Sympathies guys. I once padded (resistance) my ps fan to make it quieter and then forgot until the middle of summer 😡
I have posted the test data from the 1628SE and the Edcor CXSE25-8-5K transformers to my web site. Too much data to attach here. I will add more transformer tests as they are done. Listening test data will also be added soon.
The short story is:
These transformer sound a lot more similar than the data would suggest. The Hammonds bring more bass out of my small speakers, but the Edcors have a little more high end sparkle.
I dragged the whole setup out to the living room and hooked it up to my "big speakers." These consist of modern drivers installed into a large pair of 65 year old Zenith console radios. These fit into Sherri's decorating scheme. This is the first time that I have connected these speakers to this big of an amp (previously fed with a TubelabSE using 45's). The bass was amazing. You could hear it across the street.
I ran the setup with Edcors for 2 days, and was amazed. I didn't think that the Hammonds could beat them. When I first tried them I was disapointed. Tonight, I figured out that I have the CFB out of phase (positive). They really sound good when wired right! I have only had about 2 hours to test them, but I think that they do beat the Edcors.
http://www.tubelab.com/Output_Transformers.htm
The short story is:
These transformer sound a lot more similar than the data would suggest. The Hammonds bring more bass out of my small speakers, but the Edcors have a little more high end sparkle.
I dragged the whole setup out to the living room and hooked it up to my "big speakers." These consist of modern drivers installed into a large pair of 65 year old Zenith console radios. These fit into Sherri's decorating scheme. This is the first time that I have connected these speakers to this big of an amp (previously fed with a TubelabSE using 45's). The bass was amazing. You could hear it across the street.
I ran the setup with Edcors for 2 days, and was amazed. I didn't think that the Hammonds could beat them. When I first tried them I was disapointed. Tonight, I figured out that I have the CFB out of phase (positive). They really sound good when wired right! I have only had about 2 hours to test them, but I think that they do beat the Edcors.
http://www.tubelab.com/Output_Transformers.htm
Tubelab,
Thank you for the test. It is very helpful. I bought a 1627SEA and my giant capacitor is the same as yours. I am now more than confident that my amp will not be bad.
vax9000
Thank you for the test. It is very helpful. I bought a 1627SEA and my giant capacitor is the same as yours. I am now more than confident that my amp will not be bad.
vax9000
Tubelab,
I to want to thank you for your work and very nice documentation. I'm glad that the Hammonds are back into your interests. And it boosts my own faith in the line as well!
SET12
I to want to thank you for your work and very nice documentation. I'm glad that the Hammonds are back into your interests. And it boosts my own faith in the line as well!
SET12
I dragged the test amp into the living room (big speakers) and have been playing it for a week (Sherri is out of town). I have not turned on my TubelabSE in this week (SE using Electra-Print transformers and 45's or 300B's). I have decided that I like the sound enough that I must make an amp with enough WAF to be allowed into the living room. This will be difficult due to the size of the Hammonds. I have limited space and something will have to go. This amp will play music that the 300B amp wouldn't, mostly bass heavy rock (Pink Floyd is playing now). I think I will try the Hammonds on the 300B amp.
I got a phone call from CE distributing (commercial division of AES) to inform me that my "special order" 1628SEA's have shipped. This was about two weeks quicker than they had estimated.
This is good, BUT, they will arrive the day after I leave on my annual August road trip. I will test them and report the findings when I return (late August).
I like Hammond in guitar amps- reliable & sound good. For home entertainment amps & compared to others, the Hammond has higher distortion in the lower registers. I just do not skimp on the audio iron in my home entertainment DIY amps.
I have not seen that. This is the 11 pound Hammond 1628SE. It is the only transformer that I tested which can do 15 watts at 44 Hz without distorting. In fact the distortion VS power curve at 44 Hz is almost on top of the 1 KHz curve. I find that they have more distortion at 10 KHz at power levels above 5 watts. A situation that should not occur in music. (The curves are on my web site)
Granted there are plenty of better transformers out there. I have limited my testing to transformers that cost less than $100 USD each. This amplifier is being designed on a strict budget (as with most of my amps). These OPT's cost far more than all of the other parts in the amp combined.
I have tested a lot of transformers for this design, from $14 each to $99 each. There is no clear cut winner. It depends on what you like, and how much you have to spend. About the only thing that IS obvious is the abundant, CLEAN bass that these Hammonds put out. If you believe that SE amps don't have good bass, try these transformers, add a little CFB if you want (not necessary but it helps). Hook up some big speakers, and prepare to have your neighbors complain!
tubelab.com said:
My measurements support that. I also find they sing along with the music swinging ~40 V p-p into 8-ohms from the 4-ohm tap. 🙂
Most OPT's make some noise. You just don't notice it with speakers hooked up. The Hammonds were quieter than most, but I am running half the power that you are. One makes more noise than the other. The one that drowned in transformer varnish is the quiet one. I wonder why?
The big Edcors scream at 2 Khz and are silent above 4 KHz. I have a pair of Handwound Transformer OPT's that you can hear in the next room at 1KHz, but I am cranking 40 watts through them.
25 watts, which tube? 813? and how, triode or UL?
hi tubelab, should you have an opportunity to test the cheap MagneQuest Robin Hood series, please publish it as well.
Both my James make some noise as well. I was just happy this thing will drive almost 25 watts SE into 8.
Yep, with a 2-stage 813 triode amp. UL dropped the damping factor too much. Front end an LED biased 6C45 with just under 4 volts on cathode, 6.4 ma CCS via IXYS. That's with a 100K grid resistor on the 813, different values require slightly different currents to null the 6C45's third harmonic (into 24 bit noise at 150 V p-p swing!) The Shushang 813 seems to work best around 975 Vdc B+ and ~-100 on the grid, for about 75-80 ma. Might be the brand but higher B+ raises the higher harmonics regardless of grid bias. Haven't listened to it yet but I'm juiced about this one, it shows real promise. And glad to be making use of what I though we lost causes.
Yep, with a 2-stage 813 triode amp. UL dropped the damping factor too much. Front end an LED biased 6C45 with just under 4 volts on cathode, 6.4 ma CCS via IXYS. That's with a 100K grid resistor on the 813, different values require slightly different currents to null the 6C45's third harmonic (into 24 bit noise at 150 V p-p swing!) The Shushang 813 seems to work best around 975 Vdc B+ and ~-100 on the grid, for about 75-80 ma. Might be the brand but higher B+ raises the higher harmonics regardless of grid bias. Haven't listened to it yet but I'm juiced about this one, it shows real promise. And glad to be making use of what I though we lost causes.
tubelab.com said:
It happened to me! I got a call from my neighbor that her pictures were moving on her walls!
Our living rooms seperated by two garges! Acoustic energy traveled into my wall from my modified Klipsch Forte's up to the roof truss and down it back into her wall! Talk about transient response and people tell me that SE has no bass! I use no EQ and have no sub!
Bass produced from my 28lb Hammond 1642's from 10 watts of 572-10's running Class A2 with no CFB!
SET12
OK, you have got me beat by 17 pounds! Someday I am going to put 1642's and 833A's together. It won't be soon, too many projects already.
Lemme see, There is a box on the shelf with some 813's (RCA I believe) there are two new Hammonds coming, there is a plate transformer from an old ham radio transmitter under the bench, I bought some Xenon rectifiers at a hamfest. Sounds like another project. 25 watts in triode, maybe next month.
tubelab.com said:
I looked over the James trannys very nice looking! I like the 10k 16 lb SE! I might have the Iron! But your brains go further than mine!😀
Tubelab: Can you please tell me how to wire a Hammond 125CSE to get CFB with correct phase?
I´m working on a four channel amp with 807´s that will be finished any day now, but I´m not quite sure about the transformer phase.
I´m working on a four channel amp with 807´s that will be finished any day now, but I´m not quite sure about the transformer phase.
Hi Fulling, easiest way is try one. The output should obviously decrease relative to no CFB for a constant input level. With the 807's drive requirements getting it wrong is very unlikely to damage anything, CFB doesn't provide enough return signal to push a properly working output stage into instability.
I wasn't smart enough to write it down the first time. If I have a chance to hook one up before I leave I will post the hookup here. My amp currently has the big Hammonds in it, and they are "backwards". This means that you must swap the leads on EITHER the primary or secondary, to get negative feedback. This seems to be the case for most SE OPT's, but I think that the 125CSE is "normal." I just can't be sure without testing one.
This is usually the case, but I have had some tube - transformer combinations ($18 Edcor - EL34) oscillate when wired wrong. This is not destructive, but results in a loud buzz. Use a test load or cheap speakers for any initial amp testing. Try the transformer both ways and pick the polarity which gives the lowest gain (or doesn't oscillate).
This is usually the case, but I have had some tube - transformer combinations ($18 Edcor - EL34) oscillate when wired wrong. This is not destructive, but results in a loud buzz. Use a test load or cheap speakers for any initial amp testing. Try the transformer both ways and pick the polarity which gives the lowest gain (or doesn't oscillate).
If I remember correctly both the Edcors and the 125CSE's oscillated during my brief experiments with pentode connection of the EL34 (way more gain).
I know from my recent experience that the 1628SE (also a "backward" transformer) will not oscillate when wired wrong. I had been listening to the big Edcors through the big speakers in my living room, when I decided to swap in the Hammonds. When I turned it on, it didn't sound right. It was loud, I didnt hear any obvious distortion, it was just anoying. I turned the amp off and went to bed. The next day it was obvious that I had miswired the feedback. After the mistake was corrected, the amp rocked, literaly.
I know from my recent experience that the 1628SE (also a "backward" transformer) will not oscillate when wired wrong. I had been listening to the big Edcors through the big speakers in my living room, when I decided to swap in the Hammonds. When I turned it on, it didn't sound right. It was loud, I didnt hear any obvious distortion, it was just anoying. I turned the amp off and went to bed. The next day it was obvious that I had miswired the feedback. After the mistake was corrected, the amp rocked, literaly.
I measured the primary winding of my Hammond 1627SEA today. The DC resistance is 77 Ohms, much smaller than the 280 Ohms of 1627SE. The primary inductance is about 16.5 H, smaller than the 21-22H of 1627SE too. The 1627SE data is from the internet.