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Let me go back to 2016 so I can care...

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On 11/4/2016 at 7:24 PM, mike stehr said:

the Altec 345A

 

If anyone comes across one of these, be aware that the amplifier works best with a preamplifier or line-stage of some sort.

The volume pots on the amplifier or more like input level controls, you dial those in, and then use the main volume control from the preamplifier or line-stage.

This is shown in the video with the companion 445A preamplifier.

 

https://www.youtube.com/watch?v=u35cUQCLmWY

 

DSCN3521.JPG

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5 hours ago, mike stehr said:

 

If anyone comes across one of these, be aware that the amplifier works best with a preamplifier or line-stage of some sort.

The volume pots on the amplifier or more like input level controls, you dial those in, and then use the main volume control from the preamplifier or line-stage.

This is shown in the video with the companion 445A preamplifier.

 

https://www.youtube.com/watch?v=u35cUQCLmWY

 

DSCN3521.JPG

 

5 hours ago, mike stehr said:

 

If anyone comes across one of these, be aware that the amplifier works best with a preamplifier or line-stage of some sort.

The volume pots on the amplifier or more like input level controls, you dial those in, and then use the main volume control from the preamplifier or line-stage.

This is shown in the video with the companion 445A preamplifier.

 

https://www.youtube.com/watch?v=u35cUQCLmWY

 

DSCN3521.JPG

 

Hi Mike, 

 

An ALTEC 345A is a very special amplifier, circa 1959.  Good sounding !!   It has Peerless iron ( Altec owned Peerless ) and thus -  lovely output XFRS.  The circuit is unusual also, as it has a separate G2 supply, for the EL34s, and although run as a pentode-like tube, the voltages on the G2 are triode-like !!  Its a very good sounding amp, and quite desireable to own.  By no means would it go cheap on resale, say on eBay !!!   Notice it has two 5U4GB tube rectifiers which is exactly what I chose to use in my 2019 SE DC KT88 amp.  345As are COOL !!!!

 

Its only design flaw was that one bias pot adjusted all four EL34 tubes.  A common 345A  modification  was to use individual bias pots, to adjust each tube on its own.  In your picture, you can SEE where two red, and one black voltage sensing jacks were installed, for each channel, to monitor output tube bias, on an individual basis.

 

Jeff Medwin

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Jeffrey, as I recall, the power supply of the 345A uses a conventional capacitor input filter with resistors and no chokes.  The screen supply is simply split off from an early filter stage.  I don’t remember ever seeing one on my bench with a separate screen supply.  Is my old memory failing?  
 

It should be possible to replace the input level controls with log taper pots and drive the amp directly from a CD player as I don’t recall the input sensitivity being very high.

 

 

Maynard

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The amplifier is set-up for individual bias pots for each tube, but I'm only using two bias pots for each pair until I source more Bournes trim pots.

schematic (1).pdf

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On 1/3/2020 at 6:52 PM, Marshall J Jordan said:

Sorry I don't have a good opinion of NOSVALVES or Craig Ostby's work. It took almost a year for him to repair my Fisher 400. I payed him 500 dollars. I sent in a pre cleaned example of a Fisher 400 and it was playingwhen I sent it to him.  I plugged it up when I got it home and a puff of smoke came out of the switch . I smelled burning wires and I contacted Craig. He said replacement switches are expensive. He told me to keep the switch on and use a surge protector to turn it on or off. My Fisher wouldn't turn on Christmas day 2019 He hasn't responded to my calls or email.

 

 

 

Pretty strange situation.... I rebuilt this receiver 8 months ago? I don't believe I have spoken to you since shipping it off on May 16th of 2019 maybe I have forgot our conversation way back then...  You have left me a few messages in the last couple weeks. I'm busy with family/health issues these days please email me.  

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any Mcintosh tubr amp , sometimes they are pricey , but they are made to last -----

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Maynard, 

 

Look at how the Altec 345A amplifier's power supply PSUDs !!!

 

Pentodes are insensitive to ripple on the B+ / plate, and the ALTEC EEs took advantage of that, used small capacitance amounts.

 

Notice, from schematic, the grid stoppers on the Finals, NOT the usual 1,000 Ohms, but instead, a more artistic 100 Ohms.

 

Stock amp sounds good !!!

 

Jeff 

 

             1405128722_ALTEC345ApsudDENOTEDFINALSAVE.thumb.jpg.2cd6658f0aa0fb71dd6db483d988404f.jpg

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