Best old school Preamp?

My cats have never argued.
 
Elite-ist said:
Bob: First I had heard of that model of preamplifier, so I looked it up and found the site delving in all the upgrades. Did you upgrade yours?
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Nando, just saw this one. Yes, it got upgraded with the level 1 line and phono stage mods. Very sweet sounding this way but for some reason it ate tubes like no ones business, especially the phono stage where I had to pay extra to get the quietest ones I could find. They would just get noisy every so often. Got tired of basically buying a new pre-amp's worth of tubes every three years which is why I went to the Exposure integrated that I have now...
 
Bob: One of my friends, who is into gear, has a Motif (upscale Conrad Johnson) preamplifier. He has it paired up with a Stax amplifier. His regular amplifier is a Conrad Johnson. It also likes tubes. What is a normal period of time in operating hours for a power tube, or preamp tube to last?







Nando.
 
Elite-ist said:
Bob: One of my friends, who is into gear, has a Motif (upscale Conrad Johnson) preamplifier. He has it paired up with a Stax amplifier. His regular amplifier is a Conrad Johnson. It also likes tubes. What is a normal period of time in operating hours for a power tube, or preamp tube to last?







Nando.
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Nando, Your small signal tubes will last longer than you will, They are low voltage 200-300 volts and and have very little current through them. BUT Power tubes will last as long as you don't abuse them. In old amplifiers that have adjustable bias, Marantz, Dynaco, Grommes and Heathkit I have seen 30 year old tubes that perform like new, but I have seen some that the tube checks out like shit. Many old EL34 tubes in Dynaco and Marantz were biased at 50ma which were well below there ratings and to this day are performing very well. The new Russian made remakes perform very well if not underbiased, but they cannot take the current of the old Mullard Xf2's in my opinion
 
Thanks for your expertise, Skratch. Perhaps, that is the issue then: not being able to correctly bias to preempt premature tube failure. I have a Heathkit AA-32 I haven't used beyond ensuring all the tubes lit up. What should I be doing to correctly bring it on-line with a load, beyond letting it warm up?

It has seven tubes: 4 X ECL86 and 3 X 6EU7. Output is an advertised 12 wpc at 8 ohms and it has terminal connections for 4, 8, and 16 ohm speakers. If it indeed works, I'm going to use this amp to power a pair of 1960's British Leak Sandwhich speakers.

Nando.
 
Elite-ist said:
Thanks for your expertise, Skratch. Perhaps, that is the issue then: not being able to correctly bias to preempt premature tube failure. I have a Heathkit AA-32 I haven't used beyond ensuring all the tubes lit up. What should I be doing to correctly bring it on-line with a load, beyond letting it warm up?

It has seven tubes: 4 X ECL86 and 3 X 6EU7. Output is an advertised 12 wpc at 8 ohms and it has terminal connections for 4, 8, and 16 ohm speakers. If it indeed works, I'm going to use this amp to power a pair of 1960's British Leak Sandwhich speakers.

Nando.
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Nando, That little AA-32 is a self biasing amp. Almost all EL86 amps were, I will bet it still has all the original tubes in it and they will test like new. Where you run into problems are with the EL34, 6550, Kt88 tubes with the exception the McIntosh power amps which are not adjustable. I have purchased many of the old Dynaco ST 70 stereo and the Mark 2,3 and 4 series monoblocks that the tubes were either like new or trashed because a lot of the prior owners did not understand how to bias the tubes.
 
Mark: Really, the tubes could date back that far? If I do get it going I will post the results. Here it is:





Nando.
 
Love the looks of the old school Heathkit. Would love to have that pre over for a listen.
 
Elite-ist said:
Mark: Really, the tubes could date back that far? If I do get it going I will post the results. Here it is:





Nando.
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Sweet looking retro amp Nando. I had an Eico 4W single ended EL84 based amp that looked similar to this one in construction. This one looks pretty clean. I like the 'hum null' adjustment on it :-)
 
Thanks for all the comments, guys. With so much other stuff going on, I put the whole idea of assembling my retro system together in another bedroom on the back-burner. But, this is what I have set aside, besides the Heathkit AA-32 integrated tube amplifier:

Leak Sandwich speakers:







Dual TD-28 open reel deck:





Just looking for a nice 60's vintage turntable, next.

Nando.
 
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