply) would "rise" B+ at about 300V...

Re: Here's Guinevere/BOM [message #30091 is a reply to message #30085] Thu, 06 January 2005 21:14 Go to previous messageGo to previous message
Manualblock is currently offline  Manualblock
Messages: 4973
Registered: May 2009
Illuminati (13th Degree)
Thanks T; Haven't had lots of luck with parts ordering of late but... here we go!

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