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Old 17th November 2008, 04:19 AM   #11
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I have the older 5k and 3k large (15W) Transcendars, and the 3k and 8k smaller (10W) models. All have a future project asscoited with them, so I'll find out their qualities in due time. I've heard nothing but good things about the cost/performance ratio, so I'm expecting nice results as well.
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Old 17th November 2008, 07:18 AM   #12
kmaier is offline kmaier  United States
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Quote:
Originally posted by rcdaniel
Hi KM

Let us know how you go with those Transcendars. You have had some experience with other brands; it would be interesting to hear what you think of the Transcendars.

Cheers
Hi RC,

The Transcendars are destined for either a 45 or a 71A output stage. I designed a simple SET earlier this year (available to all DIYers). The first pair were completed with Hammond 125ESE OPTS (and Dad is breaking them in very well). There are 3 more sets to be built... OPTs being used are:

- James 6115HS
- MQ RH-40 (w/ endbells and flying leads)
- Transcendar 5K units mentioned here

The input/driver circuit can drive the 71A, 45 or even a 2A3 with ease. I also have several pairs of Hashimoto SE OPTs. The main difference is that they are wound for use with a 3-stage drive, hence they would be inverted output with the same input/driver circuit. I use a different circuit for these.... higher-gain, but they are certainly at the high end of the cost side.

Based on testing, measurements and some listening, here's some initial impressions:

- Hammond 125ESE - perform well to 1-watt, meaning they have good low-frequency support and extend flat to 25KHz within 1dB. Beyond 1-watt the low-frequency spectrum suffers. For 2-watts or more you need to limit the LF use... no lower than 100Hz. Still, listening reveals they are quite nice overall... somewhat of bargain for their cost (which keeps going up, now at $55 each from Angela).

- James 6115HS - these are quite nice for the price. They extend out around 30KHz within 1dB and have acceptable low-frequency performance at 2-watts down to 50Hz. I would consider these a good deal at the price I paid, which was $145 a pair from Euphonia Audio (now shut down). Now that there is no distributor in the US, hard to tell... but a pair just sold on ebay for $260. At this price point, I'd look elsewhere.... like below.

- Magnequest RH-40 - Mike just builds nice iron, period. I have two pairs of the RH-40s, one in standard brass U-channel with solder lugs and the more expensive ones with endbells and flying leads. No difference in performance but the latter are more acceptable cosmetically for top-side mounting. Performance is very good... solid 25Hz - 25KHz within 1dB. They also sound very very nice. I could easily live with these.... were it not for.... (see below).

- Hashimoto H507-S - Their smallest 5K/7K SE OPT, now at $180 each. Fit, finish, quality... top of the heap, but also expected to be there. My input/driver circuit is the (intentional) limit on HF response.... they are (tailored) within 1dB from 25Hz to 45KHz at 1-watt. For 2+ watts, they're good down to 50Hz and easily out past 45KHz. Response wise, they are exceptional and measured distortion even at 50KHz is very low, typically less than 1% at 2-watts. The listening test (which is extensive for me) show superb. To date nothing else performs as well (for me at least). Then again, no other amp (of mine) costs anywhere near as much to build.... so perhaps some subliminal bias is going on ;-)

Once I get back to the US in December, the RH40 amps will be completed and I'll have more to report... complete with pictures. The 45 is still one of my favorite DHTs, but you need to live within the 2-watts output, i.e., high-sensitivity speakers.

Regards, KM
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Old 18th November 2008, 04:03 AM   #13
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I'm currently using the 125ESEs in my "Miz Piggy" single ended screen driven amp, and they sound surprisingly nice. I don't notice a whole lot of bass deficiency, but I am using a feedback loop that includes the output transformer, so this no doubt stiffens up the bass. I'm planning a larger versin of this amp using the 5k 15W Transcendars.
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Old 18th November 2008, 06:48 AM   #14
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Hi KM

Thanks very much for that - appreciated.

I have heard good things about the Hashimoto output transformers. I vaguely remember reading a comparison between them at a while back and thinking that the 20W versions were probably the ones that would present music most to my liking.

If I decide to go series-feed the Hashimotos would be near the top of my list. Shunt-feed is the other option (yes, I know, hysteresis - but that what permalloy is for!). We will see.

Thanks again.
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Old 18th November 2008, 08:30 AM   #15
kmaier is offline kmaier  United States
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Hi Wrench,

Yes, the 125ESE is a good size chunk of iron... pretty low DCR as well. I think you're right regarding the feedback loop, probably helps a lot here. Now that the prices have jumped up on these ($55 each), they are less a bargain, and equal to the Transcendar units with a "buy now" price of $110 for the pair. I can put the Transcendar OPT on my 45 breadboard (shown with James 6115HS) in less than 5 minutes and do some testing once I get back. I'll post what they do compared to the others as above.

Click the image to open in full size.

RC,

I also have the 20-watt Hashimoto OPTs (30-watt ones too). These are certainly better and I would not hesitate 1-second to recommend them. I have a working prototype running... initially done for a 300B but opted for a 2A3 single-plate for the final design.

I just don't like the para-feed topology... permalloy certainly has advantages and some disadvantges (like price). Still, you have a choke in parallel with the signal path so any core saturation/collapse will be reflected in the OPT, i.e., you don't eliminate it, you just move it to a separate component. Plus you have another component in the signal path (blocking capacitor).

Regards, KM
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Old 18th November 2008, 05:05 PM   #16
Zap is offline Zap  United States
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This hasn't been mentioned yet, but I'm curious how the Transcendar compares to the Edcor CXSE. I love the CXSE in my Simple SE, but I was planning on building a headphone amplifier and I know I won't need that type of power handling, or want it to be quite that large.

I also may be building a Darling, and that isn't high power either and the price of the CXSE has gone up considerably, where the Transcendar has stayed fairly constant.
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Old 18th November 2008, 05:24 PM   #17
N1ESE is offline N1ESE  United States
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Quote:
Originally posted by Zap
This hasn't been mentioned yet, but I'm curious how the Transcendar compares to the Edcor CXSE.
I don't have the thread links handy. However, George at Tubelab has compared all of these (Hammond, Transcender, Edcors) to each other and really favors the Edcor CXSE's. This is what led me to go with the CXSE's on my SimpleSE build with KT88's. However, each transformer has their own unique and distinct sound and, therefore, it is sometimes like comparing Apples to Oranges. Try and search for George's comments on all of these as the question has been answered and he did an excellent job. If you have problems finding the post, I can probably dig it up.

Edit: Here is the post I was referring to:

http://www.diyaudio.com/forums/showt...41#post1647941
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Old 18th November 2008, 11:00 PM   #18
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Quote:
so any core saturation/collapse
I am not particularly knowledgeable in these matters, but it seems much of your reasoning rests on the "any". Would not having the plate choke separate to the transformer allow it to be designed to minimise any such saturation vis a vis series feed? As for the cap in the signal path argument, well, that has been done a gazillion times: is it better to have this or a larger final PSU cap in the signal path? I have a few half-baked reasons and have not made up my mind.

I will probably use both approaches and decide which I prefer. Each approach has a different set of technical and musical virtues and constraints; great amps have been built with each approach. Without giving it much thought, I would guess it boils down to personal preference in achieving purpose, principles and outcomes, obvious and not.

Sorry folks, back OT.

Cheers
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Old 18th November 2008, 11:17 PM   #19
kmaier is offline kmaier  United States
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Hi RC,

My reasoning is simple... as it's a single-ended design, you either drive the core into saturation when the tube conducts hard at one end and you drive the tube into cutoff at the other end and the magnetic field collapses due to no current flow.

Yes, you can use a larger choke, but you will reach a limit, either core saturation or the fact that the tube was driven to a maximum and it won't conduct anymore. At the other end, you can't avoid going into cutoff and the resultant field collapse. The point being, that you don't really eliminate this action, you simply move it. As it is tied to the OPT, it will affect it. Your argument regarding the cap is of course valid, but one can argue going with an Ultrapath topology.

Still, I would prefer to go with simplicity... I'd rather spend extra $$ on a better OPT that buy both an expensive permalloy OPT and a large choke, but again, people have indicated that great amps are around using both topologies, so it does become a personal preference.

Again... sorry, but hopefully back to the main topic now.

Regards, KM
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Old 19th November 2008, 02:46 AM   #20
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kmaier -

The lamination stack on the budget (10W) Transcendars is loads thicker than that on the Hammond 125ESE (supposedly 15W). The 15W Transcendar transformers are larger still. One might conclude from this that the primary inductance and bass performance would be better on the Trranscendars. I'll take one of the Transcendars in to work tomorrow and do a 1 kHz/120 Hz inductance measurement. I'd do the same for one of the ESEs, but both are, shall we say, in-circuit. It won't be an apples-to-apples comparison anyway, as I have the budget 3k Transcendars, and I'm running the Hammonds as 5k transformers.

I was lucky enough to buy the Hammonds a couple of years ago before copper went crazy, and I think at the time they were about $35 apiece. At their current price, I'd buy the Transcendars first, on price, looks, and construction. The Edcor GXSE series looks like a good deal, though they are also very optimistically rated. The 15W (hah!) GXSE looks to be about the same size as a 125DSE for much cheaper.
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