CarverFest Amplifier Mods

[Magnaryder]

I'd been thinking about what mods would benefit our little CF amplifiers. I had a discussion with Mark pertaining to my pre build and mentioned modding the CF amps. He pointed out several places in the schematic that a better part might improve the overall sound. So not being able to leave well enough alone, I'm going to put in some Obbligato caps and Mills or PRP resistors in the signal path. I picked the Obbligatos because they made my Fortes come alive and 'it's all about the tone, man'. Their sound has been called 'analogue' in the cap shootouts and I really like what they do for the Klipsch speakers.

Good sounding, reliable NOS tubes are getting harder to find as time goes on. I found matched quads for $450. IFAIAC that's too much money to spend on something older than I am especially when you don't know how long it's really going to last. SO... I think going with a good strong new tube that's priced right and readily available and rolling in a new high quality cap is a better option....at least for me.

I've noticed in the reading I've been doing over the past several months caps are discussed like tubes. The authors use the same language and terms when describing what they lend or don't lend to the sound. Keeping that in mind I developed a 'modding plan' for my CF amps. I've read where some modders have replaced just the resistors and that alone made huge differences.

Better parts and all huh?

I welcome discussion....what do y'all think?

ray

[Magnaryder]

http://www.carvermanuals.com/bob/Carver ... lifier.jpg

George, looking at the schematic above I plan to change the .1uf 600v caps and all of the resistors between them and the input. Mark suggested changing the 100uf 16v cap also. I thought an F&T electrolytic cap?

Alex, do you have a complete kit you'd like to sell me? or a chassis and a BOM?

ray

[Magnaryder]

I really like the the Peavey EL84s I finagled at CF12 in these amps, although I'm looking at a set of TAD(tubeampdoctor) Cryoed EL84s instead of going whole-hog and trying to find a set of NOS Mullard or Telefunken tubes. I want to wait until I get my Caps in and some of the 2.2k resistors(Mills or PRP) swapped out in the audio chain to see what it sounds like before I make a tube change.

ray

[Magnaryder]

Sherry and I finished cleaning out the garage this weekend getting my ducks in a row so I can start work on the pre amp I've been threatening to build for almost a year now. I spent 3 hours cleaning the tape residue off the Lightstar Direct Prototype chassis I'm using for this project but I've run into an issue. The fellow I bought the chassis from told me they only made 2 of them. Ordinarily I'd have ignored him BUT looking closer at the unit this display uses the word HUSH instead of MUTE like my production unit. Anyone else have a Lightstar Direct Pre like that?

Do y'all think I should drill holes all over it to build my pre?

Anyway....  I had such good luck with the repairs to my little CF amps I decided to throw caution to the wind and mod them. I have Obbligatto .1uf caps, F&T 100uf electrolytics and Mills 2.2k resistors to put in the signal path and some silver over OFC wire from DH Labs to run from the OPTs to the speaker connection and from the RCAs in. Pics to follow tomorrow...unless I electrocute myself...or nuke the amp.

Tomorrow folks

ray

[Magnaryder]

I'm trying to upload a pic but it's more aggravating than work was today.

Try this link:

http://www.flickr.com/photos/30939399@N07/10737286965/#

But I digress..With more than a little help from Mark I got the amp modded. All tolled it took me 3 hours to complete the job. I installed the .1 Obbligatto caps, 2.2k Mills resistors, F&T 100uf100v electrolytics and the 220uf 200v electrolytic Mark suggested yesterday. I planned to run some silver over 7-9s copper wire on the input line and from the OPTs to the speaker binding posts but ran out of time. I want to change the RCAs and binding posts to match the other amp.

Came home turned it on....from across the room(garage actually)...just in case don't ya know:-) First thing I noticed was it seemed to tame some shrillness in my garage KLHs. Hmmmm, let's take this inside.

I've been burning the parts in with white noise(radio static) for a little over a week, so they have a little over 200 hours on them already. I think that might have helped. At first blush the overall sound is much more articulate and sounds less 'crowded' for lack of a better term. Each instrument occupies separate space and displays a delicacy of its own. They're in bold relief. I don't have the words. The bottom end seems more robust, it seems to go deeper and is way more accurate than before the mods.

WOW!!!! Colour me impressed

....right now more listening.

ray

[Kingman]

Ray...post a pic of that Lightstar prototype body before you drill holes in it....might be worth saving!!!

[Magnaryder]

Wayne, it's the front panel that is different. The chassis is just a cheap skin. The front and rear panels appear to be production parts except for the different screening of the word HUSH.
 pic will be forthcoming.

ray

[Magnaryder]

BearJew, here is the link to the forum thread modding the CF amplifiers.

http://www.carveraudio.com/phpBB3/viewtopic.php?f=8&t=17835

ray

[Magnaryder]

Well, I can taste my fillings. Mark reminded me this evening to discharge the power supply caps. I 'thought' I did. I didn't. Got buzzed, cap read 208 volts...after it hit me. Oh well, live(maybe) and learn(not so much). I installed the 47uf JJ cap and the DH Labs silver over copper wire Jesse recommended from the output trannies to the speaker terminals. Took it in the house and fired it up. I have a dead channel. WTF!!!! Back out to the garage. Reflowed the wires I just installed. Back inside. I still have a channel out. WTF!!! Hey, check the input from the Sunfire. I switched the cables. Dead channel moved. Dumbass...I pulled an IC out of the back of the pre. Plugged it all back together and fired it up.

On a side note, I had been having an issue with little grunge from the Sunfire Tube Pre. It was noticeable at CarverFest(TheFirebug pointed it out to me) but it would go in and out. Mark and Mike Beam suggested I pinch the tube socket pins a little with a small set of needle nose pliers. I've done that several times and finally got the grunge sorted out.

The last mods I'll make before we start talking tubes will be installing the 47K and 470K resistors and replacing the little yellow caps with some polystyrenes and installing Rhodium RCAs and those nice binding posts.

The first track on Mark's '08 Carverfest disc is Boz Scaggs' Desire. It has a pretty decent bass line. I'm listening to the amp through a set of Alesis Monitor Ones I got from Harry. This combination does everything well and nothing to terrible. Tonal balance is good, mids are silky smooth, what highs I can hear are delicate and airy.

The music rises from a blacker than black background. Mark was right. That last cap in the power supply has a noticeable impact.

This has been alot of fun. And the payoff is huge.

ray

[Magnaryder]

Tonight I changed these electrolytics in my other CF amp. I installed the JJ 47uf/500V, 2 F&T 100uf/100V, 220uf/200V, 2 100pf and 150pf caps I got in Pittsburgh from Beemers. As this amp runs the same tube compliment as the other amp I might be able to see if this change is a noticeable step on the path to CF amp nirvana.

I also installed a front panel power switch.

I had left the 47uf JJ at home so it didn't get soldered in until I got home. Hey, I managed not to get shocked today. Things are looking up!

While making the changes I noticed something I'd overlooked. I can improve the wiring from the RCAs to the tube input and from the tube output to the output transformers and from the trannies to the binding posts with the DH Labs silver over 7 9s copper wire.

I'm getting alot of input from my family on the changes. They're all telling me what they're hearing. It's very kewl!

The next step will be the .1uf Obbligattos after some listening/comparison.

Replace the RCAs and binding posts with Rhodium pieces.

I think I'll change these parts in this order following the Obbligattos:

Mills 2.2K 5 watt ressistors

47K and 470K PRPs or Shinkoh Tantalums haven't decided which. The Tants are quite large and space is at a premium where they are located.

Rewire the audio path with DH Labs wire.

Now for the expensive part.....Roll tubes.

Listened/ing to Alanna Miles, Anita Baker, Manhattan Transfer, Sophie B Hawkins, Diann Shurr and Count Basie, Queensreiche, Dokken and Larry Fast/Synergy.

ray

[Magnaryder]

e="Zoot Horn"]If you can find them,,, try some older RCA(some labeled Silvertone) blackplates-- of course there ain't nothin' wrong with Tele's[/quote]

I was digging through some tubes my neighbor gave me this evening from some old stereo his FIL gave him. I now have 5 vintage HAMMOND grey plate 6bq5s supposedly from the late 50s or early 60s. Can anyone help me identify them for sure? All I can make out is Hammond in silver lettering around the middle of the tube, a halo getter, grey plates and a white six sided plate below the getter. I have them in now....I'll let you know how they sound later.

ray

btw, Mike Beam built me 2 fixtures for placing one OPT per amp on it's side to prevent field interference between OPTs. I don't know if that counts as a mod, but MANY thanks to Mike for the kindness,

Listening to Blow by Blow by Jeff Beck on the new to me Ariston TT. Sounds pretty damn good. I picked up the Jeff Beck, 2 Eagles LPs, The Babys and Sunburst Finish by Be Bop Deluxe, all for $9. Be Bop is next in rotation."
Magnaryder

[Magnaryder]

Chauss...Mullards eh? How 'bout that? We'll see how they sound in a couple of days, but they sound really good now.  Thanks for the info!

Al, thanks for the reply. I've been looking. I may have to find another set(6) of Hammonds. Having a couple of spares might be nice.

The other night I 'thought' I had dialed out a very annoying 60hz hum when I played LPs. Tonight it was back. The Ariston uses a 12V wall wort to power its motor. The Linn tonearm has Cardas wiring and the RCA connection is outside of the TT. While I was fooling with the TT I moved the wall wort close to the RCA box. Closer to the box the louder the hum became. Further away the less noise. I turned it up to full volume with the Linn arm at rest on it's stand and moved the wall wort and the Cardas RCA box around until I couldn't hear it anymore.

I have several 12volt laptop power supplies and I'm going to try them to see if they're better shielded.

Those $1 Eagles LPs sound awfully good.

ray

[Magnaryder]

Anyone know how to safely discharge caps so I can work on the amp without worrying about electrocuting myself?

ray

[Reverend]

Anyone know how to safely discharge caps so I can work on the amp without worrying about electrocuting myself?

ray

Fork.

[Anders]

heh yeah a fork may work but I use a 20 OHM 20 Watt resistor.