16 vs. 8 Ohm Taps on SET Amplifier (Drive Units)

by Cappy @, Tuesday, December 05, 2006, 01:49 (4062 days ago)

I am considering getting a new amp and the issue came up of 8 vs. 16 ohm taps.

The new amp I am looking at, a Yamamoto A08-S, has single 8 ohm taps. A special 16 ohm output transformer can be purchased at extra cost.

I was curious to see what my current amp is using, so I opened it up and looked: They have 2,4,8, and 16 ohm taps. I am using the 8 ohm tap into my Oris 200s with AER MD3s. It sounds damn good on the 8 ohm tap.

I know when it comes to impedance issues things are not straightforward, but I would still appreciate comments and experiences on 8 vs. 16 ohm taps for the AER MD3.

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16 vs. 8 Ohm Taps on SET Amplifier

by Cappy @, Tuesday, December 05, 2006, 04:08 (4062 days ago) @ Cappy

I just learned from Brian at Venus HiFi that Mr. Yamamoto gives demos using his 8 ohm 45 Sets with his 16 ohm speakers.

I then found on on the 6moons site that the speaker is: "the new YS-605P open-baffle model with a refurbished/modified 15" coaxial 16-ohm Altec 605A (or B) transducer"

I also found this regarding an Egdarhorn system:

"This system provided a challenge to the A-08 as it is a 16 ohm system and the A-08 is optimized for 8 ohms, but Yamamoto-san says is compatible with 4 to 16 ohms systems with only slight loss of performance."

In any case, I would still like to hear thoughts about 8 vs 16 ohm output transformers for the AER MD3.

Bill

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16 vs. 8 Ohm Taps on SET Amplifier

by Bert @, Tuesday, December 05, 2006, 09:44 (4061 days ago) @ Cappy

Hi Bill,

I know when it comes to impedance issues things are not straightforward, but I would still appreciate comments and experiences on 8 vs. 16 ohm taps for the AER MD3.

I have always used 8 ohm taps for the MD3's, never a problem with that.

Probably less optimal in terms of output power of the amp which is then a bit limited but it is not just about power ratings (500mW is already enough!) and linearity of the output tubes but more the quality of the transformer and the flexibility of the design itself.

Note that the AER is not 16 ohm from 150Hz to 20kHz, it varies as all speakers do. If the amplifier can't handle impedance changes very well then the design is not good, the only solution for such amps is to correct the impedance flat for 8ohms or so... (adding parts to the signal).

Ciao,

Bert

--
BD-Design - Only the Best!

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16 vs. 8 Ohm Taps on SET Amplifier

by Cappy @, Tuesday, December 05, 2006, 16:06 (4061 days ago) @ Bert

Bert,

Thanks for the reply.

I just learned that the Yamamotos 45s are 0.5v sensitivity.

I really don't like "wasting" gain so that is probably too sensitive for me. And I have a passive TVC and sources with standard (or less) voltage output.

Interestingly, the WE91-based Thorsten inspired Ladyday version I mention also has 0.5v input sensitivity. Both that amp and the Yamamoto have pentode drivers , not triodes. I wonder if the sensitivity is a result of the old pentode designs?

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16 vs. 8 Ohm Taps on SET Amplifier

by Bert @, Tuesday, December 05, 2006, 16:14 (4061 days ago) @ Cappy

Hi Bill,

Interestingly, the WE91-based Thorsten inspired Ladyday version I mention
also has 0.5v input sensitivity. Both that amp and the Yamamoto have
pentode drivers , not triodes. I wonder if the sensitivity is a result of
the old pentode designs?

I have the normal Ladyday with plenty of gain (using TVC's AND the low output TwinDAC+). Also 0,5V or even less sensitive as far as I know.

I guess it has to do with the amplifications the tubes provide and there is a different between tubes...

Ciao,

Bert

--
BD-Design - Only the Best!

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16 vs. 8 Ohm Taps on SET Amplifier

by Cappy @, Tuesday, December 05, 2006, 16:31 (4061 days ago) @ Bert

The normal Ladyday is spec'd currently at 1.5v sensitivity. I am guessing that is what your version has too.

That is what I currently have in my Welborne DRDs and that works well for me, with my passive TVC.

1.5 volts is a bit below the 2 volt CD standard, and matches my lower voltage phono preamp well.

0.5 volts is very sensitive. Not many sources have 0.5 volts output. With a 0.5 volt amp, any more output voltage than 0.5 volts gets "thrown away" in the preamp at the full output of the amp. Now TVCs are much better at throwing away gain than resistors, but still...

Even the Twindac is greater than 0.5 volt output.

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16 vs. 8 Ohm Taps on SET Amplifier

by Cappy @, Tuesday, December 05, 2006, 16:47 (4061 days ago) @ Cappy

The Ladydays have more gain than the Welbornes, apparently.

Now that I think about it, with your Twindac, the WE91 Ladyday 0.5 v sensitivity version could be very nice. It would give you a bit of headroom above the 0.8v Twindac.

That is, unless the gain in the Ladyday is too high to then give you a comfortable range on your TVC.

Thorsten's post:

http://db.audioasylum.com/cgi/m.mpl?forum=tubediy&n=71898&highlight=91+Thorsten...

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16 vs. 8 Ohm Taps on SET Amplifier

by Bert @, Wednesday, December 06, 2006, 15:44 (4060 days ago) @ Cappy

Hi Bill,

That is, unless the gain in the Ladyday is too high to then give you a comfortable range on your TVC.

Without using the +6dB switch setting on the Django I have a very nice range to play with. When I want to play loud then I can almost go full...

Perfect sensitivity balance all through... :)

Ciao,

Bert

--
BD-Design - Only the Best!

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16 vs. 8 Ohm Taps on SET Amplifier

by Cappy @, Wednesday, December 06, 2006, 19:09 (4060 days ago) @ Bert

Great, that is what matters, a good range on the TVC.

I was referring to the WE91 Ladyday version at 0.5v sensitivity. I think the version you have is 1.5v sensitivity.

I was concerned that the 0.5v input sensitivity of the Yamamoto 45 would be too much for me. My sources are 2v for CD and 1v output for K&K phono stage. Currently my DRD 45s are 1.5v, which like you and your Ladydays, works well for me.

Your source is less at 0.8v output, I think anyway from the Twindac web page. It sounds like the 0.5v WE91 might not have the best gain matching for you either, just like the Yamo wouldn't for me. Currently I think our amps have the same input sensitivity. 0.5 volts on Oris/Orphean, even with a TVC, is A LOT.

Now there have been many versions of the Ladydays so it is possible your input sensitivity differs. I am just looking at the specs on the current Diyhifisupply web site.

I have decided to stick with the Welborne DRD 45s, which have a wonderful sound. The reason I was looking at the Yamo was because of compatibility problems with the wonderful Emission Labs 45 tubes, but after a conversation with another owner, I now have some ideas on modifications to the Welbornes which have a good chance of fixing the situation.

I don't think the EML problems with the DRDs are Welborne's fault, either, since my TJ 45s have worked fine for years and are still very quiet, having < 0.5 mv hum. The Yamo runs the filament voltage lower than spec, for example.

Additionally, I learned Emission Labs made some changes to their 45s about 6 months ago, adding a soft start and changing the structure of the filaments to a serial design.

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