Just put an order in for SSE pcb. Was thinking of running this in triode mode\EL34 for my Zu Audio - Omen Dirty Weekend mk2 speakers which are 97db. Sounds rather naughty doesn't it - perhaps the manuf could have chosen a better name or its great marketing?
I would like to hear any advice on your build experience. Does the build benefit from boutique parts ? What has been your experience with tube rolling? I have a lot of tubes in my stash but no el34 and 12at7's so any advice would be appreciated.
if you have any iron or parts lying around that I could purchase off you please let me know via pm.
Thx
Neville
I would like to hear any advice on your build experience. Does the build benefit from boutique parts ? What has been your experience with tube rolling? I have a lot of tubes in my stash but no el34 and 12at7's so any advice would be appreciated.
if you have any iron or parts lying around that I could purchase off you please let me know via pm.
Thx
Neville
I built it as per the parts list. Had it running for a couple of months powering headphones,Hifiman HE6.
First I changed the coupling caps to Vcaps, big differance, better imaging and bass.
Few weeks latter changed all resistors to Audio Note no change I could detect.
Added a Khozmo Stereo Series Stepped Attenuator, 48 step found it to be a gain in imaging and highs. But not huge.
Tube rolling I change from 12at7 Mullard to Siemens alot. Siemen is better at vocals than Mullard which then is better at rock.
Changed the rectifier valve from Harmon to Gold Lion apart from the Vcaps this was poss the biggest change in sound for the better.
I built it with Edcor CXSE25-8-5K running KT88, Gold Lion reissue. As per the basic build layout.
This is my end game amp and I love how it sounds and don't think I could better it at my buget.
First I changed the coupling caps to Vcaps, big differance, better imaging and bass.
Few weeks latter changed all resistors to Audio Note no change I could detect.
Added a Khozmo Stereo Series Stepped Attenuator, 48 step found it to be a gain in imaging and highs. But not huge.
Tube rolling I change from 12at7 Mullard to Siemens alot. Siemen is better at vocals than Mullard which then is better at rock.
Changed the rectifier valve from Harmon to Gold Lion apart from the Vcaps this was poss the biggest change in sound for the better.
I built it with Edcor CXSE25-8-5K running KT88, Gold Lion reissue. As per the basic build layout.
This is my end game amp and I love how it sounds and don't think I could better it at my buget.
The output tubes that I've tried are Mullard EL34 reissue and Gold Lion KT88 reissue. The EL34 have a slight sq advantage in the midrange and are slightly more forward in the mids. However, I find them lacking in bass. To my ears, the GL KT88 really don't give up much in the mids compared to the EL34's but also have much better bass. Using them with the big Edcor CXE opts, I'm getting solid, articulate bass that rivals that of a good solid state amp. The soundstage is wide and 3d.
The preamp tubes that I've tried are Amperex Bugle Boy 12at7, Mullard CV4024, Tungsram 12at7, and GE five star 6201. My favorite here is the Bugle Boy, with the Mullard a close second.
Speakers are Klipsch Forte II, which are 99db efficient.
As always, your ears and mileage will vary.
Check out post #73 by "rknize" here:
Tubelab Simple SE with big honkin' Edcors?
Good luck with your build!
The preamp tubes that I've tried are Amperex Bugle Boy 12at7, Mullard CV4024, Tungsram 12at7, and GE five star 6201. My favorite here is the Bugle Boy, with the Mullard a close second.
Speakers are Klipsch Forte II, which are 99db efficient.
As always, your ears and mileage will vary.
Check out post #73 by "rknize" here:
Tubelab Simple SE with big honkin' Edcors?
Good luck with your build!
Wow thank you both juststeve and Yukon888 for your input. Over the years I have accumulated a huge stash of 6550,KT88 and all the various input tubes but none I can use for this project so your feedback will certainly help.
I been thinking about getting all my iron from Edcor and I believe they ask you what impedance for the OPT - my Zu Audio's are 12ohms but I want to be able to use 4 and 8 ohm if possible. Will 8 ohms have any adverse affects? What do you recommend?
I was thinking of the XPWR035 and CXSE25-8-5K but Edcors site only refers me to the CXSE25-5K. Assuming this new part is just with the drop down option of whichever ohms you want?
Thx
I been thinking about getting all my iron from Edcor and I believe they ask you what impedance for the OPT - my Zu Audio's are 12ohms but I want to be able to use 4 and 8 ohm if possible. Will 8 ohms have any adverse affects? What do you recommend?
I was thinking of the XPWR035 and CXSE25-8-5K but Edcors site only refers me to the CXSE25-5K. Assuming this new part is just with the drop down option of whichever ohms you want?
Thx
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I'm not knowledgeable enough to give you a firm answer on this, so hopefully someone else will chime in.
Thanks zman01 for that recommendation. After searching I don't see anybody using this model so kinda on the fence about this. I really want a true and tested one. I know that from Decware forums they have 12/16ohms speakers connected to the 8ohm tap and I see this on other manufacturers amps too. So I am thinking that driving 120hms from one of the Edcor 8ohms shoudn't be a problem - can somebody confirm this?
btw I can't wait to get this ordered, built and compare it to my Decware amp.
thx
btw I can't wait to get this ordered, built and compare it to my Decware amp.
thx
Neville,
Found this:
One Electron transformer good or bad?
You can drive a 12 ohms speaker from the 8 ohms tap. The tube will see a different load though. To simplify, if the speaker impedance is around 12 ohms throughout the frequency range, and if it is connected to the 8 ohms tap of a 5k OPT, the tube will see 7.5k load. (12 is 1.5 times of 8, and 1.5 x 5k= 7.5k).
For a speaker with nominal 4 Ohm spec, connected to the 8 Ohm tap of a 5k OPT, the tube will see a 2.5k load (4 is 0.5 times of 8, and 0.5 x 5k= 2.5k).
Found this:
One Electron transformer good or bad?
You can drive a 12 ohms speaker from the 8 ohms tap. The tube will see a different load though. To simplify, if the speaker impedance is around 12 ohms throughout the frequency range, and if it is connected to the 8 ohms tap of a 5k OPT, the tube will see 7.5k load. (12 is 1.5 times of 8, and 1.5 x 5k= 7.5k).
For a speaker with nominal 4 Ohm spec, connected to the 8 Ohm tap of a 5k OPT, the tube will see a 2.5k load (4 is 0.5 times of 8, and 0.5 x 5k= 2.5k).
Just to add, if you notice in my previous post I mentioned "to simplify", as speakers in real life uses cases usually do not have a flat impedance curve throughout the frequency range, rather they can go up and down a bit; however "flattish" throughout the majority of the curve is easier for the amp.
Now, if I were asked to choose a spec for the Edcor CXSE25 transformer with KT88/6550 tubes and to be using with your speakers, I would have been more partial towards a 3.0K or 3.5K transformer with 8 ohms tap.
You can check out the simulations provided by George (Tubelab) here:
Tubes and Applications | Tubelab
What power transformer are you planning to use?
Now, if I were asked to choose a spec for the Edcor CXSE25 transformer with KT88/6550 tubes and to be using with your speakers, I would have been more partial towards a 3.0K or 3.5K transformer with 8 ohms tap.
You can check out the simulations provided by George (Tubelab) here:
Tubes and Applications | Tubelab
What power transformer are you planning to use?
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I was planning on going with Edcors - power - XPWR035 and OPT - CXSE25-8-5K.
Maybe I am going about this the wrong way. I want to use El34 tubes and dont want to drive them hard and only need 2 watts. If I can get the same setup to also use 6550/KT88 then that will be a bonus (probably needing adjustments on KR). This "flea watt" will only be used to drive 12ohm speakers but also bonus if it could handle other sensitive load speakers.
Maybe I am going about this the wrong way. I want to use El34 tubes and dont want to drive them hard and only need 2 watts. If I can get the same setup to also use 6550/KT88 then that will be a bonus (probably needing adjustments on KR). This "flea watt" will only be used to drive 12ohm speakers but also bonus if it could handle other sensitive load speakers.
Neville,
No worries. There are ways to have your cake and eat it too when it comes to using EL34 and KT88 in the same setup.
If your power transformer is around 720-750 VCT, my estimation is it will support both the EL34 and KT88/6550. If 750 VCT is high for the EL34, then you can drop the B+ voltage by using a 5U4G rectifier instead of a 5AR4 rectifier. With the 2 rectifiers you can experiment with the sound at different B+ voltages.
Your choice of power transformer (XPWR035) is rated for 2 amps on the 5V tap - you should get one with 3 amps on 5V. This is one option:
EDCOR - XPWR002
Don't worry, I think you're on your way to building yourself a rocking amp.
George's simulations will tell you that both the EL34 and KT88 can work with 3K or 5K transformers and anything in between.
No worries. There are ways to have your cake and eat it too when it comes to using EL34 and KT88 in the same setup.
If your power transformer is around 720-750 VCT, my estimation is it will support both the EL34 and KT88/6550. If 750 VCT is high for the EL34, then you can drop the B+ voltage by using a 5U4G rectifier instead of a 5AR4 rectifier. With the 2 rectifiers you can experiment with the sound at different B+ voltages.
Your choice of power transformer (XPWR035) is rated for 2 amps on the 5V tap - you should get one with 3 amps on 5V. This is one option:
EDCOR - XPWR002
Don't worry, I think you're on your way to building yourself a rocking amp.
George's simulations will tell you that both the EL34 and KT88 can work with 3K or 5K transformers and anything in between.
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And just for kicks I was trying to calculate the B+ on my future build but it does not tie up with others with the same setup. Edcor XPRW035+ CXSE25-5K 8ohms x 2:
370 x 1.414 = 523V peak AC which then flows into tube rectifier (GZ34/5AR4)
523V - 30V voltage drop from rectifier - 500V DC out
I have seen others post B+ of around 460V. Where am I going wrong ?
I also have Hammond 193H choke in mind.
Thx
370 x 1.414 = 523V peak AC which then flows into tube rectifier (GZ34/5AR4)
523V - 30V voltage drop from rectifier - 500V DC out
I have seen others post B+ of around 460V. Where am I going wrong ?
I also have Hammond 193H choke in mind.
Thx
The 1.414 number is a theoretical number that will be achieved with a perfect sine wave into your transformer at exactly it's rated input voltage and zero or a very light load current. None of these are true in a real world amp. The real world number is somewhere around 1.3.
My SSE runs about 460 to 465 volts with solid state rectification and 425 to 435 with a 5AR4.
The large diodes are only needed if the solid state rectifier is used. If you plan to use only tube rectification, leave them out. No heat sink is needed if they are used.
The 10M45's are current source chips which are required in all builds. They need small heat sinks, but no compound is needed. I usually just screw the heat sink to the chip, but this will put 300+ volts on the heat sinks. Insulating thermal pads could be used if desired.
I looked up your speakers but the manufacturer does not have any impedance VS frequency data posted for the MKII version. If they are like the MKI's, the impedance drops into the 8-10 ohm range in the midrange frequencies where distortion is most audible, so an 8 OHM OPT would be the right choice.
If the speakers do actually have a 12 to 16 ohm impedance over the whole audio frequency range, then the output tubes will see a true load in the 8 to 10 K ohm range. Most tubes produce less output power, LOWER distortion, and a higher damping factor when operated class A into a higher than recommended load. This may be exactly what you want.
You could always try putting a resistor in parallel with your speakers to lower the load impedance on the tube. Yes, it will waste power, but you have plenty, and it may improve the sound, but it's just a guess. I have done this when connecting 32 ohm and higher headphones to a TSE amp and it sometimes helps.
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