Personally, i would put it in this one, and hook it to one of the inputs. I do wonder what a metal case would do to high frequency Rezeption.....
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I think there are pro's and con's.
This M77 is a traditional purist approach and hence somewhat timeless so once built will last forever. Adding an ebay bluetooth module takes something away from that which only you can decide if it matters to you or not. This ebay bluetooth module will have some unknown lifetime before failure.
The M77 you've built may or may not be designed to accommodate EMI from a bluetooth board and the ebay bluetooth board may or may not have an issue with EMI - not trying to get a scare story going here but it's mixing two different technologies that are 50 yrs apart.
This M77 is a traditional purist approach and hence somewhat timeless so once built will last forever. Adding an ebay bluetooth module takes something away from that which only you can decide if it matters to you or not. This ebay bluetooth module will have some unknown lifetime before failure.
The M77 you've built may or may not be designed to accommodate EMI from a bluetooth board and the ebay bluetooth board may or may not have an issue with EMI - not trying to get a scare story going here but it's mixing two different technologies that are 50 yrs apart.
First off, wanted to thank everyone for their contribution to this build. This has greatly helped me understand the schematic and topology of this design. After several months of tinkering and soldering, finally got some time last weekend to button it up together and gave it, its first listening experience. To my ears, they sound amazing! Along with all the phono component adjustments, I also went with hesener's linestage improvements, definitely more pronounced bass and treble with the mids still nice, clear and warm. Here's some images of my final build, having the transformer and choke in a separate unit definitely made it nice and quiet.
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Hopefully someone could confirm, was noticing my right channel was experiencing some attenuation (slightly lower in volume compared to left). So I decided to finally gave the balance pot a go and soldered it together. Originally, I assumed this was left and right, but after hearing, noticed it a bass/treble balance. Noticed most just bridged, but maybe just me, I thought this was pretty handy to have.
Got a chance to pull it apart this evening and ran the multimeter across the plate reading for the right channel output. Definitely on the lower side at 147v on both pin 1 & 6. The heaters a little higher than I would like at 13.59v. Well time take it apart and dig in and see what's causing the problem. Post back soon on my findings. Premature celebration......😅
Strange. Pretty sure that's not how my balance control works, but I'll check again.
Could be just me, since I'm experiencing a very low volume the right channel. Still have yet to find the cause, threw on the scope just for visuals. Stump, going to call it a night and hopefully have some time this weekend to go through it again and what I've overlooked.
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double checked the schematic, my mistake was not a tone control. I suspect it could possibly be my attenuated right channel messing with my ears.
This wonderful rainy morning, finally got the chance to get Dynaco ST70 paired up with the unit for some listening experience. Amazed each time, definitely gave the ST70 more a noticeable low end with the linestage suggestion from hesener. As a complete amateur, my childish description of this would be, "I'm partying with a live band by myself!". It's sounds much more full and with some thump now, something I always felt my ST70 was missing. Although, I have not resolved my channel imbalance, it's not as noticeable when paired with a pa.
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I am always amazed at the high-ish output impedances of tube amplifiers, and this M77 close is no expection, being in the 10k range or so. Transistor amps (especially with high feedback archictures eg opamps) have very low output impedance inside the current range they can drive, and that gives better bass and bottom end, and "control" (whatever that may be ) .
My best greetings to the "soggy bottom boys" 😀
My best greetings to the "soggy bottom boys" 😀
When you had a chance to do a proper listening, how was the midrange? At least in my build thats a real highlight!
I have low output level ob both channels. above 0.8V when on Input above 1.5V.
Did you ever figure out what was causing it? I was able to resolve mines, I'm guessing a bad or loose connection. I went back in and reflowed solder and did a few stuff and when I powered it back on, both channels seem pretty well balanced now. It wasn't noticeable when I ran it through my push-pull. Now that everything is working, the mids are much more presence with hesner's recommendation. I gave it a listening paired with my Dynaco st-70, with original values components and hesner's for the linestage. To my ears the mid sounds clearer and more noticeable, it also added noticeable lows (that my st-70 was missing). I'm really enjoying it, I have friends over and they are amazed at the new clarity and were expecting that I'd spent another $2k on Hifi equipment. lol
Did you also went the route of 14v diode paired together with a Darlington transistor? I was at the same path, being not so savvy at this. I just went ahead and took measurements of the whole circuit, starting with AC input, then measured each tube pins, then sweared a few times. My problem was on the linestage, I had different reading from left vs right. everything before linestage were pretty spot-on.
hesner's power section of the mod would definitely help with stabilizing heater supply, perhaps check the heaters first? I hope you get it working, I'm really enjoying the new listening experience, even as a stand-alone unit without the PA, it still sounds great!
I build KT77 power amplifier with Lundahl transformers, and it sounds fantastic. maybe will create a new thread here with all schematics and PCB's.
so, right now wanted Kondo to use as headphone amplifier. do you think it is possible ?
so, right now wanted Kondo to use as headphone amplifier. do you think it is possible ?
rzaglinskij,
A new thread is in order.
Just my opinion.
Determining the suitability of a KT77 amplifier to work as a headphone amplifier requires some knowledge of at least:
The impedance of the headphone
The sensitivity of the headphone (sound level / milliwatt)
The amplifier's ability to drive the headphone impedance, and/or proper resistors to keep both the amplifier and headphone happy.
The hum at the amplifier output
The noise at the amplifier output
KT77 amplifiers I built sounded wonderful.
But none of them would work for headphone use, unless I added a load resistor and attenuation resistor(s) at the output of the amplifier.
A new thread is in order.
Just my opinion.
Determining the suitability of a KT77 amplifier to work as a headphone amplifier requires some knowledge of at least:
The impedance of the headphone
The sensitivity of the headphone (sound level / milliwatt)
The amplifier's ability to drive the headphone impedance, and/or proper resistors to keep both the amplifier and headphone happy.
The hum at the amplifier output
The noise at the amplifier output
KT77 amplifiers I built sounded wonderful.
But none of them would work for headphone use, unless I added a load resistor and attenuation resistor(s) at the output of the amplifier.