16th July 2012
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#1 | | Gear interested
Joined: Dec 2008 Location: Nashville, TN
Posts: 22
Thread Starter | Vintage Ashly PQ-66 Parametric Eq IC Mods
Hello Gentlemen,
I recently acquired a sweet Vintage Ashly PQ-66 Parametric EQ. Apparently these are somewhat rare. I absolutely love mine.
I was wondering if a "Tech Expert" could take a look at the following attachment of the Ashly's specs and tell me their recommendation for a solid upgrade using today's available IC's. They are not soldered but the normal pull out and push in kind. I am sure I can contact Ashly for a more detailed schematic with a parts list if needed.
The most important aspect for me is what IC is best to use on what frequency range. Out of those options suggested, would Burr-Browns also be a solid option over AD, TI, Etc.
The link and attachment provided will give you the ranges.
Additionally, I am in need of the little "Silver" knob caps or a new style Knob all together to replace the current ones. You will see it in the pics. I guess I would have to measure the dimensions somehow to know the exact size, unless someone happens to know off hand.
Also,
For some reason, just about any signal I ran into the Ashly would throw a red peak. I did just find some specs on the unit that explains it is TRS Balanced. Maybe that was an issue, but I was using a patch bay and pretty much tried to maintain all balanced signals. Anyway, the headroom obviously lacked in the unit which may be due to a power issue. Maybe even new caps are needed.
On the upside, the signal never really seems to sound clipped regardless, unless I really push the gain and make it do so. Not that I would want to, just an FYI! LOL! This is an obvious for ALL equipment for the most part.
Anyway, thanks for any guidance! I am a newbie in the tech area and have been audio engineering for over 17 years. So, I decided to start learning about the actual electronics aspect as a new hobby.
Therefore... any books, manuals, videos, seminars, courses online, easy DIY first experiment suggestions are welcomed!
Thanks Guys! Cheers!
UPDATE: The brochure below is actually for the PQ 66 A. I will try to find my PQ-66 Manual and upload for you guys. I also opened up the unit, removed the "Foam" that Ashly put in these older units, like the SC stuff and took photos of the IC's and layout.
Last edited by ArtisticMixer; 16th July 2012 at 03:47 PM..
Reason: Additional Question
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16th July 2012
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#2 | | Lives for gear
Joined: Oct 2006 Location: Toronto, Canada
Posts: 816
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Hi Rob,
Vintage! Yikes, I used these when they were new. There is an even older version that has toggle switches instead of the push/push switches on the one in your brochure.
Unfortunately, the drawing you attached is just a block diagram, not a schematic so I can't see what chips they were using. Some Ashly gear from around that time (like the SC-50 comp) used 4136 IC's, which are very slow and good candidates to be replaced/upgraded. BUT, hey have a non-standard pin-out, so you need adapters like the ones that Brown-Dog make to convert to newer pin-outs. This may also open up some stability issues, so it needs to be done with some care.
Best,
Ike
__________________
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Ike Zimbel,
Zimbel Audio Productions Ltd.
Toronto
416-720-0887
"Studio House Calls". Authorized Warranty service for Allen & Heath, Clear-Com, Drawmer, Soundcraft, SPL and Yamaha. Repairs and upgrades to analog audio equipment including: AMEK, dbx, Neve, Neotek, MCI, Soundcraft and more. Ask about our RF frequency co-ordination services! www.zimbelaudio.com | 
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16th July 2012
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#3 | | Gear interested
Joined: Dec 2008 Location: Nashville, TN
Posts: 22
Thread Starter | OOPS! Vintage PQ-66
Ike,
Thanks for your reply man. I realize thats not a true schematic. I will try and get one from ashly. You are also correct. I do have the wrong brochure. I found the original manual for the one I have. Turns out that mine is NOT the PQ66-A, but simply the PQ-66 I believe.
Here is a Picture below.
Is this the older one?
Thanks man!
Rob
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16th July 2012
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#4 | | Lives for gear
Joined: Oct 2006 Location: Toronto, Canada
Posts: 816
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No, that's more like 3rd generation at least. The first ones were painted blue and had toggle switches with white rubber grips on them. The 2nd gen had the push/push switches with the "wink-eye" indicator like yours, but they were still painted blue. I can't remember exactly when they switched to the black anodized panels but it would have been around the latter half of the 80's.
Best,
Ike
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16th July 2012
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#5 | | Lives for gear
Joined: Nov 2006 Location: Hickory, MS
Posts: 2,536
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If it was late '80s they may already be using decent opamps. The NE553x and TL07x were available and reasonably priced in quantity by the late '70s (no excuses since then).
With Parametric EQ, that are typically based on state variable topology, there are several variants on how the independent Q control is executed that can impact headroom (clipping) in the SVF HP section, and/or noise gain of the SVF. The good news is this SVF noise is band passed by the EQ, but noise and distortion (from a HP or LP) filter section clipping will still show up in the audio path. Some of these subtle flaws do not show up in baseline specs since the testing would have to be performed at all possible combinations of settings.
Parametric EQ are nice for their complete adjustability, but they are not all the same. Hint: there may be something to improve other than the opamps used, depending on your desire to learn and dig into the circuit design.
JR
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16th July 2012
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#6 | | Lives for gear
Joined: Jan 2011
Posts: 879
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I can't find any info on the web for it. Can You open it up and send us pics of the guts?
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16th July 2012
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#7 | | Gear maniac
Joined: Jul 2007 Location: Sweden
Posts: 277
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I have the first version with the toggle switches, have the schematics somewere, will check.
Sent from my GT-I9300 using Gearslutz App
__________________ Jonas Ekstrom
www.mastertone.se
Audio Mastering - CD / DVD Production | |
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16th July 2012
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#8 | | Lives for gear
Joined: Oct 2006 Location: Toronto, Canada
Posts: 816
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Hi John,
Did you design the Loft parametric Eq (the 405????). I really liked that unit, very precise and consistent. Prior to that I had only used the Ashly and a Furman unit, both of which I found to be a bit "vague".
Best
Ike
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17th July 2012
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#9 | | Lives for gear
Joined: Nov 2006 Location: Hickory, MS
Posts: 2,536
| Quote:
Originally Posted by Ike Zimbel  Hi John,
Did you design the Loft parametric Eq (the 405????). I really liked that unit, very precise and consistent. Prior to that I had only used the Ashly and a Furman unit, both of which I found to be a bit "vague".
Best
Ike | IIRC it was the 401... Yes I designed it and several parametric EQ over the years. There was a Loft console made with 4 bands of parametric EQ in each input channel. That Loft 401 was popular with a few bass players back then (I won't drop names but at least one group is still around and people would recognize them), I put some extra gain in the front end gain trim circuit and raised the input impedance so it wouldn't load down bass pickups when used as an instrument preamp.
JR
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17th July 2012
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#10 | | Gear interested
Joined: Dec 2008 Location: Nashville, TN
Posts: 22
Thread Starter |
Wow John,
Thanks for the input. Sorry for the late reply guys. I have been mixing a song for a motion picture today and just got freed up for a bit. Let me find some pics of it opened up!
I know my Trident London Series T24- 44x24 came with the original TL071's in them. I personally did not care much for the console at first, as it felt muddy in the lows and low mids. 12 Channels were pulled to compensate for headroom issues, since it had its original power supply.
However, I have since put different brand new op-amps in and WOW! Huge difference. Love it! One of the best moves EVER was to Mod the Master Module and put Burr Brown OPA134's on the Master Fader Buss, Re-Cap the Entire Master, and Put all new IC's in. A custom built power supply will only rock it more.
Very under-estimated board. You simply just have to know how to drive it and what to put in it. Which is CHEAP and easy. 
Anyway, back to the Ashly...I personally would love to hear some of John's stuff he built.
Rob
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