Yes, I definitely intend to try it without UL and/or feedback. I suspect disconnecting the feedback is going to make the overall gain go up, which isn't something I necessarily want. Will disconnecting the UL tap affect the gain? I also have some New Sensor KT88 tubes which will probably get tried out this weekend. I finally found my Telefunken ECC81. I don't have strong feelings about it one way or another. It might be a little quieter (less noisy) than the GE tube I had in previously.
By the way, Dave, your chassis work looks fantastic. What type of wood is that? I want to learn how to make through dovetail joints. I'm afraid I'm not much of a woodworker.
Someone asked, so here's a (nearly) complete list of the parts I used. The list is probably missing something, so check carefully if you are going to use it yourself. I'll also attach my last layout template. If I had to do it again, I'd use a bigger chassis and give myself more room.
http://tubelab.com/
Circuit board: Simple SE
http://transcendar.com/
Output transformers: Transcendar SE 5K, 8 ohm, 10 watt
(request optional UL tap at time of order)
http://tubesandmore.com/
Power transformer: Hammond P-T374BX
Filter choke: Hammond P-T159Q
http://tubedepot.com/
PC mount sockets: 3 octal, 1 nine-pin
(could also source from tubesandmore)
http://digikey.com/
Circuit parts:
IXCP10M45S-ND (qty 2)
P7442-ND
P7451-ND
http://mouser.com/
Circuit parts:
140-PM2A474K|1
647-UPW0J152MPD|2
75-715P600V0.22|2
647-UPW1J152MHD|2
280-CR5-150-RC|1
283-150K-RC|1
281-10K-RC|1
282-150K-RC|1
271-220-RC|2
271-220K-RC|4
271-100-RC|4
271-330-RC|2
283-10K-RC|2
280-CR5-560-RC|2
282-100-RC|2
271-1K-RC|2
164-19B2-EX|2
161-0251-EX|1
161-0252-EX|1
103-R13-135B-02R-EV|1
534-1452B|5
534-744|6
532-530714B00|2
532-4880SG|2
651-1715022|9
651-1715035|3
Chassis plate: aluminum, 14" x 9"
Box frame: 2x3 pine, 2pc 16", 2pc 8"
Miscellaneous #8 hardware, washers, etc.
IEC connector, fuse holder: salvage from old equipment
By the way, Dave, your chassis work looks fantastic. What type of wood is that? I want to learn how to make through dovetail joints. I'm afraid I'm not much of a woodworker.
Someone asked, so here's a (nearly) complete list of the parts I used. The list is probably missing something, so check carefully if you are going to use it yourself. I'll also attach my last layout template. If I had to do it again, I'd use a bigger chassis and give myself more room.
http://tubelab.com/
Circuit board: Simple SE
http://transcendar.com/
Output transformers: Transcendar SE 5K, 8 ohm, 10 watt
(request optional UL tap at time of order)
http://tubesandmore.com/
Power transformer: Hammond P-T374BX
Filter choke: Hammond P-T159Q
http://tubedepot.com/
PC mount sockets: 3 octal, 1 nine-pin
(could also source from tubesandmore)
http://digikey.com/
Circuit parts:
IXCP10M45S-ND (qty 2)
P7442-ND
P7451-ND
http://mouser.com/
Circuit parts:
140-PM2A474K|1
647-UPW0J152MPD|2
75-715P600V0.22|2
647-UPW1J152MHD|2
280-CR5-150-RC|1
283-150K-RC|1
281-10K-RC|1
282-150K-RC|1
271-220-RC|2
271-220K-RC|4
271-100-RC|4
271-330-RC|2
283-10K-RC|2
280-CR5-560-RC|2
282-100-RC|2
271-1K-RC|2
164-19B2-EX|2
161-0251-EX|1
161-0252-EX|1
103-R13-135B-02R-EV|1
534-1452B|5
534-744|6
532-530714B00|2
532-4880SG|2
651-1715022|9
651-1715035|3
Chassis plate: aluminum, 14" x 9"
Box frame: 2x3 pine, 2pc 16", 2pc 8"
Miscellaneous #8 hardware, washers, etc.
IEC connector, fuse holder: salvage from old equipment
That's pretty much my list. I'll be starting my Simple SE as soon as all the parts are in hand. The Mouser stuff is here or on the way (short backorder on a couple of items). Digikey stuff is on the way. Ebay motor run capacitor is here (didn't see that on your list, BTW). When George resurfaces, I'll get the board ordered.
I'm curious as to how you arrived at your power transformer choice. I've not been able to pin down what the right size is. There are so many discussed on the Tublelab web site and in the threads here that I find myself second guessing each time I think I've figured it out.
I'm curious as to how you arrived at your power transformer choice. I've not been able to pin down what the right size is. There are so many discussed on the Tublelab web site and in the threads here that I find myself second guessing each time I think I've figured it out.
I'm back. I had surgery on Tuesday, and must go back again next Tuesday but I will make at least one or two trips to the post office each week.
Most builders go for the 750 VCT transformer since that offers the most power output and works well with most tubes. That means the Allied 6K7VG (cheapest and really a Hammong 274BX in disguise) The Hammond 274BX, and the Hammond 374BX which is slightly larger than the others and reportedly of better construction. The 374BX also has 220-230-240 volt taps.
The 5K Transcendars are a good choice for OPT's as are the Edcor CXSE 25-8-5K. I think that I like the Edcors better, but they are more expensive, and significantly larger. Haven't tried James since they are hard to get.
I find that it is not uncommon that many young people have not learned how to critically listen to the music. I have loaned tube amps to a lot of people (mostly young engineers). A significant number prefer the sound of a multi gigawatt wall shaker. Often they prefer MP3's to vinyl. Musical preference plays a big part. The tube amp doesn't offer much sonic improvement to a lot of hip hop music.
tubelab.com said:
Hope you're doing ok...
I agree with this, there are a lot of people who are not very discerning about audio reproduction, but I've had speakers that were happiest when used with very powerful amps.... these were the old Mirage bipolar speakers, which featured very complicated crossovers. The amps that worked well driving these speakers sound pretty bad driving my single drivers.
cfb reduces gain, but not by a whole lot, UL is noticeably louder than triode at the same volume setting.
Thanks...The wood I used was figured maple and walnut crotchwood for the corners. I don't use dovetails too much, but I have a Keller jig that does a pretty good job with them, only $80 through Amazon:
http://www.amazon.com/Keller-Dovetail-System-135-1500-Journeyman/dp/B000022420
Dave
Davec113 said:
That sounds encouraging. I'll definitely give triode a try, probably tonight.
On a side note - has anyone heard a very, very low level whistling/jingling type noise coming from their Simple SE? I swear it isn't coming from the output transformers, and it happens even when my preamp is switched off.
Ty,
I've noticed jingling, ringing, and sometimes pinging depending on the tubes, but I hear nothing with the current configuration. I've had a microphonic 12AT7 that made fun sounds. The 6BG6GA's and 6679 preamp tube I've got in place now are dead quiet. No feedback, triode.
George, hope you're keeping dry down there.
I've noticed jingling, ringing, and sometimes pinging depending on the tubes, but I hear nothing with the current configuration. I've had a microphonic 12AT7 that made fun sounds. The 6BG6GA's and 6679 preamp tube I've got in place now are dead quiet. No feedback, triode.
George, hope you're keeping dry down there.
Most of the wet stuff has passed us by, without harmful effects. Friends to the north (Orlando, Mebourne area) were not so lucky. They are still getting soaked. A friend of mine has 2 inches of water in his warehouse.
Does this happen with no music playing? Many tubes do emit a clicking or pinging sound as they are warming up due to thermal effects. Hammond and other power transformers can buzz or hum and even cause the chassis or other objects to vibrate, but I can't think of much else that can make sound.
Man, you and yours have had your share of medical "adventures". Here's hoping that it turns around, and soon.tubelab.com said:
The Allied 6K7VTG it is then. As this is my first foray into tube sound, I'm inclined to cut one corner though. Based on your reviews of the smaller Edcor OPT's I'm going to try them (the XSE's) first. I've got some very efficient full-range speakers that should be a reasonable match for a SET amp. If I like what I hear, larger OPT's will be a must to satisfy my jones for solid base performance.
This is going to be an expensive habit, I fear.
Same here George, I hope things pick up for you and yours, soon.
I am also in the process of beginning to place orders for parts.
My current speakers are 4ohm impedence. I have been considering the Edcor's also and was wondering if I should order the CXSE 25 - 8 - 5K or the CXSE 25 - 4 - 5K ?
I would hate to order the wrong ones but would the 8ohm work anyway and be a better choice?
Cheers
Will
I understand the EL34 datasheets usually recommend a 3K reflected impedance, but the datasheet typical applications are usually at voltages lower than the 400+ volts you'll see in a Simple SE. I did some quick load line plotting, and noted that my idle current ought to be slightly lower (~50 mA) with a 3K load than I could "safely" run if I had a 5K load (~60 mA). When I say safely, I mean the load line doesn't run across the maximum dissipation anywhere along the line. Conveniently enough, my Simple SE seems to run right at about 61 mA. I have the Transcendar 5K transformers.
All that said, my speakers claim 6 ohms nominal, 4 ohms minimum. If believed, that means my reflected impedance is 3750 ohms (2500 minimum). I recall that George has intentionally (?) run 5K-8 transformers on a 4 ohm speaker to achieve an effective 2500 ohm load on the finals.
All that said, my speakers claim 6 ohms nominal, 4 ohms minimum. If believed, that means my reflected impedance is 3750 ohms (2500 minimum). I recall that George has intentionally (?) run 5K-8 transformers on a 4 ohm speaker to achieve an effective 2500 ohm load on the finals.
Here's my lines. I guess if I were using a 750VCT power transformer, I'd want to shoot for a 5K load. If I had a 600VCT PT, I'd want the 3K. From what I understand, lower loads give you more power at the expense of higher distortion.
If your speakers don't match the rating on the OT's secondary, the reflected load on the primary will need to be adjusted proportionally.
If your speakers don't match the rating on the OT's secondary, the reflected load on the primary will need to be adjusted proportionally.
Cool,
Thats what I should have said Ty, "6 ohms nominal, 4 ohms minimum" and as you mentioned that George has taken that into consideration possibly because its a very common speaker impedence most people use, a guess on my part.
Thank you for the research.
Have you discovered the source of your cracking or poping or whatever funny noises with your SimpleSE? or have they disappeared or are they any problem still?
hdlcx2 said:
Probably. It's 2:15 AM right now, and the thing is stone silent. Not a sound comes out of it anywhere.
By the way, disregard my previous post concerning load lines until further notice. I had a long discussion tonight with an EE friend, and he cast some doubts on things I previously believed to be true. I'm going to have to do some more experiments before I'm convinced of anything anymore.
Nite Owl
WOW, You sound like me in burning the midnight oil.
It's now 12:15am here. Nice and quiet, everyone else has gone to bed, good time to either study or think. Only problem is I can't crank the music up!
Could your mysterious sounds emitting from your Simple SE just have been normal break in activity from the tubes or maybe even PT or OPT? (Not the physical part itself but in the operation).
Guess you will know in time should it return.
I'm in no hurry and will wait to hear back regarding your experiments. I am very interested as your speaker specs seem to be excatly as mine according to my documentation and also according to Polk Audio, as I have inquired to them directly. (They are some of the first Polk Monitors made but in prestine condition).
Cheers
WOW, You sound like me in burning the midnight oil.
It's now 12:15am here. Nice and quiet, everyone else has gone to bed, good time to either study or think. Only problem is I can't crank the music up!
Could your mysterious sounds emitting from your Simple SE just have been normal break in activity from the tubes or maybe even PT or OPT? (Not the physical part itself but in the operation).
Guess you will know in time should it return.
I'm in no hurry and will wait to hear back regarding your experiments. I am very interested as your speaker specs seem to be excatly as mine according to my documentation and also according to Polk Audio, as I have inquired to them directly. (They are some of the first Polk Monitors made but in prestine condition).
Cheers
Re: Nite Owl
It appears to be mechanical in nature, most likely from the power tubes themselves. I'm guessing the grids jingle/rattle a bit when you shake the tube just so. I can tap on the bases of the output tubes while the amp is off and cold, and I hear the same noise. It's virtually impossible to hear them if you pull the tube out of the socket. I'll assume the circuit board itself is acting as a sounding board. The ever-so-slight vibration of the power transformer is just barely enough to get them going. Sometimes it happens, sometimes it doesn't. I've got a quad of these tubes (EH fat bottle 6CA7) and I've made two random pairs out of the quad. Both pairs do it. I'll try out the New Sensor KT88 in the next few weeks, and see if I get anything similar.
In case you're worried, you can't hear a thing from the amp when you're more than two feet away from it, or if there is the slightest amount of noise in the room.
hdlcx2 said:
It appears to be mechanical in nature, most likely from the power tubes themselves. I'm guessing the grids jingle/rattle a bit when you shake the tube just so. I can tap on the bases of the output tubes while the amp is off and cold, and I hear the same noise. It's virtually impossible to hear them if you pull the tube out of the socket. I'll assume the circuit board itself is acting as a sounding board. The ever-so-slight vibration of the power transformer is just barely enough to get them going. Sometimes it happens, sometimes it doesn't. I've got a quad of these tubes (EH fat bottle 6CA7) and I've made two random pairs out of the quad. Both pairs do it. I'll try out the New Sensor KT88 in the next few weeks, and see if I get anything similar.
In case you're worried, you can't hear a thing from the amp when you're more than two feet away from it, or if there is the slightest amount of noise in the room.
jduffy said:Nice job man. And it's cool seeing George's stuff come to life for other people.
I hope you're happy with the results.
Thanks. Yes, I'm very pleased with the results. It's a good sounding amp.
Another dumb question - how much time should one spend worrying about heat buildup at the tube bases, sockets, or under the chassis? Should I bother drilling a ring of 3/16" holes in the chassis plate around each of the octal sockets? Will I get any (useful) "chimney" effect, or is it merely done for aesthetic value?
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