| Sherman |
I am getting to the nitty gritty of my winter amp project and all that is left before building is deciding on and ordering the iron. My budget is sufficient for either Hammond 1628SE or James 6123HS.
There was a thread here a while back about frequency response issues with the Hammonds (a big drop out at 15K IIRC and another anomaly lower down, 3K?). I haven't seen any actual data on the James, nor do I know anyone who is using them.
My feeling is that if the Hammonds have a systemic issue that hasn't been resolved I would probably go with James. But if the Hammond thing was a temporary production glitch or something that has been fixed I'd go with Hammond since the other iron, PTX and choke will be Hammond and it would be nice to have everything match. :D
Any input on either the Hammond issue or any real-world measurements and use of James? |
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| rdf |
I use the 1628Se and don't recommend it. My samples have severe issues in the 13 kHz range. For more info see:
http://www.sacthailand.com/transformerTest1.html
Edit: For what it's worth, the amp in my avatar uses them. It makes 3 watts and the problem is still evident. The PS iron is also Hammond and it appears to be wound 10% over on the primary. Both the HV and filaments read high, the latter at 7 volts which I discovered late and after cooking a few EL84's. I might consider a 125se for benching, but I'll never build another serious amp with Hammond iron again. |
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| burnedfingers |
Quote:
I use the 1628Se and don't recommend it. My samples have severe issues in the 13 kHz range.
The last time I tested my hearing I had to strain to hear 14khz.
You must either be a heck of a lot younger than me or are blessed with very good hearing. |
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| morfeas |
| Even thu I m very happy with the 1640SE I wouldn't call HIFI the recorded qualities of the 1628SE :cannotbe: |
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| rdf |
Approaching 50 and, as of yesterday, hearing still good to 15 kHz. :)
Measurement-wise the TX problem - in my amp - manifests itself as a short, quick 2 dB rise at 13 kHz under rather large amounts of purely resistive feedback, significant ringing on square waves and rapidly rising distortion with frequency. Ironically I spent the night before Sherman's post on the bench tuning the feedback capacitor trying to minimize just these issues. The best I could achieve was dead flat response to 14 kHz, a 1 - 1.5 db downward knee to 16 kHz, relatively flat to ~ 18 kHz, followed by a rapid rolloff (~ -3 dB @ 20 kHz) and then an ultrasonic rise in the 40-50 kHz range. A very odd frequency response. It wasn't possible to eliminate a large spike on the rising edge of square waves or the rising distortion with frequency. This is at 1 watt output.
The problem is suprisingly audible as a 'dirty' high end, to my ear similar to speakers with high freuqency issues, for example the Tang Band W4-657s with its very narrrow 4-6 dB rise centred at 8 kHz. It's not as obvious but very similar in character. Carefully tuning the feedback cap reduces it significantly but the highs never really sound clean and extended. Cymbals suffer the most.
Check the SAC Thailand test results. That's nasty stuff. |
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| planet10 |
I think you'll find the James in a different league from the Hammonds... i view the Hammonda as budget OPTs, the James are pushing for top tier.
dave |
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| Sherman |
| quote: | Originally posted by planet10
I think you'll find the James in a different league from the Hammonds... i view the Hammonda as budget OPTs, the James are pushing for top tier.
dave |
Dave,
That is interesting since they are the same price at ~ $90US each. I'm not discounting what you are saying but all I seem to find on James is "they used to be with xyz and build top notch trafos" etc. I have yet to find someone that has said "I have used them and they sound great" or "I use them and have measured a flat FR from 20-20K Hz +/- 1dB" or something like that.
However I doubt I could hear a -3dB dip at 15K Hz (or even a 9dB dip ;) ). But it would be nice to know the TX is making noise where it is supposed to be!
If I decide to go with James do you have any idea where I might find covers for a Hammond PTX and choke that will help them match the James OTX? (The equivalent James PTX is US $190 vs. $51 for Hammond, and the equivalent James choke is $90 vs. $25 for Hammond. I'm building monoblocs to I need 2X :bawling: .) |
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| planet10 |
| quote: | Originally posted by Sherman
That is interesting since they are the same price at ~ $90US each. I'm not discounting what you are saying but all I seem to find on James is "they used to be with xyz and build top notch trafos" etc. I have yet to find someone that has said "I have used them and they sound great" or "I use them and have measured a flat FR from 20-20K Hz +/- 1dB" or something like that. |
There was a recent joelist thread on James OPTs... quite a few stepped up and said good things about them... no one had anything to say against them.
A local fellow built a monster PSE 300B amp with James with excellent results.
Woody -- a member here -- has gotten at least a couple pairs. The latest for a 6C45pi spud amp.
dave |
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| jeff mai |
If you want "dirt" on James transformers, do a search. Someone here posted a link with measurments showing that the James universal output transformer performance was clearly inferior to some of the Tango universal units. The link was a sight showing the measured performance of many transformers.
Of course, the Tango are much more expensive. |
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| kmtang |
First of all, I believe it is not fair to take only the Hammond 1628 for comparison with others. My friend built a 2A3 power amplifier with Hammond 1627 OPT. He measured the frequency and square wave response and the result was excellent. The frequency response is very flat from a few hertz to almost 100kHz. The square wave at 10kHz has a very little spike at the edges. The important thing is, his amplifier sounds much better than the Audio Note Kit One using 300B output tube.
I built myself a 45 tube amplifier with 1628 OPT. I measured the frequency response at both 8-ohm and 4-ohm output taps. The result for 8-ohm looks a bit urgly but at 4-ohm it is reasonaly good. The frequency response at low end frequency is extremely good. I believe it is because of the big inductance it has. By the way, I having measure the response for 16-ohm tap because I am rather lazy to rewire the wires at the primary of the OPT.
My measurements for 1628 is attached in Excel file.
Johnny |
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| Sherman |
| quote: | Originally posted by planet10
... A local fellow built a monster PSE 300B amp with James with excellent results.
Woody -- a member here -- has gotten at least a couple pairs. The latest for a 6C45pi spud amp.
dave |
Well, after all these replies and a little more research (there really is surprisingly little "real" info out there on James considering the apparent value and low price) I've decided I'll go with James for the OTXs. They have the right primary impedance, can handle the current and they look awfully nice.
Now I just have to figure out the best way to "match" the Hammond PTX and Hammond choke to the look of the James. Maybe just some paint but a cover would be nice.
Once this project is complete maybe I can get started on the DIY Reference Full-Range speaker project (gotta finalize that design!). The way that is developing it might make a pretty nice match for a 4-5W SE amp. |
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| Sherman |
| quote: | Originally posted by kmtang
First of all, I believe it is not fair to take only the Hammond 1628 for comparison with others. My friend built a 2A3 power amplifier with Hammond 1627 OPT...
I built myself a 45 tube amplifier with 1628 OPT. I measured the frequency response at both 8-ohm and 4-ohm output taps. The result for 8-ohm looks a bit urgly but at 4-ohm it is reasonaly good...
Johnny |
Johnny,
Thanks for the info. My understanding is that the 1627 has a completely different construction from the 1628 and is in fact an excellent performer. Unfortunately the primary impedance is too low for my current project or I would go that route.
A wider search (more than just this forum) turned up quite a few pages on the 1628 and its less than stellar performance. To be quite honest though, I doubt I could actually hear any anomalies above 13 KHz if they were less than 6dB, so the 1628 might work fine for my ears. But as long as the cost is within reason I might as well go with James if the performance is better. |
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| kmtang |
Hi Sherman,
Just wondering what kind of power amplifier you are buiilding during this winter? Do you mind sharing the schematic with us?
Have a nice day.
Johnny |
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| Sherman |
| quote: | Originally posted by kmtang
Hi Sherman,
Just wondering what kind of power amplifier you are buiilding during this winter? Do you mind sharing the schematic with us?
Have a nice day.
Johnny |
Johnny,
It is a single-ended KT88 amp. The schematic was posted here by Mikael Abdellah. I don't think he would mind my posting it here. He built his amp as an integrated stereo. I am planning on doing mine as monoblocs. |
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| rdf |
Hi Sherman, I think you'll be much happier avoiding the 1628se in this application. If my reaction to Hammond seems a bit extreme, the PS transformer from them was also bad in every way - voltages 10% over, mismatched isolation washers, screws of different types cut to length with side cutters (!) and a finish which flaked off with a thumbnail. Neccessity drove me to strip and repaint the TX housings on my amp, not aesthetics. I've worked with Hammond product, mostly line-level and PS transformers but racks as well, for almost 25 years and never saw anything this shoddy.
Attached is a jpg of the measured results with the 1628se. The FR is resistive feedback only. That rising distortion with frequency response is audible, most bandwidth limited gear I've measure in the past shows falling distortion with increased frequency, as would be expected since the depressed high frequencies of the device under test is suppressing harmonics. |
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| Sherman |
| quote: | Originally posted by rdf
Hi Sherman, I think you'll be much happier avoiding the 1628se in this application... |
Well, all the responses here convinced me and I placed an order for James OTXs yesterday. If they sound as good as they look I'm sure I'll be more than satisfied with them.
I still haven't ordered the PTXs or chokes but know that my budget on this won't support James products for those items. They are 4x the price of similarly rated Hammonds. Everything else is either here or on order so the last piece of the puzzle is the PS iron. I hope to place an order this week sometime.
One can agonize forever over components and end up not building. Since my budget is not unlimited compromises are inevitable (heck they'd be inevitable even if my budget was unlimited). |
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| rdf |
| Mind if I ask where you're getting the James from? I want to start project two. :) |
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| kmtang |
I would say Hammond transformers are not the best transformers in the market but they have extremely good value/quality for the price.
Regarding the overvoltage issue, surely you need to provide it with sufficient loading. The voltage specification is based on full output rating. Of course, if you use it with very low loading, the voltage will rise to a small percentage.
Therefore, we need to bare in mind that if we choose the transformer that is overrated, we need to either picking transformer with lower output voltage or using extra regulators.
Just my 2 cents.
Johnny |
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| Sherman |
| quote: | Originally posted by rdf
Mind if I ask where you're getting the James from? I want to start project two. :) |
I ordered mine late Saturday night from Euphonia Audio (www.EuphoniaAudio.com). $189/pair, shipping was $12 I think. I just got an email from them saying they shipped and providing a FedEx tracking number so they may show up this week! |
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| Sherman |
| quote: | Originally posted by kmtang
I would say Hammond transformers are not the best transformers in the market but they have extremely good value/quality for the price...
Johnny |
Yeah, that's sort of my thinking right now. Nothing is perfect and I can always adjust the PS to get the correct voltage. And the price is right. |
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| rdf |
| Thanks for the link Sherman! |
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| Sherman |
| quote: | Originally posted by rdf
Thanks for the link Sherman! |
No problem. Euphonia seems to have about the best price going on the James TXs. I just checked their site today though and they now seem to be backordered until Feb 7 or so. I'm glad I didn't wait any longer to order mine!
One benefit, to me anyway, of the James units is that they are smaller than the Hammonds. I am trying to do this on a 12" square aluminum sheet and the extra inch available now opens things up a bit and makes the layout look better I think. |
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| rdf |
| I was thinking of replacing the Hammonds with James, then using the 1628s to bench the next amp. A bit of overkill, but what the hey, and it's an opportunity to hear the difference between OPTs. I have the opposite problem, space is fine but the Hammond PS TX doesn't colour match. |
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| Sherman |
| quote: | Originally posted by rdf
I was thinking of replacing the Hammonds with James, then using the 1628s to bench the next amp. A bit of overkill, but what the hey, and it's an opportunity to hear the difference between OPTs. I have the opposite problem, space is fine but the Hammond PS TX doesn't colour match. |
Well the James OPTs showed up today. That was quick. I have to say they look really nice. :D The Hammond PTXs and chokes are on order from Angela and might be here this week.
I would really like to match the colors also. It seems that the choices are-
1- Paint all the trafos a color of my choice
2- Get someone to paint the Hammonds to match the James
3- Paint the James black to match the Hammonds
4- Just live with the color difference
I think #2 would look best but I can't imagine what it would cost. :confused:
Now I'm putting all the dimensions into TurboCad to try and make a life-size drilling template. That way it would be easy to flip so I can make the monoblocs mirror images. |
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| rdf |
It'd be a shame to paint anything as nice looking as the James.
I'd be curious what you think of the fit and finish of the Hammond iron when it arrives. Maybe I got a sample of the late Friday afternoon before the long weekend production run. Repainting was easy enough. Remove the shells, strip with Scothbrite, a spray can of hammer finish black and 20 minutes in the oven at 200 (the shells, not the coil of course.) Turned out all right, though not as nice as those shots of the James. |
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| planet10 |
| quote: | Originally posted by Sherman
It seems that the choices are- |
5- mount the Hammonds under the chassis?
dave |
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| Sherman |
| quote: | Originally posted by planet10
5- mount the Hammonds under the chassis?
dave |
Hadn't thought of that one! Unfortunately I'm planning on a chassis only 3" or so high so they wouldn't fit. :(
I have also thought of option 6- cover the Hammonds with an aluminum cover that would match the top plate rather than trying to match the James trafos.
I'll decide when the Hammonds arrive and I place everything on the top plate to get a visual idea. Attached is my current layout idea. The top plate is 12" x 12". All connectors will be on the "back", the side closest to the choke and OPT. I plan on making them mirror images of each other. |
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| Sherman |
| quote: | Originally posted by rdf
It'd be a shame to paint anything as nice looking as the James.
I'd be curious what you think of the fit and finish of the Hammond iron when it arrives...
Repainting was easy enough..., a spray can of hammer finish...
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I have to say that the finish of the James transformers is awfully nice. I don't think I could bring myself to paint over them. As for the Hammonds- I'll post my impressions here when they arrive. I have my fingers crossed!
I have to go to the home store this morning so I'll check the paint section to see if anything there is even a close match. |
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| planet10 |
| quote: | Originally posted by Sherman
the side closest to the choke and OPT. [/B] |
Shouldn't the choke & trafo be 90 degrees to one another?
dave |
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| Sherman |
| quote: | Originally posted by planet10
Shouldn't the choke & trafo be 90 degrees to one another?
dave |
Yeah, technically they should and I might do it that way. I've been trying to come up with a layout that makes sense and fits the size I have in mind. I took some ideas from Derek Walton's layout. ( http://indigo.ie/~walton/300bdrawings.html ) He says he tried the choke both ways and found no difference at all.
I think though that I may put the choke in back even though it is smaller and may look a little unbalanced. It makes the wiring much more direct and allows the AC and DC to be kept completely separate and not cross as they do in Derek's layout.
Here is a shot of the potential layout with the actual pieces. |
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| Sherman |
| quote: | Originally posted by rdf
I'd be curious what you think of the fit and finish of the Hammond iron when it arrives. Maybe I got a sample of the late Friday afternoon before the long weekend production run... |
The Hammond iron arrived this morning! Both Euphonia and Angela are fast shippers.
Based on your description and on what I received it appears that Hammond builds all their stuff on the Friday afternoon before a long weekend. :( The paint is uneven on both the bells and the laminations. On the up side there are no dents or dings or bent mounting tabs.
The Hammonds will definitely be repainted. I checked the standard spray paints at Home Depot this morning and didn't find a really good match for the James color. I'll keep looking. |
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| rdf |
| Sorry to hear that. Mine had no dents or dings either, a small consolation. How's the fixing hardware? The bolts holding mine together were trimmed to length with side cutters. It's too bad. The ~ 20 year old 273X next to me, lifted from some old broadcast gear, humiliates the new stuff. |
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| Sherman |
| quote: | Originally posted by rdf
... How's the fixing hardware? The bolts holding mine together were trimmed to length with side cutters... |
The bolts on yours were actually trimmed to length? :eek: Actually one of the PTXs and one of the chokes each had a bolt that wasn't trimmed at all. It just stuck out about 3/4" past the nut. It is very disappointing to see this level of "care" put into assembly. (Of course I do own side cutters but I think I'll do it properly instead.)
At this point I'm just hoping they work properly! I'm heading downstairs now to put them on a meter to check the output of each secondary. If that checks out I'm off to search for paint. |
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| rdf |
| Hacked to length is more accurate. If any of the guys working for me did that they'ld be doing it over. Fortunately it's easy to find threaded rod in the proper guage and you can make the tranny look any way you like. I went with brass acorn nuts on both ends for the oh-so-popular 1920's Goth look. :) |
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| Sherman |
| quote: | Originally posted by rdf
... it's easy to find threaded rod in the proper guage and you can make the tranny look any way you like. I went with brass acorn nuts on both ends for the oh-so-popular 1920's Goth look. :) |
That's a good idea. Acorn nuts on both sides would look really nice.
I have a question regarding painting the Hammonds. Can I paint the laminations or only the bell ends? I was thinking I would use masking tape over the openings where the wires come out and just paint the entire transformer. I found that Rustoleum Special Appliance Epoxy spray paint in "Stainless Steel" is a very close match for the James color, probably as good as I'll get without having a color custom mixed.
BTW I measured the voltage from the Hammonds. I get 802 volts on the HV, 5.72 on the 5V heater leads and 7.28 on the 6.3 volt heater leads. The HV is supposed to be 700 volts (350-0-350). I don't think I blame Hammond for the over voltage though as my AC is consistently at 124V rather than 115! |
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| planet10 |
| quote: | Originally posted by Sherman
124V rather than 115! |
124/115 x 700 = 755
I believe those will sag a bit under load.
An extra RC stage in the power supply never hurts :)
dave |
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| Sherman |
| quote: | Originally posted by planet10
124/115 x 700 = 755
I believe those will sag a bit under load.
An extra RC stage in the power supply never hurts :)
dave |
Dave,
That's true, the measurements were no-load so I would expect some sag but if it isn't enough the the extra RC filter would be a good idea. And I do have additional ASC caps on the shelf. Heck, this over-voltage might be a good thing! :D |
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| planet10 |
| quote: | Originally posted by Sherman
Heck, this over-voltage might be a good thing! |
yep :)
dave |
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| rdf |
| quote: | Originally posted by Sherman
Can I paint the laminations or only the bell ends? I was thinking I would use masking tape over the openings where the wires come out and just paint the entire transformer. |
That's what I did, remove the end bells, paint and bake them separately, mask and spray the laminations. The PS tranny gets hot enough in normal use you'll smell paint curing for a couple of weeks anyway, the laminations still get a baked finish. The result on a 1628se is shown below. The paint's a Rustoleum Hammered Metal. Generic hardware store stuff, as were the nuts and plastic washers.
BTW, I agree with Dave about the excess HV voltage. It allowed an extra stage of RC and the result is surprisingly quiet for such a simple circuit. Now the excess filament voltage, that I'm not happy about but for now am content to drop it with a couple of .21 ohm, 100 uH iron core hash coils from the junk box. A little free filament filtering, looked at from the sunny side. |
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| Sherman |
| quote: | Originally posted by rdf
That's what I did, remove the end bells, paint and bake them separately, mask and spray the laminations... The result on a 1628se is shown below. The paint's a Rustoleum Hammered Metal. Generic hardware store stuff, as were the nuts and plastic washers...
|
Great, I think I'll paint them this weekend! Time to run out for some acorn nuts and threaded rod. I found a spray paint (also from Rustoleum) called Special Appliance Epoxy in a color called Stainless Steel that is a pretty close match for the color of the James.
I'll have to experiment a little with a load on the PS to see what the filament voltage really is. If necessary I'll follow your lead and put in a couple coils to get it down to the right range. |
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| sorenj07 |
| quote: | Originally posted by rdf
I use the 1628Se and don't recommend it. My samples have severe issues in the 13 kHz range. For more info see:
Both the HV and filaments read high, the latter at 7 volts which I discovered late and after cooking a few EL84's. I might consider a 125se for benching, but I'll never build another serious amp with Hammond iron again. |
Not that I'm a Hammond fan, but don't you think that this might well be due to your house AC being higher than 115V? I measure mine at 124VAC and following the ratio, my Hammond transformer also runs at almost 7V. I might use a power resistor to bring it down, but my Sovtek 6SN7GT's seem to have taken it pretty well so far.
edit: sorry, someone should have read the rest of the thread :D. beaten to the point. |
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| rdf |
| It never occured to me to check Hammond's primary rating. It's 115 VAC, which makes no sense here. My local utility, BC Hydro, specifies a nominal service voltage of 120 VAC with permissible CSA-regulated variance of 110-125 VAC. My outlets measure 120.3 VAC. Explains a good chunk of the variance (the filaments are still high.) Is the American standard generally 115 VAC? |
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| tubelab.com |
| 100 years ago we had 110 volts, 50 years ago we had 115 volts, now we have 120 volts (the "standard" voltage). I have measured as high as 124 volts. I am using power transformers made by Hammond (Allied Electronics). They are specified for "117 volts". The filament (and HV) voltages tend to run high, even when I overload the secondaries. |
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| 2wo |
Yea, just checked. I get 123VAC on a cool summer night here in Pa. In the winter I have seen 128V, on a hot day 113V.
In my part of the world the number of new generators on line in the last 15 years or so, Maybe 0.
Number of new "McMansions" in the last 15 years… Billions and billions
Have something to do with the problem: do you think?.. |
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| planet10 |
120.0 VAC here on my part of the island right now.
dave |
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| Sherman |
A hot day here in the Midwest- 120V. Last winter- 124V consistently. Really hot days- maybe 117.
Almost makes one wish for a power conditioner. I remember Kofi picking one up at Best Buy or similar. Not a UPS as such, it wouldn't last two minutes in a power failure, but it evens out the fluctuations. |
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| anatech |
Hi Sherman,| quote: | | Not a UPS as such, it wouldn't last two minutes in a power failure, but it evens out the fluctuations. |
Yes, and they put out a rectangular "equivalent power" wave. Transformer powered equipment really does not like this.
Switching power supplies are looking a little more attractive after reading this thread.
-Chris |
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| kmtang |
I have seen some very large size UPS that it's inverter works continuously. It runs from the rectified DC supply from AC and from batteries when the aC is out. This is kind of true UPS.
However, the cost of such UPS is very expensive.
Johnny |
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| anatech |
Hi Johnny,
Yes. I work with those. Someone in my office ordered and installed some 2 kW rectangular wave units. Burned them out on installation test, and the battery packs too! Of course I told them not to and they did anyway (yuck, yuck, yuck). :D
The normal sine wave models are horrendously expensive, and heavy! Never mind the battery chassis'. Someone thought they could save some money.
The phone switch survived with tripped breakers. (ITT 3100, full tower)
-Chris |
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| vax9000 |
| Is the SOLA constant voltage transfomer a good idea for tube amplifiers? |
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| poobah |
Same deal... they flatten the sine. Spreads out the conduction angle but knocks down the supply voltage a bit.
Google "Ferroresonant"
:) |
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| Tweeker |
| quote: | | Is the SOLA constant voltage transfomer a good idea for tube amplifiers? |
They tend to make audible 120hz hum/buzz noise. |
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| rdf |
| quote: | Originally posted by poobah
Same deal... they flatten the sine. Spreads out the conduction angle but knocks down the supply voltage a bit.
Google "Ferroresonant"
:) |
Hey poobah, are you sure that's true for all? For years we ran on a >10 kW Best Ferrups ferroresonant UPS and they claimed low harmonic content. Most claim to reduce line harmonics.
I don't like SOLAs because they run BBQ hot and in our applications and generate a lot of acoustic noise. |
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| poobah |
No rdf, not sure if that applies to all. They rely on saturation of the core to limit voltage, hence the flattening of the wave... but if there were enough capacitance in the tank maybe that would improve? Or maybe post filtering?
I bet: MORE MONEY = BETTER WAVEFORM
And yes, they do run hot as hell; and they weigh more than I do!
:) |
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| rdf |
| quote: | Originally posted by poobah
... but if there were enough capacitance in the tank maybe that would improve? |
Could be. When I decomissioned the pig I also salvaged near a dozen 30 uF 660VAC oil motor run caps for a Big Tube project. And yah, the Best wasn't cheap.
| quote: | And yes, they do run hot as hell; and they weigh more than I do!
:) |
Wet? |
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| tubelab.com |
I have three 1500 volt 1/2 amp power supplies salvaged from old tube type transmitters. The power transformers are ferroresonant types. They weigh 75 pounds each. Yes they will warm up the room, especially with light loads. All of those are drawbacks, but the deal breaker for audio use is that BUZZZZZZZZ. Why would you chase all of the hum out of the audio path only to have the transformer make a racket.
When we used to do manufacturing, there was a room full of Solas to run the ATE systems. That whole room went BUZZZZZ for at least ten years. They powered Teradyne, LTX and Data General equipment with no problems. Most of this equipment used linear power supplies (1970's equipment), and ran OK on the solas, but they were in a seperate room to contain the noise. |
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| anatech |
Those ITT 3100 phone systems used ferroresonant transformers as well. They hum like a, well I can't say but they are very loud. Hit those with a standard rectangular wave and watch what happens!
I don't think you need to regulate a tube amp that tightly. Get the voltage adjusted in range and don't worry about it.
-Chris |
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