I've been listening to a pair of Antek AT-0358's strapped to the PMillett DCPP "red board". I've tried it on big Tannoy HPD's and my Audio Nirvana horns. The lower frequencies are all there and seem tight. Midrange is good too. I can't comment about the high frequencies yet where I've had a bit of a head cold lately, and I need to try another pair of speakers first.
More later. Hopefully my scope will be able to share some insight about what is going on.
More later. Hopefully my scope will be able to share some insight about what is going on.
Can you measure frequency response with dummy load (wire-wound 50W resistor), with ARTA or RMAA software for example? In this case its possible to distinguish personal sonic impressions from engineering data.
I'm assume Plitron transformers are good (I even bought a book written by Menno van der Veen, designer of Plitron trafos).
HOWEVER, lowest frequency (from datasheet) 0.8Hz is certainly valid only for very little output power (probably 1W). IMHO price 300 EURO/pc is nothing but crazy. Real cost price of these items (manufactured in China or India) is about $30/pc, ordered in qty of 300+ pcs or 1000 kg.
Unfortunately, buying small qty of high-quality audio output transformer for affordable and reasonable amount of money is a problem I have not solved till today.
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Has anybody tried the Mars transformers here?
http://www.vt4c.com/shop/program/main.php?cat_id=112
There are a range of power/LF response options depending on how much you are willing to spend. They have shiny chrome end bells if you are into that sort of thing...
http://www.vt4c.com/shop/program/main.php?cat_id=112
There are a range of power/LF response options depending on how much you are willing to spend. They have shiny chrome end bells if you are into that sort of thing...
Just checked. LM-9904U 75W RMS transformer 92 x 82 x 99H listed for $82 - this core is just enough for 40 - 45 W.
If you load them with only 40 - 45W they possibly will work fine.
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I have no idea. Please start a new thread asking for feedback for these particular vendor's trafos. Quite possible someone already used them.
I'll need to whoop up an attenuator for the probe so I don't smoke my soundcard. Any suggested circuits? I'll test it on the computer's integrated sound chip before I do it on my Emu 1212m.
I'm somewhat doubtful of my own listening so I'd like to confirm what I'm hearing with some numbers too.
I'm somewhat doubtful of my own listening so I'd like to confirm what I'm hearing with some numbers too.
I used 25W wire-wound potentiometer as dummy load to lower output signal level. 2x 3V zenner diodes, or just 4 conventional diodes + 5K resistor should work fine to protect sound card input.
Look at this tutorial from analog devices.
http://www.analog.com/static/imported-files/tutorials/MT-069.pdf
Mars OPT
Hi torrence,
My experience only for Mars SE Output. I use it with 6SL7-45, 5842-300B, RE134-PX25 and what I can say from that experience is satisfied.
I have compared it between AE Amorphous C-core OPT 5K-8ohm and Mars SE OPT 4.8K-8ohm using the above SE tube configurations
Automatic Electric Europe
Audio Catalog
Unfortunately I cannot compare them by equipment but from what I hear I want to say that the cheaper one Mars SE OPT didn't dissapointed me at all.
The only significant difference from what I hear is at the top end. The Mars SE OPT is good but the AE just brilliant.
What I didn't like from this Chinese product is only the chrome shiny cover
You can also read the other using them in this site:
2A3 Tube Amplifier Construction Project
Hi torrence,
My experience only for Mars SE Output. I use it with 6SL7-45, 5842-300B, RE134-PX25 and what I can say from that experience is satisfied.
I have compared it between AE Amorphous C-core OPT 5K-8ohm and Mars SE OPT 4.8K-8ohm using the above SE tube configurations
Automatic Electric Europe
Audio Catalog
Unfortunately I cannot compare them by equipment but from what I hear I want to say that the cheaper one Mars SE OPT didn't dissapointed me at all.
The only significant difference from what I hear is at the top end. The Mars SE OPT is good but the AE just brilliant.
What I didn't like from this Chinese product is only the chrome shiny cover
You can also read the other using them in this site:
2A3 Tube Amplifier Construction Project
I finally broke down and tried one of the 20W Antek OPTs without the UL taps. I had ordered the one with taps, but it came in a case the size of the 70W unit - too large for my application, and not per specs on Antek's website. Upon contacting John at Antek, he said they still had some of the older non-UL units that were in the "correct" case, and since I wasn't planning to use the UL taps, I tried one. I was duly impressed - it sounded GREAT! It replaced the Hammond 1650F I had been using with a pair of P-P 807's in a Williamson-like guitar amp circuit. The freq plot is flat as a pancake, and the output sounded like the plot was pretty accurate. I didn't think they were any more expensive than the Hammonds I had been using...
Just to keep the amp uniform, I also used an Antek 700VCT PT - with my own 5v winding added (try THAT with an E-I transformer!!!) to light the 5U4... made for a "different-looking" amp chassis.
Overall, I'm happy with the Anteks - the only thing I could say bad against them is that the case dimensions didn't match the specs advertised...
Bud
Just to keep the amp uniform, I also used an Antek 700VCT PT - with my own 5v winding added (try THAT with an E-I transformer!!!) to light the 5U4... made for a "different-looking" amp chassis.
Overall, I'm happy with the Anteks - the only thing I could say bad against them is that the case dimensions didn't match the specs advertised...
Bud
The sizes don't match the web site dimensions (I got one that doesn't fit my amp). Sometimes the filament voltage doesn't match what is specified on the web site. The 70 volt tap on the 4TK400 is totally useless since it is wound wrong (and I bought 2 of them). Other than that they are the cheapest way to power a tube amp, and I haven't been able to blow one up yet.
To measure the frequency response of the Antek OT's, put a resistor in series with the primary, equal to the primary Z, and drive it with a 50 Ohm signal generator. Load the secondary with the specified load Z. Then measure the secondary voltage versus frequency to find the 3 dB (70% V of say the 1 KHz point) voltage frequencies.
Ordering an Antek OT at this point is, in my opinion, totally a crap shoot still. Inconsistant construction, errors, no specification of how the frequency plots were done (I'll guess they just used a 50 Ohm generator without the series resistor, which greatly inflates the freq specs).
Just putting it in an amplifier does not give any real measurement, since a random wound xfmr will have horrible internal capacitance. Driving it with a low impedance stage will make the frequency response still look good, but the hidden penalty is bad distortion from the capacitive loading.
Ordering an Antek OT at this point is, in my opinion, totally a crap shoot still. Inconsistant construction, errors, no specification of how the frequency plots were done (I'll guess they just used a 50 Ohm generator without the series resistor, which greatly inflates the freq specs).
Just putting it in an amplifier does not give any real measurement, since a random wound xfmr will have horrible internal capacitance. Driving it with a low impedance stage will make the frequency response still look good, but the hidden penalty is bad distortion from the capacitive loading.
George, can you tell me more about this? I am in the process of discovering this about one of these transformers myself and it has me all confused about how to connect it up.
It seems that the 70V windings are out of phase, so you can't use both, but maybe I can use one with a half wave or bridge rectifier and use it for a low current application like bias? Does this seem coherent with your experience, or have I not got it yet...
That is exactly it. If I were winding a transformer I would arange the taps so that I would get a 400-70-0-70-400 transformer if I put the two windings in series. They are wound so you get 400-70-0-330-400 which is useless to me. I need to design a power supply that generates -100 volts and +100 volts for PowerDrive and +500 for B+. 4 amps of 6.3 volt filament current on a transformer this big isn't enough either. It now looks like I will need 3 different power transformers in my amp.
One of the 70 volt wires could be used with a single half wave diode for bias as is common with Hammond and Fender power transformers. You can't use a bridge if you ground one end of the winding so that you can use a tube rectifier.
The presence of a 5 volt winding indicates that the transformer was intended to be used with a tube rectifier, but the HV windings were not wound for this. It seems that John or whoever is specifying these transformers does not truly understand the needs of a tube amplifier. I sent John an email attempting to explain what was needed about 2 years ago, but got no response. Too bad if he made what we needed he could sell a bunch.
There have been over 100 Simple SE's made. US users often use the Allied 6K7VG because it is cheap. 240 volt users need to purchase a Hammomd 374BX. Make us a toroid like the 6K7VG with dual primaries for under $50 and they would sell. I could specify a few more but it doesn't seem to matter.
Yeah, that one bit me too. I was still able to use the 70V tap for bias on Pete's Red Board, but it wasn't quite what I was hoping for.
Do you have the 4TK400 powering the red board? Sand rectifiers? If so how much B+ are you getting? Tried the 6HJ5's with it?
Right now I am about 1200 miles from home and I will depart for the Dayton hamfest Thursday, returning home Sunday or Monday. After finishing my dual SPP amp I may hook up the red board again. One of my thoughts was to try the big Antek.
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