I am building my first 300B SE (Audio Note type design) and I found EDCOR CXSE OPTs are nice.
I tried to contact EDCOR for advices but got no response.
Can any one please tell me the difference between them and recommend one for 300B SE apm?
CXSE25-8-2.5K
CXSE25-8-3K
CXSE25-8-3.2K
Thanks a lot
Jack
I tried to contact EDCOR for advices but got no response.
Can any one please tell me the difference between them and recommend one for 300B SE apm?
CXSE25-8-2.5K
CXSE25-8-3K
CXSE25-8-3.2K
Thanks a lot
Jack
That is not generally the case. The GXSE is a smaller transformer intended for use in guitar amps. The CXSE25 is a large (about 10 pounds) OPT intended for use in HiFi amps. In my opinion the CXSE25 is by far the best SE OPT that you can get for under $100.
A 300B in most circuits wants to see a 3 to 3.5K ohm load. That is the accepted norm. Reducing the load to 2.5K would offer a slight increase in power but a considerable increase in distortion with a loss of damping factor. I tend to favor going the other way. I use a 5K CXSE25 in my 300B amp. This drops the power output slightly but also lowers the distortion and raises the DF.
Examine the characteristics of your speakers. An "8 ohm" speaker is rarely 8 ohms and may be 8 ohms at only one frequency. The impedance VS frequency curve should be available from the manufacturer. If the curve is below 8 ohms a lot, then go for a higher value of OPT. If the curve is above 8 ohms a lot, you consider a lower valued OPT.
I must have mixed up which OPT. I didnt check, only used memory. Scary!!! I mean the opt with BW from 40Hz, not the ones from 100Hz (the guitar versions). The 15watt version I meant is the same size as the 25watt version I thought he meant.
Im not going to argue with u about best impedance, u are a lot more experienced than me
Im not going to argue with u about best impedance, u are a lot more experienced than me
Since you live in New Zealand you might also want to check out Silk from Thailand, and James from HK - both of which I'd think would offer affordable alternatives to Edcor, particularly when you factor in the shipping costs from the U.S.
I've no direct experience of transformers made by Silk, however they are very well regarded in Asia, (by friends of mine) and James makes very good transformers indeed based on my very limited direct exposure to them.
If you tried to contact Edcor within the last few days the Labor Day holiday may be why you have not heard back from them.
George is right, 3K - 3.5K is ideal where you are trying to extract maximum power without excessive distortion, and 5K provides exactly the benefits he elucidates.. All of my commercial 300B SE amps used 3 - 3.5K opts, the PP amps 3.8K - 5K..
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You contacted Edcor, and got no response?
That's quite odd, Iv never had a issue calling, and when i send a email, its (at most) 2 days for a proper response.
Try contacting Phyllis!
Phyllis Weston
EDCOR Electronics Corporation
7130 National Parks Hwy.
Carlsbad NM 88220
Phone (575) 887-6790
Fax (575) 887-6880
pweston@edcorusa.com
That's quite odd, Iv never had a issue calling, and when i send a email, its (at most) 2 days for a proper response.
Try contacting Phyllis!
Phyllis Weston
EDCOR Electronics Corporation
7130 National Parks Hwy.
Carlsbad NM 88220
Phone (575) 887-6790
Fax (575) 887-6880
pweston@edcorusa.com
Thanks a lot everyone, I think I have learnt something
I will check my speakers' "VS frequency curve" before making decision on the input impedance of the OPT. I am using a pair old Tannoy M15 which I am still loving..
I will talk to Phyllis at EDCOR about the options and cost tomorrow as it is too late in US.
Good to know the alternative OPT (Silk from Thailand, and James from HK, I will check them out as well.
Cheers
Jack
I will check my speakers' "VS frequency curve" before making decision on the input impedance of the OPT. I am using a pair old Tannoy M15 which I am still loving..
I will talk to Phyllis at EDCOR about the options and cost tomorrow as it is too late in US.
Good to know the alternative OPT (Silk from Thailand, and James from HK, I will check them out as well.
Cheers
Jack
I have checked the Silk OPT and James OPT, they both look very nice with outstanding test results vs others, but they cost more than the EDCORD CXSE25-8-3.2K (us$83/each).
Also talked to Phyllis at EDCORD on phone (they just back from holidays), she said that the shipping cost of a pair of CXSE25-8-3.2K to NZ will be US$48.00 only.
Given that 2 x EDCORD CXSE25-8-3.2K plus shipping to NZ= us$214, I believe I will go for the EDCORD in my first SE AMP.
Thanks again everyone
Also talked to Phyllis at EDCORD on phone (they just back from holidays), she said that the shipping cost of a pair of CXSE25-8-3.2K to NZ will be US$48.00 only.
Given that 2 x EDCORD CXSE25-8-3.2K plus shipping to NZ= us$214, I believe I will go for the EDCORD in my first SE AMP.
Thanks again everyone
Yeah I brainfarted big time
I surfed on my Iphone, and for some reason I cannot open Edcor's site on it to check, so tried to use memory...Not sure if it's fumes from the solder, alcohol, or a mix of both, but my memory these days isn't much to brag about
I have used the GXSE15 series in a 6AS7 amp with great results, espescially considering the price of those OPT. (Not sure I can tell the difference between those and the One Electrons I use in a similar amp, tho the latter measure a little bit better).
No worries SemperFi, I am sure the GXSE series is also good, considering the spec difference between GXSE and CXSE, I would go for the CXSE for 300B. And I planned to got a pair of full range speakers later on, I believe the 3.2k will be ok to provide enough output power (8W??) to derive the speakers.
Thanks for your response
Jack
Thanks for your response
Jack
I'm using the CXSE25-8-5K in my 300B design. I run it at 375 V, 95 mA and get 11 W @ 3 % THD with 5 kOhm load; 13 W @ 3 % THD with 3.3 kOhm load. THD measured at 1 kHz. I would run at 400~410 V if my supply allowed it. That gives 13-ish W with 5 kOhm load.
As others have said already, going with 3 kOhm load gives higher THD than 5 kOhm load. To me the couple of extra watt at the 3 kOhm load isn't worth the increase in THD. We're talking less than a 1 dB difference here. A 1 dB difference is about the limit of what I'm able to detect when performing an A/B test.
I really like the sound of the JJ 300B with the Edcor CXSE25-8-5K at the 375 V, 95 mA quiescent point. The sound stage is rather incredible - almost freaky at times.
The trick with the 300B is to have the right driver for it. If you want a half-decent amount of power out that is. The driver has to be able to source a bit of current as the 300B will draw a little bit of grid current even with Vgk slightly negative.
~Tom
As others have said already, going with 3 kOhm load gives higher THD than 5 kOhm load. To me the couple of extra watt at the 3 kOhm load isn't worth the increase in THD. We're talking less than a 1 dB difference here. A 1 dB difference is about the limit of what I'm able to detect when performing an A/B test.
I really like the sound of the JJ 300B with the Edcor CXSE25-8-5K at the 375 V, 95 mA quiescent point. The sound stage is rather incredible - almost freaky at times.
The trick with the 300B is to have the right driver for it. If you want a half-decent amount of power out that is. The driver has to be able to source a bit of current as the 300B will draw a little bit of grid current even with Vgk slightly negative.
~Tom
That is a very open-ended question. The short open-ended answer: One that provides enough voltage and current to supply the 300B...
If the 300B is self-biased (resistor on the cathode), you'll need 450~500ish volt on the anode. A 450-0-450 (900 V CT) transformer is probably just the ticket if you're using vacuum tube rectification. 400-0-400 (800 V CT) for solid state rectification.
If the 300B cathode is grounded, you'll need 400-ish volt on the anode. So a transformer that provides 340-ish volt (680~700 V CT) for solid state rectification, or upward of 375 V (750 V CT) for tube rectification.
The transformer should be able to supply at least 100 mA per 300B. I'd probably add a good 50 % margin and spec 150 mA per 300B.
Above assumes that you'll be running the 300B rather hot - my preference - at near its maximum voltage and anode dissipation.
~Tom
I'm open to all suggestions as I am determining a suitable design like this one:
6SN7 / 300B Single-Ended (SE) Tube Amplifier Schematic
I am considering driving it with a two stage 6SN7.
SS rectification and either stereo block, or mono block.
And Electro-Harmonix 300B.
I have an EICO ST70 and just want to try a 300B without breaking the bank.
6SN7 / 300B Single-Ended (SE) Tube Amplifier Schematic
I am considering driving it with a two stage 6SN7.
SS rectification and either stereo block, or mono block.
And Electro-Harmonix 300B.
I have an EICO ST70 and just want to try a 300B without breaking the bank.
Looks pretty standard. Nothing wrong with it, but it'll suffer from the same issues as the rest of the common cathode drivers - blocking distortion. George Anderson has a good summary here: PowerDrive. Blocking distortion is nasty. I saw it in my 300B design before I changed to a PowerDrive-inspired circuit. On transients, the amp "farts out" and the result is a few hundred ms of violent speaker cone movement as the 300B bias settles. It sounds nasty.
I chose to solve this issue by using a source follower to drive the 300B. That way it'll enter A2 operation on the high transients and not fart out. I really like the sound of this amp... You can check out my design here: DeathTrap 500. I do admit that I went a little overboard on complexity - especially in the power supply. But you could rework that if you feel like it...
If you don't want sand in your glass, I'd look at the 300B DRD from ElectraPrint. I love that design for its simplicity. I would love to build one, though, I'd like to find a different solution for the choke and 50 W rheostat required.
~Tom
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