Comments on: Pioneer SR101 ‘Reverbe’ Unit

By: Camlite

Camlite — Thu, 09 Mar 2023 08:17:51 +0000

I found one of the “reverbe” 500K pots was bad. It caused noise to increase in one channel as reverb was increased.

By: Oli

Oli — Wed, 28 Dec 2022 16:51:12 +0000

Hi, my SR-101 sounds fine powered up, but a loud hum increases as the “Reverbe” level is increased. Also, it sounds like most of the reverb is on the right side. I have zero knowledge of electronics, so took it to be serviced and was told that the sound was fine and there was no hum. I thought, maybe it’s my old phono cables, so bought brand new ones, but still have exact same issues.

I don’t know what this guy was hearing when he tested it. Could be something about my particular setup at home that’s making the hum? But if the hum only relates to the reverb control, doesn’t that indicate an internal problem rather than external, cables, other connected units, etc?

I see other comments that sound like they could describe the same issues I’m having, but the fact that a professional said it was all fine has made me confused… I’ve heard recordings of the unit on YouTube, and there doesn’t seem to be a noticeable hum, so I don’t think mine is normal.

Could anyone help point me in the right direction? Thanks 🙂

By: Giles Thomas

Giles Thomas — Sun, 07 Mar 2021 01:07:28 +0000

I’m confused as to why a DPDT switch and not just a DPST?
Is it not just a case of breaking the circuit of the 2 red highlighted cables?

Many thanks in advance.

By: Val Headlee

Val Headlee — Thu, 11 Apr 2019 02:27:08 +0000

I bought my SR 101 new. Haven’t used it in many years. Will it work with the newer multi channel units and what would be the best hook up procedure.

By: Ben Fischer

Ben Fischer — Wed, 07 Nov 2018 03:36:04 +0000

Hi all,

For what it’s worth, I spent some time debugging my recently purchased SR-101 and adding the dry-cut mod. In the end, even with fresh tubes, I couldn’t get rid of a pretty aggressive buzz (15 to 20 dB SNR) until I realized that the heaters weren’t ground referenced! Balancing them by tying both sides to ground through 1/2W 100 ohm resistors essentially eliminated the buzz for me. I did this for both the audio tube heaters and the 6X4 heaters just for good measure.

I learned about this “humdinger” configuration from Merlin Blencowe’s books. Essentially, the rectifier tubes in the high voltage circuit creates pulses in the transformer which couple to the heater circuit, which then couples to the audio path. Not sure how they overlooked this in the original design! This reverb sounds amazing now 🙂 if anyone in Brooklyn needs help on their sr101 (or anything else) feel free to send me an email or follow @yumyumaudio on Instagram.

All the best,
Ben

By: 0=0

0=0 — Wed, 03 Jan 2018 02:42:40 +0000

i got one of these..i love it. one channel sounds way better than the other channel but it’s a great sound.

i haven’t rewired the stereo of mine because i actually like to saturate the uneffected side

0=0

By: 0=0

0=0 — Wed, 03 Jan 2018 02:40:32 +0000

In reply to chris. "it’s a 45 year old piece that needed no caps or resistors changed."

By: Dwight evans

Dwight evans — Thu, 23 Mar 2017 19:02:59 +0000

Sorry for such a late response to an old thread. But, better late than never (I guess)… The two wires reversed in the schematic appear to be the CH 1 and CH 2 FEEDBACK loop wires. Seems, at first glance anyway, that the unit utilizes the feedback circuits of channels 1 and 2 to mix the reverb signal in OPPOSING polarity to the originals. Cheers.

By: Bruno

Bruno — Sun, 29 Nov 2015 13:54:04 +0000

Very instructive repport, and very interesting website !

Mine is now repaired, with the help of the schematics.
A faulty resistor on the input…
It’s sounds very powerfull, wide, and not much noisy !

But, can you please show us the points for the DPDT ?!

Bruno from France !

By: Doug Walseth

Doug Walseth — Fri, 06 Feb 2015 23:53:21 +0000

In reply to Charlie Brewer, Tech Services, Nashville, TN. Charlie, I just got one with the exact same issue as listed here! How much does it cost to fix and apply the mods listed here?