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AUDIO FORUMS >> General Discussion and Support >> ZROCK2-25 Perfomance Question
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Message started by Jeff of Arabica on 12/20/20 at 17:51:54

Title: ZROCK2-25 Perfomance Question
Post by Jeff of Arabica on 12/20/20 at 17:51:54

I just received my ZROCK2-25. A couple of years ago I had a ZROCK2 (no mods) in my system so my memory of exactly how it behaved is a bit faded.

That said, this 25th modded version does not seem to align with what I remember in terms of how it behaved when the unit is engaged or bypassed.

First of all, the "Bypassed" mode is WAY louder than when the unit is engaged. I remembered the opposite with my first ZR2 which was significantly louder when the Bypass was NOT engaged.

The attenuator knob definitely effects the sound when the unit is engaged (bass/tone), and when bypassed the sound is not EQ'd and the attenuator does not affect the bass/tone.

That said, the sound level is not even close comparing engaged with bypassed, even when the knob is at 12 O'clock. This does not seem to align with this statement on the ZROCK2 product page:

Quote:

At the 1/2 way point, the output level and the sound exactly match the way the ZROCK2 sounds when it is bypassed.

It almost seems as though the ZROCK2 gain stage is not boosting the signal enough to overcome the loss caused by the resistive nature of the EQ circuit. I would love to hear others' thoughts or experiences regarding this topic.

Title: Re: ZROCK2-25 Perfomance Question
Post by Archie on 12/20/20 at 18:16:04

Hey Jeff, I was wondering if you got that yet.

Mine seems to work a bit differently (had Steve do all the mods, type II caps, silver RCAs). When the bypass is flipped to bypass, the sound gets lower (which is what the manual says will happen) and there IS a subtle but definite change in the sound when in bypass and the knob is turned. I do/did like the equalized sound but wondered if there was something overlaid that might be undesirable. Also, I always preferred (by a lot) the "B" curve. The B curve seems to cause a nice mid bloom on my system.

At 12 o'clock I remember the sound being equal between bypassed and engaged.

Title: Re: ZROCK2-25 Perfomance Question
Post by GroovySauce on 12/20/20 at 18:46:43

Mine (full 25th mods, tube regulation and stepped attenuator) I need to be around 2-4 o'clock to be the same volume depending on the tube. This is by ear and usually referencing vocals.

I did just tried a JJ ECC802-S that sucker is HIGH gain! I thought I made a mistake and put the wrong tube in. With that tube 12 o'clock is about equal volume with the bypass switch on/off.

Another note about that JJ tube. with 2v in (DAC), it will distort around 1 o'clock. I've never had any other tubes cause distortion with the ZR2. From my ZP3 (~1v?) I didn't get distortion until around 3-4 o'clock.

I tried it in my ZP3 and it did pump up the output, which was really nice, it was also really grainy so it doesn't suit my taste.

Title: Re: ZROCK2-25 Perfomance Question
Post by Jeff of Arabica on 12/20/20 at 18:50:02

Hi Archie,
Thanks for sharing your experience with regard to this topic. I am wondering if something may not be wired correctly in my unit. What you describe is pretty consistent with what I remember with my prior ZROCK2. This unit however, is acting much differently. In bypassed mode, the volume jumps significantly higher, even when the knob is at 12 O'clock which is at odds with the description on the product page.

Title: Re: ZROCK2-25 Perfomance Question
Post by Jeff of Arabica on 12/20/20 at 19:05:16

Thanks @Groovy. This is all good to hear and learn. It further concerns me that something is awry with my unit. I cannot ever get "bypassed" volume to be even remotely close to "engaged" no matter where my knob is positioned. Bypassed is always at least 10 volume clicks louder than engaged which just doesn't seem right.

Title: Re: ZROCK2-25 Perfomance Question
Post by lobo on 12/20/20 at 19:12:27

At the 1/2 way point, the output level and the sound exactly match the way the ZROCK2 sounds when it is bypassed.
Mine is a standard build and its working like this.

Title: Re: ZROCK2-25 Perfomance Question
Post by Archie on 12/20/20 at 19:15:04

Have you tried different tubes?

Title: Re: ZROCK2-25 Perfomance Question
Post by Lon on 12/20/20 at 19:16:43

Jeff, something seems amiss. When bypassed the volume should be considerably lower than when EQ is increased as gain is added with the EQ progressively as the knob is turned clockwise. So. . . I'd place a call to Steve, it may need to be beamed back to the mothership.

Title: Re: ZROCK2-25 Perfomance Question
Post by GroovySauce on 12/20/20 at 19:19:02

Jeff,

When your's is in bypass, does the knob effect the output volume? When mine is in bypass the volume/EQ knob doesn't do anything.

meaning true bypass, I'm guessing the signal inside goes from input RCA to the switch to the the output RCA.

Title: Re: ZROCK2-25 Perfomance Question
Post by Jeff of Arabica on 12/20/20 at 19:23:42

Thanks Lon, Lobo, and Groovy for your great feedback.

Lon- I am thinking you are absolutely right. It seems the gain stage is not affecting the EQ'd signal. It attenuates and the bass/tone is affected by the knob, so that is working. It just seems as though the gain stage is not boosting the signal as it should. I have tried two different tubes and both behave the same.

Groovy- When in bypassed mode, the knob does not affect the volume or sound at all, so that seems to be correct. It really just seems to an issue with the gain stage not functioning as it should. I opened the bottom panel and there are two wiring paths for the input signal to travel. One path goes from input jacks to switch to output jacks and that is the "Bypass" journey. The second wire path coming off the input jacks goes to the input tube>attenuator>toggle switch>output jacks. There is also wires that come off of a resistor network that also attaches to the attenuator contacts. My assumption is that this is what controls the bass/tone.

Title: Re: ZROCK2-25 Perfomance Question
Post by Archie on 12/20/20 at 19:59:06

Groovy, thanks for posting that. I've been asking that question for a while. In my case, with the bypass on bypass, the knob DOES have a slight effect on the sound. Sometime I ought to try it with different tubes although with a true bypass the tube shouldn't come into play.

Title: Re: ZROCK2-25 Perfomance Question
Post by Rivieraranch on 12/20/20 at 20:53:29

My anniversary modified unit doesn’t behave the way yours does. I've been quite pleased with mine.

Title: Re: ZROCK2-25 Perfomance Question
Post by Jeff of Arabica on 12/20/20 at 20:59:00

This is all very strange. I looked at the wiring at the tube socket and it is all correct. There is power to the tube because it is glowing. From what I can tell, everything looks to be in order but I don't have a wiring diagram for the ZROCK2, so I can't be certain. Scratching my head as to why I am experiencing such a drop in volume with the ZR2 engaged.

Title: Re: ZROCK2-25 Perfomance Question
Post by Brian on 12/21/20 at 02:04:01

Steve,
Am I right in thinking that if one of Jeff's volume pots (A100K) were defective, or has a solder join which is not flowing current, it would produce the effect Jeff is reporting?

Brian

Title: Re: ZROCK2-25 Perfomance Question
Post by Jeff of Arabica on 12/21/20 at 06:57:35

Thanks for the diagram Steve. I am not getting any voltage at pins 1 and 6. Pin 9 is 2.8v and pins 4/5 are 3.5V

Voltage regulator tube is at .22V

116v at the IEC

Title: Re: ZROCK2-25 Perfomance Question
Post by Steve Deckert on 12/21/20 at 16:56:43

The VR tube isn't striking. Try a different 12AU7 and see what happens.

Title: Re: ZROCK2-25 Perfomance Question
Post by Jeff of Arabica on 12/21/20 at 17:30:03

Hi Steve,
I have tried two different tubes, the one that was sent with the ZR2 and one I had purchased separately. Both were the same, but I have a third I can try. Ill pop it in and take another reading.

If the tube swap doesn't work, is there anything else you want me to test and measure while I have it open?

Title: Re: ZROCK2-25 Perfomance Question
Post by Jeff of Arabica on 12/21/20 at 17:37:36

Just tried another 12AU7 and still no voltage to pin 1 & 6.

Title: Re: ZROCK2-25 Perfomance Question
Post by Steve Deckert on 12/21/20 at 18:28:18

It means the VR tube has failed. Send it back, we'll cover the shipping.

Steve

Title: Re: ZROCK2-25 Perfomance Question
Post by Jeff of Arabica on 12/21/20 at 18:47:46

Ok, Ill reach out to Sarah to arrange the return. Thanks for the troubleshooting help.