no brakes. I will probably wedge a wheel if it moves on making connections.
btw I did not have the time to look up the schematic I have somewhere to see if the component numbering matches those you used when pointing me to after the phase inverting circuit past which amp runs as balanced.
Do you happen to know what kind of input impedance I could have with the balanced input? I would be using Aleph P preamp which has a volume attenuator at its output and a highish output impedance.
btw I did not have the time to look up the schematic I have somewhere to see if the component numbering matches those you used when pointing me to after the phase inverting circuit past which amp runs as balanced.
Do you happen to know what kind of input impedance I could have with the balanced input? I would be using Aleph P preamp which has a volume attenuator at its output and a highish output impedance.
And I thought the amp I was building was going to be heavy. Holy crap, 150 pounds? Hope you don't have to carry it up any stairs.
I only now noticed that the input sensitivity of D150 was only 2.2V for full rated power?? than there is nothing to worry about as it will not take much gain. preamp will really be for driving the volume attenuator.
A few years ago i did a complete rebuild on a KSA250. Had i waited a couple more years, it would have been past my lifting abilities.
There is a clear danger of exceeding the scope of such a job. I wish someone had warned me 🙂
There is a clear danger of exceeding the scope of such a job. I wish someone had warned me 🙂
3 12v 4 to 5 inch fans should do the job. run them from the heater ( 6.3v) winding with rectifier and 1000uf / 25v cap. rectified voltage should be around 10v so the fans will be quieter.
I have been using Noctua fans successfully in my FirstWatt clones; class A, run hot 
, so that choice has been made already. Thanks.
here is the detail that shows how crazy the package is in this amp. they have cut outs for two caps in an 1/8 inch steel plate . for those who wanted more pics I also show the back of the same plate, i.e. wiring under the tube pcb.
I remember a guy complaining online how much ARC charged him for refurbishing electrolytics. Well I could tell him that they probably did not make anything on the work, especially if they did all the pieces.
, so that choice has been made already. Thanks.here is the detail that shows how crazy the package is in this amp. they have cut outs for two caps in an 1/8 inch steel plate . for those who wanted more pics I also show the back of the same plate, i.e. wiring under the tube pcb.
I remember a guy complaining online how much ARC charged him for refurbishing electrolytics. Well I could tell him that they probably did not make anything on the work, especially if they did all the pieces.
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FWIW ... Back in the mid seventies, when the D150 was a current model for Audio Research, I was lucky enough to own two of them - one for home and the other for work (work was a record store at that point). Each amp drove its own set of Fulton Modular "J" speakers. The preamp in both cases was an Audio Research SP3a2. A charming, involving sound that was of it's time. I hope you enjoy yours -Edward
wow, those were both amp and speakers considered top of the line back then. I know my D150 should get a chance to drive some modern speakers since a new pair is in the making planned for next Summer 😉).
I actually (not being a tube guy so far) always pegged tube amps for low power/high-sensitivity speaker applications. So I wonder if they still could have some of their pleasing distortion/tonal qualities show up with less sensitive speakers for which a powerful amp like D150 is destined. Well I guess only one way to find out!
I actually (not being a tube guy so far) always pegged tube amps for low power/high-sensitivity speaker applications. So I wonder if they still could have some of their pleasing distortion/tonal qualities show up with less sensitive speakers for which a powerful amp like D150 is destined. Well I guess only one way to find out!
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the bank of toll PS capacitors is being replaced with modern caps. It was not possible to find caps with the exact same footprint. The best I could do was to match the distance between the + and - pin but there was no way to match the two dummies used for the added mechanical support. So instead of desoldering the original caps I decided to save the original board intact and substitute an aluminum board for it on which I siliconed new caps upside down and used gage12 wire as a busbar. Imagine for the bleeder caps I found the same as the original ones from the mid 70's ("made in Canada") 😉. a friend had them in his old stock.
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meant the bleeder resistors!..but you get the typo.. probably should not have been posting past midnight 🙄
