Hi,
I'm currently planning to build a Tubelab Simple SE amplifier, and I'm at the stage of choosing output transformers.
My initial plan was to use the Hammond 1628SEA, but after some research, I'm considering other options that might offer better sound quality.
I've been eyeing the Hashimoto HC-507U and Iso FC-20s. Both transformers are smaller and lighter than the Hammond, they deliver 20 Watts vs 30W for the Hammond.
I'm concerned that they might not be powerful enough for my speakers, which are Monitor Audio GS20s rated at 89db (6 ohms). My room is quite small (4x5 meters), so I guess don't need an overly powerful amp.
I'm hoping to get some insights from experienced tube amp builders on this matter.
Would you recommend the Hashimoto HC-507U or Iso(tango) FC-20s for a Tubelab Simple SE, or would the Hammond 1628SEA be a better choice ?
Any advice or recommendations would be greatly appreciated. Thank you in advance!
I'm currently planning to build a Tubelab Simple SE amplifier, and I'm at the stage of choosing output transformers.
My initial plan was to use the Hammond 1628SEA, but after some research, I'm considering other options that might offer better sound quality.
I've been eyeing the Hashimoto HC-507U and Iso FC-20s. Both transformers are smaller and lighter than the Hammond, they deliver 20 Watts vs 30W for the Hammond.
I'm concerned that they might not be powerful enough for my speakers, which are Monitor Audio GS20s rated at 89db (6 ohms). My room is quite small (4x5 meters), so I guess don't need an overly powerful amp.
I'm hoping to get some insights from experienced tube amp builders on this matter.
Would you recommend the Hashimoto HC-507U or Iso(tango) FC-20s for a Tubelab Simple SE, or would the Hammond 1628SEA be a better choice ?
Any advice or recommendations would be greatly appreciated. Thank you in advance!
Isn't Hammond quite expensive for you in Europe relative to what we would be paying in US or Canada?
Why not Lundahl, Toroidy, Ogonowski, or some other EU-based source?
Do you have way too much money on your hands and nowhere else to spend it? Then buy something expensive so you can sleep at night and not wonder if you "made the wrong choice" on output transformers.
Tubelab's own site details some experiences with blind listening tests. Have you read that?
In my own experience, I auditioned the HC-507U against an Edcor 5K transformer on a 45 amp. Quite honestly I couldn't tell the difference. They both sounded great.
Why not Lundahl, Toroidy, Ogonowski, or some other EU-based source?
Do you have way too much money on your hands and nowhere else to spend it? Then buy something expensive so you can sleep at night and not wonder if you "made the wrong choice" on output transformers.
Tubelab's own site details some experiences with blind listening tests. Have you read that?
In my own experience, I auditioned the HC-507U against an Edcor 5K transformer on a 45 amp. Quite honestly I couldn't tell the difference. They both sounded great.
Hello,
Thanks for your answer @cogitech, that's what I thought thanks for the confirmation
@Thekak I don't understand (most of) your reply, I made a budget for this amp and can afford a pair of nice transformers, so what ?
Like i said I initially planned for the Hammond, but on Tubelab's website George said this trafo seemed to roll off some of the high frequencies, reason why I'm looking for a (better) alternative.
You said you auditioned the Hashi vs Edcor and couldn't tell the difference that's more interesting, thanks for the feedback
Did someone else had the opportunity to hear the HC-507U or the Iso FC-20S on a SSE ?
Thanks for your help
The usual, KT88, EL34
Thanks for your answer @cogitech, that's what I thought thanks for the confirmation
@Thekak I don't understand (most of) your reply, I made a budget for this amp and can afford a pair of nice transformers, so what ?
Like i said I initially planned for the Hammond, but on Tubelab's website George said this trafo seemed to roll off some of the high frequencies, reason why I'm looking for a (better) alternative.
You said you auditioned the Hashi vs Edcor and couldn't tell the difference that's more interesting, thanks for the feedback
Did someone else had the opportunity to hear the HC-507U or the Iso FC-20S on a SSE ?
Thanks for your help
Apologies for being dour--I often project my previous component obsessions onto the posts of others.
Your posts indicate you may not know what the various specifications of an output transformer mean or do. So I assumed that you were looking for the OPT with the most magic.
All the big names are going to sound good aside from their budget or non-full-range offerings.
You literally will never know which is better without direct A/B comparison in your system, in your room, with your ears.
That said, there are some good ETF (European Triode Fest) articles / pages out there. IIRC at least a couple have published crowd ratings and some OPT measurements.
There are also lots of audiophiles (JE Labs, for example) that prefer their systems to have a specific "character" to their systems and therefore prefer some vintage components which are not really full-range but produce cultish/faddish appreciation.
It's so easy to swap OPT in and out of a test system that I usually recommend people just try a few options.
Your posts indicate you may not know what the various specifications of an output transformer mean or do. So I assumed that you were looking for the OPT with the most magic.
All the big names are going to sound good aside from their budget or non-full-range offerings.
You literally will never know which is better without direct A/B comparison in your system, in your room, with your ears.
That said, there are some good ETF (European Triode Fest) articles / pages out there. IIRC at least a couple have published crowd ratings and some OPT measurements.
There are also lots of audiophiles (JE Labs, for example) that prefer their systems to have a specific "character" to their systems and therefore prefer some vintage components which are not really full-range but produce cultish/faddish appreciation.
It's so easy to swap OPT in and out of a test system that I usually recommend people just try a few options.
Roger,
The interesting thing about the BIG Hammond rolling off the highs it that it is not due to it being low quality. Rather, it is simply too big for the power delivered by the SSE and typical tubes. The goal is to match the OPT size to the output power. In the case of the SSE, the sweet spot is "10-15" watts. I use quotes here because any wattage rating needs to be taken with a grain of salt. As George explains (and I am sure you have read) the weight says more than the wattage rating.
Example:
Edcor XSE15-5K is a "15 watt" OPT. It weighs 1.6lbs
Transcendar TT-338-OT is a "10 watt" OPT. It weighs 4.2 lbs.
What is going on here? Well, if you dig a bit deeper, you realize that the Edcor is rated 15 watts at frequency response of 70Hz-18KHz, +/- 1dBu. It can produce 20Hz for sure, but probably only up to 3 or 4 watts (if that). The Transcendar is rated to do 10 watts at full bandwidth, and it does.
The biggest downside of going too big isn't the rolled off highs, it is the price you pay in efficiency. You have relatively inefficient speakers, so you don't want a big OPT wasting a full watt or more of your power.
I suggest you look at the specs of the OPTs you are considering. Specifically the weight and the frequency response that the wattage is rated at.
I discovered that the Hashimoto weighs 4.4lbs and the frequency response at the full 20w looks good to me. Yes, they roll off on the low end, but you are only going to be pushing half that wattage (at the very most!) so these OPTs will do just fine. Most of the time you are probably going to be using 1 watt*:
I can't imagine you would be disappointed or be missing anything. I wouldn't hesitate to use them, that is for sure.
*Am I the only one who thinks 89dB from each speaker is loud enough most of the time?
The interesting thing about the BIG Hammond rolling off the highs it that it is not due to it being low quality. Rather, it is simply too big for the power delivered by the SSE and typical tubes. The goal is to match the OPT size to the output power. In the case of the SSE, the sweet spot is "10-15" watts. I use quotes here because any wattage rating needs to be taken with a grain of salt. As George explains (and I am sure you have read) the weight says more than the wattage rating.
Example:
Edcor XSE15-5K is a "15 watt" OPT. It weighs 1.6lbs
Transcendar TT-338-OT is a "10 watt" OPT. It weighs 4.2 lbs.
What is going on here? Well, if you dig a bit deeper, you realize that the Edcor is rated 15 watts at frequency response of 70Hz-18KHz, +/- 1dBu. It can produce 20Hz for sure, but probably only up to 3 or 4 watts (if that). The Transcendar is rated to do 10 watts at full bandwidth, and it does.
The biggest downside of going too big isn't the rolled off highs, it is the price you pay in efficiency. You have relatively inefficient speakers, so you don't want a big OPT wasting a full watt or more of your power.
I suggest you look at the specs of the OPTs you are considering. Specifically the weight and the frequency response that the wattage is rated at.
I discovered that the Hashimoto weighs 4.4lbs and the frequency response at the full 20w looks good to me. Yes, they roll off on the low end, but you are only going to be pushing half that wattage (at the very most!) so these OPTs will do just fine. Most of the time you are probably going to be using 1 watt*:
I can't imagine you would be disappointed or be missing anything. I wouldn't hesitate to use them, that is for sure.
*Am I the only one who thinks 89dB from each speaker is loud enough most of the time?
Last edited:
First off there is a Hammond 1628SE and a Hammond 1628SEA. These are two very different transformers and you don't want the older 1628SE, they are pretty bad in the HF department. Many years ago I ordered a pair of 1828SEAs from AES and they shipped me a pair of the 1628SEs. They sounded gross so I called AES to return them since it was THEIR error. They wanted me to ship them back at MY expense which would have cost some considerable money then. Things got ugly so I called Hammond who basically told me to deal with AES. Finally, after dealing with both companies, I got a pair of 1628SEAs for product cost. I sold the 1628SEs to someone who was making big SE guitar amps and still have the 1628SEs in their boxes. I also have a pair of the biggest Edcor SE OPT's still in their boxes, both from about 15 years ago. Why?
I got a bunch of mid sized (about 4.5 pounds) Transcendar OPT's from Gerry, the company's owner back when he quit the transformer business the first time. These beat the big Edcors and Hammonds in listening tests every time in a SSE or TSE amp. The These were not apples to apples tests though, The Transcendars were specially designed for 300B amps. When the amp company died the excess OPT's appeared on Ebay so I bought a pair, listened to them for about 5 minutes, then bought all Gerry had. I used them as a 3000 ohm OPT in 300B, 2A3, KT88 and some EL34 amps, and wired for 6000 ohms with 45s, and 6L6GC. The Hammond and Edcor OPT's are both 5000 ohm models weighing in at about 10 pounds each. The Hammond can be wired for 2500 ohms though.
All that iron and copper requires energy to repeatedly magnetize and demagnetize at an audio rate. The big Hammonds are the lossiest OPT's that I have ever measured. They consume about 10% more power than the big Edcors. That is an amp that makes 10 watts with the big Edcors will make 9 watts with the big Hammonds. Higher frequencies will be attenuated slightly more than the mids and lows. This "loss factor" depends on the amp / tube combo driving it. A very low impedance (plate resistance) tube like the 300B will do a better job of driving all the excess capacitance and other parasitic losses present in a big transformer than a wimpier tube like a 6L6GC.
I have used the big transformers for testing and experimenting with new topologies like UNSET for their entire life, and finally found two places for them where they sound good. One is a UNSET based SE amp that is running a pair of large TV sweep tubes in parallel for over 30 watts of pawer, and the other is actually a high voltage mosfet based SE amp. Both of these run a good bit of feedback around the output device to present a very low driving impedance to the transformer. I would not put a 1628SEA in an SSE amp as there are better and cheaper choices.
Given my experience, I would use a Toroidy toroidal OPT especially considering that they are close to you. I have two different pair of their SE OPT's and they sound great. I got mine from TME, but there may be better options in Europe.
I got a bunch of mid sized (about 4.5 pounds) Transcendar OPT's from Gerry, the company's owner back when he quit the transformer business the first time. These beat the big Edcors and Hammonds in listening tests every time in a SSE or TSE amp. The These were not apples to apples tests though, The Transcendars were specially designed for 300B amps. When the amp company died the excess OPT's appeared on Ebay so I bought a pair, listened to them for about 5 minutes, then bought all Gerry had. I used them as a 3000 ohm OPT in 300B, 2A3, KT88 and some EL34 amps, and wired for 6000 ohms with 45s, and 6L6GC. The Hammond and Edcor OPT's are both 5000 ohm models weighing in at about 10 pounds each. The Hammond can be wired for 2500 ohms though.
All that iron and copper requires energy to repeatedly magnetize and demagnetize at an audio rate. The big Hammonds are the lossiest OPT's that I have ever measured. They consume about 10% more power than the big Edcors. That is an amp that makes 10 watts with the big Edcors will make 9 watts with the big Hammonds. Higher frequencies will be attenuated slightly more than the mids and lows. This "loss factor" depends on the amp / tube combo driving it. A very low impedance (plate resistance) tube like the 300B will do a better job of driving all the excess capacitance and other parasitic losses present in a big transformer than a wimpier tube like a 6L6GC.
I have used the big transformers for testing and experimenting with new topologies like UNSET for their entire life, and finally found two places for them where they sound good. One is a UNSET based SE amp that is running a pair of large TV sweep tubes in parallel for over 30 watts of pawer, and the other is actually a high voltage mosfet based SE amp. Both of these run a good bit of feedback around the output device to present a very low driving impedance to the transformer. I would not put a 1628SEA in an SSE amp as there are better and cheaper choices.
Given my experience, I would use a Toroidy toroidal OPT especially considering that they are close to you. I have two different pair of their SE OPT's and they sound great. I got mine from TME, but there may be better options in Europe.
The OP might also look at van der Veen OPTs with some models specifically designed for SE amps in triode mode and with CCS. Not cheap but Menno knows toroidal transformers.
van der Veen
I guess the grass is always greener. In the US I've never thought of Hammond as a high end transformer. I've looked through the European brands people have mentioned and thought "those look nice, if only shipping wasn't so much!" Meanwhile, it turns out, on the other side of the ocean someone is looking at our brands and saying the same thing.
Thank you all for your answers and sorry for the late reply.
@cogitech that was exactly the answer I was looking for
The HC-507U turned out to be cheaper than expected, I ordered a pair.
Thank you @tubelab for continuing the reflection (very interesting), however I'm not looking for a toroidal transformer this time, going for a more classic design for my first build
Yen being low, I am considering staying with Hashimoto for the power transformer (probably not the choke), however the only model that could be suitable (PT-165-R) is 380-0-380. I think it will work for B+, but the intensity on the 5AR4 might be too high (was planning for tube rectification only). Is there a way to lower that ?
Thanks again
@cogitech that was exactly the answer I was looking for
The HC-507U turned out to be cheaper than expected, I ordered a pair.
Thank you @tubelab for continuing the reflection (very interesting), however I'm not looking for a toroidal transformer this time, going for a more classic design for my first build
Yen being low, I am considering staying with Hashimoto for the power transformer (probably not the choke), however the only model that could be suitable (PT-165-R) is 380-0-380. I think it will work for B+, but the intensity on the 5AR4 might be too high (was planning for tube rectification only). Is there a way to lower that ?
Thanks again
Would have been cool, but it's almost twice the price of the Hashi and no SG tap 😱Another option that is well reputed is Monolitics Magnetic. No personal experience yet, but they are in Belgium so your amp will use "local products"
For another build, who knows...?
I asked for a quote for a power transformer though, still hesitate between this and a Hashimoto combo
Seems to me that'll be fine. The commonly used Hammond 274BX is 375-0-375 @201mA, so 380-0-380 @180mA (as per PT-165 specs) will be virtually identical. A decent quality 5AR4 will have no issue. If you want to reduce the B+ a bit you can do so in several ways but you probably won't need to.
Yen being low, I am considering buying a whole lot of Yen!
Indeed. However, I was not recommending the 274BX, only using its HV output (375-0-375) as a comparison to the Hashimoto (380-0-380) that the OP is considering, as evidence that he need not worry about the HV of the Hashimoto.
Yes understood that - perhaps should have written in a more detailed way. Just wanted to make it clear to the OP that he should consider the model that can support 230V AC mains input. And agree with your point cogitech that 375-0-375 and 380-0-380 HV output will be virtually the same for his application.
Just wanted to make it clear to the OP that he should consider the model that can support 230V AC mains input. And agree with your point cogitech that 375-0-375 and 380-0-380 HV output will be virtually the same for his application.
Thanks for your reply @cogitech and @zman01, I'll go for the PT-165R then 🤘
I'll have to wait 6 weeks to get them, which gives me plenty of time to read George's website another dozen of times
I'll have to wait 6 weeks to get them, which gives me plenty of time to read George's website another dozen of times
Looks tempting, almost back to the 2008 bottom on jpy/eur pairYen being low, I am considering buying a whole lot of Yen!