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Old 11th April 2018, 09:06 PM   #1
mudiwater is offline mudiwater  United States
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Default Distortion? Poor Bass Response?

hello all,
I had posted yesterday, that I was having distortion problems with my newly built SSE. Today I'm not so sure that it is distortion, or just really bad bass response? Highs and mids sound really pretty good, forward in the mids, but the bass is terrible, kick drums and bass lines are flabby, and broken up sounding, kind of like a blown speaker.

I put my old amp back in place, and everything is fine again. I have to assume that I have missed something or have something wrong in my SSE. Any ideas or suggestions of where I should start looking? It is wired in triode mode without feedback, speakers are 90 -91 db sensitivity.

Thanks
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Old 11th April 2018, 10:16 PM   #2
w5jag is offline w5jag  United States
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In both of your threads, you really haven't given out much information for anyone to work from.

90-91 dB, if accurate, is not that sensitive, but should be fine at reasonable volume levels.

Triode mode puts out the least power, and you haven't mentioned what tubes you are using. It makes a difference.

"Turning it up", while descriptive, is not very precise.

No pictures to try to see if something is wired wrong.

My rule of thumb is to get enough power to make 102 dB. You get 3 dB by having a second speaker, so with your speakers, 1 watt gets you 93 dB. 2 watts gets you to 96 dB. 4 watts gets you to 99 dB. 8 watts gets you to 102 dB. You can see the advantage of high sensitivity speakers ....

You might want to consider using KT88's or 6550's in Ultra Linear for your speakers.

This assumes you have adequate drive level going into the SSE. Devices ahead of the SSE may be clipping.

Other folks may have other opinions, this is my $0.02.

Win W5JAG
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Old 11th April 2018, 10:52 PM   #3
mudiwater is offline mudiwater  United States
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Thank you for your reply, I am using EL34 output tubes. I apologize for the lack of needed info. I am new to this, have only build a few Bottlehead kits and a couple Dynaco clones, i don't know much except to follow directions.

The preamps I have tried with it are a Bottlehead (12AU7) based, Hafler 110 and a Nikko Beta II, all of them work fine with my ST-70 and Rotel amp?

I am sure that its something I did wrong in the SSE, it just seems to have no bottom end at all, at any listening level to be honest. I was hoping there may be a common mistake that causes this.

Thanks again
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Old 11th April 2018, 11:15 PM   #4
PDL is offline PDL  United States
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What is your cathode current?

What is your B+?
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Old 12th April 2018, 11:01 PM   #5
mchrismag is offline mchrismag  United States
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I would try hooking up the cathode feedback and see if that makes a difference
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Old 12th April 2018, 11:18 PM   #6
mudiwater is offline mudiwater  United States
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I did get a chance to check B+ voltage today, it is 452 vdc. That seems about right, correct? I used the 6K7VG power transformer. I was thinking that I should try UL with feedback?

I know its a different animal, but with my Dynaco ST-70 Clone, there is not a huge drop in perceived power from UL to triode mode.

Thanks for your help, very much appreciated
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Old 13th April 2018, 02:10 PM   #7
mudiwater is offline mudiwater  United States
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ok, may have found the culprit. My speakers are actually only 87-88 db sensitivity. I'm thinking this amp will not drive them very well.


I am using EL34, 452 vdc at B+, with 560 ohm cathode resistor. SSE is wired to triode mode without feedback.


thanks,
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Old 13th April 2018, 11:53 PM   #8
mchrismag is offline mchrismag  United States
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I would at least try cathode feedback and ul before you give up on the combination of the sse and your speakers. I have the same power transformer and output transformers (except mine have 8 ohm secondaries). I have the same cathode resistors. My b+ has always been a bit high, typically in the 470s with el34 and 460s with kt88s (they draw more current). I'd say try cathode feedback, ul and some kt88s. It does make a difference with this amp. I have several pairs of speakers and I prefer different combinations of operating modes and tubes with each of them. I have one pair that sounds dull and a bit muddy with triode mode and el34s. Those same speakers sound much better with kt88s in ul with cathode
feedback. All of my speakers are rated between 86-89 sensitivity. They all get loud enough. I am not an expert by any means. The sse is my first tube amp. I just would hate to see you give up on it when the answer could be right in front of you. Hope this helps.

Last edited by mchrismag; 13th April 2018 at 11:55 PM.
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Old 14th April 2018, 12:06 PM   #9
mudiwater is offline mudiwater  United States
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Thank you for the encouragement. I am now convinced that I have simply done something wrong, installed something incorrectly, something. No way this amp can sound this bad. I did wire amp to UL with feedback, it did increase the power output, but still have the terrible low end breakup.

Also, I am positive now that its not my speakers or preamp, etc...... a friend of mine brought over his SE low watt amp (5 watt) and it sounded wonderful through my current setup.

So, I'm thinking I have overlooked something, installed an incorrect part, etc.... trouble might be finding it. The only thing that I have really checked is the B+, it measures 452 vdc

Thanks
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Old 14th April 2018, 04:52 PM   #10
mudiwater is offline mudiwater  United States
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Default Some Measurements

I finally went through Ty Bower's SSE checkout list, everything seemed fine except for the #4 and #6 pin on the rectifier socket. His meter was showing around 440 volts, I am only getting 234 volts? Any suggestions would be most appreciated.

Thanks
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