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Post subject: Roc Pro 700 - seeking a Smooth Volume Fix
Posted: Fri Jun 06, 2014 8:29 am
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After trying a Roc Pro 1000 head and half-stack at a local guitar shop, I decided the Roc Pro "Tube Drive" tone was something I'd been searching for. Tone preference for me leans towards the tone of overdriven JCM 800's, and bands like... Priest, Queensryche, GNR, Sabbath, Ozzy, Dio, Cult, even a little Metallica. I really like the Priest type tone, I read that KK Downing of Priest used a Roc Pro, and the Roc Pro seems to have close to what I perceive is his tone, on a live Priest DVD I have.

All my guitars have EMG 81/85's, and I like pinch harmonics to ring out easily, and power chords to have long sustain. I'm in an apartment, so low volume is a must. I recently acquired a mint condition Roc Pro 700 combo for $100, and am very pleased with it's tone, but not the volume it takes to get it. There's a volume issue, and based on internet forums, seems to be common.

The volume pot on the "tube drive" channel is ultra sensitive and I want to resolve/tame it if possible. There's no "0" on the amps knobs, and all knobs start at "1". When I turn the volume knob extremely slow from 1 to 2, it always hits a spot where it goes from a quiet whisper, to "OMG, my neighbors will call the cops", and there's no inbetween. The volume increase is shocking and not smoothly incremental. I want to see if there's a way to tame that, or do I throw in the towel and say "this amp is useless in an apartment", before dumping a lot of money into it.

I've spent at least 4 hrs over the last 2 days Googling and reading everything I can find in other forums about the Roc Pro 700, and am unsure of the cure for this, without spending a fortune on try-this-try-that. Can someone please give me their thoughts on the following, and prioritize possible solutions for me?

1. "Tube Drive" Volume Pot - I believe this model may have what Fender refers to as a 100K type "B" pot, but not 100% sure. I'm basing that on what I read on another site. What would be the best replacement (brand & "K" rating) to try for an apartment volume? Should I look at a type "A" pot or something else?

2. Volume Attenuator in the Effects Loop - From what I've read, these work best in a "series" effects loop, but one forum said they think on this amp it's a "parallel" loop. Is that correct, and will a volume attenuator get me the low apartment volume/tone I need, or not work on this amps effects loop?

3. Tube Replacement - Would a 12AT7 or 12AU7, instead of the 12AX7 in it, achieve a lower volume, or would it kill the tone I like, and which tube/mfgr should I consider?

4. Pedals - Is there any chance an overdrive pedal would get me the tone I seek at the "whisper" level it currently has, before it kicks-in to "the cops are coming" volume?

5. Speaker Replacement - I believe the stock Fender speaker is 8 ohm. Would replacing that with a 16 ohm speaker reduce the "cops are coming" volume and still keep the tone I like? Any speaker recommendations?

6. Internal Mod - I read something about a resistor mod on a Marshall forum. Is there anything similar to that which might be possible? http://www.marshallforum.com/workbench/ ... olume.html

7. Are there other things I could try or haven't thought about?

Thanks


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Post subject: Re: Roc Pro 700 - seeking a Smooth Volume Fix
Posted: Fri Jun 06, 2014 8:49 am
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Have you heard about changing a stock linear tapered pot to an audio (or logarithmic) tapered pot? Many newer amps have linear pots to give you that "wow" factor, while in a noisy showroom (at least this is what I've been told).

By going to an audio or log-tapered pot, the range of control becomes more manageable in these amps. No sudden onset of volume. Now, I've never worked on a ROC Pro 700, so I don't know what would be involved in changing same value linear volume pot to a log one. Some of these pots are soldered directly to the circuit board.

Anyhow, maybe someone else knows the specifics of your amp's layout.


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Post subject: Re: Roc Pro 700 - seeking a Smooth Volume Fix
Posted: Fri Jun 06, 2014 9:06 am
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BMW2002Ti wrote:
By going to an audio or log-tapered pot, the range of control becomes more manageable in these amps. No sudden onset of volume.


+1

This method is preferable to swapping the 12AX7 out for a lower-gain tube. Virtually all of the amp's overdriven tones are developed within the pre-amp stage and anything with a reduced "mu" factor will reduce the amp's growl and grunt.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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