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Hammond 125ESE bandwidth when used at lower power?

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Posted on December 25, 2020 at 16:37:47
LowRedMoon
Audiophile

Posts: 1091
Location: Central PA
Joined: February 28, 2006
 I'm giving SE another try. I had Bottlehead Paramours years ago and liked them, but sold them to try other things.

Waiting for Edcor to fill an order isn't a good choice given my circumstances. I'm looking for "off the shelf" SE transformers that don't cost a lot.

The two I'm looking at are the Classic Tone 40-18031 (5K/8K pri., multiple sec.), and the Hammond 125ESE. I don't know if the Classic Tone SE transformers have an air gap. I emailed but no reply yet.

I'd be using them with 2A3 and EL84 tubes, so around 3 watts. My novice thinking is that I will get better low end response with larger transformers. My speakers are Cornwalls, so low frequency quality will be perceived.

Any thoughts or experiences to share in this application?

Thank you,

Adam

 

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RE: Hammond 125ESE bandwidth when used at lower power?, posted on December 25, 2020 at 17:27:26
Paul Joppa
Industry Professional

Posts: 7296
Location: Seattle, WA
Joined: April 23, 2001
 I have not measured any of the 125xSE units, but I did do an analysis of the published specs with some plausible assumptions a few months ago. I concluded that the 125ESE should work quite well with a 2A3 at 2500 ohms. The bass might be a little weak at 5Kohms, but not terrible.

 

RE: Hammond 125ESE bandwidth when used at lower power?, posted on December 25, 2020 at 20:09:39
LowRedMoon
Audiophile

Posts: 1091
Location: Central PA
Joined: February 28, 2006
 "I concluded that the 125ESE should work quite well with a 2A3 at 2500 ohms. The bass might be a little weak at 5Kohms, but not terrible."

I was wondering about, and trying to research this.
Without getting too far into it (unless you want to), are the following correct?
1. The secondary "taps" are all taps at different points on one physical wire.
2. If "1" is true, then using the taps for higher effective primary impedance increases leakage inductance and decreases mutual inductance. The best scenario is to use a transformer with a single secondary impedance, or to use the tap for its highest secondary impedance.

Thank you for being tolerant of my questions.

Adam

 

RE: Hammond 125ESE bandwidth when used at lower power?, posted on December 25, 2020 at 22:03:04
Paul Joppa
Industry Professional

Posts: 7296
Location: Seattle, WA
Joined: April 23, 2001
 I don't know how they are wound, so it's hard to answer. The secondary must be contiguous, of course, but it may be made of several different diameter wires, and could be non-sequentially wound. These things make a difference to the leakage inductance. There are a lot of tricks, and I only know a couple of them! So for the treble I just note that they are specified to extend to 15kHz at -1dB which is good enough for most people..

My analysis was primarily concerned with the bass. The 125ESE is quoted at about 10 henries, which is the same as the Magnequest TFA-204 with a 3K primary, so small-signal bass extension would be a bit better than the MQ at 2.5K. The old Paramour used a 10 henry plate choke and a 4K transformer impedance (albeit in parafeed) so it's probably adequate at 5K.

The other question is power handling - at what point does it go into saturation? You can deduce that from the full-power spec of 100Hz; I got 3.75 watts at 25Hz into 2.5K, which is fine for a 2A3. At 5K it takes 7.5 watts at 50Hz, so 3.75 watts down to 35Hz.

Obviously these are crude calculations with many possibilities for error, so no promises ... :^)

 

RE: Hammond 125ESE bandwidth when used at lower power?, posted on December 26, 2020 at 15:52:09
LowRedMoon
Audiophile

Posts: 1091
Location: Central PA
Joined: February 28, 2006
 That's useful information, Paul. Thank you for that.
I'll order a pair and give those 2A3s a chance in a single ended amp.
By the way, I got the RCAs to perform correctly in the Millett 6B4 amp by adding a 100uF cathode bypass capacitor to each 2A3 (if you remember that thread). I'm not sure what what causing the increasing grid voltage without the caps (oscillation, maybe?), but I'm going to disconnect them and probe around to see if I can track it down.

Thanks again,

Adam

 

you could biamp, posted on December 27, 2020 at 07:28:07
elblanco
Audiophile

Posts: 3486
Joined: August 20, 2004
 if you want to give SE a shot with 125ESE , give it something it can easily handle.

you could use SS amp (if you have one) for lows and 2a3 for 200hz on up.

it would sing like Caruso.

 

RE: you could biamp, posted on December 27, 2020 at 08:00:43
Tre'
Industry Professional

Posts: 17305
Location: So. Cal.
Joined: February 9, 2002
 That's what I do because I am convinced that no SE output transformers really have enough inductance to play bass properly. Volt Second had a paper about this. When you limit the frequency to 200Hz the load line gets real resistive and the mids and the highs benefit greatly.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

Bass driver might prefer an EL-84 PP anp anyway...., posted on December 27, 2020 at 08:58:23
Ivan303
Audiophile

Posts: 48887
Location: Cadiere d'azur FRANCE - Santa Fe, NM
Joined: February 26, 2001
 Best I've ever heard a Cornwall sing was being driven by an EICO EL-84 PP amp which was maybe 16-17 watts?

Bass was fine but that was a lot of years ago.

Volt Second?

That's a blast from the past.

Met him a VSAC MANY years ago. Is he still about?




First they came for the dumb-asses
And I did not speak out
Because I was not a dumb-ass

 

That's a reasonable solution..., posted on December 27, 2020 at 09:14:16
LowRedMoon
Audiophile

Posts: 1091
Location: Central PA
Joined: February 28, 2006
 and I may try it, but one thing that grabbed me about the Paramour (stock, no C4S) was the bass tone. It was beautiful.
Now, the Paramour was a parafeed design and I may not get that kind of performance out of a conventional SE amplifier. I wish I hadn't sold them, or at least kept the schematic so I could build one. The follies of youth...

Adam

 

RE: Bass driver might prefer an EL-84 PP anp anyway...., posted on December 27, 2020 at 09:21:02
Tre'
Industry Professional

Posts: 17305
Location: So. Cal.
Joined: February 9, 2002
 Voltsecond's last post here on the AA was on December 29, 2014

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: you could biamp, posted on December 27, 2020 at 10:16:50
Paul Joppa
Industry Professional

Posts: 7296
Location: Seattle, WA
Joined: April 23, 2001
 One of the benefits of parafeed is the ability to keep the load more resistive around the LF cutoff. Just sayin' ...

 

yep, posted on December 27, 2020 at 10:42:13
elblanco
Audiophile

Posts: 3486
Joined: August 20, 2004
 no standing dc, no air gap, allows more inductance, right?

 

RE: yep, posted on December 27, 2020 at 13:44:41
Paul Joppa
Industry Professional

Posts: 7296
Location: Seattle, WA
Joined: April 23, 2001
 That's true, but I was mostly thinking of matching the parafeed capacitance to the plate choke inductance, so they partially cancel each other's reactance.

 

RE: yep, posted on December 28, 2020 at 08:41:47
elblanco
Audiophile

Posts: 3486
Joined: August 20, 2004
 choke is essentially the new "primary".

should all components be spec'd with parafeed in mind for optimal results?

 

RE: yep, posted on December 28, 2020 at 09:19:33
Tre'
Industry Professional

Posts: 17305
Location: So. Cal.
Joined: February 9, 2002
 The choke is in parallel with "the coupling cap in series with the primary of the output transformer". Parallel feed. By adjusting the value of the coupling cap you can change the low frequency behavior of the whole.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: That's a reasonable solution..., posted on December 28, 2020 at 14:07:24
91derlust
Audiophile

Posts: 1101
Joined: December 25, 2014
 I'm pretty confident this can be achieved a good series feed transformer. The series feed 4K2 output transformer in my 2A3 daily drive delivers roughly 45H. Sounds transparent, extended and coherent top to bottom; bass is really quite nice and sounds as good, but certainly not the same, as my Metaxas SS power amp.

Quality transformers and suitable speakers, amongst other things, matter.

"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein

 

RE: Hammond 125ESE bandwidth when used at lower power?, posted on December 29, 2020 at 11:00:36
rage
Audiophile

Posts: 793
Joined: December 17, 2010
 The favorite of Vinnie!

 

re: gone but not forgotten ..., posted on December 30, 2020 at 11:08:24
deathtube 667
 "The favorite of Vinnie!"

Vinnie2 loved the modest attributes of 125ESE and took some abuse for it.

I miss that old guy.

 

+2*, posted on December 30, 2020 at 11:21:24
rivervalley817
 *

 

no, vinnie loved 125se, different animal..-nt, posted on December 31, 2020 at 06:11:32
elblanco
Audiophile

Posts: 3486
Joined: August 20, 2004
 .

 

RE: no, vinnie loved 125se, different animal..-nt, posted on December 31, 2020 at 08:12:51
Tre'
Industry Professional

Posts: 17305
Location: So. Cal.
Joined: February 9, 2002
 I can't find a 125se. I find 125 (a through g) se.

What is a 125se?

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

you're right, my bad, sorry vinnie...-nt, posted on January 3, 2021 at 14:35:05
elblanco
Audiophile

Posts: 3486
Joined: August 20, 2004
 .

 

It was probably the 125E, posted on January 4, 2021 at 08:26:12
Paul Joppa
Industry Professional

Posts: 7296
Location: Seattle, WA
Joined: April 23, 2001
 I played with them some 20 years ago. They were at the time advertised as "single ended or push-pull" but currently they are said to be push-pull only - which I can confirm based on measurements I made back then. Presumably that's why the 125*SE series came about. The SE units are larger than the corresponding 125* units because of the air gap.

I've noticed that Hammond's specifications have been greatly improved and expanded over the last several years,for which they are to be commended.

 

RE: you could biamp (Dr.P), posted on January 10, 2021 at 14:12:45
VoltSecond
Audiophile

Posts: 2523
Location: Arizona
Joined: October 14, 2000
 Don't forget about Damped Resonance Parafeed. The RC across the parafeed cap gives us a free variable to adjust. It doesn't do a lot into some resistive loads, but when the reactance kicks in, it can provide damping.

-Volt

Play safe and play longer! Don't be an "OUCH!" casualty.
Unplug it, discharge it and measure it (twice) before you touch it.

. . .Oh!. . .Remember: Modifying things voids their warranty.

 

Yes, I'm a round., posted on January 10, 2021 at 14:31:37
VoltSecond
Audiophile

Posts: 2523
Location: Arizona
Joined: October 14, 2000
 I haven't been active in the forums in years. I'm hoping to change that soon. I only check my email once a quarter at this point.

When I have time, I've mostly been playing with headphone amps. The best one I have built of my own design so far is from my evil twin, AmpSecond. It is a solid state design, output driven by the collector of the power stage, not an emitter follower.

My tube headphone amp didn't pan out, it did soft and sweet nicely, but when it came time to rock, it just wouldn't roll . . . (So much for puns!)

With respect to tubes, on paper, I've been trying to reduce the voltage needed by the power supplies in Gary Pimm's VSAC design. The bias gets quite complicated when you give up the DC coupling from the stacked power supplies.

-Volt



Play safe and play longer! Don't be an "OUCH!" casualty.
Unplug it, discharge it and measure it (twice) before you touch it.

. . .Oh!. . .Remember: Modifying things voids their warranty.

 

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