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Old 30th March 2010, 02:05 AM   #21
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Different folks with different 'lobes but I really luv the EH 'fatbottle' 6CA7 and recommend them highly.

With the Simple set-up the way you see it in the above pic including Transcendars, they rock, swing and pizzicato like nothing else I've tried. I have thought about 'stepping out on them' tho' with the Genelex re-issue KT-66s.
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Old 30th March 2010, 02:16 AM   #22
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Quote:
Originally Posted by rknize View Post
...you have to design for the least common denominator and so you end up running the bigger tubes at a lower bias than you'd want.
I think that sums up how I felt about the KT90 in my Simple SE. The power transformer I used is rated for 175mA, and the filter choke only 150mA. I probably need a fair bit more than that to properly feed a pair of KT90.

Click the image to open in full size.
http://i69.photobucket.com/albums/i4...E/P1120152.jpg
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Old 30th March 2010, 03:05 AM   #23
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Quote:
Originally Posted by BillEpstein View Post
Different folks with different 'lobes but I really luv the EH 'fatbottle' 6CA7 and recommend them highly.
I like them too...better than the 6L6, actually.

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Originally Posted by Ty_Bower View Post
I think that sums up how I felt about the KT90 in my Simple SE. The power transformer I used is rated for 175mA, and the filter choke only 150mA. I probably need a fair bit more than that to properly feed a pair of KT90.
Indeed, they like to be run hard. They end up idling a little under 100mA with the lowest bias resistor setting I have and they don't seem to break a sweat doing it.
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Old 30th March 2010, 11:16 AM   #24
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Quote:
Originally Posted by BillEpstein View Post
Different folks with different 'lobes but I really luv the EH 'fatbottle' 6CA7 and recommend them highly.

With the Simple set-up the way you see it in the above pic including Transcendars, they rock, swing and pizzicato like nothing else I've tried. I have thought about 'stepping out on them' tho' with the Genelex re-issue KT-66s.
Bill, I've located the Aerovox company site and was pleased to learn that one can buy from them direct.

But when looking at the run cap section of their online catalog, I'm not sure which one (or pairing) would be the best option. I've linked to their on line catalog here, could you by chance, if you have the time, look at it and share some thought on what would be the best bet? I'd certainly appreciate it.

AC Motor Run Capacitors

Thanks for the input guys, I'll be ordering iron today.

Rick
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Old 30th March 2010, 11:28 AM   #25
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Quote:
Originally Posted by rknize View Post
I like them too...better than the 6L6, actually.



Indeed, they like to be run hard. They end up idling a little under 100mA with the lowest bias resistor setting I have and they don't seem to break a sweat doing it.
Russ, okay, here's where I prove just how newby I regrettably am.

Lets say I just simply use the resistor values as listed on George's tutorial, what would be the best tubes to use in that instance? While I'm obviously wavering here, I'd probably just order the Genalex KT-88's if I had to do it today. In your opinion how well (or optimum) would these be with the "stock" configuration?

Thanks for your patience.

Rick
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Old 30th March 2010, 01:14 PM   #26
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All my experience is with the "Z" coded Supermet units with a "P" that indicates Supernol impregnate of 370 and (apparently obsolete) 400 VAC units in 1 3/4" oval cans.

I use them in speaker crossover, as final PSU caps and parafeed caps.

I've heard that voltage parameters effect cap performance so you may want to stick with 370 to 440 VAC, which, if you're not familiar with the conversion to vDC is times 1.5, I think.

No doubt someone will come along and insist the round cans are better or SuperSoy sounds better than SuperNol but I think you'll be fine with most of the listings.

These guys eBay Store - JEA CAPACITORS: Capacitors, Snap-in, Computer Grade have been good suoppliers for me and a search of E-Bay just now for "aerovox motor run" yielded this aerovox motor run, Business Industrial, Electronics. Great deals on eBay!

Hope this helps...
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Old 30th March 2010, 03:20 PM   #27
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Quote:
Originally Posted by Rick J. B. View Post
Russ, okay, here's where I prove just how newby I regrettably am.

Lets say I just simply use the resistor values as listed on George's tutorial, what would be the best tubes to use in that instance? While I'm obviously wavering here, I'd probably just order the Genalex KT-88's if I had to do it today. In your opinion how well (or optimum) would these be with the "stock" configuration?
The answer to your question, unfortunately, depends on a great many things. The long version of the answer is contained in this table:

Tubes & Transformers

You can see from the Diss numbers (orange meaning you are running them hot, but not dangerously so...those are the red numbers). These are all computer simulations, but they give you an idea of the trade offs. You can see how the resistor value affects Diss, but you can also see how the B+ voltage and the primary impedance of the OPT does as well. If you look at the far right, the 2nd order distortion values tend to go down and the dampening factor goes up as you run the tube hotter. You are trading tube life for improved sound.

However, since you have chosen the same iron that I have, I can actually answer your question a bit more directly, in this case. My SSE has six resistor settings (they have funny values because it is actually a switched resistor in parallel with a fixed 680 ohm) and I use them as follows:

564 ohm - EL34s and smaller 6L6s that run hot
468 ohm - EL34s hot...don't use this one much
434 ohm - JJ 6L6GC and I think EH 6CA7
389 ohm - SED KT88 likes this setting
357 ohm - Use this one if I don't want to run the next two really hot
340 ohm - Tung-Sol (reissue) 6550 and EH KT90 sound their best here

Since I have never tried the Gold Lion KT88, I can't say where it will sound its best. However, since it is made by New Sensor just like my Tung-Sol 6550 and George's EH KT88, I'd bet they would like to be run hot. However, they are expensive tubes.

These resistors are cheap, so just get a few different pairs. Maybe a pair of 560 (in case you want to try a smaller tube) and a pair of 390 and 330 to play around with big tubes.

That's just my opinion.
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Old 30th March 2010, 07:13 PM   #28
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Thanks Russ, obviously I need to give this some thought.

By the way, I've been admiring your SSE as laid out on your website. That's very attractive and looks to be a first rate build!

I did get a run cap and a choke ordered today so that's some progress. Now I just need Edcore to respond to my shipping quote request and I can get the iron headed this way. Hopefully later I can sit down and get the other items ordered from Mouser and Digikey. I guess I'll get tube sockets from Antique Audio Supply.

Rick
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Old 30th March 2010, 07:21 PM   #29
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Quote:
Originally Posted by Rick J. B. View Post
By the way, I've been admiring your SSE as laid out on your website. That's very attractive and looks to be a first rate build!
Thanks! It was one of those things where I was in so far with it that I just wanted to get it done. I wouldn't want to do that again...at least not until enough amnesia kicks in that I no longer remember how long it took...LOL.

Quote:
I did get a run cap and a choke ordered today so that's some progress. Now I just need Edcore to respond to my shipping quote request and I can get the iron headed this way. Hopefully later I can sit down and get the other items ordered from Mouser and Digikey. I guess I'll get tube sockets from Antique Audio Supply.
I have had sketchy communication with them over email. Give them a call. Once you get them on the phone they are easy to work with and you can get the ball rolling right away.
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Old 30th March 2010, 07:47 PM   #30
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Ah, okay, thanks for the heads up on that. Sheesh, you'd think by 2010 that companies would take e-mail seriously, especially when there's money to be made.

I'll give em a call first thing in the morning.

Rick
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