The Amp Garage

the oddball stuff (please explain the PI light bulbs). It's rather odd design from QS, the neon bulb is used as a DC level shifter to couple the input stage to the PI - just to get rid of a coupling capacitor from the signal path. This particular model is well known to have noise and hum issues as ...

double post

I don't have any more info on the chokes other than the part numbers stamped on them. They are about the size of a Fender reverb transformer, smaller than you might expect from just looking at a schematic. From the voltages shown on p. 4, it seems the inductance of the chokes in AO-63 are quite low...

Hi everyone. Thanks very much for all the input! I'm not able to reproduce the PSU results. I guess I don't remember the exact inputs. I have new numbers for the 5U4GB. It says 609 at VC1. Is that 2x because I input 855VAC? If so, then 305VDC at C1 is consistent with what Strelok posted. Have a loo...

Here's what I got from Duncan's PSU, voltage at C1: 5U4GB, 535VDC 5Y3GT, 520VDC GZ34, 552VDC All the above voltages seem high. Could you please post a screen shot of PSUII? I just did a conversion that uses a 430-0-430 PT, GZ34 and choke input. Would you know the inductance of the chokes in the AO-...

gktamps wrote:I'll also have a gallery for listeners' race cars - wanna send some?

Me? No race car unfortunately... I just like classic Italian cars, ok, some Porsches too...

What a surprise to find your podcast on a guitar amp forum! Like the cliff-hanger that you threw in at the end, looking forward to the next one. Are you going to have a forum on your website? Perhaps adding more pictures to the gallery, please?! I regret selling my Alfa GTA, Duetto and Spider, but I...

David Root wrote: If the Zpri is not right, use a Hammond 125E like I did and pick your Zpri!

Even though the 125E is an Universal PP OPT, it is rated to handle 80mA of DC current. Do not try to run SE with other PP OPT's unless they have similarly DC current spec.

"I realize the majority of amp builders are cut and paste, paint by numbers, kit builders, cloners, and copy experts, but some days copying a 50 year old flawed amp, just gets old and boring. These are for the person who can read a transfer curve chart, know how to use it and how to design around i...

Littlewyan wrote: The graph was also very interesting showing the impedance curve differences, I've always wanted to know that.

The image from tgp isn't showing up for me, could please you repost it here?

Just want to verify where the 3.5k OPT figure came from...

teemuk wrote:About that Trace Elliot power amp architecture...

It does not seem possible to use a "valve-spec" 3.5k:8 OPT in the schematic as shown.

Jaz, It couldn't hurt? Why would the engineers add an additional $150.00 or more to the production costs each unit, if it didn't add to the quality of the product? I doubt it's anywhere near $150, more like a few dollars, bear in mind that the SS amps have very low output impedance to begin with, s...

I think whoever that said it had a "tube spec" OPT was doing some marketing-speak... Clearly, the impedance ratios would be quite different, anyway, they will do whatever it takes to sell a few more amps - if the players all want the tube sound, fine, slap an OPT in it, couldn't hurt...

Yes, it's a bit confusing, if no speaker damping could be detected then it contradicts ...the change in frequency response caused by the high output impedance of the tube amp is by far the predorninant cause for differences. :roll: In most guitar amps, there is a lot less NFB applied than the hi-fi ...