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Old 15th February 2010, 12:32 PM   #1
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Default Am I clipping my Simple SE?

So I finally got my amp up and working and spent some time listening today. I started out with my Omega 3's which are great little speakers with 93 dB efficiency but they lack bass. I next tried out my Quad 11L2's; great sounding speakers, but only 86 dB efficient. I then tried my Quad 22L2's; much bigger speaker, much lower bass, 89 dB efficient. I compared the Simple SE to my recently acquired Suppo Audio EL84 amp (super cheap, Chinese P-P amp rated at roughly 8 WPC).

I'm using a Bottlehead Quickie as my pre and I'm wondering if either I'm clipping my amp or if something's not right. With the Omega's, ear splitting volume is easily obtainable with either the Simple SE or the Suppo but I miss the bass. With the Quad's the Suppo does pretty well (and really sounds good) but volume is somewhat limited. With the Simple SE/Quickie combo it gets MUCH louder but the bass sounds really pretty bad and it gets very hard to listen to. I'm wondering if this is what is meant by "clipping" an amplifier; is my preamp pushing the Simple SE beyond its limits?

My Simple SE is running in triode mode with the big Edcor OPT's so I would assume it would be good all the way down to 20 Hz without breaking up. I do have one concern in that the PT has a distinct hum that I can hear when I lean in close to it (virtually dead silent on the speakers, but the PT makes some noise). Is this normal? Have I done something wrong?

I listened to the Simple SE with 6l6GC's, EL34's, and the Russian 6p3s-e tubes (with appropriate resistor values for each tube) and I know with those tubes in triode mode I'm definitely getting no more than 6-8 WPC; am I just asking too much of these amp with the inefficient Quads? Is this just a bad match with my pre? Something I'm missing?

I've got a 35 wpc P-P EL34 amp on the way that I would like to try with the Quad's as well but I really want to make sure there's nothing wrong with my new Tubelab amp. It's my first DIY job and I really want it to work!

Thanks in advance.
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Old 15th February 2010, 12:48 PM   #2
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Quote:
Originally Posted by bigjppop View Post
With the Simple SE/Quickie combo it gets MUCH louder but the bass sounds really pretty bad and it gets very hard to listen to. I'm wondering if this is what is meant by "clipping" an amplifier; is my preamp pushing the Simple SE beyond its limits?
It's possible that you are clipping, The Simple SE has a fair amount of gain. It may have more gain than your other amp, which is why it seems louder.

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My Simple SE is running in triode mode with the big Edcor OPT's so I would assume it would be good all the way down to 20 Hz without breaking up. I do have one concern in that the PT has a distinct hum that I can hear when I lean in close to it (virtually dead silent on the speakers, but the PT makes some noise). Is this normal? Have I done something wrong?
To give you some examples. I have two sets of speakers I regularly use: a pair of Klipsch KLF10s (98dB) and a pair of Boston Acoustic A70s (89dB, IIRC). The Simple SE in triode with EL34s has no trouble with the KLFs. I get a bit more bass with bigger tubes, like the KT88, but those speakers are so efficient that even my Tubelab SE with 2WPC sounds impressive.

However, the A70s are a different story. They are acoustic suspension and their woofers seems to be harder to drive. In triode, the Simple SE just doesn't have enough oomph and the bass is very laid back. However, in UL with CFB the Simple SE can drive them well. If you have your heart set on driving those Quads with the SSE, consider UL mode with CFB.

A little buzz is normal and is nothing to worry about.
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Old 16th February 2010, 06:38 AM   #3
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I for sure want to try UL and CFB, just wanted to make sure everything was working in Triode mode first. My problem is, I haven't settled on a speaker yet so I think I'm trying to just do too much with what I've got. I'll do some more fiddling and see what I can come up with.

Also, just to clarify, are you saying a little buzz on the PT is normal?
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Old 16th February 2010, 12:49 PM   #4
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Quote:
Originally Posted by bigjppop View Post
Also, just to clarify, are you saying a little buzz on the PT is normal?
Completely normal. In my experience, every power transformer I've seen does it to some degree. Some are much better than others. I would say my Hammond 374BX is inaudible, but you can still feel a faint hum if you put your hand on it. I believe the environment can make a difference, too. The power lines at your residence may be more or less likely to induce PT hum than at some other location.

I've found the best cure is to locate the amplifier as far away as reasonable from the listening position. Mounting the PT on rubber grommets or other isolating washers may help prevent the hum from resonating with the amp chassis.
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Old 16th February 2010, 01:42 PM   #5
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I keep hearing about the buzz, never experienced it. I operate 4 Hammond 300 series transformers, not one buzzes. Being a belt and suspenders man, tho', I always mount'm on EAR SD-40 pads, with, for you safety cats, a separate ground lug to chassis.

Hey BigJ, you want to rock in triode mode, build yourself some 4Pi Pro speakers. Mine are my last. Shameless plug for my pal, Wayne Parham", the designer

AudioRoundTable.com: Pi Speakers

Here's mine

Click the image to open in full size.
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Old 16th February 2010, 05:24 PM   #6
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The buzz varies from unit to unit and also depends on how much load. I have a slew of different Hammonds. Some buzz and some don't...even the same model number. Another factor is your power line. If there is a lot of distortion in your mains due to various electronics in your house and other loads on your grid, it can induce more buzzing in any transformer.
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Old 19th February 2010, 01:48 AM   #7
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I built 3 Tubelab amps using Hammonds 300 series and no buzzing at all. I read somewhere that the 300 series are built sturdier than the 200 series. I might be wrong. Never had an Edcor tranny. Godspeed.

John Revilla
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Old 19th February 2010, 01:01 PM   #8
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Quote:
Originally Posted by bigjppop View Post
...but the bass sounds really pretty bad and it gets very hard to listen to. I'm wondering if this is what is meant by "clipping" an amplifier; is my preamp pushing the Simple SE beyond its limits?
Wicked1 had some issues with his Tubelab SE 300B amp. The symptoms were similar - quality suffered in the bass region, especially when the volume was turned up. He put a high pass filter right at the input of the amp to roll off some of the low frequency stuff and reported excellent success. If you have power hungry speakers and bass heavy material, six watts gets used up in a hurry. Sometimes it is better to make a sacrifice at 20 Hz in order to improve the rest of the audio band.

noticing way more distortion in my 300b
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