Home » Audio » Thermionic Emissions » Help with '45' problem?
Help with '45' problem? [message #11192] Thu, 18 August 2005 03:29 Go to next message
Bill Epstein is currently offline  Bill Epstein
Messages: 1088
Registered: May 2009
Location: Smoky Mts. USA
Illuminati (2nd Degree)
The DRD 45 sounds fine with FM Tuner and Fono. With CD it develops a fuzzy then raspy distortion that increases as the volume gets turned up.
Same in both mono-blocks.
Present with pre-amp and without.
Can't drive them hard enough with Fono to tell but don't think so.
97 dB speakers are really about 94 as they are 16 ohm.
Changed the IC's: no difference.
Changed the 45 tubes: no difference.
6N1P drivers (Sovtek) are new.
5AR4's are NOS Bugle Boys.
CD has the highest output of the 3 sources followed closely by the Tuner. I can't hear it on the Tuner so can it simply be clipping?
Some weird digital mis-match?

Re: Help with '45' problem? [message #11193 is a reply to message #11192] Thu, 18 August 2005 08:29 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18670
Registered: January 2001
Illuminati (33rd Degree)

What's the input impedance of that amp? I wonder if it's a bit low for that CD player.

Another thing I've seen a lot is mechanical connections causing those symptoms. They can almost seem like magic too; You'd think they'd be consistent but they're not. If the junction makes contact but poorly, it's an intermittent connection with highly changing resistance. Places it can develop are volume pots, switches and tube sockets.

Then there's those weird Valve Art tubes. Remember them on the Paramours? More magic. Sound great when running, but like Geiger counters when idle. Sometimes. And only every other tube does it, some sound great. Don't guess that's what's up with your amp, but I thought it worth mentioning. 'Spose it could be something like that.

Those are some of the things I'd look at.


Re: Help with '45' problem? [message #11194 is a reply to message #11192] Thu, 18 August 2005 14:25 Go to previous messageGo to next message
akhilesh is currently offline  akhilesh
Messages: 1275
Registered: May 2009
Illuminati (3rd Degree)
Some thngs to check:
1. Are you using the same RCA jack for all inputs?
2. Have you tried a couple of different CD players?
3. Have you switched interconnects and tried it?

thanks
-akhilesh

Re: Help with '45' problem? [message #11197 is a reply to message #11192] Fri, 19 August 2005 06:36 Go to previous messageGo to next message
spkrman57
Messages: 522
Registered: May 2009
Illuminati (1st Degree)
Bill,

2 watts is not much for 94db speakers, what decibel levels are you hitting(spl meter). I have a pair of JBL 4800 (10" 3-way/91db) that when I play on my 45 SET amp will sound just loud enough to hear, but on a pair of Edgarhorns(105db) will run you out of the room.

I wonder if the output of the cd player is a difficult impedance for the 45 amps to take????

Bring them to my house this saturday and lets check it out. What about the 300B amps, does this situation also occur?

Ron

Re: Help with '45' problem? [message #11201 is a reply to message #11192] Wed, 24 August 2005 07:50 Go to previous messageGo to next message
bob pace is currently offline  bob pace
Messages: 4
Registered: May 2009
Esquire
Given that the CD is the highest level, why not test the theory that your input is too sensitive. Rig up a 100K pot between your interconnect and the input to the amp. Top of pot to center conductor of interconnect and bottom to ground. Take the wiper to the input of the amp referenced to ground. Adust the pot to see if the problem goes away. If it does, you may be overdriving your input tube and will need to attenuate the output of the CD player.

Bob

Seems simple enough... [message #11202 is a reply to message #11192] Wed, 31 August 2005 16:19 Go to previous messageGo to next message
Thrint is currently offline  Thrint
Messages: 43
Registered: May 2009
Baron
the obvious answer is that the SE45 does not have enough power for your app.

The more helpful idea would be to suggest an exhaustive look into where is the overload taking place? You can go so far as to seperate stages, but this might not give a clear picture if there is stage-stage interaction in the PS.

If you it is an open loop, or short loop NFB amp you ought to be able to proceed from the input stage to the final and see some evidence of overlaod/clipping. Be thorough, and ask questions as required.
cheers,
Douglas

Re: Thanks to all who replied [message #11203 is a reply to message #11202] Thu, 01 September 2005 03:35 Go to previous messageGo to next message
Bill Epstein is currently offline  Bill Epstein
Messages: 1088
Registered: May 2009
Location: Smoky Mts. USA
Illuminati (2nd Degree)
I'll be trying some 101dB speakers very soon as well as another CD player. It has to be the efficiency issue.

Re: Help with '45' problem? [message #11204 is a reply to message #11192] Thu, 01 September 2005 06:17 Go to previous message
ghpicard is currently offline  ghpicard
Messages: 1
Registered: May 2009
Esquire
I have a SE45 too. Not DRD though, but a WE91-like. When I used a 12AX7 in SRPP as driver, before switching to the WE91 config, that happened to me often. After some measurings, I came to realize that the SRPP stage was unable to fully drive the '45, and had severe rise time problems. I'd rather have distortion in the output stage than in the driver, but that is just my opinion.

Bottom line, I think it could be that you are trying to squeeze too much output power and you are getting driver stage distortion.

Good luck
Gastón

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