A few pointers for a beginner in tubes?

Dampdog

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Apr 10, 2021
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Greetings. Occasional poster in the What's Best forum, but not for a while.

I recently listened to a few tube amps from Sun Audio and Audio Professor, two small makers in Tokyo where I live. I was taken aback by the clarity on a range of speakers, from huge vintage Altecs to Harbeth floor standers and even an ancient Diatone one-way pair. I now want one, as an occasional alternative to my Accuphase integrated amp. Trouble is, I'm a total beginner.

I heard that speaker efficiency is important. I have JBL L82s, which are 88 dB (2.83V/1m).

The Sun Audio guys seemed to say their amps would work well on any speakers, but the Audio Professor guy said 88dB would require a push-pull type with relatively high power, as opposed to a single (whatever that is).

And they both said I don't need an integrated amp, just a power amp with RCA inputs.

Anyone have and advice? Also, I know 300B tubes are well regarded, but any pointers on tubes in general would also be much appreciated.

Thank you!
 

Lowrider75

Active Member
Dec 4, 2019
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Greetings. Occasional poster in the What's Best forum, but not for a while.

I recently listened to a few tube amps from Sun Audio and Audio Professor, two small makers in Tokyo where I live. I was taken aback by the clarity on a range of speakers, from huge vintage Altecs to Harbeth floor standers and even an ancient Diatone one-way pair. I now want one, as an occasional alternative to my Accuphase integrated amp. Trouble is, I'm a total beginner.

I heard that speaker efficiency is important. I have JBL L82s, which are 88 dB (2.83V/1m).

The Sun Audio guys seemed to say their amps would work well on any speakers, but the Audio Professor guy said 88dB would require a push-pull type with relatively high power, as opposed to a single (whatever that is).

And they both said I don't need an integrated amp, just a power amp with RCA inputs.

Anyone have and advice? Also, I know 300B tubes are well regarded, but any pointers on tubes in general would also be much appreciated.

Thank you!
First of all, what is the rated power of these amps?
Your JBL's are 8ohms nominal, although the impedance curve shows much of the lower midrange is down around 4ohms. It would be best to drive these speakers from 4ohm speaker taps.
But need to know the power of the amps.
 

Dampdog

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Apr 10, 2021
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Lowrider75

Thanks so much for the response. As you can tell, I'm a total beginner. Perhaps these photos will give more of an idea.

The Sun Audio guys sell a range of amps. The Audio Professor guy says he builds them order-made, so I assume that means to all kinds of specs.
 

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Lowrider75

Active Member
Dec 4, 2019
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The Sun Audio guys sell a range of amps. The Audio Professor guy says he builds them order-made, so I assume that means to all kinds of specs.
The pics help. They're all integrated amps like your Accuphase (nice) so they have a preamp and a volume control.
The KT88 is a Push-Pull amp with higher power than a 300B SET amp (single ended triode). A SET typically has between 6W to 12W per channel, not enough to power your speakers. You'll hear music just fine but you'll be missing bass and low-end punch. You need power to drive bass and your speakers go from 8ohms to 4ohms (which is low impedance). These specs are more important than the 88dB sensitivity.

You need more information about the power of these amps including the Push-Pull. Are the adverts in Japanese, can you read them? You need a minimum of 20 watts/channel to drive the JBL's, more is even better. You want to get the full dynamics of the music.

Please find out the power of each amp you're considering. I'm here to help.
Jim
 
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Lowrider75

Active Member
Dec 4, 2019
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The pics help. They're all integrated amps like your Accuphase (nice) so they have a preamp and a volume control.
The KT88 is a Push-Pull amp with higher power than a 300B SET amp (single ended triode). A SET typically has between 6W to 12W per channel, not enough to power your speakers. You'll hear music just fine but you'll be missing bass and low-end punch. You need power to drive bass and your speakers go from 8ohms to 4ohms (which is low impedance). These specs are more important than the 88dB sensitivity.

You need more information about the power of these amps including the Push-Pull. Are the adverts in Japanese, can you read them? You need a minimum of 20 watts/channel to drive the JBL's, more is even better. You want to get the full dynamics of the music.

Please find out the power of each amp you're considering. I'm here to help.
Jim
Wait a sec. I zoomed in and can read the specs. The SET amps are 3.5 watts & 8W low power amps. You can't drive your speakers with these.
There's also a KT66 amp in addition to the KT88 Push-Pull. I can see the KT88 is only 8W and does not have a 4ohm output. KT88 amps are very popular and can sound great.
*Ask the dealer if he has Push-Pull with 20 watts or higher. Tell him you need an amp with 8ohm and 4ohm taps (outputs). Your speakers need 4 ohms.
 

Al M.

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Wait a sec. I zoomed in and can read the specs. The SET amps are 3.5 watts & 8W low power amps. You can't drive your speakers with these.
There's also a KT66 amp in addition to the KT88 Push-Pull. I can see the KT88 is only 8W and does not have a 4ohm output. KT88 amps are very popular and can sound great.
*Ask the dealer if he has Push-Pull with 20 watts or higher. Tell him you need an amp with 8ohm and 4ohm taps (outputs). Your speakers need 4 ohms.

All good advice. I'd go further and recommend at least 50 W/ch push-pull for 88 dB sensitive speakers.

Personally I like overkill. My speakers (Reference 3A Reflector) are pretty flat 8 Ohm and 92 dB sensitive. I drive them with an Octave push-pull KT150 amp of 100 W/ch into 8 Ohm. But I can drive them with my 15 W/ch parallel push-pull 2A3 triode amps as well to very good dynamics, even though not the same as with my Octave amp.
 
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bonzo75

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Feb 26, 2014
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Greetings. Occasional poster in the What's Best forum, but not for a while.

I recently listened to a few tube amps from Sun Audio and Audio Professor, two small makers in Tokyo where I live. I was taken aback by the clarity on a range of speakers, from huge vintage Altecs to Harbeth floor standers and even an ancient Diatone one-way pair. I now want one, as an occasional alternative to my Accuphase integrated amp. Trouble is, I'm a total beginner.

I heard that speaker efficiency is important. I have JBL L82s, which are 88 dB (2.83V/1m).

The Sun Audio guys seemed to say their amps would work well on any speakers, but the Audio Professor guy said 88dB would require a push-pull type with relatively high power, as opposed to a single (whatever that is).

And they both said I don't need an integrated amp, just a power amp with RCA inputs.

Anyone have and advice? Also, I know 300B tubes are well regarded, but any pointers on tubes in general would also be much appreciated.

Thank you!

The altecs are very easy to drive. I have heard a Sun audio vt25 amp and at 2 watts or so it was quite enjoyable for barely 2k cost.

But for your JBL you will need more power. You should also look for used audio music 833c can be good power (120w) for not much cost and has the SETs magic. Clean, neutral, nuanced, and with power
 

Lowrider75

Active Member
Dec 4, 2019
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All good advice. I'd go further and recommend at least 50 W/ch push-pull for 88 dB sensitive speakers.

Personally I like overkill. My speakers (Reference 3A Reflector) are pretty flat 8 Ohm and 92 dB sensitive. I drive them with an Octave push-pull KT150 amp of 100 W/ch into 8 Ohm. But I can drive them with my 15 W/ch parallel push-pull 2A3 triode amps as well to very good dynamics, even though not the same as with my Octave amp.
I agree, more than 20wpc would be better. The issue is that the JBL's drop to 4ohms in the lower mids, upper bass, (Stereophile).
I use a 30W tube amp with 90dB 8ohm (flat curve) speakers. I've also had a 88dB 4ohm pair of speaks with a benign load which performed very well. The JBLs don't have a benign load.
 
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Dampdog

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Apr 10, 2021
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Thank you all very much for your advice, I feel like I’m learning something!

I’m pretty set on going for a Japanese tube amp, like I did with the solid state Accuphase, given where I live.

Clearly I should be looking for a push-pull with power, so I think my best option will be to ask the Audio Professor to see what he can build and for what price, instead of a Sun Audio. They offer a set range, but apparently there isn’t much to suit me.

In fact, the pic I sent of an actual amp was for sale in the Audio Professor workshop. It’s old, cheap, 25W, but I don’t know about the ohms. It was playing into Harbeths. The source was the guy’s phone via a Bluetooth device he said he made for 300yen (a couple dollars). It sounded so spacious.

I attached more images of the place, just in case you’re interested to see.

This may be a dumb question: is it possible to make a high powered push pull amp with any tubes? I’d prefer something produced by a range of brands, like the 300b.

Thanks again
 

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facten

Active Member
Feb 13, 2022
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Good advice given. I know that you have stated that you want to go with a Japanese amp, that said I'd like to suggest that maybe you also take a look at Line Magnetic , very well built and sounding Chinese tube amps. The link below I think might interest you given the need for power ( it is 48 wpc) and also the desire for a 300B in the amp (it includes 300Bs) . I don't have this particular amp but I have read posts from folks that have it and are very pleased. I have their 22wpc 845 tube integrated and it is very enjoyable, especially with some tube rolling. Anyway, I just wanted to pass this along for 'food for thought' ; good luck with your search

LM-805iA Integrated tube amplifier - Single Ended 805 - 2x48W (line-magnetic.eu)
 

Dampdog

New Member
Apr 10, 2021
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Thank you, facten

That Line Audio amp is handsome, and muscular, and the consensus online is very positive. Not sure if it’s easily available here in Japan though. I’ll look into it a little more.
 

consocmap1

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Jun 23, 2022
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Oh man,

Wish I could be there. All those systems look great and I think there will be 1 matching well with my Klipsch RP-400M.
 

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