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zom-zom wrote:
I have a Sound City SMF Tour Series with a Partridge. It sounds like shit and always has since I purchased it in 1978.

Sorry to change the subject. Is this the amp with 8 EL34's, two of which are a phase splitter/driver pair? If so, this amp had what I believe to be a DESIGN ERROR. If you fix it it will sound much better. This is not a mod to improve something subtley, the amp has an honest to god flaw in the driver stage so that the two EL34's can't behave like a true long tailed pair and therefore are horrendously badly balanced. Basically, the EL34 that's driven directly from the master volume wiper is fine. The other EL34 should have its grid shorted to ground at AC (or actually the negative feedback point) in order to work properly as a common grid amplifier. This AC connection is omitted in the SMF. Normally it would be made by a .1uF (or something) capacitor to ground (or the NF point). In the SMF, the .1uF capacitor is there, but it goes NOT to ground, NOT to the NF point, but to the cathode junction IN PARALLEL with the grid bias setting resistor, where it is doing exactly NOTHING. This basically means the second EL34 amplifies way less than it should. If you know how phase splitters work, this really appears to be an error, but the funny thing is, it not only appears in the circuitry in the amp, but on the schematic as well!

If you make the repair, the amp will be quieter, more powerful and, will have reduced crossover distortion.

I'll draw a pic and stick it here in a sec.

Ned

I don't have the schematic for the smf tour in front of me, so I can't remember the values. As I recall the capacitor in question is a .1uf 400 volt "mustard" cap. If you can locate the nodes in question, it's a super easy thing to fix.



I hope you can see that with the cap in parallel with the resistor (into the high impedance grid), the cap doesn't really do anything. The amp would not sound one iota different if it was snipped out of the circuit. The fact that the cap is there at all is pretty good evidence that this was just a mistake made in the design process that somehow got carried clear through manufacture.

Anyway, if it's not an error, it's very strange decision, and the amp I worked on definitely sounded much better rewired as shown.


Ned

ned clayton wrote:

zom-zom wrote:
I have a Sound City SMF Tour Series with a Partridge. It sounds like shit and always has since I purchased it in 1978.

Sorry to change the subject. Is this the amp with 8 EL34's, two of which are a phase splitter/driver pair? If so, this amp had what I believe to be a DESIGN ERROR. If you fix it it will sound much better. This is not a mod to improve something subtley, the amp has an honest to god flaw in the driver stage so that the two EL34's can't behave like a true long tailed pair and therefore are horrendously badly balanced. Basically, the EL34 that's driven directly from the master volume wiper is fine. The other EL34 should have its grid shorted to ground at AC (or actually the negative feedback point) in order to work properly as a common grid amplifier. This AC connection is omitted in the SMF. Normally it would be made by a .1uF (or something) capacitor to ground (or the NF point). In the SMF, the .1uF capacitor is there, but it goes NOT to ground, NOT to the NF point, but to the cathode junction IN PARALLEL with the grid bias setting resistor, where it is doing exactly NOTHING. This basically means the second EL34 amplifies way less than it should. If you know how phase splitters work, this really appears to be an error, but the funny thing is, it not only appears in the circuitry in the amp, but on the schematic as well!

If you make the repair, the amp will be quieter, more powerful and, will have reduced crossover distortion.

I'll draw a pic and stick it here in a sec.

Ned

Mine uses 6 EL34s, not 8. I'll have to look at it and see if it's wired in the manner you describe. I suppose it isn't as it doesn't use the big tubes for phase splitting.

The EQ section is bizarre and very touchy. It is extremely loud and "tight" sounding. It's put together like a tank, but that's not of much use when it inherently just sounds bad.

Having personally used both hiwatts and sound city's, I can honestly say that sound city's are not even in the same league as hiwatts, I've greatly disliked most of the sound city's I've played through, apart from a conchord combo that when cranked sounded lovely. I mean, i think you would have to be deaf to not hear rather pronounced sonic differences between sound city's and hiwatts. But this will unfortunately happen if you have an old dr103. I have a 73 and it is the most horrifically punchy and loud amp I have ever been near. I literally haven't played it for years because it is just stupid for any home application. I never played a gig with it above 3. Although not bass heavy in anyway, it is an amazing amp. It has a very particular immediate and aggressive punch to the tone. It hits you, I love the old ones. They look nuts when you open them up, the build quality is really something. Don't know about all these creepy fans that zom speaks of, frankly I don't want to know, but these are fantastic amps if you like a punchy aggressive tone. These things will greatly exaggerate any fuck up you make though, extremely clear and unforgiving amps. Take this from someone who usually hates vintage tone snobs, these amps have a very unique sound quality and are fucking invincible. Nothing I have heard other than a make called wienbrock sounds similar. They cost too much money now though.

Anyone come across any of the brand new (2013-14) Hiwatts?

I had a 50 watt Hiwatt lead combo like z-z does, and it sounded really cool. If I got another is probably want a 100 watt amp as my favorite sounds from that style of amp were when it was just starting to breakup. Still sounded great cranked!

I built my girlfriend a triwatt from Tinity's kit and I can't say enough good things about it (Except the overdrive layout wasn't forgiving to my bad lead dress and shitty EH tubes...) http://www.trinityamps.com/Product\_Triwatt.htmIt has the character of a hiwatt without the ear splitting volume - built in adjustment to switch it from 6v6 to el34s if it doesn't have enough volume (I found with a heavy drummer the 6v6 was just slightly underpowered). has the overdrive section of the 80s hiwatts but it's on a pull knob so you can take it right out of the circuit. The kit without a cab or anything ended up costing me about $750. It was a lot of work but it was fun, and it's just fantastic sounding. What I love about it is the EQ actually acts like an EQ.

There are reports in this forum of Dr Tony Balls building very nice Hiwatt (and Orange!) clones.

ImDADA wrote:Anyone come across any of the brand new (2013-14) Hiwatts?Not sure who's actually making them now, until recently at least they were being manufactured by the folks that ran the Music Ground chain of shops, who by all accounts were a bunch of crooks (widespread allegations of fraud and both of them were convicted for handling stolen goods). If they're still involved I'd steer well clear of new Hiwatts, there are plenty of good builders who could make you an amp of comparable or identical quality who would be more deserving of your business, plus it'd probably actually be cheaper.Of course if they're no longer involved then current Hiwatt might be worth a look...

That would be excellent. I'm not sure a Hiwatt (custom/dr103) is exactly what I need tbh but it's in the right ballpark. If it's not a lot of effort then let me know.