Tubelab SimpleSE: Edcor XSE15-8-5K or XSE25-16-7.6K?

[pukka]

Happy New Year!

I assured a friend interested into speaker tube amps that a good performing SE can be built for far less than he has seen on Audio retailers, and sound as good, and proposed the SimpleSE as an example.

To make the story short, we're going to build a pair.

I'm still reading all the info I can find, but have a doubt. We will probably settle on KT88's. I wonder which one of these transformers will sound better with 8 Ohms (>90dB) speakers. I read something but nothing conclusive...

George you have a couple mails, know you're dealing with serious matters, just hope your spam filter didn't ate my email

 

[chrish]

I have used the XSE15-8-5K (and now 15-4-5K for my 4 Ohm speakers) and they work well. I have an active crossover, however, that pulls off the sub 80Hz frequencies and sends them to a separate solid state power amp to power a set of stereo woofer units. I have a set of JJ E34Ls in the amp at the moment and prefer these to the JJ KT88s. More detailed mid range. The KT88s are supposed to have better bass performance, at the expense of some mid range clarity.

I would look to the Edcor GXSE series (guitar output transformers). The 15 watt version is essentially a 25 watt XSE. I recall a forum member writing to Edcor and asking them if their guitar output transformers were designed for "guitar distortion". Their reply was (if I remember correctly) that hey are designed for accuracy, but have been designed to go down to 40Hz to allow for low notes on guitar. The GXSE also have a wider range of impedances, so you can get a 5K:8Ohm. I have purchased a set of these, but have yet to try them out on an amp. Some day!

http://www.edcorusa.com/products/transformers/gxse/gxse15-8-5k.html

 

[Tubelab_com]

George you have a couple mails, know you're dealing with serious matters, just hope your spam filter didn't ate my email

I have been home for 2 weeks out of the past 5. Most of that time I have been at work until late (8PM tonight) and answering Tubelab email is expressly forbidden. I have managed a few forum posts after the bosses are gone. I have seen your email, but haven't got to them yet. Maybe tomorrow.

Most users build their Simple SE's with a Hammond or Allied power transformer that delivers 375-0-375 volts or more. This results in a B+ of 440 to 460 volts. This much B+ requires a fairly high load impedance even with a KT88 tube. The XSE25-16-7.6K would reflect a 3.8K ohm load. I have found this to cause an unacceptable level of distortion.

The OPT is the most critical component in any tube amplifier, and one that is not likely to be upgraded later. The ability of an OPT to reproduce low frequencies is directly related to its size. Accurate low frequency reproduction requires more inductance meaning more wire and a larger core, both of which raise the cost.

The XSE15-8-5K is a good transformer for the price. It will not be capable of serious low bass (below 80 Hz) without distortion simply because of its size. It does however work well when an active subwoofer is used to remove the requirement for the tube amplifier to reproduce frequencies below 80 Hz. It also works well when the speaker system is not capable of reproducing these low frequencies.

I have used the XSE15-8-5K in a Simple SE on my studio monitor speakers that have 7 inch woofers. They work quite well on these speakers. The "8 ohm" impedance of these speakers is not constant and rises below 80 Hz removing load below resonance so that the amp does not audibly distort on strong bass. That same amp connected to a speaker system with a 15 inch woofer will audibly distort.

I have not tried any transformers from the XSE 25 series or the GXSE series, since my experimentation budget has decreased. I have used the CXSE25-8-5K, and I can reccomend it if it fits in your budget. Othere have tried the Guitar (GXSE) series and report good results. I would not go below 5K with a 400+ volt B+.

I have a Transcendar 3 K OPT in my "industrial" amp. The amp exhibits noticible bass distortion when the 8 ohm speakers are connected to the 8 ohm taps, but works quite well when they are connected to the 4 ohm tap resulting in a 6K ohm load. Transcendar OPTs are another good low cost choice. They have a 5K SE version available on Ebay.

 

[Ty_Bower]

I'm quite certain the Edcor transformers are a good value, but I'd suggest you expand the budget slightly and test your patience. Watch eBay carefully for the Transcendar 5K:8, 10 watt transformers. I used them on my Simple SE and I can't complain about their performance. They will likely cost $122 shipped. The eBay seller's name is ggaet. He does not have any up for sale right now - this is where the patience part comes in.

Edit: Here's a pair that sold a few days ago:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=280302185258

 

[Tubelab_com]

Totally off thread post

I have the TV on while catching up on email. The sound started beeping which attracted my attention to the "Severe Weather Alert" warning on the screen. The following is quoted from the National Weather Services web site in MIAMI FLORIDA! The caps are theres:

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE MIAMI FL
124 PM EST TUE JAN 20 2009

THE COLDEST AIRMASS SO FAR THIS WINTER SEASON WILL SPREAD SOUTHWARD ACROSS MAINLAND SOUTH FLORIDA TONIGHT. TEMPERATURES ARE EXPECTED TO FALL INTO THE 30S OVER MUCH OF INTERIOR SOUTH FLORIDA.....WHEN COUPLED WITH NORTHERLY WINDS IN THE 5 TO 10 MPH RANGE...THESE TEMPERATURES WILL RESULT IN WIND CHILL VALUES BETWEEN 25 AND 35 DEGREES FOR SEVERAL CONSECUTIVE HOURS OVER MOST OF MAINLAND SOUTH FLORIDA FROM LATE THIS EVENING UNTIL A FEW HOURS AFTER SUNRISE TOMORROW.

A WIND CHILL ADVISORY MEANS THAT VERY COLD AIR AND STRONG WINDS WILL COMBINE TO GENERATE LOW WIND CHILLS. THIS WILL RESULT IN FROST BITE AND LEAD TO HYPOTHERMIA IF PRECAUTIONS ARE NOT TAKEN. IF YOU MUST VENTURE OUTDOORS...MAKE SURE YOU WEAR A HAT AND GLOVES.

and the latest update:

THE COLDEST AIR TEMPERATURES ARE FORECAST WEDNESDAY NIGHT. WINDS BECOME CALM AS HIGH PRESSURE MOVES OVER THE AREA FROM THE NORTHWEST. THIS SETS THE STAGE FOR A HIGH POSSIBILITY OF FREEZING TEMPERATURES ACROSS A LARGE PORTION OF INTERIOR SOUTH FLORIDA WEDNESDAY NIGHT
INTO EARLY THURSDAY MORNING. LOWS BY EARLY THURSDAY MORNING ARE FORECAST TO FALL INTO THE UPPER 20S

This is not uncommon in most of North America in the winter, but it is totally wierd here, I was in the swimming pool yesterday after mowing my lawn (we have to mow in December). I haven't been home much and my yard was starting to look like one of the local forclosures.

 

[Ty_Bower]

Re: Totally off thread post

...THESE TEMPERATURES WILL RESULT IN WIND CHILL VALUES BETWEEN 25 AND 35 DEGREES FOR SEVERAL CONSECUTIVE HOURS...

You poor bastard. I feel for you - no, really, I do. So sorry to hear about the few consecutive hours of very nearly cold temperatures. If only you had a pair of these around - http://www.audioresearch.com/ref610T.html - you could use them as space heaters to protect yourself from freezing.

/sarcasm off

 

[wrenchone]

George, I grew up partially in Orlando. I remember coming home one Christmas in the mid '80s and getting a 19 degree Christmas as a present. We still had well water at that time, and our pump froze. My Dad had to deal with the resulting mess. We also lost a few of the more tender citrus trees (lemon, a couple of our orange trees). When I got back to California, it was 65 degrees. Having said that, I also remember an 85 degree Christmas one time when I came home from college.

 

[sorenj07]

I would like to put my 2 cents in and recommend the GXSE line. I'm running a pair of the 25 watters in a 3-3.5 watt SET amp and they sound pretty OK. Pushing about 65mA of current at 320V. They're just a bit bulky, at 4" long (including mounting tabs)x2.5" tallx2.25" wide, not counting the quarter inch quick connects. I haven't done any measurements but I imagine they're pretty solid, given what people have been saying about the regular XSE line, which is rated at 70Hz as opposed to 40.

 

[wrenchone]

When I made my "Shrine" 1625 SE amp, the XSE and CXSE were the only things available from Edcor. I ended up using a pair of the 5k/8 ohm XSE series and they sounded pretty good, though with obvious limitations on the low end. I have since refitted the amp with a pair of the GXSE 15W (hah!) transformers. I haven't done much critical listening with the amp, as it also has an RF oscillation issue, but I'll report back once that is straightened out. I expect more bass, at least. I'm currently running the 1625 outputs at about 60ma, 350V (probably more like 320V or so across the tube when you subtract the cathode bias), in ultralinear mode. I bought 3 pairs of the GXSE, and I''ll be finding homes for the other two pairs when I get a chance. The Edcors are a nice bit of iron for the money, especially since Hammond has really jacked up the prices on their 125 SE series. I paid 35 apiece for a pair of the 125ESEs when I started tooling up for my first tube amp - now they're over 50 dollars apiece. Both Transcendar and Edcor are better value these days - nicer finish, too. The baby Transcendars are a good alternative to the 125ESE at about the same price, the only disadvantage being the single impedance outputs on the Transcendars.

 

[DimZ]

I'm quite certain the Edcor transformers are a good value, but I'd suggest you expand the budget slightly and test your patience. Watch eBay carefully for the Transcendar 5K:8, 10 watt transformers. I used them on my Simple SE and I can't complain about their performance. They will likely cost $122 shipped. The eBay seller's name is ggaet. He does not have any up for sale right now - this is where the patience part comes in.

I use the Transcendar 5K:8, 15 watt with 40% ultralinear and both 4 & 8ohm, sounds just fine. With my diy fullrange 8ohms(fostex 126E) is pretty much what I was looking for (though a fast system i.e adding a sub might help the lf), with my other set of loudspeakers AUDIO SPECTRUM ARTEMIS (http://www.audiospectrum-hifi.com/english/index.htm) I have an amazing sound but a get some distortion when playing loud (sensitivity 91db / 6ohm), but thats quite normal I guess ...

tubes (JJ EL34, EH 12AT, china GZ34), waiting for a pair of KT88 and a sovtek 5AR4 ...

 

[pukka]

thanks to all for the extensive input!!

George hope weather doesn't get troublesome...

I have been home for 2 weeks out of the past 5. Most of that time I have been at work until late (8PM tonight) and answering Tubelab email is expressly forbidden. I have managed a few forum posts after the bosses are gone. I have seen your email, but haven't got to them yet. Maybe tomorrow.

Never mind! I read almost all your website and posts in this forum and am aware of your situation, my only worry was spam filters eating my email

Most users build their Simple SE's with a Hammond or Allied power transformer that delivers 375-0-375 volts or more. This results in a B+ of 440 to 460 volts. This much B+ requires a fairly high load impedance even with a KT88 tube. The XSE25-16-7.6K would reflect a 3.8K ohm load. I have found this to cause an unacceptable level of distortion.

We're going to order Edcor a custom power transformer, with 240V 50Hz primary (Spain) and 800VCT@200mA, 6,3@4A, 5V@3A secondaries, essentially a XPWR110 with euro primary and a 5V tap. BTW, how do people using Allied's heat the rectifier? another transformer?

I did a quick check on PSUDII and using the optional choke (have several 125C1A, those are found on Fenders) and tube rect will end up with a B+ of about 395V with a 5U4G, or 428 w/ 5AR4 is this right? maybe I over simplified the PSU in PSUD... I see higher B+ from the posts... 5K will be a must then, point noted.

I've been told that choke (I already have some) measures about 5H and is rated for 100mA, though I have used it @ 160mA with no problems, and other knowledgeable tubehead told me they can stand 200mA w/o problems. Maybe you know them, guess they will be fine for the SimpleSE?

The OPT is the most critical component in any tube amplifier, and one that is not likely to be upgraded later. The ability of an OPT to reproduce low frequencies is directly related to its size. Accurate low frequency reproduction requires more inductance meaning more wire and a larger core, both of which raise the cost.

The XSE15-8-5K is a good transformer for the price. It will not be capable of serious low bass (below 80 Hz) without distortion simply because of its size. It does however work well when an active subwoofer is used to remove the requirement for the tube amplifier to reproduce frequencies below 80 Hz. It also works well when the speaker system is not capable of reproducing these low frequencies.

We will be using what I believe are SE suitable speakers, all 8 Ohm >90dB fullrange drivers on DIY horns:

I have a pair of Cyburgs's "Viech" using Beyma's 8AG/N (96dB, 35W, 60-18000Hz) and in process of building a couple Cornu's-like using Monacor's SP-50X (91dB, 50W, 60-20000Hz).

My friend is building a couple Helix AG-150 horns (measurements) using Fostex FE126E (93dB, 15W, 70-25000Hz).

I believe all of those fall into the not being able to reproduce below 80Hz (at least the driver, dunno if I have to take into consideration the overall driver+enclosure performance), so the XSE15-8-5k will be a good choice?

I have used the XSE15-8-5K in a Simple SE on my studio monitor speakers that have 7 inch woofers. They work quite well on these speakers. The "8 ohm" impedance of these speakers is not constant and rises below 80 Hz removing load below resonance so that the amp does not audibly distort on strong bass. That same amp connected to a speaker system with a 15 inch woofer will audibly distort.

Know them, good 'ol yamaha NS-10 (worked as studio engineer a decade ago) is incredible the abuse they can take... if I remember correctly they had a specific amp to suit them. I almost bought them back then, my reasoning being most music being mixed/mastered in the world is checked with those as near-field, consumer-quality reference point monitors, so little chances something not sounding decently through them...

I have not tried any transformers from the XSE 25 series or the GXSE series, since my experimentation budget has decreased. I have used the CXSE25-8-5K, and I can reccomend it if it fits in your budget. Othere have tried the Guitar (GXSE) series and report good results. I would not go below 5K with a 400+ volt B+.

Ok, so is clear we want 5K OPTs. Know the CXSE are superior, but the point here is to end up with a sweet, good sounding SET system with the best deal in "compromises" so that its as cheap as possible.

Given the speakers we will be using (would they benefit from a CXSE??), do you think the XSE or GXSE would be the best compromise?

We don't seek wall-shaking bass, we look for a sweet sounding, enjoyable and listenable for hours tirelessly system, that also means moderate sound levels. Bass must be there, but my understand is if you want real bass (thump in the chest kind) you need either subwoofers, or really big drivers. Just want the freq. spectrum to be balanced through all the (limited) range.

I have a Transcendar 3 K OPT in my "industrial" amp. The amp exhibits noticible bass distortion when the 8 ohm speakers are connected to the 8 ohm taps, but works quite well when they are connected to the 4 ohm tap resulting in a 6K ohm load. Transcendar OPTs are another good low cost choice. They have a 5K SE version available on Ebay.

tubelab, ty_bower, I have emailed them. I would like however to order all iron from a single vendor or shipping costs will add up... Edcor could supply all, power and opts for a reasonable price, the power one being the most problematic to source from others.

I think maybe the Edcors GXSE25-8-5K could be the best compromise for our intended setups... so the thing is between XSE or GXSE now.

sorenj07, are yours 25W custom ordered? Cannot see any GXSE bigger than 15W. I assume by tubelab.com tests that in spite of their ratings (75mA DC) they're best run at those (~80mA) bias points and conservatively rated in that area?

I understand 25W with 5K should be better in terms of bass?

Regarding tubes, I have a load of russian NOS tubes bought several years ago that I would like to use. For rectification, sourcing good and cheap 5AR4 is difficult here, while I have some Svetlana NOS 5c3s (5U4G equivalents) that showed to be quality rects. They have 30V higher voltage drop than the 5AR4 but are much toughter. Guess I will be fine using them? Jimazz, I read your initial problems with the rect tubes, and saw you used a 5U4G, but now you're back to use a GZ34?

Sourcing quality ECC81 is also somewhat complex here (at good prices) while I also have lots of 6N1P in its -IV and -EB versions (PDF), and one I loved in every application I tried: 6H30P-DR. Do you think they will fit fine for the ECC81 task in the SimpleSE provided proper adjustments are done in bias?

 

[Tubelab_com]

When Gery (Transcendar) started putting OPT's on Ebay I bought a pair of his "300B SE transformers". I liked them so much that I bought 10 more pairs. Most of them went into 300B Tubelab SE's, but I have a pair on my "industrial" Simple SE. As I stated before I run that amp with the 8 ohm speakers on the 4 ohm tap. Those "300B transformers" are no longer available, and I have not tried any of his newer transformers, but I have only heard good things from those who have.

You poor bastard. I feel for you

I just returned from 10 days in the Pittsburgh area, it was cold, but that is to be expected. When it was too cold to work outside, I grabbed my laptop and did some PC board layout, but that will be the subject of another thread.

...... getting a 19 degree Christmas as a present....... also remember an 85 degree Christmas

As Wrenchone can attest winter in Florida can be highly variable. It can be 19 degrees, or it can be 85 degrees. It is common for the two extremes to be seperated by days or even hours. In this case it was in the high 70's on Monday, about 65 last night at 10 PM and 37 when I got up this morning. It is supposed to be 25 tonight. It will be back in the 70's by Saturday. It is this kind of thermal shock that contributed to the demise of the space shuttle Challenger. This is the first time that I can remember "Severe Weather Warnings" being flashed on TV because of cold though.

 

[DimZ]

Jimazz, I read your initial problems with the rect tubes, and saw you used a 5U4G, but now you're back to use a GZ34?

I used the 5U4G only cause it was the only available at the time to check if the JJ GZ34 was faulty.., it suited fine though ..

 

[Tubelab_com]

800VCT@200mA, 6,3@4A, 5V@3A

800VCT is too much. Another user got the same transformer from Edcor and had trouble with that amp because the B+ was over 500 volts. Most European users build their amps with a Hammond 374BX which works good. Edcor lists a clone of the Hammond called an XPWR059. 120/240 primary, 375-0-375 @ 175 ma, 50V @ 50 mA, 6.3V CT @ 6A, and 5V CT @ 3 A. I have not tried it though.

BTW, how do people using Allied's heat the rectifier? another transformer?

The Allied is a clone of the Hammond 274BX which has all of the correct secondary voltages, it only has a 120 volt primary though.

Maybe you know them, guess they will be fine for the SimpleSE?

Not familiar with that choke, but it will probably work OK. I have been using chokes that I got out of some old HP test equipment. They work OK.

I almost bought them back then, my reasoning being most music being mixed/mastered in the world is checked with those as near-field, consumer-quality reference point monitors, so little chances something not sounding decently through them...

I was setting up a home PC based studio about 10 years ago, and that was my thinking. The fact that Sam Ash music had them on sale sealed the deal. I was feeding them with a home made SS amp until I made a tube amp..... and then another tube amp....and.......

Given the speakers we will be using (would they benefit from a CXSE??)..... do you think the XSE or GXSE would be the best compromise? We don't seek wall-shaking bass, we look for a sweet sounding, enjoyable and listenable for hours tirelessly system, that also means moderate sound levels.

Honestly, on the NS-10's the CSXE's are not blatantly better. They do sound better on some bass heavy music if the volume is increased. The NS-10's are 87 db and I often play rock, so I can hear a difference in them. I have two amps that get used most often on those speakers. One is the "industrial" amp with the Transcendars, and the other is a Simple SE with 6v6's and XSE15-8-5k. My amp preference is guided by the type of music I play and how loud I want to get. I use the CSXE's on my big speakers with a 300B Tubelab SE where they can really shake the walls.

The XSE15-8-5k has a remarkably clear sound, and it is the best of the small OPT's that I have tried. I have a pair of them in the 6V6 version of the Simple SE and at that power level I can find no better affordable OPT's. They will make clear undistorted bass down to 25 Hz at the 1.8 watt level.

I am guessing that the XSE15-8-5k will be OK for your setup, but I can't guess your listening habits, volume level, or musical choices. I have not tried the GXSE's. The increased size should improve the bass, but I don't know if it compromises the highs, or that "crystal clear" that I get from the XSE15-8-5k. One user on this forum talked about "increased leakage inductance" that will compromise the sound. Based on this information, I would tend toward the ones that I know, the XSE15-8-5k. I have planned to try some of their newer transformers, but my experimentation budget is essentially zero right now.

 

[Boris_The_Blade]

I've had good results with the Edcor SE line as well: http://www.audioasylum.com/cgi/t.mpl?f=tubediy&m=142814

 

[pukka]

Hi,

800VCT is too much. Another user got the same transformer from Edcor and had trouble with that amp because the B+ was over 500 volts. Most European users build their amps with a Hammond 374BX which works good. Edcor lists a clone of the Hammond called an XPWR059. 120/240 primary, 375-0-375 @ 175 ma, 50V @ 50 mA, 6.3V CT @ 6A, and 5V CT @ 3 A. I have not tried it though.

Ok, just asked Edcor for that one. I thought if rectified voltage were too high I could modify the PSU to be choke loaded, but why complicate things.

I wouldn't mind having 500V B+, as I have some 750Ohm 50W aluminum armature resistors that would be fine for the Kt88 Rk as I see in the application chart. But guess caps would be rated accordingly and it may limit driver application.

How much B+ reaches the driver tube?

Not familiar with that choke, but it will probably work OK. I have been using chokes that I got out of some old HP test equipment. They work OK.

great. I guess as long as I don't notice heat or buzzes they will not suffer.

I was setting up a home PC based studio about 10 years ago, and that was my thinking. The fact that Sam Ash music had them on sale sealed the deal. I was feeding them with a home made SS amp until I made a tube amp..... and then another tube amp....and.......

snowballed It's curious I tried the same (to stablish my own small studio) and got a PC... just to see they wouldn't be up to the task (486) started tinkering, things snowballed and ended up working as a sysadmin... but got the love for tubes from these studio mic preamps, guitar amps, etc days.

Honestly, on the NS-10's the CSXE's are not blatantly better. They do sound better on some bass heavy music if the volume is increased. The NS-10's are 87 db and I often play rock, so I can hear a difference in them. I have two amps that get used most often on those speakers. One is the "industrial" amp with the Transcendars, and the other is a Simple SE with 6v6's and XSE15-8-5k. My amp preference is guided by the type of music I play and how loud I want to get. I use the CSXE's on my big speakers with a 300B Tubelab SE where they can really shake the walls.

The XSE15-8-5k has a remarkably clear sound, and it is the best of the small OPT's that I have tried. I have a pair of them in the 6V6 version of the Simple SE and at that power level I can find no better affordable OPT's. They will make clear undistorted bass down to 25 Hz at the 1.8 watt level.

That's what I was hoping to hear. Then I'll get the XSE's, for wall shaking I'm building a "winter amp" with 6C33C with UBT-1 OPTs.

I am guessing that the XSE15-8-5k will be OK for your setup, but I can't guess your listening habits, volume level, or musical choices. I have not tried the GXSE's. The increased size should improve the bass, but I don't know if it compromises the highs, or that "crystal clear" that I get from the XSE15-8-5k. One user on this forum talked about "increased leakage inductance" that will compromise the sound. Based on this information, I would tend toward the ones that I know, the XSE15-8-5k. I have planned to try some of their newer transformers, but my experimentation budget is essentially zero right now.

For the price I'm sure (we) will be happy. I guess my listening habits are similar to yours, I like "good" (for me) music, the only kind I'm not into is Classical, I like all kind of genres from reggae, rock, metal, pop, R&B, Jazz, Carribean, Vocal... what I seek is what all of us which worked in music expect: to sound as closely as the real thing, i.e. not-canned, live music. And what I end up loving is good recordings/mixes, not genres.

Most times music won't get played too loud as there are 4 kids in the house and I should be always be alert, in fact the SimpleSE will go to the kitchen/dining room where I expect to be on at all hours at "ambient" levels or slightly above. The amp will be hanged from the wall (have to think a chassis for that) so the smaller the transformers, the better, I may build a vintage radio mockup or alike...

The story about the cats runing and hiding from movie gunshots they had heard before when they heard them through a SimpleSE says a lot for me is what I say to people asking me why do I prefer tubes given the distortion figures: nothing is heard clean in this world, there's always "distortions" reflections, etc due to the environment (but in an anechoic chamber)... but in nature they're always even harmonics.

 

[pukka]

George, you mention in the tubelab.com pages that the 5842 was your favourite tube, I've found Raytheon JAN at same prices that most ECC81, are they preferred against regular ECC81?

 

[pchw]

5842 and ECC81 are 2 totally different beasts, not interchangeable.

 

[pukka]

I know, I meant provided proper Rk and CCS adjustments... I still have to buy the parts.

 

[chrish]

The Edcor XPWR059 looks to have the same specification as the Hammond 374BX, 120/240V 50/60 Hz primary, secondaries of 375-0-375 175mA, 50 V 0.05A, 6.3V CT 6A, 5V CT 3A. This should be a perfect fit for the Simple SE and save you some on shipping if you get the Edcor output transformers. I am pretty sure you could also get them to do a choke for you too.