Upgrading and servicing my Audio Research Classic 60

[abelb]

G'day Ampex,
I've been meaning to post back here to see if you'd received your amp yet. The Mazda tubes look like a pretty good deal, let me know what you think of them in your STAX preamp. Now that I've got about 30 hours on my tubes I'm planning to put the thing back on the bench to re-check the bias so I'll have a look at the tubes. I'm no tube expert so you'll have to tell me what to look for and where the "filament windings" are. I'll take a macro pic and put it up here. I'm enjoying the amp, no issues at all but that niggling doubt planted by the ARC guy is still knawing at me so I might try calling ARC back to see if I can chat to someone else who isn't so keen on getting me off the phone with a photocopy answer. Else I might still put the tubes on eBay for 50% of what I paid before they get too old and just get a set of =C= 6550's as originally used by ARC in this amp.

[Ampex53]

Hi mate ... I'm not sure I can help you but certainly post & ask.
And yes I'll post about the Mazda/Brimars ... the guy at Upscale Audio - Kevin Deal - raves about them but he charges $45 each so Ned's price is reasonable.
I'm not quite sure how the biasing works or where you adjust on this 115. I've been trying to locate an old mate - Nick bajenov - who did most of the servicing for the ARC amps sold by Audio Excellence in Sydney - Ceto Sandaval - back in the 70/80's when they were the Australian distributors. I'm sure he'd have a service manual. I checked the ARC site & they don't have an email address, so will probably send a fax & see if they'll send me a service manual. There are a couple of zener diodes which appear to be disconnected and I think, a sub bridging the solder pads. Its at the least very sloppy work & at best a worry.
I'm contacting the guy in WA I got it from just to confirm that he had it up & running successfully when he got it 12 months ago. The date codes on the Output Tx's indicate its a late 1987 build ... which is good. I'd love to know its history with repairs.
cheers .... cb

[Ampex53]

Hi abelb .... What time did you phone them to get a service person? I want to speak with someone in the service dept about a service manual or copy. I'd like to find out from ARC exactly what the bias adjust procedure is - I've had a couple of different versions * I'm assuming there is some detail listed in either the owner's manual or the service manual.

cheers .... cb

[abelb]

Hi Ampex,
Midnight in Melbourne is 9:00AM in Minnesota. I didn't get through until about 1:00AM though, as transferring to the service department went to voice mail each time. I eventually told the very helpful reception staff that I was calling from Australia and couldn't accept a call back so they kept me on hold until they found someone who could talk to me. Do let me know if you get another opinion on using the KT120 in the older amps. I'm very curious about what a different tech may say. I've decided to keep my amp as is, I'm enjoying it a lot. Sometimes it's easy to get caught up in the technical side of things and actually forget about what the amp is for.
I'll let you know how the tubes are looking in a few days when I put the amp back on the bench for the bias re-check.

[jazzwallah]

Hi abelb
I have a Classic 60 and found your posts extremely helpful as I am thinking of ordering KT120s to replace my aging KT88s. Are you still using the KT120s or did you switch to 6550s? Would appreciate your comments.

[abelb]

Hi jazzwallah,
I decided to keep the KT120 as I've been happy with the performance and I haven't had any issues or noticed high temperatures at the power transformer. I beleive the heaters in the KT88 draw 1.6A where the KT120 can draw anywhere between 1.7 and 1.95 amps. Just make sure you get the tubes matched for the lower end of the KT120 current draw range. Also remember that it's a tight squeeze under the chassis hood with the KT120's installed. If you do end up getting KT120's please post back here and share your thoughts!
Cheers,

[jazzwallah]

Hi abelb,
Thanks for the information. Chris Johnson of the Parts Connexion has also said that the KT120s will work in the Classic 60. So I will order these tubes. I have bi-amped my Vandersteen speakers with the Leak TL50 mono blocs and the Classic 60, so I shall report back about my impressions in due course to you.
Best regards,
Jazzwallah

[Ampex53]

Well that's interesting that the Parts Connexion agrees that the KT-120's are OK for the Classic 60 ... I wonder if that applies to the D-115?

Ampex53

[jazzwallah]

Well I finally installed the KT120s in the ARC Classic 60 and my modified Leak TL50 mono blocs and let the tubes warm up for an hour. I put on a record and was quite astounded by the richness of the sound. The sound stage was wider and deeper and the frequency extremes more resolved and mellifluous . I sat back and listened for a couple of hours. The transformers did not feel too warm on either amps.
I have also fired up my ARC SP10 and run it through the processor input of my ARC Reference Two MK2 line stage and the sound is wonderful. I think I prefer the SP10 phonostage over the ARC reference 1 Phono stage.
To answer Ampex53's question about the KT120s in the D-115, I would suggest sending an email to Chris Johnson of Parts Connexion and also to Kalvin Dahl of ARC. Consider their replies and then decide on how much risk you want to take. ARC may advise that the transformers will be stressed and could possibly fail as they are operating close to specs. I don't have the technical knowledge to suggest you use the KT120s. I have taken advice from audiophile friends with the technical expertise and abelb's reporting on retuning the Classic 60.
I'll end my observations by telling you that last night I had left my system on and went down close to midnight to turn it off. I decided to listen to one track on a favorite LP "A perfect match" by George Shearing and Ernestine Anderson on Concord records and I was still listening until the LP ended. I am just enjoying the music. My thanks to abelb for giving me the confidence to use the KT120s in the Classic 60.
Happy listening to all!

[abelb]

Hi jazzwallah,
Thanks for posting your thoughts on the amp with the new tubes. I'm glad to hear that the KT120's have worked out well for you. You seem to be quiet experienced with ARC pre-amps. Can I ask you, have you had any experience with the LS22? What are your thoughts on this pre? Another option for me is a ref 1, but it's quiet a bit more expensive than the LS22.
Cheers,

[Coffee Phil]

I have been following this string for some time and a thought about it has entered my head. Has any consideration been given to lighting the tube heaters with an external power supply and giving the internal power transformer an easy life? While this may seem a bit "off the wall" it is from an engineering standpoint a conservative way of getting more margin.

To alleviate any concern about AC causing hum I would use DC. A switching power supply won't be too large.

Phil

[jazzwallah]

Hi jazzwallah,
Thanks for posting your thoughts on the amp with the new tubes. I'm glad to hear that the KT120's have worked out well for you. You seem to be quiet experienced with ARC pre-amps. Can I ask you, have you had any experience with the LS22? What are your thoughts on this pre? Another option for me is a ref 1, but it's quiet a bit more expensive than the LS22.
Cheers,

Unfortunately I haven't heard the LS22. I own the SP10 and a REF phono which I bought used from a friend who bought a REF phono 2. I would recommend the REF phono though I did have some repair issues with it. However I bought it used so that can be part of the deal. It is now working fine and is very dynamic and detailed. It doesn't have the bloom that some tube preamps can have. If you have a good line stage then think about the REF phono for your vinyl needs. The ARC Dtabase website will give you details as well as reviews of both preamps. If you can find either phono used in the area you live in, then an audition will be the best way to make your decision.