CHANGSTAR: Audiophile Headphone Reviews and Early 90s Style BBS
Lobby => Amp and DAC Measurements => Topic started by: ultrabike on September 03, 2014, 09:25:03 AM
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This is a loaner from OJ. Thanks mang!
This came with three tubes: 6J6W, 5844, and Telefunken (E90CC). The layout and presentation of this amp is pretty spectacular IMO. It's all black and I like that. It doesn't get too hot. Seems easy enough to build and comes with plenty of support.
Here is the BOM and info: http://www.diyforums.org/Torpedo/TORPEDObom.php
The kit is available at http://beezar.com/catalog/product_info.php?cPath=42&products_id=153
From my impressions (with my HD600s) I felt the 6J6W and the 5844 where a little brighter but perhaps more accurate than the E90CC which I thought was more mellow and forgiving. The E90CC carried IMO a tad more impact and warmth. Still when pushing the volume at Lo-Z things degraded a little with cymbals and detail when using the E90CC. I liked the E90CC better though. Less strident perhaps.
Overall, the amp is pretty involving and dynamic with my HD600s at the volume I usually listen. I think I prefer to listen at Hi-Z w the Torpedo though, at least with the E90CCs.
The following are some impedance measurements:
6J6W: Lo-Z = 21 ohms / Hi-Z = 146 ohms
5844: Lo-Z = 19 ohms / Hi-Z = 119 ohms
E90CC: Lo-Z = 16 ohms / Hi-Z = 96 ohms
The following are some voltage swing measurements (rms):
6J6W (Lo-Z) = 2 V (into 300 ohms) / 2.15 V (open)
5844 (Lo-Z) = 1.7 V (into 300 ohms) / 1.8 V (open)
E90CC (Lo-Z) = 1.43 V (into 300 ohms) / 1.5 V (open)
E90CC (Hi-Z) = 3.48 V (into 300 ohms) / 4.59 V (open)
Lowest distortion was achieved w the 6J6W which was also the tube that yielded highest output impedance, and highest voltage swing... Guess Low-Z does not always correlate to lower non-linear distortion. Highest distortion was present with the E90CCs.
Into 300 ohms and @ 400 mV (rms) the following are THD numbers:
6J6W (Lo-Z) = 0.476%
5844 (Lo-Z) = 0.538%
E90CC (Lo-Z) = 0.602%
E90CC (Hi-Z) = 0.383%
Hi-Z yields lower distortion numbers for all tubes.
IMD SMPTE 60Hz + 7kHz (300 ohms @ 400 mV rms)
6J6W (Lo-Z) = 1.28%
5844 (Lo-Z) = 1.37%
E90CC (Lo-Z) = 1.48%
E90CC (Hi-Z) = 0.935%
IMD DIN 250Hz + 8kHz (300 ohms @ 400 mV rms)
6J6W (Lo-Z) = 1.28%
5844 (Lo-Z) = 1.38%
E90CC (Lo-Z) = 1.52%
E90CC (Hi-Z) = 0.964%
IMD CCIF 19kHz + 20kHz (300 ohms @ 400 mV rms)
6J6W (Lo-Z) = 0.851%
5844 (Lo-Z) = 0.850%
E90CC (Lo-Z) = 0.756%
E90CC (Hi-Z) = 0.434%
My understanding is that < 2% IMD for this class of amps is considered good, but I'm not an expert.
The following are plots for THD with the 6J6W and E90CC at Lo-Z
6J6W
(http://www.changstar.com/index.php?action=dlattach;topic=1756.0;attach=7519;image)
E90CC
(http://www.changstar.com/index.php?action=dlattach;topic=1756.0;attach=7521;image)
The following are plots for IMD (SMPTE) with the 6J6W and E90CC at Lo-Z
6J6W
(http://www.changstar.com/index.php?action=dlattach;topic=1756.0;attach=7523;image)
E90CC
(http://www.changstar.com/index.php?action=dlattach;topic=1756.0;attach=7525;image)
While I felt the E90CCs had more warmth to them, relative to E90CCs there seems to be more upper bass distortion (THD and IMD) with the 6J6W. I did feel the E90CCs where more pleasant though.
However, the 6J6W while lower in THD, does seem to have more harmonics up into the treble area. Not sure if this would become significant with complex music and indeed be one of the reasons I felt more stridency with the 6J6Ws, which may or may not explain why I felt the E90CC were more warm and pleasant.
The following are plots for HD600 distortion (@ 96dB SPL) being driven by 2i2, Torpedo E90CC Lo-Z, and Torpedo E90CC Hi-Z:
2i2
(http://www.changstar.com/index.php?action=dlattach;topic=1756.0;attach=7527;image)
Torpedo E90CC Lo-Z
(http://www.changstar.com/index.php?action=dlattach;topic=1756.0;attach=7529;image)
Torpedo E90CC Hi-Z
(http://www.changstar.com/index.php?action=dlattach;topic=1756.0;attach=7531;image)
As can be seen, the amps do seem to impart their distortion characteristics. In terms of linearity, HD600 seems to perform better with Torpedo in Hi-Z mode relative to Lo-Z. However, there will be about 1 dB of bass gain due to output impedance increase.
Subjectively I feel this amp was pretty enjoyable and paired well with my HD600s.
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Wow thanks for posting this Ultra, this is rather interesting! Both the amps and the effects they impart on the headphones.
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My comments from the Shoutbox:
The tube with the highest mu should yield the best measurements. Not because high mu tubes are inherent more linear, but rather because feeding the input a hot source (anywhere near 2Vpp) will create distortion
Therefore, a tube with higher mu can achieve an equivalent voltage on the output whie having the loweswt voltage at the gate, hence lowest distortion
It took a bit of poking around with my DMM to figure that out; fortuntely my D/A's output can be set for 0dBV which avoids the problem
It's also worth keeping in mind that 2V into an HD600 is 110dB :-0 And the HD600 is one of the harder to drive hi Z phones out there in terms of sensitivity.
If you're looking to drive lo Z planars, this isn't the amp for you. It failed to drive the HE560 to any effect at the meet.
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Yup. Tubes voltage swing correlated to non-linear performance. All the non-linear distortion tests were done at 0.4 Vrms into 300 ohms (output voltage), except the ones where HD600 SPL was measured (96 dB @ 1kHz).
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Did anybody try to drive the HD-800 with it?
Would this be considered a good amp for it?
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Possible. The HD800 is around 300 ohms and fairly sensitive so large amounts of current may not be needed. On Hi-Z it might bring up more warmth to the 800s + good voltage swing headroom. Furthermore Hi-Z seems to give better linear results.
On Hi-Z this amp is proly close to the IEC Standard:
http://www.changstar.com/index.php/topic,90.msg403.html#msg403
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Clem, I have an HD800 incoming. I'll let you know. I did give a brief listen to the combo at the SF meet and I thought it was pretty solid. Marv and Anax agreed unless I'm mistaken. There are a few other good cheap-ish tube amps around the Torpedo's price though. Valhalla2 and BH Crack + SB come to mind. A more in-depth comparison would be needed to eek out the champion.
BTW ultra, love the new avatar :)p12
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(http://www.buddy-icons.info/img/smile/1703.gif)
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Yes. Works with HD800 very well. It's a really good amp for the price + effort of putting it together. I pretty much like all of Doug's designs.
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Agreed. I enjoyed a Torpedo for a good 6 months. I was continually impressed by the performance level of this little amp. Torpedo being a 'Parafeed' had much to do with me trying the Mainline.
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Thanks ultra, very interesting! Hopefully we can get a good comparison going with the Valhalla 2 and BH Crack + SB. Assuming I keep my HD650 around for a while, I'd like to invest in one of these.
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Clem, I have an HD800 incoming. I'll let you know. I did give a brief listen to the combo at the SF meet and I thought it was pretty solid. Marv and Anax agreed unless I'm mistaken. There are a few other good cheap-ish tube amps around the Torpedo's price though. Valhalla2 and BH Crack + SB come to mind. A more in-depth comparison would be needed to eek out the champion.
BTW ultra, love the new avatar :)p12
Looking forward to reading your thoughts!
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:)p1
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Let me say this about the Torp+800. Good to tonal synergy so pleasant to listen to. On the micro stuff it is a bit congested which negates the strength of the HD800 IMO. I know OJ is playing with different caps to improve this but last I heard the Vali did better in those areas.
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What could/would be considered a good amp for HD-800 under $1k?
They would be my last headphone purchase, most likely. Getting rid of the gears I don't plan on using anymore.
M7 + Rag + HE-6 is end game worthy for me (should such a thing exist, of course :-\).
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Any way you cut it, this amp leans to the warmer side. I've tried 2 different coupling caps (cheaper polyprops at this point) and 6 different tube pairs and none of them (except one perhaps) makes the modded HD800 unlistenable. You can take that for what you will. It's not a dull and smoothed over sound; in fact it's quite dynamic and can definitely bite with the HD800. Although this amp doesn't lie to you, it's not an analytical sound by any stretch.
Tonally it's spot on with HD800. Perfect synergy there. Stage is also quite wide. Comparing directly the ECZD it doesn't quite dig as deep into the mix and it isn't quite as spatially satisfying. ECZD seems very good at placing images in the headstage. But the ECZD has some other overt problems which make me less inclined to listen to it. From what I remember of the Vali, it leaned toward a brighter sound too. Haven't heard it with HD800 but something tells me I might find it objectionable. Keep in mind I have lower tolerance for brightness due to my preference in listening levels and musical inclinations.
Anax: You've only heard the Torp with the gamma2, and surprisingly enough, it does become the limiting factor. The Hilo is a better match tonally and lets the Torpedo show of its technicalities a bit more. I hear an improvement in low-level rendering with the Hilo into the Torpedo which you might like. Other than that, we'll see what a more expensive cap can bring. But this is pretty much where I get off in terms of HD800 amplification. I'm able to tailor the sound well enough by switching out tubes and the hi-lo Z switch offers some extra flexibility WRT different music and mood swings.
For all the blue whales out there chasing that plankton:
(http://ppcdn.500px.org/1034286/f2f439a218b8ab71265c6f867e42e2b324a3e5e2/5.jpg)
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Kit arrived at Monday, and finally had time to assemble it. Very good sound. I prefer 6J6 to E90CC tubes.
Assembled without top cover
(http://i.imgur.com/g2rD170l.jpg)
Fully assembled and working
(http://i.imgur.com/5O9DqRkl.jpg)
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Which caps are those?
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Claritycap SA series, 630V 4.7uf.
I love this little amp.
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Claritycap SA series, 630V 4.7uf.
I love this little amp.
I have the Clarity MR's in 10uF for both 630v and 400v. Definitely a distinct timbre.