help solve huge feedback when using ARC push-pull 30W power amp

kip.duff · 986

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Offline kip.duff

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Always had intended to try different amps, but now realize the are major compatibility issues.

I had 6A3s in the BeePre- but installed a new set of EH 300B Golds to rule out possible issues- not much change.  The BeePre has IsoNode feet.  Normally using with my Paramount 1.1 monoblocs (Psvane 300B TII or EH 300B) and Altec A7 VOTTs with acceptable hum.  I have an Audio Research Classic 30 30W hybrid push-pull tube amp (6550s) and subbed it for the Paramount 1.1s.  I have attached a spec sheet.  But things got crazy with the ARC amp: kinda like guitar solo feedback and beaucoup hum.  If I put my hand above the tube, hum would go way up more.  Would eventually develop a shriek in one channel.  Though hard to tell, I think the combo of the more snappy power amp behind my BH gear has potential if it can be tamed.  At any rate, I wanna try it- and other amps.

Apparently, I need to make an "L-pad" to reduce gain of the amp- assuming that this combo can work at all.  If someone could give me more details, specs, or photos, I would appreciate it- and any other advice.  If there's room and is feasible, I would like to install whatever I need in either the amp or preamp to avoid extra interconnects and clutter.

Apparently, using more powerful amps is a known issue with the BeePre I- and I noticed that the BeePre II addresses this to some degree.  Before I consider buying a BeePre II kit or another preamp, I want to see what I can do with my current BeePre I (which has Bee Quiet upgrade and nice caps). 

Thanks, Kip.....

Dr. Feickert Blackbird II w Reed 2A tonearm and Lyra Skala cartridge.  Eros 2.  Audio Note DAC 2.1 Signature.  BeePre with BeeQuiet and Paramount 1.1 monoblocs into A7 VOTTs or Nagoaka folded horns.


Offline Doc B.

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It's not an issue of more powerful amps. It's an issue of power amps with high gain.

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.


Offline Paul Birkeland

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The AR has about 31dB of gain, which is a ton.  It's absurdly high for a 30W power amp.  I would use two Harrison labs -24dB attenuators at each input of the ARC, or just not use it.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline kip.duff

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The AR has about 31dB of gain, which is a ton.  It's absurdly high for a 30W power amp.  I would use two Harrison labs -24dB attenuators at each input of the ARC, or just not use it.

Well, I will try this. 

Do you believe this is a bad match?  A doomed marriage?

Thanks for your input...... 

Dr. Feickert Blackbird II w Reed 2A tonearm and Lyra Skala cartridge.  Eros 2.  Audio Note DAC 2.1 Signature.  BeePre with BeeQuiet and Paramount 1.1 monoblocs into A7 VOTTs or Nagoaka folded horns.


Offline Paul Birkeland

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Paul "PB" Birkeland

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Offline aroide

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Even with my Rogue Atlas Magnum amp, I need an L-pad to reduce noise on my beepre 1.  It was easy for me to solder some nice carbon film resistors in the Rogue Atlas.  But when driving the Bryston I used to have (high gain and DC coupled!), I purchased some -12db RCA pads which worked very well.

With the L-pad, noise is not really audible.

Mac mini running Roon->
Mytek Brooklyn DAC+->
Darwin Truth RCA IC->
BeePre (BeeQuiet,  Mundorf Ag/Au/Oil, Sophia Royal Princess 300B)->
Audioquest Colorado->
Rogue Audio Atlas Magnum amp (Psvane small signal tubes, KT150s)->
Audioquest Gibraltar-speaker cables>
Magnepan 1.7 & REL T-5