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In Reply to: RE: Tube amp for EMI DLS 529 Dangerous Loudspeaker? posted by Eli Duttman on April 22, 2017 at 16:32:06
Thanks Eli. I don't DIY but there is a very nice man in town who works on old tube stuff for very reasonable rates. What about an HK A500. Ad says no hum or noise and a website says it handles 4 - 16 ohms. It's a little over budget but maybe I could stretch for it. I do worry that if it needs work that would blow my budget. - Peter
It's never too late to turn back the clock.
Follow Ups:
Simply because of the out of production 7355 O/P tubes, I'd avoid the H/K A500. Perhaps a conversion to EL34 category tubes, with "reissue" GL KT77s or less costly EH 6CA7s as prime contenders can be undertaken.
There are several things about the A500 that (IMO) need tending to besides "unobtainium" O/P tubes.
1. The "Cheap Charlie" method of DC filaments for preamp tubes is employed, where the heaters form part of the O/P tubes cathode bias network. H/K had plenty of company in using the method, which, frankly, SUCKS. :> (( The O/P signal modulates the preamp tube heater current.
2. PECs, an early form of integrated circuits, are employed. PECs frequently go bad and need replacement by discrete parts. H/K was not the only manufacturer to use PECs.
3. As is so often the case with units from this time frame, source selection should (IMO) be upgraded/modernized. Tape head I/Ps are passe and switches in mV. level signal lines are a source of trouble. A single set of I/P jacks should be directly wired into the low level magnetic preamp section, which is permanently configured for RIAA. All other I/Ps are line level and source selection is done only at line level. A suitable Lorlin brand rotary switch can be sourced from Mouser for approx. $5, but labor expense is present.
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Before you give up on your NAD, definitely replace the caps. in the speaker crossovers. What you hear may simply be the capacitors. Better crossover caps. will surely help with tubed power amplification too.
Dig around for methods which reduce SS amp damping factor. Aside from "bad" crossover caps., the "Dangerous" speakers could be over damped.
Eli D.
Thanks again Eli! The c-j website says Teflon caps are the best because they have the least 'memory' of the earlier signal. One nice thing about the EMIs is you can just unscrew the back and take it right off! Oh those Brits, they are so practical!
As for me I wouldn't know a Teflon cap from a Teflon president. But I hope to learn some DIY after I finish some unrelated projects.
So you think the NAD might be okay with a 1960s low-impedance speaker? I am trying it in soft-clipping mode for the first time (not with the EMIs) just out of curiosity.
It's never too late to turn back the clock.
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