This is what I expect when I finally wrap up recapping my ARC D-150:
http://www.audioresearch.com/ContentsFiles/ARC.D150web.pdf
Please feel free to use this thread for contributing both, anything funny and anything D-150 amp related. I will also post pics about my refurb of the unit. Thanks.
http://www.audioresearch.com/ContentsFiles/ARC.D150web.pdf
Please feel free to use this thread for contributing both, anything funny and anything D-150 amp related. I will also post pics about my refurb of the unit. Thanks.
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When I fire up a first build and put on a really good track this is how I feel-
Usually with my girl in the background yelling "babe turn it down the bass is hurting my chest!
Usually with my girl in the background yelling "babe turn it down the bass is hurting my chest!
If you haven't already, removing the input coupling capacitor, and reducing
the value of the input hf filter capacitor to around 39pF, will make a big
difference as well.
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Yes, with four 6550 output tubes per channel, and a larger power supply.
Similar cross-coupled drive circuitry.
Audio Research D-150 - Manual - High Definition Amplifier - HiFi Engine
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D150 refurb
I thought the thread was going to invite more funny contributions but instead there is interest in D-150. That is Ok. I already meant to show my effort to refurbish it so might as well put it here.
Long story short, in 2017 I got an amazing deal. A friend acquired a D150 in an auction. It came from the estate of a local audiophile. And I traded an Oscope I did not need for this baby.
The unit came in an unbelievable condition. Not a scratch. One could tell it was not used for a long time since the dust was all from the top and not from the bottom where it draws air.
Here is what I saw on the first opening. More to come.
I thought the thread was going to invite more funny contributions but instead there is interest in D-150. That is Ok. I already meant to show my effort to refurbish it so might as well put it here.
Long story short, in 2017 I got an amazing deal. A friend acquired a D150 in an auction. It came from the estate of a local audiophile. And I traded an Oscope I did not need for this baby.
The unit came in an unbelievable condition. Not a scratch. One could tell it was not used for a long time since the dust was all from the top and not from the bottom where it draws air.
Here is what I saw on the first opening. More to come.
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Thanks! I will take baby steps with the mods though. first goal is stock version with only changed electrolytic caps, then we can finesse it from there on 😉
mine will only be used to drive a top section (starting from lower mid) of a bi-amped speaker. So bass performance is not a concern right now. As for hf I imagine the mod effect may depend on the speaker's top end performance? I guess the transformers here are the ones that set the tone for spectral distribution.
You dont need valves just a use a soft limiter,
I found this in wireless world in the 1980's.
You can the adjust amount of valve distortion.
softlimiter | harrabylad | Flickr
I found this in wireless world in the 1980's.
You can the adjust amount of valve distortion.
softlimiter | harrabylad | Flickr
To not detract from the OPs thread, could you please point me to a thread, discussion or commercial device using this soft limiter circuit?
Or perhaps the original wireless world article?
Or perhaps the original wireless world article?
that IS a different subject. I actually am a Pass guy and this tube amp wrecked my plans for my next system. I already built two BA-3b class A mono blocks for it, but the curiosity got better of me and I decided to try tubes in D150 for a while. So the refurb is under way; almost done actually (just got busy with other things).
On the subject of creating a distortion pattern that brings some "warmth" mainly to vocal reproduction you can check this:
https://www.diyaudio.com/forums/pass-labs/327746-h2.html#post5553294
On the subject of creating a distortion pattern that brings some "warmth" mainly to vocal reproduction you can check this:
https://www.diyaudio.com/forums/pass-labs/327746-h2.html#post5553294
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Koja, touch base with Jim McShane, as you do your refurb. He's both very knowledgeable and honest. If you need new O/P tubes, there is a bit of a conundrum. Really good 6550s are not currently being manufactured. IMO, the "best" replacement you can currently obtain is the "reissue" Gold Lion KT88. If, as is ARC's pattern, 1 or more big tubes are being used as screen grid regulators, a less costly variant (such as the EH KT88) can be used in that/those position(s).
Thanks for the contact. All info is welcome as I am a newbie to tubes. I am still hoping that all tubes will be functional. Naturally I had to remove them all so that I could take the amp apart. I see that all O/S tubes have been numbered presumably when they were paired by measurements. I wrote down all positions so they go back to the same sockets.
This amp has been built like a tank, but boy they sure did not have serviceability in mind when they did the tight layout. Plus with 134lbs weight this thing is a 2 man job to flip around, especially when it comes to pieces and can no longer hold together. I had a friend help me do all the flips to get to the screws in a manageable order. I am lucky he is an electronics professional and had real sense to figure this one out. We left transformers alone which made flipping the boards connected just with wire harnesses a challenge.
Here is what I was trying first to get to, the big electrolytic caps on the back board and under the unit.
This amp has been built like a tank, but boy they sure did not have serviceability in mind when they did the tight layout. Plus with 134lbs weight this thing is a 2 man job to flip around, especially when it comes to pieces and can no longer hold together. I had a friend help me do all the flips to get to the screws in a manageable order. I am lucky he is an electronics professional and had real sense to figure this one out. We left transformers alone which made flipping the boards connected just with wire harnesses a challenge.
Here is what I was trying first to get to, the big electrolytic caps on the back board and under the unit.
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More Pics!!!😀 This is a tube legend!
I would love to get my hands on one of these... Thanks for documenting this. Hopefully those GE 6550's are still good, they are great tubes in my experience..
I would love to get my hands on one of these... Thanks for documenting this. Hopefully those GE 6550's are still good, they are great tubes in my experience..
Amen to that. 🙂
Like sayin' "I'm new to cars", and starting by restoring a lamborghini Miura!
I cant wait to see it up and running!!
Like sayin' "I'm new to cars", and starting by restoring a lamborghini Miura!
I cant wait to see it up and running!!
I know about "the legend" part, less than 200 made. But like I said, D150 really wrecked my plans since in this audio system I have all balanced signal gear including these class A mono blocks:
https://www.diyaudio.com/forums/pass-labs/201281-burning-amp-ba-3b-balanced-57.html#post4794952
So it is just a curiosity on my part that I will try it for a while. I think in a couple of years someone will luck out and get an amp which will be made to run for another 40 years 😉.
As a matter of fact, people were telling me "Do not mess with it. there are vintage nuts out there who will pay more for it in its original condition etc.". But I let that boat sail since I am too much into amps to settle for anything less than the best performance possible if I am going to try it.
All power supply caps are being changed with these:
https://www.diyaudio.com/forums/pass-labs/201281-burning-amp-ba-3b-balanced-57.html#post4794952
So it is just a curiosity on my part that I will try it for a while. I think in a couple of years someone will luck out and get an amp which will be made to run for another 40 years 😉.
As a matter of fact, people were telling me "Do not mess with it. there are vintage nuts out there who will pay more for it in its original condition etc.". But I let that boat sail since I am too much into amps to settle for anything less than the best performance possible if I am going to try it.
All power supply caps are being changed with these:
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You can easily convert the D150 to full balanced operation,
and it will sound much better that way.
You can remove the unity gain polarity inversion stage (V1 and V2),
as the inverter is outside of the overall negative feedback loops.
Feed the balanced inputs directly to the 12AX7 input amplifier (V3 and V4) grids,
via the 10k resistors R12 and R15.
The rest of the circuit is balanced, including the output transformer
secondary and feedback loops.
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These are the original caps being replaced: the rear board features 8 x 200uF and the PS at the bottom 12 x 600uF.
they are all being replaced with 20 x 820uF. So the back board gets four times as much capacity 😉 and the bottom gets more capacity in half the length (thanks to the advances in cap technology since 1975).
they are all being replaced with 20 x 820uF. So the back board gets four times as much capacity 😉 and the bottom gets more capacity in half the length (thanks to the advances in cap technology since 1975).
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Thanks Rayma. I will look into it. If you guys continue supporting me like this I may just end up making a servo to get read of the variac and the adjustments and keep the damn thing 😀 (that is IF it makes it by my better half; I will even have to have a new TV stand made just to bring that thing into the room 🙁). like I said: my friend going to the auction wrecked a perfect plan.