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Silvertone 3902 P/P 6BQ5 Console amp

Pio1980

Pio1980

AK Member
Came into one from another AKer in a pending trade. He's done a beautiful job of dressing it out, I'm doing the circuitry upgrading replacing ceramic caps and such.
This is a very interesting and elegant amp with DC-coupled front end-to-splitter/ single cap signal chain potential. Front end resistors should and will be "blueprinted" to get it's proper operation due to the "trick" circuit's voltage relationships. After changing a badly drifted resistor and recapping and some minor tweaks we have an amp with no obvious sound characteristic, very like the "straight-wire-with-gain" ideal. It is quite dependent on the quality of the signal source and speakers as the limiting factors, IMO, at this point of eval. Pix to follow soon.
I know there are others with them, any input/opinions welcome.
 
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oldhifiguy said:
pictures please. O sorry your doing them.
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Don't think Pio will mind.....here are two pics before he got it for additional underside mods:

First pic is "before" pic while still in the old console.

Second pic (amp on the right) is "after" with oak base, IEC power cord, speaker binding posts, toggle power switch, painted PT, and partial recap (not PS or ceramics).
 

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"Vivid" is the first word that comes to mind. Natural transparent presentation, neither "tube"-like nor solid-state in nature.
 
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Quick Pic. Chassis plating has a unique and very attractive copper bronze Damascus steel appearance.

Running in simplified minimalist mode via passive controller with custom interconnects from Sony 444ESX tuner, NPR source, Advent/2 Min-E-Waves. Absolutely stunning realism.
Hornhead has heard it in his system before tweaks, awaiting meet-up for his assessment of revision.
 

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Well, rejoined the Silvertone with its original partners - EV cornerhorns, Yamaha c-800 pre, and an old CD deck today - after Pio had done his mods underneath.

Firts impression - now get this, was loud! Had to severely reduce the attenuator on the yamaha to get it into reasonable listing level (as opposed to driving my Maggie 8802.)

Listened to tracks familiar to both of us and generally like what we heard (at least i did). Interesting note is that the high end seems rolled-off like when I tried it about 8 months ago.....but the rest was so much more compensating.

Still don't know what Pio did under there. It sounded punchy where previously sounded 'normal' with big bottom end.

Played some fantastic tracks through an old '90s CD 1bit MASH Panasonic into the amp and then to the EV cornerhorns.

Lot's of headroom is what I'll say. Bass was more than substantial and got down to 50 HZ strong using test tones.

Nothing below that though.

All mids and highs blended....and Pio tried to teach me to hear for absolute polarity. Think I heard it a couple times in blind testing.

Listened to wide variety fom old Genessis to Starcastle to Vangelis, to Van Halen....the amp put up power and tone sufficient for pretty loud and controlled sound on those horns.

Hope Pio keeps tweaking...sounds pretty good now. I'd probably have to open up the top end attenuator on the xover to get a bit more brightness in there - if using these amps again.

Anyway, a good day of listening and I think Pio did a great job on the Silvertone. Very good swap for the Silvertone 1483 guitar amp!

Will definatly be making a passive attenuator box for a "pre" after hearing his....very stunning - especially for a frankenstein looking box...
 
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Pio1980 said:
Quick Pic. Chassis plating has a unique and very attractive copper bronze Damascus steel appearance.

Running in simplified minimalist mode via passive controller with custom interconnects from Sony 444ESX tuner, NPR source, Advent/2 Min-E-Waves. Absolutely stunning realism.
Hornhead has heard it in his system before tweaks, awaiting meet-up for his assessment of revision.
Click to expand...

Sounds like your happy with the Silvertone ,have you gotten a schematic for it ,would like to see it if you have .
 
Don't have a skiz yet. It's a 12AX7 DC-coupled phase splitter cap-coupled into P/P 6BQ5 pentode finals (running ca 310V from Silicon doubler PS) with a light 120k resistive FB loop paralleled by 150pF HF comp. Addl HF stab via 47pF to gnd at the P-G splitter DC coupling and 1k series grid OP tube resistors. Heater string elevated via cathode bias from one channel, bias split to each pair by 100^ 2W CC and 470uF with .33 uF shunts added. Elegant ckt somewhat dependent on having spot-on front end resistor values and good front-end tubes for proper performance, not as forgiving as the Maggies IMO but more sophisticated design. Like to know OEM and designer.

Am going to do a freq sweep on the Min-E-Waves and report back. Very much enjoyed the listening sessions at Hornheads place, haven't done audiophile GTG's since the mid-'80s and miss that. The cornerhorns have magnificent bold large presentation that serve the Vangelis large scale works well but are not the last word in neutrality or clarity, his secondary system MTMs are very precise and neutral and would be worth moving into the tube set-up on stands for a time IMO for a comparison. Hornhead has excellent hearing and I am somewhat hearing impaired/deaf. Anything that affects clarity or intelligibility is immediatly apparent to me like blurring of driver interferences, polarity issues, or phase shifting. Others are affected by factors that I cannot hear or recognise, so the parity check between the two of us is good for both. I will miss having his good company available regardless.

Why does it seem so hard to produce an affordable solid state amp with the dynamically open transparency of these simple little tube amps? This amp's open dynamics and clarity has been a bit of a shock and thrown my expectations back toward "Hi-end" standards, may signal the end of mid-fi for the secondary play-around system. Have my eye on a Conrad-Johnson FET pre with reference grade phono stage to replace the passive controller box. Really good solid state pre's are hard to find at any price never mind cheap compared to tube pre's for sound, but tube pre's tend to sound like whatever tubes are in them in whatever cdx they are in at the moment and I find that troubling for establishing a consistent baseline standard of performance. I have a tube phono/line pre that is presently out-of-service due to system change-overs.
 
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On the Advent/2 Min-E-Waves in the room on stands, I'm getting useful output toward ca 32cps with audible rolloff at ca 35. Upper end extends to at least 9kc, can't take it further without benching w/scope and load as my DMM and my ears quit about there. I think the early LF roll-off was probably a room/speaker interface artifact and I do have more HF "sparkle" here with the Min-E-Wave's Selenium D220ti/JBL 6x6 waveguide horn.
The Min-E-Waves do not have the bottom extension or authority of my main system towers which have no problem doing the distant thunder/truck-rumble next-to-lowest octave that beyond requires a good true sub.
 
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Power supply mod in, found 2x150R 2W put them in parallel, voltages look good with output anode rail residual ripple at ca .75 down from 6. something AC V. 4 ACV at rectifier and 304 DCV to plates, all good stuff!
Gloryosky! tightened it up and while not bass-shy definitely deeper and better resolution thru the Min-E-Wave Advent/2. Useful response goes down-down-down.
 
Pio1980 said:
Power supply mod in, found 2x150R 2W put them in parallel, voltages look good with output anode rail residual ripple at ca .75 down from 6. something AC V. 4 ACV at rectifier and 304 DCV to plates, all good stuff!
Gloryosky! tightened it up and while not bass-shy definitely deeper and better resolution thru the Min-E-Wave Advent/2. Useful response goes down-down-down.
Click to expand...

Thats a pretty good improvement getting the ripple down from 6 volts to 3/4 of a volt , not to mention the stiffining of the power supply would do for the bass and imiging .

If you know what year Silvertone your amp is you might look in the beitnamans to find a schematic .

http://makearadio.com/beitmans/index.php

Check you PM's
 
Dudes, Reading these threads is like watching that bar scene in the Starwars movie where all types of languages were being spoken.....and you're the guy who doesn't understand any of them. Hmmmm, maybe someday with enough reading and coaching.

PIO....do those mods and would love to here again any subtle changes produced. Only have less than a month before I pop smoke and vanish from AL. But with the beauty of this internets thing...hope to tap into your brain from afar.

Also....finally got that CD burned - with all the pics before and aft as well as cabinet pics and such of the silvrtone cab. Ready for you anytime before I launch northward.

And again....really liked the listening session. Want to explore mods to the maggies (beyond stock value replacements).

v/r, HH
 
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Looking at a concurrent thread on Mag upgrades it looks like I can consider upping the value of that added 100uF cap and the cathode bypasses from 470uF, found a 330uF/400v and 2 lo-ESR pulse-rated 1000uF/25V in the salvage and am getting good ESR checks on them. Also adding 120uF to the screen rail. All that should make the output stage as rigid as necessary.

battradio said:
Hi Steve ,

Good talking with you , let me know when yo try the power supply improvemet we talked about
Click to expand...
 
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I have the PS mods in, here are pix with a "before" of another similar Silvertone amp from another older thread.
 

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