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zk1-betsy k's (Read 15681 times)

mkoepsel

Verified Member

Posts: 32

zk1-betsy k's
09/19/13 at 05:51:01

New here, first post.
I have some betsy k's in DIY MLTL enclosures. I previously used a RH-84 SEP amp with them. I liked the combo but, I'm wanting a SET amp.
I've read all the info on the Zkit1. It looks like it would work well with the speakers.
I have a few questions about the OPT's, Hazen Mod and Upgraded caps.
I read a post that stated the Hazen mod is on the new board. Is this correct?
Will the 6ohm 8k opt's be ok with the Betsy k's 8 ohm drivers? If not what should I use?
What upgraded caps are being used and where?

Looking forward to building the amp. Thanks for any info and help.

Mark

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Lon Seasoned Member "Love without guts is worthless!" Philip K. Dick Posts: 23495	Re: zk1-betsy k's Reply #1 - 09/19/13 at 11:59:34 Mark, no experience building and don't have an answer to your questions but wanted to say: Welcome.
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mboxler

Senior Member

Posts: 89

Re: zk1-betsy k's
Reply #2 - 09/19/13 at 14:43:01

Hey Mark

Welcome! Here's what I know...

The Hazen mod IS on the new board, as well as the virtual CT for the AC heaters. Hazen mod uses two of the 4 Cornell Dubilier Polyester Film Capacitors 400V .1UF in the BOM.

Not sure on the OPT's. I'm using the 6 ohm OPT's into 8 ohm speakers...seems to work fine for me.

I believe Steve is now using the Jupiter HT-Series Beeswax Paper Aluminum Foil Capacitors for the coupling caps.

http://www.partsconnexion.com/capacitor_film_jupiter.html

They are $33.25 each (plus shipping). I'm using them. Can't remark on the improvement, but others may be able to discuss this further. You can always try the Cornell Dubilier's first. The upgrade is easy to do.

Hope this helps.

Mike

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mkoepsel Verified Member Posts: 32	Re: zk1-betsy k's Reply #3 - 09/19/13 at 16:42:52 Thanks for the welcome! I saw the extra .1uf caps in the BOM. I was wondering where they went. :-? Now I know. Those jupiter caps are expensive. If I build this, I might use Russian k40's PIO caps. On the PT, I wonder if I could use a real CT 6.3 instead of using the two resistors. Mark
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mboxler Senior Member Posts: 89	Re: zk1-betsy k's Reply #4 - 09/19/13 at 19:17:36 Yes you can. Here's a link to an article that describes any small advantage a virtual CT would have. http://www.valvewizard.co.uk/heater.html Good Luck! Mike
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mkoepsel Verified Member Posts: 32	Re: zk1-betsy k's Reply #5 - 09/20/13 at 00:23:29 Hey that is a good link. Thanks! Both methods have their advantages. I'm currently finishing up my Fender 5F1 clone amp. The zkit1 is next. It takes Edcor a while. I'll get the PT and OPT's ordered. I might simulate the PS in PSUDII. I'll see if I could add a LC section in the PS. Mark
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mkoepsel Verified Member Posts: 32	Re: zk1-betsy k's Reply #6 - 09/20/13 at 16:14:10 I have another question. On the Hazen mod the caps goes from pin 6 to pin 3 on the SV83. Does that sound correct? I looked all over the forum couldn't verify what's done. Mark
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mboxler Senior Member Posts: 89	Re: zk1-betsy k's Reply #7 - 09/20/13 at 21:10:16 Yes...between the cathode and the suppressor grid. https://www.decware.com/newsite/paper145.htm Again...the Zkit1 board has a place to solder the capacitor. Mike
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mkoepsel Verified Member Posts: 32	Re: zk1-betsy k's Reply #8 - 09/23/13 at 20:27:12 I have all the parts ordered. Just have to wait for edcor to build the transformers. Mark
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mkoepsel Verified Member Posts: 32	Re: zk1-betsy k's Reply #9 - 10/12/13 at 20:23:08 Edcors are here. Less than three weeks wait. Bought some Russian k40 PIO.1u/400v coupling caps. I'm not going to use a choke with it. I saw somewhere here about using a 80u to 100u cap for the second cap in the PS. Can't find it again. I might add this mod. Mark
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mkoepsel Verified Member Posts: 32	Re: zk1-betsy k's Reply #10 - 10/24/13 at 02:44:51 Amp is finished and working great. Zero hum. I'd post a pic but, I don't have a photobucket account. Love the amp. :) Mark
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mkoepsel Verified Member Posts: 32	Re: zk1-betsy k's Reply #11 - 10/25/13 at 02:19:19 Been letting the amp burn in. It just keeps getting better. I bought a nos bugleboy 6DJ8. That really did the trick for me. The amp works real well with the MLTL Betsy k's. Bass is tight and the speed of the amp is dead on. MK
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mboxler Senior Member Posts: 89	Re: zk1-betsy k's Reply #12 - 10/25/13 at 13:46:21 Congrats, Mark! Other than the coupling caps, did you do any other mods? If you have a picture, just attach it to your post. The main issue is the file size. I use Windows Paint to reduce the pixels, until the saved picture is below the 350 KB size. Mike
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mkoepsel Verified Member Posts: 32	Re: zk1-betsy k's Reply #13 - 10/25/13 at 15:28:55 Hey Mike, The only other mod I made was a 100uf cap in the second PS cap. I'll keep trying on the pics. Still cant get it to work. Mark
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mkoepsel Verified Member Posts: 32	Re: zk1-betsy k's Reply #14 - 10/28/13 at 18:03:50 Pic. I got it to work! ::)
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deucekazoo Seasoned Member Posts: 461	Re: zk1-betsy k's Reply #15 - 10/28/13 at 18:13:41 Looks great.
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mkoepsel Verified Member Posts: 32	Re: zk1-betsy k's Reply #16 - 10/29/13 at 04:27:57 Thanks!! Mark
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4krow Seasoned Member IMAGINE WHIRLLED PEAS Posts: 1607	Re: zk1-betsy k's Reply #17 - 02/18/14 at 02:03:30 Mark, as good as this looks, I just gotta see the underside.
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mkoepsel Verified Member Posts: 32	Re: zk1-betsy k's Reply #18 - 03/25/14 at 03:20:01 I've been using the amp for 6 months now. It's performing well. Just wanted to update. I have just finished building Pensil's with Alpair 10p drivers. Although the 10P's are 89.7db spl, the amp works very well with them. SQ is greatly improved over the BetsyK's. It's a good combo for smaller listening rooms. Mark
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