Heathkit (Mono) A-9C Integrated Amp questions.

[SixCats!]

Hi all,

I was visiting the McIntosh page and asked some questions about MONO McIntosh Amps. In that thread, I mentioned that I have several other MONO Amps waiting "on deck" for repair. A very nice gentleman responded to
my thread and provide me with some insight on the different Heathkit models. In this gentlemans opinion, he suggested that the A-9C is NOT one of the better Heathkit Integrated Amp due to the "so-so" power transformer
(as well as other things such as the A-9C was meant to be a BUDGET hobbiest/entry level unit and hence not a great Hi-fi performer).
So gentleman, I ask you, can one upgrade/mod the A-9C for good performance (on a budget) or would I just be trying to make a
"Silk purse out of a Sows Ear ?" Perhaps I might be better off just
"FLIPPING" the A-9C and apply the money towards the repair of one of my other Mono Amps such as my PILOT AA-920 (needs a PT and Recap). I also have a PILOT PT-1030D (AA-903B). In addition, I have a second
SCOTT 99A, a AMPEX 620F and a vintage HK TA-10 Solo Mono Receiver all needing repair. I had been leaning towards first repairing the HIGHER power A-9C (20 Watts) as I have a BIG (circa 1960's) "homemade" Cabinet filled with UNIVERSITY drivers (15" Woofer and Horns) that is NOT fairing too well when using my SCOTT 99A Mono Amp (approx 12 Watts) when driven to moderate LOUD volume on certain material. In fact, I thought perhaps a driver was BLOWN until I reconnected the Speaker back to my MARANTZ 1060(30 Watts per) SS Integrated Amp and it played beautifully! The funny thing is, when I use the SCOTT 99A with the much LARGER "homemade" Cabinet with ELECTROVOICE drivers (15" Woofer and Horns) it sounds fine! Ummmm....At any rate, while I could use and would like to own a HIGHER POWER MONO Amp, I certainly do NOT want to waste money on a "also ran".
Thanks you all in advance for any suggestions/help in this matter.

HAPPY NEW YEAR ALL!
Regards,
SixCats! aka Tom Patrick

 

[thunderroad]

Hello again, SixCats! I saw that post on the Heathkit A9-C and was real surprised with that low opinion of it too! While I am certainly not qualified to dispute it, a Web site that I used to frequent, but is now sadily offline, the Belgian Audiophile School always had a very high opinion of the A9-C. When discussing music or comparing components they always referred to their "reference system" which included among it's components, a pair of Tannoy Heritage coaxial speakers driven by restored mono Heathkit A9-C's. They used this system as a reference to all the other modern and vintage tube and SS gear they evaluated. That was my first introduction to the Heathkit tube amplifiers and I always considered the A9-C to be the cornstone of those products. Maybe it's just a case of "one man's trash is another man's treasure"? :scratch2: But on the other hand, if a silk purse is beyond your reach, then a well-polished sow's ear may be just the ticket when enjoying the music is the goal!

Happy New Year to you too!

 

[SixCats!]

Hello Thun,

Good to see you here at the Tube pages! Thun, thank you for that very insightful information regarding the Belgian Audio School. The information you provided gives me hope that the A-9C is more than an "also ran" and can (once gone through) be used as part of a nice mono system.
I am rather new to TUBE Audio and have much to learn!
This much I have learned, mating Audio gear is truly trial and error. As I mentioned earlier, it would appear that my SCOTT 99A Mono Amp is NOT a good match with my large (circa 1960's homemade) cabinet with it's
15" UNIVERSITY Woofer, horn mid-range and horn tweeter. However, when I hook up that same Amp to my (MUCH larger circa 1970's homemade) cabinet with it's 15" ElectroVoice Woofer and horn mid-range and horn tweeter,
it appears to work fine. Thankfully, using the SCOTT 99A on my vintage (circa 1959) STEPHENS E-3 TRU-SONIC with it's 15" Woofer, mid-range horn and horn tweeter, the end results are STUNNING! I hope some other AK'ers will offer their opinions on the Heathkit A-9C and Heathkit in general.
HAPPY NEW YEAR !

Regards,
SixCats! aka Tom Patrick

 

[soundmotor]

The Heath A9 performance is limited by the output transformer. I'd sell it and repair the Pilot.

 

[thunderroad]

I'm learning alot of new stuff here too! The jist of the earlier conversation over in the McIntosh forum that spawned this thread, was exactly the same as soundmotor's feedback; and that is the performance of the Heathkit A9-C is limited by it's output transformer. One poster even called the output transformers "whimpy" which implies to me that they are undersized for their application. I don't own an A9-C and have never heard one, but I have seen alot on ebay and on the previously mentioned Web site. Surely those transformers can't be undersized, they're monsters! What I don't understand is what is the imitation? They seem to be large enough to prevent the iron from saturating at low frequency! Are they non-linear or have a high order of harmonic distortion? I don't get it! :scratch2:

I remember reading somewhere that when Marantz first came out with the Model 8 stereo amplifier it's performance was adequate, but nothing exceptional. Shortly after the start of production, Marantz introducted a new opt design and it improved the performance of the amplifier so much that they issued a new model designation for amplifiers with the new transformers and that is where the 8b came from. The reason that I'm bringing this up is, is this the kind of thing we're talking about here, the limits of the technology at the time? Or are we talking about Heathkit scrimping on the transformers, trying to save money on the product? I'd like to hear your thoughts!

 

[SixCats!]

Hi Thun,

Man, you sure raised some fantastic questions! These are the exact same questions I want to learn the answers to as well. I am hoping that the gentleman at the Mc forum who used the word "Whimpy" discribing the Heathkit's A-9C PT's will (per my request) be able to provide a bit more
in-depth information as to the A-9C's PT short comings. I (of course) have seen the size of the A-9C Transformers and as you mentioned, they are MONSTERS! Then again, my being a Tube newbie, perhaps the size is not all that important ? Perhaps it's "what's inside" that makes the difference ?
I dunno. Well, let's hope some other members with knowledge on Heathkit will join in the fun! Inquiring minds want to know!

Regards,
Tom Patrick aka SixCats!

 

[soundmotor]

Or are we talking about Heathkit scrimping on the transformers, trying to save money on the product? I'd like to hear your thoughts!

It all has to do with how well the output transformer is wound. To wind a good one takes more complex operations which means time. The longer it takes to make the more expensive it will be. When the transformer was being wound, to build a good one would require the winding core to be removed from the machine and hand operations done in order to it get wide frequency response or low inter-winding capacitance for example. Some of the high-end transformers had multiple sections for the primary and they would need to be interleaved a specific way in order to meet these goals. For a cost sensitive product such as the Heathkit, they may have "scramble-wound" the transformer. As I understand that process, the output transformer was never taken off the winding machine. It was wound pretty much at one shot. Size does not mean much in output transformers either. A large one on a cheap amp probably means cheaper steel for the laminations. Better steel cost more money and could be much smaller. Lastly, the A9 was at the low-end of a range of amplifiers that Heathkit offered. IIRC the A9, W4, W5, & W6 were all available within the same model year w/ the A9 near the bottom.

 

[Steve O]

Hi Thun,

Man, you sure raised some fantastic questions! These are the exact same questions I want to learn the answers to as well. I am hoping that the gentleman at the Mc forum who used the word "Whimpy" discribing the Heathkit's A-9C PT's will (per my request) be able to provide a bit more
in-depth information as to the A-9C's PT short comings. I (of course) have seen the size of the A-9C Transformers and as you mentioned, they are MONSTERS! Then again, my being a Tube newbie, perhaps the size is not all that important ? Perhaps it's "what's inside" that makes the difference ?
I dunno. Well, let's hope some other members with knowledge on Heathkit will join in the fun! Inquiring minds want to know!

Regards,
Tom Patrick aka SixCats!

Soundmotor has more-or-less described the probable physical shortcomings of the A9 OPT. Electrically, the result is reduced output or less than ideal transformer action at the frequency extremes. There will also be excessive phase shift betw input and output at these extremes which can cause amp instability with some speaker loads when the feedback loop is closed (the A9 is a feedback type amp). Instability usually shows up as ringing on transients in the mild cases to sustained ultrasonic oscillation in the worst cases. Transient ringing usually sounds to me like an addeded edge to the sound, like everything has a hissy sounding sibilant character added to it. Oscillation usually causes weak bass, low volume (gain) and fried tweeters for no apparent reason. If you don't have a scope, these defects will be difficult to pin down objectively.

Also don't be deceived by the size of an OPT can. Unless you know what's in the can, it's all cosmetic. I haven't unpotted an A9 OPT but I have unpotted a few PTs. Typically, they're 1/2-2/3 potting compound and 1/3-1/2 transformer on vol basis.

 

[SixCats!]

HAPPY NEW YEARS!

Thank you Steve O and Soundmotor for enlightening me with such useful information. Well, I guess I was (more or less) on target when I metioned earlier that perhaps OPT SIZE isn't all that important. I gotta tell ya, when I first saw this Amp and those BIG OPT's, I'd thought I hit the Jackpot lol!
Oooh well, it's not like I spent too much money and after all, I did get two Amps and a tuner! Oooh, I am however a bit confussed by something CARL said on my original thread on the McIntosh page. Carl mentioned that the
A-9C OPT's were GRAY in color whereas my A-9C OPT's are BLACK. Do you think it's too much to hope for that the
BLACK OPT's might be a better OPT or am I just suffering from
"wishful thinking" ? Ooooh, Steve O, might there be a way to TEST
the quality/performance of the A-9C's OPT's before I invest too much money ?
Thank you both again for your help.

Regards,
SixCats!

 

[Steve O]

HAPPY NEW YEARS!

Thank you Steve O and Soundmotor for enlightening me with such useful information. Well, I guess I was (more or less) on target when I metioned earlier that perhaps OPT SIZE isn't all that important. I gotta tell ya, when I first saw this Amp and those BIG OPT's, I'd thought I hit the Jackpot lol!
Oooh well, it's not like I spent too much money and after all, I did get two Amps and a tuner! Oooh, I am however a bit confussed by something CARL said on my original thread on the McIntosh page. Carl mentioned that the
A-9C OPT's were GRAY in color whereas my A-9C OPT's are BLACK. Do you think it's too much to hope for that the
BLACK OPT's might be a better OPT or am I just suffering from
"wishful thinking" ? Ooooh, Steve O, might there be a way to TEST
the quality/performance of the A-9C's OPT's before I invest too much money ?Thank you both again for your help.

Regards,
SixCats!

Carl's comment refers to the chassis, not the transformers. Early A9s (and most Heath HiFi components of the era) had hammertone grey chassis. Later ones were usually a straight metallic gold color. Power transformers on all were matte black. OPTs were hammertone grey if Acro or Peerless or matte black if Chicago or the Peerless on the W6.

If stock, the Chigago OPT on the A9 will always be the weakest link...always...regardless of what you read on the net or in some tweako mag (if paper mags are still published)...always!

There are indeed tests that can be performed on an OPT or any trans for that matter that can help characterize its performance in a specific application. Some parameters that come to mind would be primary inductance, leakage inductance, interwinding capacitance, initial resonance, frequency response at low and high power etc. etc. etc. Many years ago, there was an article in "Glass Audio" that discussed transformer tests and how to conduct them. Could be worth a search if you're really interested. Some specialized test equip will be required. OTOH and IMO, the real test of an OPT is in the circuit designed for it. So...as before, if you're really interested in the A9, refurb it as nec to make it a safe and reliable runner and listen with the speaker(s) you plan to use. If it satisfies, great. If it doesn't satisfy, there's that auction place. Or maybe even an acquaintance who wants one and could trade you something for it.

I gotta say however, based on what you've stated here and on the Mac forum, you REALLY want a Mac MC30/40 with a C8 mono preamp. Yeah, it'll cost a few $ but you probably won't feel compelled to be flippin it in a couple of months either. And even if you do, you'll most likely get your investment back +. That's a better deal than even real-estate with a sub-prime mortgage.

Good luck
...and be aware of your inner needs...
...you REALLY need a Mac...

 

[thunderroad]

What a great bunch of guys! :thmbsp: As an interested bystander in this whole discussion, I really appreciate soundmotor and Steve O taking the time and energy to educate us novices. That's what I love the most about AK, great people willing to share their knowledge freely. Thanks very much!

May your New Year be a happy and healthy one!

 

[SixCats!]

Hi Thun,

Man, you've said a mouthful! Thank you Thunderroad, Steve O and Soundmotor. I've learn a LOT! I'll keep ya'll posted when this projects is up and running!

Regards,
Tom Patrick aka SixCats!

 

[SixCats!]

Hi all,

I found this old thread while doing some Google research. Just an update...
I still have and use the HEATHKIT A-9C Integrated Amp. I recently hooked the A-9C up to one of my vintage (Klipsch designed) "The Rebel" Corner Horns (which houses a single 15" Stromberg Carlson Series 400 Coaxial) and it sounds lovely when listening to Classic Jazz. I am currently using the Fisher 500 Mono Receiver with a vintage Brociner Back loaded Corner Horn housing a single 12" UNIVERSITY 6201 Coaxial driver. This combo again sounds very lovely on Class Jazz. I sometime listen to the Scott 99A mono Amp with my EV "Aristocrat" three way Corner Horn. Of course I mostly listen to my Pilot PT1030D (AA-903B) with the Stephens Tru-Sonic Horn Speaker. The Scott 222D is connected to a pair of Klipsch KG 3.2's as part of a small Bedroom system. I enjoy all these systems (and more).

Regards,
SixCats!

 

[chinacave]

Interesting.

I have a sentimental fondness for the A9-C, as it was the first tube anything that I was able to repair / make work (with MUCH help from an an actual electronics engineer pal), and a pair were my only system for about 5 years after being converted to mono power amps.

They sounded pretty good to me!

 

[SixCats!]

Hi Chin,

First of all, welcome to the MADNESS! I understand you're being sentimental about the A-9C for the reasons you stated. If memory serves, I picked up the A-9C (which is in beautiful physical condition) along with some other tube items (which I no longer own) for silly (read cheap) money a few years ago. I have little invested (money wise) in the purchase of the A-9C and it's update. The A-9C brings me much pleasure for little cost. Besides it's sound, I really dig the looks of the A-9C (Gold & Black). As I type this, I am listening to the A-9C and the "The Rebel" (Stromberg Carlson) mono Corner Horn. I find this system wonderful for just "kicking back" and listening to the MUSIC (mostly Classic Jazz) and not worry about the gear. I'm playing Jimmy Smith "Back at the Chicken Shack" and it sounds good to me too!

Regards,
SixCats!