Howdy fellas, I've some simple SE questions...

[BillEpstein]

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.

 

[Ty_Bower]

...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.

http://i69.photobucket.com/albums/i43/Ty_Bower/Simple SE/P1120152.jpg

 

[rknize]

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.

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.

 

[Rick J. B.]

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

 

[Rick J. B.]

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

 

[BillEpstein]

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...

 

[rknize]

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.

 

[Rick J. B.]

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

 

[rknize]

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.

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.

 

[Rick J. B.]

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

 

[Rick J. B.]

Shoot!

Well I called Edcore this morning to order tranny's and they told me they would be at least 8 weeks out filling the order. I'm going to do some looking to see what my other options are. I was really wanting to go with the Edcore units as they looked to be a good value, and others have had good luck with them on the SSE. But I really didn't want to wait 2 months on them. Ugh.

Rick

 

[rknize]

They tend to arrive before their expected ship date, but yes they have a fairly long lead time. They are worth the wait, though.

 

[neonthecat]

Shoot!

Well I called Edcore this morning to order tranny's and they told me they would be at least 8 weeks out filling the order.....

Rick

Yep...that's the main downside of Edcor. I'm waiting on a set of iron for my build of the Pete Millett "Engineer's Amplifier", which is totally done otherwise.

For my SP-P, I decided on Edcor as well. I could get Hammond xfmrs locally way faster, but they are almost double the price of Edcor.

 

[Rick J. B.]

Well, hopefully they were being conservative with the time line because I called them back and placed the order. I guess I shouldn't have an issue with having everything else in hand by the time the Edcor's show.

I went ahead and went with an Eyuda run cap. I ordered it off ebay from an outfit called Midori Meadows, it shipped yesterday as did the choke from Allied.

Now I just need to decide on output caps.

Rick

 

[Rick J. B.]

Woo hoo! My tubes have shipped.

I'll be trying different combos in the SSE once built, but I had to start with something. So, I went ahead and got a pair of the new issue Gold Lion KT88's, along with a NOS Mullard 12AT7, and for now a Shuguang GZ34 rectifier.

I've been watching several NOS Mullard GZ34's on ebay and have even bid on a few. Thus far I've not had any luck as I haven't bid over $60 to date. Man, some of these sell for a pretty penny.

Speaking of the rectifier tube, I'd appreciate any of youse guys input on the topic.

Rick

 

[nic6paul]

You may want to pick up some cheap chinese tubes just for the intial testing phase. You would hate to have anything go wrong with your nicer ones in there. I have a set of chinese tubes I used in my SSE just for that purpose.

 

[rknize]

Yeah, pickup a set of Chinese 6L6s and a 12AT7 or two. If they go poof, you will only be out $20 or so.

 

[Rick J. B.]

That's pretty good advice fellas, will do.

Nic, Russ, what have you guys tried for rectifier tubes thus far?

Rick

 

[rknize]

For the SSE...just 5AR4/GZ34 types. I have one or two each of Chinese, JJ, and Sovteks. I can't really hear a difference between them that is worth commenting on, possibly because I have so much capacitance in the PSU (220uF + 100uF motor run). In fact, I can't really hear the difference switching between the tube and SS rectifier unless I am pushing the amp to the extreme with big tubes biased hard in UL. Then the few extra voltage of the SS gives me a tad more headroom before I hear breakup. I've even removed the 5AR4 to unload the transformer and give me more VA for B+.

 

[Rick J. B.]

For the SSE...just 5AR4/GZ34 types. I have one or two each of Chinese, JJ, and Sovteks. I can't really hear a difference between them that is worth commenting on, possibly because I have so much capacitance in the PSU (220uF + 100uF motor run). In fact, I can't really hear the difference switching between the tube and SS rectifier unless I am pushing the amp to the extreme with big tubes biased hard in UL. Then the few extra voltage of the SS gives me a tad more headroom before I hear breakup. I've even removed the 5AR4 to unload the transformer and give me more VA for B+.

Russ, the 220uF cap you mentioned, is that at C2? My run cap is only 80uF, not sure if that matters much.

Rick