Marantz 2220B (Later '78?) Restoration Advice/Questions
- Thread starter hhspunter
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Waiting for parts at this point, so I decided to do a little "as-is" listening with some JBL 62Ts I had sitting around, just threw them on the desk. Wow, does it sound good already! Tone, volume, balance pots all work perfectly now. These speakers and amp definitely like being pushed a little, might have to move the amp to the other room and try them with my 4410s 
Going to try figuring out some measurements on the PC - I played around with FFT on my 'scope yesterday but it was a huge pain trying to figure out appropriate sample rates and apparently dynamic range isn't great anyway. I think mostly I was seeing the distortion of the scope front end with its limited resolution more than anything. I have a halfway-decent USB DAC and I guess REW makes THD, frequency response, etc. much easier than trying to do it with the scope.
Going to try figuring out some measurements on the PC - I played around with FFT on my 'scope yesterday but it was a huge pain trying to figure out appropriate sample rates and apparently dynamic range isn't great anyway. I think mostly I was seeing the distortion of the scope front end with its limited resolution more than anything. I have a halfway-decent USB DAC and I guess REW makes THD, frequency response, etc. much easier than trying to do it with the scope.
On you other scope picture, don't you mean green is left? The noise occurs looks like it occurs in both channels at the same time. I would guess it is not an amplifier problem, but rather a power supply problem (common to L & R).
Oh good catch! Will fix that, it was just a typo. I do plan to go through the whole signal chain to see if I can narrow down where that's occurring. I did spend a little time looking at the DC outputs on the 'scope and the 35V looks very clean, I didn't see any sign of those spikes there. The amp does output some hiss/noise when cranked up with nothing playing. I guess I should also look at the 33.7V +B/-B too.
FWIW this amp seems to invert the output, I guess that's fairly common for amps of this era?
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650kHz is on the low end of the AM radio band... Hmmm, wonder if your AM tuner or oscillator has anything to do with this? Approximately where on the AM tuner dial was your dial pointer when you took these measurements? From your photo above it looks like around 700kHz. Maybe as a test you can tune your station to a higher frequency and see if the oscillation freq changes.
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Oh that's a good question! I'll have to play around some more to replicate and measure again.
Ran some initial tests on the amp last night - this was with a M-Audio M-Track Solo USB DAC/interface, going into the 2220B Aux input, and measured into a 10ohm load (ceramic case 10W resistor). All tone controls at mid and loudness off. Used a 2.2k/22k voltage divider across the 10ohm load to send the signal back to the DAC. DAC's loopback response was not calibrated for in these measurements, and I'm still getting the hang of things, so take with a grain of salt.
First, the original color was using warm/toward yellow incandescents behind a blue dial face. So that was less blue than intended because of the incandescents. If you use warm white LED’s you probably get pretty close to the original.
Also, pretty sure incandescents go warmer over time, and vellum for sure yellows, that all works to mute the blue.
Seems like a slight color difference is better than a melted/broken housing. Some modelsyou can get new housings for but I don’t think those are available for this model.
Yeah, totally understood. I did just replace the vellum, still on the "original" bulbs which were obviously replaced at some point since they are 300mA (should be 200mA, and certainly didn't help the melting). I have 200mA incandescent on the way and will get some LEDs too to compare, and if I can get it close and they still look diffused I will definitely go with LED.
That said, I am not sure what you mean though about it being "less blue than intended" because they surely did the design at the time knowing the color temperature of incandescent bulbs (and reviewing a bunch of mid-70s catalogs, the lighting is definitely a minty/aqua color.
Another note, and I will probably add this to the "service manual errors" thread even though it's technically correct, because it applies to at least 2230B as well: R805, 330ohm/2W seems like a sketchy design choice. It has 21V across it 100% of the time the receiver is powered on, which equates to 1.33W. It gets HOT, like burn your finger pretty quickly hot. I replaced mine yesterday because the leads were very corroded, and the new one (albeit questionable quality) is already showing some signs of heat discoloration right in the center. I'm going to use a bigger one, I have 3W and 5W on the way, not sure if they are physically bigger/how they will fit.
Nice post. Just retired my 2270 and replaced it with a 2220B with Decade 26s. Like the sound of it. Get 40 FM stations. Sadly most are IFart or Clear Channel crap. Pulls my NPR stations. You won’t be disappointed.
My dad had a 2270 and JBL L55s when I was growing up that got used off and on. He's got lots of stories attached to those speakers, and in high school and visits home from college (mid-30s now) I remember really shaking the walls with that setup
I just did a whole bunch of testing in REW with my USB DAC/interface (M-Track Solo) after finally figuring out a hardware setup that would give me results I somewhat trust. Without any new components (well, except for the dead cap and transistor, and the 2 2W resistors on the power supply board, and a new output relay), it's already doing pretty well. Frequency response within 1dB from 20-20k both channels, decent, maybe even good THD, and somewhat high noise floor (although that may be the DAC/interface). I have quite a lot of data to process so there will be another post with the initial results.
Also swapped out the RCA jacks and changed the binding posts to banana jacks, nice and fresh again, may get nicer banana jacks later. Tough fit without cutting the rear panel. This involved making new FR4 RCA jack and binding post plates, hand-cut based on original dimensions and painted flat black:
Test setup, RCA out to receiver, 8ohm 100W load resistor, 2.2k/22k divider across load resistor going into shielded XLR cable to interface input (to keep safe voltage level for the interface). DMM to measure AC voltage at the speaker terminals:
New RCA jacks on the new backing plates and new banana jacks installed. Banana jacks are a tight fit, opening for them is only 48mm, meaning they definitely cannot be any more than 12mm diameter!
I just did a whole bunch of testing in REW with my USB DAC/interface (M-Track Solo) after finally figuring out a hardware setup that would give me results I somewhat trust. Without any new components (well, except for the dead cap and transistor, and the 2 2W resistors on the power supply board, and a new output relay), it's already doing pretty well. Frequency response within 1dB from 20-20k both channels, decent, maybe even good THD, and somewhat high noise floor (although that may be the DAC/interface). I have quite a lot of data to process so there will be another post with the initial results.
Also swapped out the RCA jacks and changed the binding posts to banana jacks, nice and fresh again, may get nicer banana jacks later. Tough fit without cutting the rear panel. This involved making new FR4 RCA jack and binding post plates, hand-cut based on original dimensions and painted flat black:
Test setup, RCA out to receiver, 8ohm 100W load resistor, 2.2k/22k divider across load resistor going into shielded XLR cable to interface input (to keep safe voltage level for the interface). DMM to measure AC voltage at the speaker terminals:
New RCA jacks on the new backing plates and new banana jacks installed. Banana jacks are a tight fit, opening for them is only 48mm, meaning they definitely cannot be any more than 12mm diameter!
Okay, some data, using the Aux input. Probably not comparable to other measurement methods done elsewhere (this is my first time doing this) but I think it is within reason.
Specs on the 2220B are:
Specs on the 2220B are:
- 0.5% THD at 20W, decreasing at lower output
- At 1kHz, I measured 0.22% on both channels at 20W. Doesn't exceed 0.5% until all the way down to ~1mW/-28dBu
- +/-1dB 20-20kHz frequency response (from 2220 in 1974 catalog, phono stage is listed as +/-2dB)
- Measured at -0.6/+0.2dB from 5mW to 20W (-12dBu, 0dBu, 12dBu, 24dBu)
- -77dB high-level hum and noise (referenced to 20W into 8ohm)
- Measured at -68dB left, -65dB right. MUCH higher at lower power levels (when referenced to those lower power levels)
- e.g. right channel is -29.1dB during a -12dBu/5mW 1kHz sine wave
- Definitely audible as volume pot is cranked up with no signal from connected DAC. Not outrageous though. Hopefully I can improve it.
- Measured at -68dB left, -65dB right. MUCH higher at lower power levels (when referenced to those lower power levels)
- Channel separation 30dB (minimum)
- Need to figure out how to measure this one. Haven't even thought about it yet.
- First, seems like overall it is doing alright for having nothing substantial replaced other than a few power supply components that were dead/dying.
- Next, noise floor seems very high at low levels. I suppose this makes sense, but it also may be a USB interface user error:
- I left the line in gain and 2220B volume pot untouched for testing at all the output levels, simply adjusted the REW output
- This probably screwed up both interface output and input resolution
- I set output to 0dBFS and adjusted the 2220B volume very close to 20W output, and adjusted input to be maybe 10% below clipping, then didn't touch any knobs for all testing
- So, I think only full power was getting full interface output and input resolution, so the very low power stuff is probably off by a lot. I might try again tonight.
- 3rd harmonic is dominant
- Pretty happy with the frequency response! I haven't played much with the tone controls, but bumping up the bass knob one or two notches definitely shows up in the measurements!
- Will be interesting to see if I can clean up the 60Hz noise. Audibly, it's not very bad at least.
- I thought about updating x-axes below with power, but I think dB makes them much more legible/relevant.
- If power is more relevant to you, here's are some conversions:
- -32dBu = ~0.045mW
- -12dBu = ~5mW
- 0dBu = ~75mW
- 12dBu = ~1.18W
- 24dBu = ~18.84W
- 24.25dBu = ~20W
- If power is more relevant to you, here's are some conversions:
Following up, adjusting the tuner didn't make a visible difference in that high frequency blip.
I will post more plots/measurements later, but this amp is doing quite well compared to Marantz specs after recapping power supply, main amp, tone amp, and big filter caps! To be fair it was doing pretty well before that too, but better now.
With 1kHz sine wave, here are a few THD and THD+N readings, left channel only for now. Keep in mind this 20W model has specs of 0.5% THD and -77dB "hum and noise" at 20W:
For now, here's the 1kHz 30W RTA:
With 1kHz sine wave, here are a few THD and THD+N readings, left channel only for now. Keep in mind this 20W model has specs of 0.5% THD and -77dB "hum and noise" at 20W:
- 630mW: 0.0052% THD, 0.057% THD+N
- 1.25W: 0.0051% THD, 0.041% THD+N
- 2.5W: 0.0082% THD, 0.03% THD+N
- 5W: 0.016% THD, 0.026% THD+N,
- 10W: 0.056% THD, 0.058% THD+N, -77dB N
- 20W: 0.15% THD, 0.15% THD+N, -79dB N
- 30W: 0.20% THD, 0.20% THD+N, -81dB N
For now, here's the 1kHz 30W RTA:
-Thanks for posting! Have a 2220B that had the power supply recapped. Preamp board. The specs are quite good. Running a pr of JBL Decade 26s. The watts specs are impessive. Have several low watt Marantz receivers. Even at 30 watts the THD isn’t bad. The Decades need little power. The 2220 replaced a 2270. Like the sound better.
Philvbo
New Member
Lots of great comments here and several have been very helpful to me. I still have my Marantz 2220B receiver which I bought in 1977 and placed in storage about 22-23 years ago. Short story, I recently took it out and lit it up to see if it still worked. It did but I hadn't bought new speakers yet so I via my AKG 240 headphones, I discovered that the output was scratchy and the left FM channel was not working. So I took the unit apart and did what everybody does: cleaned the pots, replaced the lamps and did a complete clean up of the entire unit inside and out. It looks brand new... no exaggeration. So I bought JBL Studio 630 speakers and found the left channel still worked and it still sounds fantastic after de-oxing the pots. Unbelievable. But since it is on its last legs, I bought a refurbishment kit on eBay I will be giving the unit a good listen for 4-6 months and inspect the parts in the kit before starting. The plan is to start with the relay and power assemblies and testing as I proceed from one section to the next. Two questions:
- I noticed that several of the replacement caps are of a higher voltage. In fact, the 2 replacement relay caps in the kit are also now identical and at substantially higher voltage. I have been assured they are higher quality than the old caps but how does the higher voltage impact the performance? Are the other non-cap parts being replaced to accommodate this? Maybe my plan to test after each section is refurbished doesn't make sense and could even damage the unit.
- Should I be expecting a noticeable improvement in sound quality after the refurbishment? Considering it still sounds excellent already, I've been advised to expect some minor improvement in clarity if that.