That rectifier may be too much for the EL84.

I agree - a 5Y3 may be a better choice.

Anyone want to guess what these are?
 

Or better yet, what they're going to wind up as?

http://i443.photobucket.com/albums/q...psndxnukbq.jpg

EDITED/duplicate post

Speaking of tube rolling, I had an afternoon off last week, so I went over to the shop with a bag full of vinyl and a bag full of old toobs.

http://i443.photobucket.com/albums/q...psgufgy2kq.jpg

http://i443.photobucket.com/albums/q...psejbio9uc.jpg

http://i443.photobucket.com/albums/q...ps5ho4dyra.jpg

Also did a little measuring on the bench, but that's a story for when I have more time.....

http://i443.photobucket.com/albums/q...pspw9qvq0r.jpg

Also saw this lying around on the assembly bench....

http://i443.photobucket.com/albums/q...pse9kiwbeu.jpg

Wouldn't a 5U4G or 274B (this is the stock tube) drive the EL84 harder than a 5V4GA? Dennis told me that using a 5V4GA was fine. The only power tube I can use in this amp is the EL84.

Tube Type DC mA PIV FIL AMPS Max ACV DCV DCV DROP

5AR4 / GZ-34 250 1500 1.9 450 415 10
5V4-GA 175 1400 2 375 400 25
GZ37 350 1000 2.8 450 388 37
5U4-GA 250 1550 3 450 381 44
5U4-G 225 1550 3 450 381 44
5U4-GB 275 1550 3 450 375 50
5Y3-G/GA 125 1400 2 350 365 60
5R4GYB 250 3100 2 900 362 63
5R4G/GY/GYA 250 3100 2 750 358 67

The last number on the table is the voltage drop. Smaller numbers drive the tube harder. You can use the 5V4GA but it apparently is not driving the EL84's in the sweet spot. I quit trying to analyze the circuit and just use the tubes that sound best.

BTW, do you ride a Bombadil? I have a Bleriot and ordered a Chevoit frameset.

Oh Oh Oh!... I know! Pick me! Pick me!

I have dibs on one of these PSE chassis already.

I thought the first number in your table, the max DC output current, was the primary factor in how hard the output tubes are driven. The stock 274B is 225, the 5V4GA is 175, and the 5Y3GT is 125. Then the voltage drop is the sag in those volts when the rectifier is driven hard, i.e. how much voltage can be drawn on peak demands. So if one subtracts the sag, the 274B drops 44 volts to a max of 181 on peaks, the 5V4GA is 150, and the 5Y3GT is just 65.

Now, I'm no expert on such things and I could be wrong. If the above is true, then the 274B should always be able to deliver more voltage than a 5V4GA. And the 5AR4/GZ34 is highly desired by those wanting to get max power out of the output tubes, as it can deliver up to 250V with a sag of just 10V, thus it is almost linear in its output.

No, I don't. I wouldn't mind having one. That frame is made here in Wisconsin, I've toured the small factory where it, and a few other Rivendell frames, is made. I think they discontinued that massive Bombadil frame set. I like more relaxed frames now, so I'd probably go with a Clem Smith Jr., but I mostly ride recumbents now. Have a RANS Stratus steel frame which I like a lot.

Do you have your new amp? First impressions?

The first number is DC millivolts. The plate voltage is what drives the tube. That less the drop is what the tube plate sees. Google 5 volt rectifier table and click the 'fourwater' link. It is a better table. :thumbsup: These amps are single ended and the tubes may sound better not driven as hard as in a push pull amp.

The Russian 6P14P-EV can handle more voltage on the plate than regular EL84's but I don't know how they would sound in your amp.

What speakers are you driving?

That appears to be the same amp that Twanny, Musica and I have. However, they are triode strapped and have less power. The last pic looks like the innards of a LP27a. I'm curious about the measurements. :D

I'm not fessing up until I get enough of the tubes that Dennis and I both liked the most.....:smoking:

Okay, so then most of the time if I am using a 5V4GA the plate voltage will be 400V vs when using the 274B it will be 381V. The drop should only occur on volume peaks / maximum demand. As I am filtering sub-100Hz signals from the amp, there may be few drops occurring.

I do have the 5V4GA back in right now. Running a comparison between it vs the 274B, a 5U4G, and a 5Y3GT. But using a different 5V4GA, this one is a very old RCA and the glass has a slight bronze'ish cast. Very pretty when lit up. The one I used the other day is an ancient Remington Rand. Perhaps it wasn't up to spec. This one is sounding better.

As to being driven hard, Dennis' current KT88 amp that produces 17 watts per channel, is driving that tube at its estimated max in single-ended mode.

I don't know if it's been commented on before, but logically, Dennis is an amp designer, not a tube collector. In general, he doesn't care if that expensive set of NOS Tung Sol Black Plate 6550s only last 2000 hours instead of 5000 hours. Instead he is looking to squeeze maximum performance out of the tubes so that the amps perform to the max. One of my favorite "Dennisisms" is when a tube starts to look just a little bit orange around the plates, hardly noticeable unless you turn out the lights...."Its good for them!"

Yes, I have had if for about a week or so. Very nice amp. I am still burning it in, but currently using a 5u4 with 6sn7, a pair of KT 88's, and a pair of Pope 6v6's. Very nice combination! I am driving it with an Audionotekits Mentor preamp.
The amp has a nice "live" sound. Very open, detailed, and nuanced.

[QUOTE=Bombadil;796799]Okay, so then most of the time if I am using a 5V4GA the plate voltage will be 400V vs when using the 274B it will be 381V. The drop should only occur on volume peaks / maximum demand. As I am filtering sub-100Hz signals from the amp, there may be few drops occurring.

I do have the 5V4GA back in right now. Running a comparison between it vs the 274B, a 5U4G, and a 5Y3GT. But using a different 5V4GA, this one is a very old RCA and the glass has a slight bronze'ish cast. Very pretty when lit up. The one I used the other day is an ancient Remington Rand. Perhaps it wasn't up to spec. This one is sounding better.

As to being driven hard, Dennis' current KT88 amp that produces 17 watts per channel, is driving that tube at its estimated max in single-ended mode.

It just may have been your 'state of mind' when you heard the edginess. Sometimes I'll think my rig sounds weird and it often occurs during the daytime. Rectifiers of the same type should not sound different but to my ears they do. It appears that you have the issue resolved and that's all that matters.

Rectifiers of the same type usually sound the same to me. Perhaps it was a time of day thing. But perhaps it was just a 60 to 70 year old tube not being at its best anymore. :)

I'm going to keep on rolling them. Having 4 different tube types and about 10 rectifier tubes in all gives me a project.

Neil Young playing now ...

This is good for me. I've never dropped big bucks on a rare NOS tube. Have been able to pick up some decent vintage tubes at reasonable prices. I have 11 matched pairs of various EL84 tubes. That should hold me a while, even if I don't get maximum tube life.

Burn baby Burn!

Congrats Dave! The ability to mix the power tubes is very cool. So is your preamp.

I remember reading that the higher output KT-88 SE amp could run at 10 watts with KT-66 tubes, 12 watts with KT-88, and 14 watts with KT-120 tubes.

Later Dennis introduced his High Output KT-88, advertising that it could produce 17 watts with KT-88s and that it had 20 watt output transformers. And he claims in his eBay description of it that the power transformer could run 4 of these amps.

Does anyone know if this second amp can run KT120 tubes? I can't recall ever seeing any mention of this. Or for that matter, KT150 tubes? Two years ago there was a discussion on this board about Dennis' claims that his KT88 amp could safely run KT150s.

Yes, I had one of those amps and put KT150's in it. Sounded great.
I really like that tube. I am thinking I should try a quartet of them in my PSE...

My amp has the 20 watt transformers bit it is single ended runs the output tubes in triode. 6V6's in this amp are about 5 watts. I tried KT150's and did not care for them. These amps can run many tubes. However, there will be two or three that *sound the best* to your ears. A few extra watts will not be noticed unless you have very efficient speakers. Power needs to double for the next 3db of output. I have Heresy III's, 99db on paper, and they work well. They have a complex crossover and I do not know how flat the impedance is. You can get by with less power if the speakers are less efficient but have flat impedance. I don't feel like I need a subwoofer or more power.

When I took my amp and pre to a friends house last year and connected them to his 104 db La Scalas there was a huge difference in the presentation. We were shocked at how life like the Pope 6V6's and 5Z3/5U4G sounded. We used one of his Treasure CV181's for the input tube.

Google 'speakers for low power tube amps'.

The KT150 must work better in an amp that is not triode wired/strapped. It sounded good but was not my favorite. Could be my room. :scratch2:

Did Dennis wire your amp in triode by your request?

I have a European PP amp wired in triode, running a quad of Sylvania Fat Boy 6CA7s. Produces around 18-20 wpc. It sounds fabulous. Has Audio Note output transformers. It runs so cool, even after two hours of playing the OTs are barely warm.

No, he just built it that way. I believe a switch could be added to allow it to be simply run single ended. I may have that done someday but I don't feel that I need to. I'm done chasing my tail in audio.

In general, Dennis has not been a huge fan of the KT-150s. And a suggestion for you from me and Dennis. If you try your amp with the La Scalas again, try using a 5Y3G rectifier.....

Would not it be even better to use one of the NOS 6V6 G ST (1940's shouldered) types along with either the 80 (4 Pin) or the 5Y3 G/GT (Octal 80)? I know I would try that first with such a high sensitivity speaker. In my setup, with 98 dB's, the 80 comes short to boost the G ST (which in another amp fares much better through a 12AT7), so it's not the tube, is the combination plus the lower sensitivity, I believe. But once the G ST sings ... It is a dream!

My amp is wired as a SE in triode mode. Two quotes from Dennis confirm this:

"Speaking of special sounds, the KT88 (6550) sounds fabulous in class A, triode SET operation. I spent a couple of hours this afternoon listening to your amplifier in the shop listening room. Love it."

"This amp is pure SET. Hugh output transformers ... this is a life-time music machine. I run the output tubes in the triode mode. "

My amp has a UX4 rectifier socket. We used an 80 first and then a 5Z3 with the Pope 6V6GT's. They really came alive with the 5Z3. The Pope tubes can easily handle the additional voltage.

X3,

I inquired about an amp and Dennis replied with 'you have to get the one I am working on now.' 20 watt transformers built on the 45 chassis single ended, triode wired. It is the same amp you have and is one I'll never part with. Ditto for the LP27a. All the amps Dennis is building are excellent...just different.

I did change the coupling capacitors in both units. Just personal preference. I have a good selection of old production 6SN7's but prefer the Shuguang/Psvane CV181's.

http://i65.tinypic.com/2wfp852.jpg

http://i66.tinypic.com/akcxvd.jpg

That sounds like a fine amp.

FWIW and IMHO, the current price of most vintage power tubes is based on rarity not sonics. Many audio nuts believe that the top tier new production power tubes are better sounding than old production. As always, there are exceptions.

Dennis has some interesting opinions on tubes. He is the only person I have ever heard who prefers the JJ KT77 over the Genalex, many people have a strong preference in the other direction. And, while not all, most like the KT150, with some very expensive amps running them.

Floridaboy, what rectifier is that in your amp?

How much improvement did you notice in your LP27a with the Jupiter caps? Those look really nice and if they sound the same, I'd like to do the same :thumbsup:

Although I would not trust my soldering skills to do that job. How much do you charge? Just kidding, last thing you want is a bunch of us sending our Inspire amps and preamps to you.

Yes, I have a ref75se and they are great in that. Of course it is optimized for that tube. But it is a spectacular amp in every way.

It's an 'old stock' Full Music 274a, 4 pin 5U4G, from 2000 or so. I found several of them for little $$$ on the auction site

Caps are a personal thing, you need to research and experiment to decide what works for you. The Jupiters just made the music sound more natural. My perception FWIW. Caps, like tubes, do sound different. The pre amp uses 1.5uf caps and the amp uses .022uf which are much less $$. I used a .01uf copper V-Cap paralleled with a .015uf Vitamin Q in the amp. V-Cap copper are bass champs and the Vitamin Q's are smooth, rich and detailed. The combo works for me. I changed them first and let them fully settle in before I did preamp. There is a lot of info on the web Google 'the sound of capacitors'.

There wasn't anything 'wrong' with the caps Dennis used. My amp came with KT88's but I prefer the 6V6 6L6 family. :D

It is not difficult to do the work. Only 4 solder joints.