I am thinking a lot about building myself a Tubelab SSE or SE amplifier. I have been reading on here and the Tubelab site. I have alpair 7.3 that are not sensitive (86db) they are apparently 4 ohm but I think that a lot of people assume that they are 8 ohm and treat them as such. I have also noticed that mine sound better when they are plugged into my 8 ohm sockets on my current amplifier.
With these factors in mind I have been looking for reasonable output transformers. Power transformers and chokes. I have made a few assumptions so far that I don't know if I am correct. And I realise that assumptions can be costly, particularly if you have little knowledge. They are shown below.
1) to drive the Alpair 7.3 at a high volume I will need 10 - 15watts, so I am thinking of kt88 in ul configuration. Possible 10-15 watts.
2) due to the limitations of bass response for this small driver it is probably better to purchase smaller lighter, cheaper OT's. I am at present thinking 2 x edcor gxse15- 8 -5k, 1x hammond 374bx power transformer & a 10h 200mah enclosed hammond choke as my transformer set up. The use of 15-8-5k seems like they would be a good compromise between low end grunt and primary inductance (17h). I have read that lower primary inductance can make the amp sound more fluid, fast and less muddled. Do these items seem like good choices? I am aware that my drivers are officially 4 ohm and the edcor are rated at 8 ohm.
3) I like the idea of the simple se board a lot, but I can't make up my mind whether I should build SSE or SE. I am aware that SE mkII will be available any day now. Is the se really worth building or does the convenience off SSE pay off.
4) going to the extra expense of cxse 25 - 8-5k would be wasted on my drivers that apparently can only reach 40hz bass response. So I am better of going for the smaller transformers that will have better transient response. Is this logic correct?
Can anyone help me with my decisions so far please? Am I on the right tracks? I am in the UK so OT choice is limited.
Cheers
With these factors in mind I have been looking for reasonable output transformers. Power transformers and chokes. I have made a few assumptions so far that I don't know if I am correct. And I realise that assumptions can be costly, particularly if you have little knowledge. They are shown below.
1) to drive the Alpair 7.3 at a high volume I will need 10 - 15watts, so I am thinking of kt88 in ul configuration. Possible 10-15 watts.
2) due to the limitations of bass response for this small driver it is probably better to purchase smaller lighter, cheaper OT's. I am at present thinking 2 x edcor gxse15- 8 -5k, 1x hammond 374bx power transformer & a 10h 200mah enclosed hammond choke as my transformer set up. The use of 15-8-5k seems like they would be a good compromise between low end grunt and primary inductance (17h). I have read that lower primary inductance can make the amp sound more fluid, fast and less muddled. Do these items seem like good choices? I am aware that my drivers are officially 4 ohm and the edcor are rated at 8 ohm.
3) I like the idea of the simple se board a lot, but I can't make up my mind whether I should build SSE or SE. I am aware that SE mkII will be available any day now. Is the se really worth building or does the convenience off SSE pay off.
4) going to the extra expense of cxse 25 - 8-5k would be wasted on my drivers that apparently can only reach 40hz bass response. So I am better of going for the smaller transformers that will have better transient response. Is this logic correct?
Can anyone help me with my decisions so far please? Am I on the right tracks? I am in the UK so OT choice is limited.
Cheers
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If you want a kt88, then you would need to go SSE.
SE is for 45, 2A3 or 300b DHT's.
Did you see this page for SSE Tubes?
Tubes and Applications | Tubelab
There is a great table for different tubes and operating points.
Maybe you want to go SPP with a 86 db speaker?
SE is for 45, 2A3 or 300b DHT's.
Did you see this page for SSE Tubes?
Tubes and Applications | Tubelab
There is a great table for different tubes and operating points.
Maybe you want to go SPP with a 86 db speaker?
Thanks for the reply. I have a PP amp at present (not Tubelab though), and I fancied trying SE. So if I want most possible power it looks like SSE is the option for a simple build.
Has anyone built an SSE or SE for alpair 7.3's is there a recipe for success or is this not really possible.
Thanks
Has anyone built an SSE or SE for alpair 7.3's is there a recipe for success or is this not really possible.
Thanks
Measures across 100s of A7.3s is just over 87 dB average. The 5.5Ω DCR is just a bit lower than one would expect for an 8Ω nominal driver.
dave
Dave, quick question whilst you are here (hope you don't mind OP):
Tubelab SE 300B putting out 7.5w, will it adequately drive the new Alpair 11 MS (in either a Pensil or Frugal) or is that a similar sensitivity to the 7.3?
Thanks.
I generally say that you should have 10w but there is a lot of latitude. Even in my big room, an SE 2A3 (3.5w) was wonderful… we could push the amp into audible strain, in a smaller room that would be less of an issue. I used the 5W ACAs for a long time and was rarely short on loudness levels.
Maybe more important than absolute power is how well your amp handles clipping. SE amps tend to be very good in that respect.
Of course how loud you play comes into it as well.
I should also say that the Alpairs all seem to play louder than their sensitivity would indicate.
dave
Maybe more important than absolute power is how well your amp handles clipping. SE amps tend to be very good in that respect.
Of course how loud you play comes into it as well.
I should also say that the Alpairs all seem to play louder than their sensitivity would indicate.
dave
sounds familiar
fmb - sounds like you are building a system very similar to mine.
The tubelab sse was my first tube amp and I was a bit skeptical about how the low power output would sound so I did a fairly budget conscious build with all edcor iron( xpwr035-120 pt, cxc100-5h choke, and the gxse15-8-5k OTs) and nothing exotic in the way of audiophile capacitors/resistors/wiring/connectors etc. While I did wire it up with ultralinear capability I generally use it in triode mode with el34s.
Before I built a case, i hooked the wireball up to an old pair of car speakers for a test drive and when nothing caught fire, I tried them with some early 1990s Polk S8s (89db efficient i believe). These had plenty of volume for me even with an old ipod as the source input.
Later I used the mark audio alpair 7.3s in the Pensil enclosure and this also has plenty of volume for my listening in a fairly small room (15ft x 15ft x 8ft ceiling). I use the hifiberry dac hardware volume control at less than 50% and with the SSE at 100%. I have used some kt88s but i didnt change the cathode resistor to extract maximum power. I have even experimented with a 5u4g rectifiers which lower HT voltage some without problems.
I bought two more SSE boards intending to do a "high quality" build with much nicer casework and a super cheap parts bin version for my little brother but I've never finished the highend version since my first one works so well.
I also intend to build the TSE2, but I won't be able to say how it works with the Alpair 7.3s for quite a while -- (it is boating and motorcycle season after all!)
fmb - sounds like you are building a system very similar to mine.
The tubelab sse was my first tube amp and I was a bit skeptical about how the low power output would sound so I did a fairly budget conscious build with all edcor iron( xpwr035-120 pt, cxc100-5h choke, and the gxse15-8-5k OTs) and nothing exotic in the way of audiophile capacitors/resistors/wiring/connectors etc. While I did wire it up with ultralinear capability I generally use it in triode mode with el34s.
Before I built a case, i hooked the wireball up to an old pair of car speakers for a test drive and when nothing caught fire, I tried them with some early 1990s Polk S8s (89db efficient i believe). These had plenty of volume for me even with an old ipod as the source input.
Later I used the mark audio alpair 7.3s in the Pensil enclosure and this also has plenty of volume for my listening in a fairly small room (15ft x 15ft x 8ft ceiling). I use the hifiberry dac hardware volume control at less than 50% and with the SSE at 100%. I have used some kt88s but i didnt change the cathode resistor to extract maximum power. I have even experimented with a 5u4g rectifiers which lower HT voltage some without problems.
I bought two more SSE boards intending to do a "high quality" build with much nicer casework and a super cheap parts bin version for my little brother but I've never finished the highend version since my first one works so well.
I also intend to build the TSE2, but I won't be able to say how it works with the Alpair 7.3s for quite a while -- (it is boating and motorcycle season after all!)
flyingmattyboy,
The Tubelab SSE is a good project for the beginner. Both of the amplifiers sound good, but there are some differences. I have listened to the SSE with EL34, 6CA7, and 6L6GC tubes and to the TSE with 300B tubes. From memory, the TSE with 300B tubes sounded more detailed and imaged better. However, the SSE amp also sounded fine and is a much more straightforward build. The cost of the output tubes (a wide choice depending on your configuration) is generally much lower vs the TSE with 300B. The input tube for the TSE which is a 5842 or 417A is also more expensive and difficult to find compared to the widely available 12AT7 / ECC81 required for the SSE (unless you are going for a rare NOS model).
From memory, the SSE configured in triode mode sounded different vs UL mode. In triode mode you get higher level of second harmonic and that has a different sound to it vs UL; configured in UL the same amp had a brighter, slightly more aggressive sound, while triode is sweeter more relaxed. I am not saying one is universally superior vs the other, and it is a matter of preference.
In my experience, a modestly sized wide band driver like the Alpair 7.3 has limits of playing loud. Depending on your room size and listening tastes, even 5 watts might be enough.
Eyeballing the Alpair 7.3 impedance curve, you'll see that it does not go below 6.5 ohms, and throughout most of the mid and higher frequency the driver impedance is a bit higher than that. Assuming that you are using a tube amplifier, it is likely you are getting lower H2 (and higher H3 vs H2) when running the speakers from the 4 Ohm tap. Possibly the speakers sound a bit dry and harsh when connected to the 4 Ohm terminals?
Since you are in the UK, maybe these are worth checking out:
TTG-EL34SE TOROIDY - Transformer: speaker | TME - Electronic components
I have not used any toroidal output transformers, but have come across builder feedback that the toroidy units are good. Please note that Edcor has a lead time.
With 3.2k primary impedance you can use them for a KT88 build with SSE to start off with, and even a 300B build later on if you fancy. With a higher primary impedance OPT (like 5K) you will get lower watts of output power, lower distortion, and more damping factor. George provides an excellent table of simulations with different tubes at various points of operating voltage, bias, and primary impedance on this page:
Tubes and Applications | Tubelab
The Hammond 374BX is a good choice for power transformer for your project. For choke you can consider the Triad Magnetics C-14X - quite inexpensive and works fine; however it is open frame - so for both safety and aesthetics you will either need to use a transformer cover of sorts or install the choke inside of the amplifier chassis.
Any amp you build may some day see service with a different set of speakers so I’d be tempted to build for wider bandwidth than you think you need. Your call for sure. My speakers are 88db (Alpair 10p) and a 5W el34 triode amp gets them too loud to try and talk around. Triple the power won’t add much to the perceived loudness.
Good to know. Admittedly, 3db is a significant difference in sensitivity but at 20db max and the diminishing returns of increased wattage I’d be tempted to take the less is more approach.
I am more than happy with those OT it in a music only system playing a wide variety of alternative and classic rock, americana, electronica, jazz, and classical music.
Sound like the matching of the transformers to the drivers is not an issue then which is good because I couldn't part with 7.3's or frugal' s.
Thanks all for the advice, zman I looked up the toroidy OT's and got very excited and then read many mixed opinions on the use of Toroids as OT. It would be too much of a gamble..I have approached a company about getting bespoke ones made up. If this is not cost effective I think it will be back to the 15-8-5k.
Pretty sure I will go for sse now, I might even order the board.
Cheers
MATT
Thanks all for the advice, zman I looked up the toroidy OT's and got very excited and then read many mixed opinions on the use of Toroids as OT. It would be too much of a gamble..I have approached a company about getting bespoke ones made up. If this is not cost effective I think it will be back to the 15-8-5k.
Pretty sure I will go for sse now, I might even order the board.
Cheers
MATT
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Yeah I looked at their pricing after I posted, and they are pretty pricey. But good iron is not cheap from anyone, I think its pretty labor intensive to wind a good output tx.
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