Going to build Gunevere with you guys... [message #30630] |
Sun, 20 February 2005 12:58 |
PakProtector
Messages: 935 Registered: May 2009
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Illuminati (2nd Degree) |
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slight changes to accomodate what I have on hand. Hammond 261G6 with a hybrid SS/valve rectifier( still a 6CA4). Amplifier valves are 12B4's 'cause I don't need the gain and I already have two holes in the chassis from when it was the Foreplay Imposter built with 5687's. L-C supply with the big cap and a 157G Hammond. Chassis is only 5 3/4 by 11. space is at a premium. I hope I can cram it all in. regards, Douglas
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but of course... [message #30637 is a reply to message #30636] |
Mon, 21 February 2005 16:34 |
PakProtector
Messages: 935 Registered: May 2009
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Illuminati (2nd Degree) |
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I have to get the R-set 1k trip pots. I hope R-S has them. I'm getting the little heatsinks from themtoo. 4-40 screws from Lowes to attach them to the TO-220 MOSFETS. I loked at the box, there is no way I'm getting one of those 100-mike Pop-can sized caps under there. the sol'n is even cheaper. A trip to the photo shop for some disposable flash cameras. They have 100 uF/330 volt flash caps inside. a few hundred mikes of them ought to do the trick. I may put in a 6NO30 delay relay to turn on the 6CA4's heater...probably just put in a 40k bleeder resistor. Perhaps 33k as I have soem IRC GS3 3W metal film. The small resistro provides enough draw to pull the voltage significantly lower than root2* RMS. I hope my camera works well enough with close ups. This is what it looked like with two 5687 and ForePlay circuit. regards, Douglas
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Eiclones? [message #30639 is a reply to message #30638] |
Mon, 21 February 2005 17:58 |
PakProtector
Messages: 935 Registered: May 2009
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Illuminati (2nd Degree) |
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Please check the scale. those power valves are KT90's not EL84's. The OPTx is the Dynaco A441 and the choke in the middle is as big as a Mk.III OPTx. There's 280 uF of GE oilers underneath. they're two person amps. The parts compromises are Time expedients. I could make another plate, but that would take a bit ov time. Poke one more hole or start from scratch. The photo-flash are a second choice by a mile. They are easy to get and small enough. they're better than a lot of 'lytics. Just not all that compared to a good oiler. I am putting in a Hammond 157G, the little one from the cheap build I think. I have a 193C and may try cramming it on top. Look at my new linestage, I'm not restricting myself. I also want it done in time for the Bottlehead meet in Maryland in March. Nice exposure with pix and everything. regards, Douglas
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Re: Eiclones? [message #30642 is a reply to message #30641] |
Tue, 22 February 2005 07:25 |
PakProtector
Messages: 935 Registered: May 2009
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Illuminati (2nd Degree) |
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Hey-Hey!!!, I don't think the ForePlay comes with Photo-flash caps. I think they are Panasonic TSHA. The circuit of those amps uses the tertiary widing in the OPTx for cathode feedback. Cascaded diff amps, a 6BL7 to a 7236 was the last combo I tried. It sounded great. The OPTx was definately the limiting factor. I am designing a replacement on a smaller core with a better interleaving schedule. I am aiming for the Quad II 9 3/8:1 ratio. It is taking a bit of iterating, that's for sure. Remember, the flash caps are a budget and space expediency, I don't think they are designed for continious charge storage. They seem to survive it adequately( and I can put together a few hundred uF from a parallel connection ). If I didn't already have most of a chassis ready to go, I'd use the motor run caps I have in a box in a second. regards, Douglas
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changes [message #30645 is a reply to message #30643] |
Tue, 22 February 2005 19:56 |
PakProtector
Messages: 935 Registered: May 2009
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Illuminati (2nd Degree) |
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Well, after I got the little DH amp up and running, I did some surgery. I had been experimenting with pentode front ends. same general format, ground one grid, apply signal to the other and put a good CCS under the cathodes. So I took out the A441( had been runnig it Quad II style with cathode NFB with its Tertiary winding ) and put in the A431( the Mk.III OPTx ). I needed the screen taps for the E-Linear connection for the front end. 12BY7A's with a shunt regulator for its screens. It Rocks. Almost 40 watts. It makes a lot of heat though. The Dynaco OPTx is what is holding it back. I need better Iron. Not that it's bad, just the rest is that good. regards, Douglas
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