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6T9 valve RCAs and GEs
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=97
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Author:  mwhouston [ 30 Aug 2008, 21:50 ]
Post subject:  Re: 6T9 valve RCAs and GEs

billnchristy wrote:
Yeah I was going to go Edcor too...definitely the best low priced ones I have seen.
Has anyone used their guitar trannys? They are spec'd 40-18k vice 70-18k and are in a lot lower impedances.


I may just add the Edcors I got were only rated to 18Khz. But good manufactures spec. the trannies at full power. So if the tranny is under driven a better response can be obtained. The Edcors I used were rated 15W I'm lucky to drive 1 or 2W through them therefore 20Khz response.

Author:  Gio [ 31 Aug 2008, 10:54 ]
Post subject:  Re: 6T9 valve RCAs and GEs

mwhouston wrote:
Gio, maybe I'm using the wrong term but to me in the 6T9 cct. here are input caps and one coupling or interstage cap (.01uf). Have I used the wrong term for the wrong term??

Yeah, input coupling is the proper term. My bad. So you changed these both to 0.22uF?

billnchristy wrote:
Has anyone used their guitar trannys? They are spec'd 40-18k vice 70-18k and are in a lot lower impedances.

Do you mean for hi-fi usage? I looked at the pages a while back and was wondering the exact same question. I know Bruce is a fan of Edcor iron, hopefully he will chime in.

billnchristy wrote:
This looks like a fun project! Maybe I can make a bi-amp system and run tweeters off these. :P

That is exactly what I do with my 50EH5 Tube Amplifier and Radio Shack 40-1310 Super Tweeters.

Author:  billnchristy [ 31 Aug 2008, 11:07 ]
Post subject:  Re: 6T9 valve RCAs and GEs

Yeah for hi-fi...they have the same rating on the upper end but lower extension. Not only that but they come in some nice low impedances to run silly tubes. Nothing I have found is low enough for the 6as7 though...I really wanted something to work with those since AES has them for $2 now.

Author:  mwhouston [ 31 Aug 2008, 17:29 ]
Post subject:  Re: 6T9 valve RCAs and GEs

Gio wrote:
mwhouston wrote:
Gio, maybe I'm using the wrong term but to me in the 6T9 cct. here are input caps and one coupling or interstage cap (.01uf). Have I used the wrong term for the wrong term??

Yeah, input coupling is the proper term. My bad. So you changed these both to 0.22uF?

billnchristy wrote:
Has anyone used their guitar trannys? They are spec'd 40-18k vice 70-18k and are in a lot lower impedances.

Do you mean for hi-fi usage? I looked at the pages a while back and was wondering the exact same question. I know Bruce is a fan of Edcor iron, hopefully he will chime in.

billnchristy wrote:
This looks like a fun project! Maybe I can make a bi-amp system and run tweeters off these. :P

That is exactly what I do with my 50EH5 Tube Amplifier and Radio Shack 40-1310 Super Tweeters.

Gio, amazed to hear you used your small valve amp to drive a tweeter. I would used the 6T9 and your 50EH5 as general amps rather than anything specific. If I was going for a tweeter only amp I would use a simple transistor amp. Or a low wattage chip amp direct coupled. Don't need a lot of watts and design it for the upper frequency range. We both know the chip amps (with no sig. caps) have a very extended and clean frequency range.

Small tube amps to drive mid-range, maybe, to get the nice warms and natural mids that transistor amps appear to struggle with. What is the upper frequency range of your 50EH5??

Can't see any reason why you can't used guitar OPTs for hi-fi if the specs are OK. It also depends on how high you want you Hi in Fi?

Author:  Gio [ 31 Aug 2008, 20:39 ]
Post subject:  Re: 6T9 valve RCAs and GEs

Hi Mark,

You are 100% correct. The only reason I use it is because I have it lying around. Yes, a Class AB chip would be all that is required. That little 50EH5 is only good from about 100-150Hz up.

Author:  mwhouston [ 31 Aug 2008, 21:09 ]
Post subject:  Re: 6T9 valve RCAs and GEs

Gio wrote:
You are 100% correct. The only reason I use it is because I have it lying around. Yes, a Class AB chip would be all that is required. That little 50EH5 is only good from about 100-150Hz up.

That is an impressive frequency range!!!!! Are the OPTs wound on cryptonite????

Thanks for putting the OBs up. There sound is better than my book shelfs. More detail.

Author:  billnchristy [ 04 Sep 2008, 09:29 ]
Post subject:  Re: 6T9 valve RCAs and GEs

I am really interested in the UL mod. I know it sounds easy but I need to see it...I am that kinda guy. Did you put a switch in so you can run either way?

I think I am going to try the 5k GSX-10-4 for mine. I really wish they made OPTs with multiple impedence taps on the output side.

Author:  billnchristy [ 04 Sep 2008, 11:24 ]
Post subject:  Re: 6T9 valve RCAs and GEs

Another couple of questions:

1) all non-listed resistor values are 1/2w correct? (edit, actually they look like 1/4?)
2) Snubbing is the same as bypassing no? basically just a small cap around the big cap?

I am working on a parts list sheet like I did with the 24v aikido, I will post it when it is finished.

Author:  Gio [ 04 Sep 2008, 12:17 ]
Post subject:  Re: 6T9 valve RCAs and GEs

billnchristy wrote:
I am really interested in the UL mod. I know it sounds easy but I need to see it...I am that kinda guy. Did you put a switch in so you can run either way?

Hi Bill. Mark gave me this project a while back but I have been busy. I will get the UL Conversion page up tonight.

Yes, you can use a switch. Alex used a switch on his Single Ended KT88 Tube Amp. For even more flexibility, I would put a switch on the NFB so you can turn that on and off too.

Author:  billnchristy [ 04 Sep 2008, 12:37 ]
Post subject:  Re: 6T9 valve RCAs and GEs

Don't rush on my account!

Mark,

It is a good thing you beefed up the power supply because I started digging and the 6T9 will pull a total of 36.5ma per tube so that 60ma tranny they specify is severely under-powered.

I just PSUD'd a new design, it gets 243v on the output but is simpler and has mucho more capacitance:

It is an Edcor XPWR105 (180-0-180v) 250ma to a 2200uf cap (C filter) then to an RC filter with 50 ohm and 100uf cap.

Would I be safe to assume I can keep the 5w rating on the resistor or should I step up to a higher wattage?

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