Home » Audio » Group Build » Going to build Gunevere with you guys...
Going to build Gunevere with you guys... [message #30630] Sun, 20 February 2005 12:58 Go to next message
PakProtector is currently offline  PakProtector
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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


Photographic report, then?:-) /nt/ [message #30636 is a reply to message #30630] Mon, 21 February 2005 15:45 Go to previous messageGo to next message
Damir is currently offline  Damir
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nt

but of course... [message #30637 is a reply to message #30636] Mon, 21 February 2005 16:34 Go to previous messageGo to next message
PakProtector is currently offline  PakProtector
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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

Re: but of course... [message #30638 is a reply to message #30637] Mon, 21 February 2005 17:09 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
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So now you tell us. Disposable camera's; let me see $1.99 vs. $8 for oilers. Hmmm.
O'Kay.
So how can you fit the Heyboeur on that tiny plate? The trans is bigger than the chassis.
Seriously; those amps look like Eiclone's. Nice.
So far my chssis is the size of a microwave oven.

Eiclones? [message #30639 is a reply to message #30638] Mon, 21 February 2005 17:58 Go to previous messageGo to next message
PakProtector is currently offline  PakProtector
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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


Re: Eiclones? [message #30641 is a reply to message #30639] Tue, 22 February 2005 05:56 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
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Yes they are gorgeous. Eiclones use KT 88's and Dyna Iron also. They are on the DIY tube site. Or some build them with custom Iron. They are copies of the old Eico HF-89 circuit. The photoflash caps like the ones in a Foreplay; right?

Re: Eiclones? [message #30642 is a reply to message #30641] Tue, 22 February 2005 07:25 Go to previous messageGo to next message
PakProtector is currently offline  PakProtector
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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

Re: Eiclones? [message #30643 is a reply to message #30642] Tue, 22 February 2005 10:15 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
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Ahh;I see, I remmember where I saw the photo flash caps now. The Eiclones use the Dyna 441 trans also.

changes [message #30645 is a reply to message #30643] Tue, 22 February 2005 19:56 Go to previous messageGo to next message
PakProtector is currently offline  PakProtector
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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

Re: changes [message #30648 is a reply to message #30645] Wed, 23 February 2005 06:48 Go to previous messageGo to previous message
Manualblock is currently offline  Manualblock
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Wait a minute; how do you know that? Is it the fact of lots of heat? The 431 is a pretty good trans right? What was it that clued you in to the trans? This anecdotal evidence is enlightening.

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