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Old 27th October 2007, 04:49 PM   #1
laiben is offline laiben  Hong Kong
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Default Any SE project for 91db speaker?

Hi,

I mostly listen to rock and jazz music. I am going to build a power amp for my paradigm monitor5 speakers which is 91db in efficiency. I want a SE amp, so what about a 2A3 SE amp? Should it be enough power to drive my speaker?

I am not thinking about 300B as they are very expensive. I would prefer to spend my budget on the transformers and caps. BTW the search tells me 300B will be lack of bass for rock music..

Any suggestion?

Thanks

laiben
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Old 27th October 2007, 05:22 PM   #2
jayme is offline jayme  United States
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What about a single-ended pentode, run in triode mode, like an EL-34 or KT-88?
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Old 27th October 2007, 05:37 PM   #3
Svein_B is offline Svein_B  Norway
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Looking for Mikael's KT88 Schematic
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Old 27th October 2007, 06:58 PM   #4
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laiben,

A 2A3 SET amp will be UNSATISFACTORY. Paul Joppa has provided a useful rule of thumb, which says, in a "typical" room, that an amp/speaker combo should be capable of 102 dB. SPL peaks, at a 1 M. distance. Your speakers require at least 16 W. A taste for "head banger" rock music suggests that yet more power is necessary.

A KT88 operating in pentode mode and using regulated screen grid B+ will do the job. Loop NFB of some kind is needed to provide an adequate damping factor.

If your heart is set on having a DHT amp, look for designs employing the 845. However, you will have to deal with 1.2 KV. B+ and expensive O/P trafos, to use 845s.
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Old 27th October 2007, 07:02 PM   #5
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Tubelab Simple SE
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Old 28th October 2007, 01:59 AM   #6
laiben is offline laiben  Hong Kong
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Thanks for the suggestion guys. I will look further about the KT88 SE schematic floating on the Internet. I am running grounded grid preamp but the Mikael looks like a integrated amp with volume control. Could I just short the volume control in the input stage to make it as an power amp?


I am not going to use 845. Though I've bulit an 50W pull-push guitar amp with ~600V, it is pretty scary to touch anything >1000V......


Thanks
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Old 28th October 2007, 02:00 PM   #7
Sherman is offline Sherman  United States
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You can build it without the volume control. I built that schematic as monoblock power amps and they sound very good. Measurements on mine indicate a power output of about 7.5 watts before clipping run in UL mode.

I'm using a B+ of about 424V and idle current in the KT88 is 82mA.
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Old 29th October 2007, 09:20 AM   #8
18thell is offline 18thell  United Kingdom
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Quote:
Originally posted by laiben
Thanks for the suggestion guys. I will look further about the KT88 SE schematic floating on the Internet. I am running grounded grid preamp but the Mikael looks like a integrated amp with volume control. Could I just short the volume control in the input stage to make it as an power amp?


I am not going to use 845. Though I've bulit an 50W pull-push guitar amp with ~600V, it is pretty scary to touch anything >1000V......


Thanks
How can you manage to use ten dollars to settle a hundred bucks bill??? Unless magic!!!

Your spk. only 91db. and your favorite music is pop -----

in order to drive such efficiency spk. at lease required 20 watts.

From data, for Single end design, only transmitting valve could fit.
the common tube like EL34, KT88, KT100 and 6550 only deliever a max. of 12 watts. then back to the tropic, use ten bucks to settle a hundred dollars bill???

Scare of the high voltage, switch to transistor.
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Old 29th October 2007, 09:28 AM   #9
18thell is offline 18thell  United Kingdom
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Quote:
Originally posted by lousymusician
Tubelab Simple SE
Did you notice the tube socket were employed was made in China, what happen? after a long run, the damn socket will melt and deformed, short cct. is the result. Chinese people use re injected PVC and mixed with the scrapped plastic to produce their sockets.
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Old 29th October 2007, 12:55 PM   #10
chrish is offline chrish  Australia
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18, I have built the SimpleSE and I like all kinds of music, from quite jazz to classical to progressive rock to techno dance music. I have 92dB speakers actively crossed over at 80Hz. The only real issue I have had with this amp is trying to play choral/orchestral music at very high volumes when in triode mode (can switch to U/L with switch on the front). For all other music my ears run out before the amp does. I find it quite loud enough for my taste for home use. Previous to this I had 60 watt home brew chip amps and before that 200 watt Adcom 555.

The SimpleSE comes simply as a PC board. You can put whatever sockets you like on it. I used the part numbers recommended, they are ceramic sockets and after about four months of continuous use the only problem that I have had is a blown rectifier tube (JJ GZ34) and blown silicone diodes. I put the blown tube down to poor manufacturing (not Chinese - Slovac) and the blown silicone diodes down to implementation of the standby switch. Since removing the standby switch option and switching to Sovtek 5AR4 and Winged C 5U4G diode I have had no problems. I think that those sockets might be Chinese, but so is the Apple Macbook Pro I am typing this message on. Poor quality is poor quality no matter where it is made.
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